Ablation: Surgical destruction or removal of tissue, an organ, or a
precise region of a particular structure. Ablation may involve surgical cutting
(excision); chemical destruction, such as injection of phenol; or the use of
high frequency electrical current or radio waves. For example, pallidotomy is a
procedure used in the treatment of Parkinson’s disease or certain other movement
disorders. The procedure involves surgical ablation of part of the internal
portion of the globus pallidus (GPi)–i.e., a brain region involved in
regulating movement–in an attempt to "rebalance" movement and posture control.
Once a wire probe is inserted into and precisely positioned within the GPi, it
heats and destroys adjacent tissue through the emission of radio waves.
Accelerometer: A device used to measure the
rate of change in velocity over a specific period of time. Measures the rate or
"speed" of the tremor cycle.
Acetylcholine (ACh): A neurotransmitter
present at junctions of nerve and muscle cells and various sites of the central
nervous system, including the cerebral cortex and the basal ganglia. Primary
functions of acetylcholine include regulating the delivery of messages from
neurons to skeletal muscle fibers, smooth (involuntary) muscle fibers, and
effector organs as well as between nerve cells in the brain and spinal cord.
Acetylcholine also functions as a vasodilator and triggers certain actions
within the parasympathetic nervous system, such as lowering blood pressure and
slowing heart and breathing rates.
Action tremor: a tremor that occurs during
the performance of voluntary movements. Such tremors include postural,
isometric, kinetic, and intention tremors.
Activities of daily living (ADL): functions
that are typically performed as part of a person’s daily routine, such as
dressing, bathing, eating, toileting, leisure activities, socialization, and
other functions of daily living.
Acute: Referring to symptoms of abrupt
onset, often of marked severity or intensity.
Adenosine triphosphate (ATP): ATP is the
molecule that provides the energy in the cells of all living things.
Agonist: A muscle whose contraction executes
an intended movement.
Akathisia: a neurologic condition of motor
restlessness, manifested by a sensation of muscular quivering, an urge to
constantly move about, and an inability to sit still.
Akinesia: absence of movement or loss of the
ability to move such as temporary or prolonged paralysis or "freezing in place."
Akinetic: Referring to absence or poverty of
voluntary movement; loss of the ability to move all or part of the body.
Alpha 2-adrenergic agonist: A drug that
reduces the activity of the neurotransmitter norepinephrine by stimulating
certain receptors within the central nervous system (central presynaptic alpha
2-adrenergic receptors). The release of norepinephrine triggers action within
the sympathetic nervous system. This part of the nervous system regulates
certain involuntary activities during stress, such as increasing the heart rate,
deepening breathing, and raising blood pressure. Norepinephrine also plays a
role in regulating mood and emotion. The administration of alpha 2-adrenergic
agonists may result in a reduced heart rate and lowered blood pressure and have
depressive or sedative effects.
Alzheimer’s disease: A progressive
degenerative disease of the brain of unknown cause. Alzheimer’s disease is
characterized by widespread loss of nerve cells, particularly in the outer
region of the brain (cerebral cortex), with distinctive neurodegenerative
changes (including "senile plaques" and "neurofibrillary tangles") and reduced
activity of acetylcholine and other neurotransmitters of the brain. The disease
is the most common cause of dementia or progressive deterioration of thought
processing and acquired intellectual abilities. Associated symptoms include
initial forgetfulness with increasingly severe memory impairment; disorientation
and confusion; loss of the ability to recognize familiar people or objects
through sensory stimuli (agnosia); and speech disturbances. The disorder may
also be characterized by restlessness and agitation; an increasingly impaired
ability to conduct purposeful movements; personality disintegration; and
symptoms of psychosis, such as the perception of sights, sounds, or other
sensations in the absence of external stimuli (hallucinations) and false beliefs
of persecution despite evidence to the contrary (paranoid delusions).
Ambulant (ambulatory): Able to walk; may be
used to describe patients who do not require a wheelchair or are not confined to
Ambulation: The act of walking.
Amino acid: The chemical "building blocks"
or basic structural units of proteins. All proteins in the body are formed from
a "pool" of 20 different amino acids. Some are essential amino acids and must be
supplied by the diet. The remainder are classified as "nonessential." These can
be made by the body and need not come from the diet.
Amniocentesis: A screening or diagnostic
procedure during which a sample of amniotic fluid surrounding the developing
fetus is withdrawn by means of an ultrasound-guided needle. The amniotic sac is
a fluid-filled membrane that surrounds and protects the developing fetus within
the uterus. Amniotic fluid contains cells that may be used for DNA analysis,
chromosomal testing, and enzyme studies. Such testing may detect certain genetic
disorders, metabolic diseases, chromosomal abnormalities, or developmental
defects. This procedure is typically performed between the 14th and 18th week of
Amplitude: the "size" or "height" of a
tremor; the extend or breadth of a tremor’s range.
Analog (Analogue): (1) A chemical compound
or agent that is similar to another in structure yet differs concerning a
particular element; it may have a similar or different mode of action. (2) A
tissue, organ, or other bodily structure that has the same function or
organization as another yet has a different evolutionary origin.
Antagonist: (1) A drug that blocks a
receptor, preventing stimulation. (2) A muscle whose contraction opposes an
Antibodies: Specialized proteins that
function as an essential part of the immune system. Antibodies are produced by
certain white blood cells (B cells) in response to the presence of specific,
usually foreign proteins (i.e., antigens), helping the body to neutralize and
destroy the invading microorganism, foreign tissue cell, or other antigen in
Anticholinergics: Drugs that block the
action of acetylcholine, a neurotransmitter whose effects oppose dopamine. By
blocking acetylcholine’s action, these drugs increase dopamine’s ability to
Anticholinesterase: An agent that inhibits
action of acetylcholinesterase (AChE). AChE is an enzyme that inactivates
acetylcholine, a neurotransmitter at the junctions of nerve and muscle cells
(neuromuscular junctions) that regulates the delivery of messages from neurons
to muscle fibers. By inhibiting the activity of AChE, such medications allow
high levels of acetylcholine to accumulate, potentially enabling repeated
stimulation of nerves at neuromuscular junctions.
Anticonvulsant medication: An agent that
prevents or arrests convulsive seizures.
Antiemetic: A drug that reduces nausea and
Antigen: Any substance that may trigger a
particular immune response, such as the production of antibodies. Antigens may
be foreign proteins of invading microorganisms (e.g., viruses, bacteria),
toxins, or foreign tissue cells (e.g., used in transplantation).
Antihistamine: a drug that counters the
effects of histamine, a compound that causes dilatation of capillaries,
contraction of smooth muscle, and stimulation of gastric acid secretion and that
is released during allergic reactions.
Antioxidants: Agents that inhibit or
neutralize potentially harmful compounds known as free radicals. Free radicals
are produced during metabolic activity. High levels of free radicals may
eventually lead to impaired functioning and destruction of neurons and other
bodily cells. Certain antioxidants are thought to neutralize free radicals
before cellular damage occurs.
Aorta: The main artery of the body. The
aorta receives oxygen-rich (oxygenated) blood from the lower left chamber
(ventricle) of the heart for distribution to most arteries of the body, with the
exception of the pulmonary artery, which distributes oxygen-deficient
(deoxygenated) blood from the lower right ventricle to the lungs.
Apoptosis: Cell death due to a programmed
pattern of gene expression; a form of cell death in which certain enzymes
activate to degrade DNA within the nucleus, resulting in cellular degeneration
Apraxia: Loss of the ability to sequence,
coordinate, and execute certain purposeful movements and gestures in the absence
of motor weakness, paralysis, or sensory impairments. Apraxia is thought to
result from damage to the cerebral cortex, such as due to stroke, brain tumors,
head injury, or infection. It may also occur as a result of impaired development
of the cortex as in certain neurodevelopmental disorders, including Rett
syndrome. Apraxia may affect almost any voluntary movements, including those
required for proper eye gaze, walking, speaking, or writing.
Archimedes spirals: a relatively simple test
used to evaluate tremor severity. During this test, the patient is asked to draw
increasingly wider circles on a piece of paper.
Asterixis: involuntary, jerking or flapping
movements, especially of the hands. Extending the patient’s arm with the wrist
bend in a backward position may induce this form of tremor, which may be
associated with advanced liver disease.
Astrocyte: A type of glial cell. Glial cells
are the connective tissue cells of the central nervous system (CNS), serving as
the supportive structure that holds together and protects neurons. Astrocytes
are relatively large glial cells with thread-like projections that connect with
neurons and small blood vessels (capillaries). These projections form part of
the so-called "blood-brain barrier." This barrier slows or prevents the passage
of unwanted substances, such as harmful chemicals, infectious agents, etc., from
the bloodstream into the brain. Astrocytes also accumulate in areas where nerves
have been damaged (astrocytosis), sealing off these areas. An excess of
astrocytes in damaged areas of the CNS is known as gliosis.
Ataxia: A condition characterized by an
impaired ability to coordinate voluntary movements. Ataxia may result from
damage to the cerebellum, cerebellar pathways, or the spinal cord due to various
underlying disorders, conditions, or other factors. These may include infection,
head injury, stroke, brain tumors, neurodegenerative disorders, alcohol or drug
intoxication, or certain hereditary diseases (e.g., Friedreich’s ataxia,
ataxia-telangiectasia). Associated symptoms may vary, depending upon the site of
damage within the central nervous system. However, the condition is often
characterized by incoordination, postural imbalance, and a lurching, unsteady
manner of walking (gait). Additional findings may include slurred speech
(dysarthria); rapid, involuntary, rhythmic eye movements (nystagmus); and/or
Ataxia-telangiectasia (AT): A hereditary,
progressive disorder that typically becomes apparent in early childhood and is
characterized by increasing neurodegenerative changes of the cerebellum, a brain
region involved in producing coordinated voluntary movements, sustaining
balance, and maintaining proper posture. Associated symptoms typically include
delayed motor development; an unsteady, awkward manner of walking; drooling;
impaired articulation of speech (dysarthria); dependence on thrusts of the head
to achieve proper focusing of the eyes; and involuntary, rapid, jerky eye
movements (nystagmus). Affected children may also develop involuntary,
"shock-like" muscle spasms (myoclonus); sustained muscle contractions that
result in repetitive twisting motions or unusual postures or positions
(dystonia); or irregular, jerky, relatively rapid involuntary movements
(chorea). AT is also typically associated with permanent widening (dilation) of
groups of blood vessels (telangiectasias), particularly in sun-exposed skin
regions of the face and the transparent membranes covering the whites of the
eyes. In addition, AT is characterized by deficient functioning of the immune
system (immunodeficiency), leading to recurrent respiratory and skin infections
and an increased risk of certain malignancies (e.g., certain leukemias or
lymphomas). The disorder, which is transmitted as an autosomal recessive trait,
is thought to result from defective repair of DNA.
Athetosis: Involuntary, relatively slow,
writhing movements that essentially flow into one another. Athetosis is often
associated with chorea, a related condition characterized by involuntary, rapid,
irregular, jerky movements. Although athetosis may be most prominent in the
face, neck, tongue, and hands, the condition may affect any muscle group.
Athetosis may occur in association with certain neurodegenerative diseases, such
as Huntington’s or Wilson’s disease, or cerebral palsy (CP). It may also result
from infections affecting the brain or the use of particular medications.
Atrophy: Wasting away or loss of a cell,
tissue, or organ due to disease, malnutrition, insufficient blood supply, or
other causes, such as loss of skeletal muscle mass due to peripheral nerve
Attention-deficit/hyperactivity disorder: a
diagnosis applied to children and adults who consistently display certain
characteristic behaviors over a period of time. The most common behaviors fall
into three categories: inattention, hyperactivity, and impulsivity.
Atypical: Irregular; not standard or
characteristic; not conforming to type.
Atypical neuroleptics: Antipsychotic drugs
that cause less parkinsonian side effects than older treatments for psychosis.
Auditory: Pertaining to the sense of hearing
or the organs involved in hearing.
Augmentation: A phenomenon that may occur as
a result of the use of certain medications (particularly levodopa). Augmentation
is characterized by the emergence of worsening symptoms earlier in the day
(e.g., early evening, afternoon, or morning). Many people who take levodopa and
some who take other dopamingeric agents develop augmentation, especially those
who have severe symptoms or are taking high doses of the drug.
Autoimmune: Referring to an immune response
against one’s own tissues or organs. Autoimmune diseases result from abnormal
immune reactions in which the actions of certain white blood cells (T cells) are
directed against "self proteins" (autoantigens) or normal tissue components
(i.e., cell-mediated immune response)–or in which specialized proteins
(antibodies) produced in response to specific, usually foreign proteins
(antigens) improperly act against certain of the body’s own cells (i.e.,
antibody-mediated immune response). In certain disorders, the autoimmune process
may be primarily directed against one organ, such as the thyroid gland in
Hashimoto’s thyroiditis or the pancreas in insulin-dependent diabetes mellitus,
or may involve multiple organs and bodily systems, such as associated with
systemic lupus erythematosus (lupus or SLE).
Autonomic: The autonomic nervous system
controls most of the involuntary reflexive activities of the human body. The
system is constantly working to regulate the glands and many of the muscles of
the body through the release or uptake of the neurotransmitters acetylcholine
and norepinephrine. The autonomic nervous system is made up of two primary
parts: the sympathetic and parasympathetic systems. The sympathetic nervous
system prepares the body for emergencies or times of stress and is responsible
for the body’s "fight or flight" response when faced with a dangerous situation.
During this response, the heart rate and blood pressure increase, the pupils of
the eye dilate, and the digestive system slows down. The parasympathetic system
helps the body’s functions return to normal after they have been stimulated by
the sympathetic nervous system and also has some responsibility for keeping the
body’s immune system properly functioning.
Autonomic dysregulation: This term infers
the malfunction of the autonomic nervous system, the portion of the nervous
system that conveys impulses between the blood vessels, heart, and all the
organs in the chest, abdomen, and pelvis and the brain (mainly the medulla, pons
Autonomic nervous system: The autonomic
nervous system (ANS) controls most of the involuntary reflexive activities of
the human body. The system is constantly working to regulate the glands and many
of the muscles of the body through the release or uptake of the
neurotransmitters acetylcholine and norepinephrine. The autonomic nervous system
is made up of two primary parts: the sympathetic and parasympathetic systems.
The sympathetic nervous system prepares the body for emergencies or times of
stress and is responsible for the body’s "fight or flight" response when faced
with a dangerous situation. During this response, the heart rate and blood
pressure increase, the pupils of the eye dilate, and the digestive system slows
down. The parasympathetic system helps the body’s functions return to normal
after they have been stimulated by the sympathetic nervous system and also has
some responsibility for keeping the body’s immune system properly functioning.
Autosomal dominant trait: Human traits,
including an individual’s eye color, hair color, or expression of certain
diseases, result from the interaction of one gene inherited from the father and
one gene from the mother. In autosomal dominant disorders, the presence of a
single copy of a mutated gene may result in the disease. In other words, the
mutated gene may dominate or "override" the instructions of the normal gene on
the other chromosome, potentially leading to disease expression. Individuals
with an autosomal dominant disease trait have a 50 percent risk of transmitting
the mutated gene to their children.
Autosomal recessive trait: Human traits,
including an individual’s hair color, specific blood group, or expression of
certain diseases, result from the interaction of one gene inherited from the
mother and one from the father. With autosomal recessive disorders, two copies
of the disease gene must be inherited in order for an individual to potentially
develop the disease. If both the mother and father carry a copy of the disease
gene, each child has a 25 percent risk of inheriting the two genes for the
disease. There is a 50 percent risk that their children may inherit one copy of
the disease gene and be carriers for the disease trait (heterozygous carriers).
In addition, there is a 25 percent chance that the parents’ offspring will
inherit two normal copies of the gene and will not develop the disorder nor be
carriers for this disease trait.
Axons: Nerve fibers. Axons are the
relatively slender extensions of neurons that transmit nerve impulses away from
nerve cell bodies. The ends of the axons or "terminals" release chemical
substances known as neurotransmitters, enabling the transmission of nerve
impulses to other neurons or effector organs. The whitish, fatty,
protein-containing substance called myelin forms an insulating, protective,
cylindrical sheath around some axons, serving to increase the speed and
efficiency of nerve impulse transmissions.
Baclofen: A mainstay of antispastic drug
therapy, baclofen is a GABA agonist that stimulates the GABAB autoreceptor. When
stimulated, this autoreceptor inhibits muscle activity. In experimental systems,
baclofen inhibits the release of noradrenaline, and acetylcholine from
peripheral nerve endings, and acetylcholine, noradrenaline, dopamine, serotonin,
and glutamate from CNS neurons.
Ballismus: An abnormal neuromuscular
condition that is generally considered a severe form of chorea. Involvement of
the upper muscles of the arms and legs results in uncontrolled, violent,
flinging or throwing actions. These swinging or jerky movements may be sporadic
or continuous and, in some patients, restricted to one side of the body
(hemiballismus). Ballismus often occurs in association with other abnormal
involuntary movements, including athetosis, chorea, and dystonia.
Basal ganglia: Specialized nerve cell
clusters of gray matter deep within each cerebral hemisphere and the upper
brainstem, including the striate body (caudate and lentiform nuclei) and other
cells groups such as the subthalamic nucleus and substantia nigra. The basal
ganglia assist in initiating and regulating movement.
Benign myoclonus of infancy: A neurologic
condition that typically becomes apparent by approximately 4 months of age.
Affected infants and children experience relatively short, mild episodes of
myoclonus, or sudden, involuntary, "shock-like" spasms of muscles, particularly
of the head, neck, trunk, and arms. Development is typically normal, and
myoclonus usually ceases by age 2 or 3.
Benzodiazepines: A class of medications that
act upon the central nervous system to reduce communication between certain
neurons, lowering the level of activity in the brain. Benzodiazepines are
effective in reducing anxiety, stress, or agitation; promoting sleep;
alleviating restlessness; and relaxing muscles.
Beta-adrenergic receptor: a specialized
molecular structure on the surface membrane of a neuron that selectively
receives the neurotransmitter norepinephrine. Reception of this neurotransmitter
causes changes in the neuron that increase its likelihood of "firing" or sending
its own signal to other neurons. The activities of norepinephrine affect that
part of the nervous system involved in the control of some involuntary body
functions, such as blood pressure regulation, etc. (sympathetic nervous system).
Bilateral: Having or affecting two sides.
Biosynthesize: To form or produce (during
normal physiologic functions) a chemical compound in the body.
Biphasic: having two distinct stages or
Body mass index: The body mass index is a
measure of body fat that is based on a person’s height and weight.
Botulinum toxin (BTX): Any of a group of
toxins, designated as A through G, produced by Clostridium botulinum bacteria.
Localized injection of minute amounts of commercially prepared BTX may help to
relax an overactive muscle by blocking the release of acetylcholine, a
neurotransmitter responsible for the activation of muscle contractions. BTX-A is
currently the only form (i.e., serotype) of botulinum toxin approved for
clinical use. (BTX-A [BOTOX®] is produced by Allergan, Inc. and used in the
United States and many other countries. Outside the U.S., it is available as
Dysport® from Ipsen, Ltd.) It was originally introduced in the 1970s for the
treatment of misalignment of the eyes (strabismus) and involuntary contraction
of eyelid muscles (blepharospasm) associated with dystonia or facial nerve
disorders. BTX-A is now increasingly being used as a therapeutic option for
selected patients with other disorders characterized by severely increased
muscle activity (hyperactivity), such as tremor, other focal dystonias, and
spasticity. BTX-B is currently under investigation (by Athena Neurosciences,
Inc.) for patients with cervical dystonia.
Bradykinesia: The gradual loss of
spontaneous movement; slowness of voluntary movements.
Brainstem: The region of the brain
consisting of the medulla oblongata, pons, and midbrain. The brainstem primarily
contains white matter interspersed with some gray matter. This area of the brain
serves as a two-way conduction path, conveying nerve impulses between other
brain regions and the spinal cord. In addition, most of the 12 pairs of cranial
nerves from the brain arise from the brainstem, regulating breathing, digestion,
heartbeat, blood pressure, pupil size, swallowing, and other basic functions.
Branched-chain amino acids: the essential
amino acids, isoleucine, leucine, and valine.
Bruxism: Involuntary grinding, clenching, or
gnashing of the teeth, particularly during sleep or times of stress. Without
appropriate protection, such as the use of night guards that cover the teeth,
severe dental problems may result. Bruxism may also be a feature of certain
neurologic movement disorders, including dystonia of the jaw, mouth, and lower
face (oromandibular dystonia [OMD]), Rett syndrome, or tardive dyskinesia.
Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS):
The BFMDRS is a weighted scale that measures the severity and provoking factors
for dystonia in 9 body areas, including the eyes, mouth, speech or swallowing,
neck, right and left arms, trunk, and right and left legs.
Cabergoline: Cabergoline is an
ergotamine-based dopamine-receptor agonist with a half-life of 65 hours. In the
United States, it is marketed as Dostinex for the treatment of the rare
disorder, hyperprolactinaemia, or high levels of the hormone prolactin.
Carbidopa: Carbidopa is a drug that, when
combined with levodopa, slows the peripheral breakdown of the levodopa, thereby
allowing more of the levodopa to enter the brain.
Carbonic anhydrase inhibitors: A class of
medications that inhibits activity of the enzyme carbonic anhydrase. This
zinc-containing enzyme is present in red blood cells and the renal tubules.
These tubules form part of the filtering units of the kidneys. Carbonic
anhydrase activity serves to accelerate the transfer of carbon dioxide from
tissue to the blood and on to the lungs. By restricting carbonic anhydrase
activity, these agents decrease hydrogen ion concentrations in the renal
tubules, increasing excretion of sodium, potassium, bicarbonate, and water.
Certain carbonic anhydrase inhibitors are prescribed to promote urinary
production and excretion (i.e., as diuretics) or to lower fluid pressure within
the eyes for those with glaucoma. They are also used to treat other conditions
including epilepsy or certain neurologic movement disorders.
Carnitine: A natural substance found in
skeletal and cardiac muscle and the liver. Carnitine serves to transport fatty
acids across mitochondrial membranes, thereby playing an important role in
energy production and the metabolism of fatty acids.
Catecholamine: any of a group of hormones
that are catechol derivatives, e.g., adrenaline and noradrenaline.
Caudate nuclei: One of the 3 major
substructures that, together with the globus pallidus and putamen, form the
basal ganglia. The caudate nuclei and putamen, which are relatively similar
structurally and functionally, are collectively known as the striatum.
Specialized clusters of nerve cells or nuclei within the caudate receive input
from certain regions of the cerebral cortex. This information is processed and
then relayed (by way of the thalamus) to areas of the brain responsible for
controlling complex motor functions. The caudate nuclei are specifically thought
to process and transmit cognitive information that influences the initiation of
complex motor activities.
Central nervous system (CNS): The brain and
spinal cord. The CNS, which receives sensory impulses from and sends motor
impulses to the peripheral nervous system (i.e., nerves outside the CNS), plays
an essential role in the coordination and control of the entire body.
Central oscillators: nerve cells that
discharge signals that result in alternating fluctuations of electrical impulses
along certain tracts of the central nervous system.
Cerebellum: A two-lobed region of the brain
located behind the brainstem. The cerebellum receives messages concerning
balance, posture, muscle tone, and muscle contraction or extension. Working in
coordination with the basal ganglia and thalamus, the cerebellum integrates,
adjusts, and refines messages transmitted to muscle groups from the cerebral
cortex (i.e., motor cortex). Thus, the cerebellum plays an essential role in
producing smooth, coordinated voluntary movements; maintaining proper posture;
and sustaining balance.
Cerebral cortex: The outer region of the
brain’s cerebral hemispheres. Comprised of gray matter, the cerebral cortex
contains several deep folds (gyri) and grooves (sulci or fissures). Two sulci
divide the surfaces of both cerebral hemispheres into four distinct lobes that
are named for overlying bones of the skull. These include the frontal, temporal,
occipital, and parietal lobes. The cerebral hemispheres are joined by a thick
band of nerve fibers known as the corpus callosum. The cerebral cortex is
responsible for integrating higher mental functioning and conscious thought,
sensations, and general movements.
Cerebrospinal fluid (CSF): The fluid that
flows through and protects the 4 cavities (ventricles) of the brain, the spinal
cord’s central canal, and the space (known as the subarachnoid space) between
the middle and inner layers of the membrane (meninges) enclosing the brain and
spinal cord. Laboratory analysis of CSF, usually obtained via lumbar puncture,
may help to diagnose central nervous system infections, certain tumors, or
particular neurologic disorders. During lumbar puncture, CSF is removed from the
spinal canal via a hollow needle inserted between certain bones of the spinal
column within the lower back (i.e., usually the third and fourth lumbar
Chemodenervation: Interruption of a nerve
impulse pathway via administration of a chemical substance, such as botulinum
toxin (BTX). For example, intramuscular injections of BTX produce local
relaxation of treated muscles by inhibiting the release of acetylcholine, a
neurotransmitter that is present at the junctions of nerve and muscle cells and
that regulates the delivery of messages from neurons to muscle fibers.
Chorea: Jerky, irregular, relatively rapid
involuntary movement that primarily involves muscles of the face or extremities.
Choreic movements are relatively simple and discrete or highly complex in
nature. Although involuntary and purposeless, these movements are sometimes
incorporated into deliberate movement patterns. When several choreic movements
are present, they often appear relatively slow, writhing, or sinuous, resembling
athetosis. Chorea may occur in association with certain neurodegenerative
diseases, including Wilson’s disease and Huntington’s disease, or systemic
disorders, such as lupus. In addition, chorea is a dominant feature in
Sydenham’s chorea or may result from the use of certain medications, such as
particular anticonvulsant or antipsychotic agents.
Chorionic villus sampling (CVS): A screening
and diagnostic procedure performed during which tissue samples are obtained from
a portion of the placenta using a specially guided needle via ultrasound. The
placenta is the organ attached to the lining of the uterus that links the blood
supplies of the developing fetus and the mother. The tissue sample is obtained
from the layer from which the chorionic villi develop. Blood from the fetus
flows through the umbilical cord to the placenta and enters minute blood vessels
arranged in multiple "thread-like" projections or chorionic villi surrounded by
maternal blood. Tissue samples obtained during chorionic villus sampling are
analyzed to detect certain genetic or chromosomal abnormalities.
Chromosomes: The thread-like structures
within the nuclei of cells comprised of DNA. Deoxyribonucleic acid or DNA
carries genetic information involved in directing cellular activities, thus
controlling bodily growth and functioning and determining the expression of
inherited traits. The chromosomes contain thousands of hereditary units known as
genes or segments of DNA molecules. The nuclei of all human cells–except the
reproductive (i.e., egg and sperm) cells–normally contain 46 chromosomes, with
one of each pair from the father and one from the mother. The chromosomal pairs
are numbered from 1 through 22, as well as a 23rd pair that includes one X
chromosome from the mother and an X or a Y chromosome from the father. In
females, the 23rd pair consists of two X chromosomes, whereas males have one X
and one Y chromosome. All chromosomes have a short arm known as "p" and a long
arm known as "q." Both chromosomal arms are subdivided into numbered bands.
Circadian: A rhythm of biological functions
occurring in a 24-hour periodic cycle (e.g., sleeping, eating, etc.).
Clonus: movements characterized by alternate
contractions and relaxations of a muscle, occurring in rapid succession. Clonus
is frequently observed in conditions such as spasticity and certain seizure
Co-contraction: The simultaneous contraction
of agonist and antagonist muscles.
Cognition: Cognition involves thinking
skills such as perception, memory, awareness, reasoning, judgment, intellect,
Cogwheel phenomenon: rhythmic brief increase
in resistance during passive movement about a joint.
Complementary and alternative medicine:
Complementary and alternative medicine, as defined by National Institutes of
Health, is a group of diverse medical and health-care systems, practices, and
products that are not presently considered to be part of conventional medicine.
Composite Autonomic Scoring Scale: The
Composite Autonomic Scoring Scale is a battery of validated, sensitive, and
specific tests for the assessment of autonomic nervous systems, resulting in a
10-point composite score.
Computerized tomography (CT) imaging or scanning:
An advanced diagnostic scanning technique during which cross-sectional images of
tissues and organs are produced by passing x-rays through the body at various
angles. In some cases, a contrast medium, which is opaque on x-rays, may be
injected intravenously to produce enhanced images of certain tissues, organs, or
COMT inhibitors: Drugs that block
catechol-O-methyltransferase, an enzyme that breaks down dopamine. COMT
inhibitors include entacapone (Comtan®) and tolcapone (Tasmar®).
Congenital: Existing at birth.
Contractures: Fixed resistance to passive
stretching of certain muscles due to shortening or wasting (atrophy) of muscle
fibers or the development of scar tissue (fibrosis) over joints.
Contralateral: the opposite side. For
example, during brain surgery for essential tremor, if the surgery is performed
on the right side of the brain, the left side of the body will be affected.
Controlled-release formulation: A form of a
drug (e.g., L-dopa) that is absorbed slowly by the digestive system, prolonging
the duration of effect of each dose.
Corticobasal degeneration (CBD): A slowly
progressive disorder characterized by neurodegenerative changes of certain brain
regions, including the cerebral cortex (particularly the frontal and parietal
lobes) and parts of the basal ganglia. Most patients initially develop symptoms
in their 60s or 70s. Primary findings may include stiffness (rigidity); slowness
of movement (bradykinesia); loss of the ability to coordinate and execute
certain purposeful movements of the arms or legs (limb apraxia); the sensation
that a limb is not one’s own ("alien limb phenomenon"); and other sensory
abnormalities. Affected individuals may also develop slurred, labored speech
(dysarthria); dystonia; and irregular, involuntary, "shock-like" contractions of
certain muscle groups, particularly of the hands and forearms, that may be
provoked or aggravated by voluntary movement and certain external stimuli
(action and reflex myoclonus).
Corticospinal: Referring to or connecting
the outer region of the brain (cerebral cortex) and the spinal cord.
Corticosteroid agents: Synthetic medications
similar to corticosteroid hormones, which are naturally produced by the outer
regions of the adrenal glands (adrenal cortex). Corticosteroid agents may be
prescribed to treat inflammatory conditions; as long-term therapy to suppress
the immune system (immunosuppressive therapy) in order to prevent rejection of a
transplanted organ; as hormone replacement therapy for those with insufficient
levels of natural corticosteroid hormones; or as therapy for other conditions.
High dose, long-term corticosteroid therapy may result in various adverse
effects, including an increased susceptibility to infection; osteoporosis, a
bone disorder characterized by a progressive loss of bone mass; high blood
pressure (hypertension); tissue swelling (edema); or retarded bone growth in
Cranial: Of or from the cranium or skull.
Cranial nerve nuclei: Specialized groups of
nerve cells (nuclei) that give rise to and convey or receive impulses from
sensory and motor constituents of the cranial nerves, which are the 12 pairs of
nerves that emerge from the brain. These nerve pairs convey sensory impulses for
various functions including taste, smell, hearing, and vision; motor impulses
involved in controlling eye movements, chewing, swallowing, facial expressions,
etc.; and impulses for transmission to certain organs and glands for regulation
of various involuntary or autonomic activities.
Cranial neuropathy: Disease or damage of a
cranial nerve or nerves. The cranial nerves are the 12 nerve pairs that arise
directly from the brain and are involved in conveying impulses for various
functions including smell, hearing, vision, and taste; pupil contraction; eye
movements; facial expressions; movements of the tongue, head, and shoulders;
etc. Cranial neuropathy may result in associated muscle weakness; abnormal
sensations, such as numbness, tingling, or pain; or other findings. Specific
symptoms depend upon the specific nerve(s) affected.
Creutzfeldt-Jakob disease (CJD): A rare,
degenerative, life-threatening brain disorder characterized by severe,
progressive dementia; visual disturbances; muscle weakness; and abnormal
involuntary movements, such as sudden, brief, "shock-like" muscle spasms (myoclonus),
tremor, and relatively slow writhing motions that appear to flow into one
another (athetosis). Although CJD usually appears to occur sporadically, about
10 percent of cases are familial, potentially suggesting a hereditary
predisposition to the disease. In rare cases, CJD may also result from exposure
to contaminated surgical instruments during brain surgery and was reported in
the past due to therapy with pituitary-derived human growth hormone. In
addition, a variant form of CJD (V-CJD) has been reported primarily in the
United Kingdom; V-CJD has been potentially linked to consumption of beef from
cows with bovine spongiform encephalopathy or BSE (so-called "mad cow disease").
Evidence suggests that CJD may be caused by mutations in the human prion*
protein gene or contamination with abnormal prion protein. (*The term "prion"
was named for "protein infectious agent.") Changes in the prion protein appear
to lead to distinctive neurodegenerative abnormalities, i.e., relatively small,
round, "sponge-like" (spongiform) cavities or gaps in certain brain regions. CJD
and BSE belong to a group of related neurodegenerative disorders categorized as
"transmissible spongiform encephalopathies."
Crossreact: Refers to the interaction of an
antibody with an antigen that did not specifically or originally trigger its
production. For example, in an abnormal autoimmune reaction, an antibody that
was initially formed in response to an invading bacterium may inappropriately
react against certain of the body’s own tissues that contain some of the same
amino acid sequences as within the microorganism.
Cytokine: Cytokines are small proteins that
regulate the body’s immunity, inflammation, and blood-cell production responses.
Cytoplasm: The cytoplasm is the part of the
cell that surrounds the nucleus.
DC inhibitors: Drugs that block
decarboxylase, one type of enzyme that breaks down dopamine. Also called AADC
inhibitors, they include carbidopa and benserazide.
Decarboxylase: A category or subclass of
enzymes that removes or eliminates a molecule of carbon dioxide from a
carboxylic group. Carbidopa is an inhibitor of the decarboxylation of levodopa.
Degenerative: Marked by or pertaining to
deterioration; particularly, deterioration of the function or structure of
tissue or changes from a higher to a lower or less functionally active form.
Delirium: A state of frenzied excitement or
Delusions: Persistent, aberrant beliefs
Dementia: A neurological condition
characterized by a progressive decline in intellectual functioning, resulting in
impaired judgment, memory, and abstract thinking; disorientation; and
personality disintegration. Dementia may result due to various underlying
conditions, including certain neurodegenerative diseases, such as Alzheimer’s
disease or Huntington’s disease; brain injury or tumors; inflammation of the
brain (encephalitis); successive strokes; or a condition known as
normal-pressure hydrocephalus, which is characterized by enlargement of cavities
(ventricles) of the brain, with cerebrospinal fluid (CSF) pressure at the upper
end of normal. (CSF flows through and protects the ventricles of the brain, the
spinal canal, and the space between layers of the membrane [meninges] enclosing
the brain and spinal cord.) Normal-pressure hydrocephalus is associated with
dementia, gait disturbances, and an inability to control urination (urinary
Dendrites: The relatively narrow, branching
projections that extend from the cell bodies of neurons. Nerve cells may contain
multiple dendrites, which are stimulated by neurotransmitters, receive impulses
from the nerve fibers (axons) of other neurons, and convey them toward their
nerve cell bodies.
Dentatorubropallidoluysian atrophy: A rare
genetic disorder that is most commonly described in Japan. Associated symptoms
may become apparent in adolescence or adulthood. Early-onset disease may be
characterized by rapidly progressive neurodegenerative changes, including
seizures, cognitive impairment, and brief, "shock-like" muscle spasms of certain
muscles or muscle groups (myoclonus). Late-onset disease may be associated with
progressively impaired control of voluntary movement (ataxia) and symptoms often
seen in Huntington’s disease (HD), including chorea and gradual loss of thought
processing and acquired intellectual abilities (dementia). Brain imaging studies
typically reveal degenerative changes of the globus pallidus and specialized
nerve cell clusters within the cerebellum (dentate nucleus). Similar to HD, the
disorder may result from abnormally long sequences or "repeats" of particular
coded instructions (unstable expanded CAG repeats) within a gene (located on
Detoxification: Detoxification is the
process of removing or neutralizing toxins in the body
Diaphragm: The dome-shaped muscle that
separates the chest and abdomen. The diaphragm plays an essential role in
breathing, contracting when air is drawn into the lungs and relaxing upon
Differential diagnosis: Distinguishing
between two or more diseases and conditions with similar symptoms by
systematically comparing and contrasting their clinical findings, including
physical signs, symptoms, as well as the results of laboratory tests and other
appropriate diagnostic procedures.
Diuretics: Medications that promote the
excretion of urine. Such medications are often prescribed to help reduce excess
fluid levels in the body, such as associated with chronic heart failure, high
blood pressure (hypertension), or certain kidney (renal) or liver (hepatic)
disorders. Diuretics help to remove excess water from the body by increasing the
amount that is excreted as urine.
DNA: Deoxyribonucleic acid. DNA is a
spiraling, ladder-like (helical) molecule that is the carrier of the genetic
code. Nucleic acids are the primary components of the chromosomes within the
nuclei of cells. DNA is also found in mitochondria, the rod-like structures
outside the nuclei of cells that function as a primary source of cellular
Dopamine: A neurotransmitter that controls
movement and balance and is essential to the proper functioning of the central
nervous system (CNS). Dopamine assists in the effective transmission of
electrochemical signals from one nerve cell (neuron) to another.
Dopamine agonist (DA): A drug that acts like
dopamine. DAs combine with dopamine receptors to mimic dopamine actions. Such
medications stimulate dopamine receptors and produce dopamine-like effects.
Dopamine autoreceptor: A type of dopamine
receptor that acts like a thermostat, preventing excess dopamine release as
Dopamine receptor: A molecule on a receiving
nerve cell (neuron) that is sensitive (or receptive) to stimulation (arousal) by
dopamine or a dopamine agonist. At least five types have been identified
including D1, D2, D3 receptors and the dopamine autoreceptor.
Dopamine receptor antagonist: A
pharmacologic agent that binds to and blocks the action of dopamine receptors,
essentially hindering receptor activity by preventing stimulation by dopamine.
Dopamine transporter: Dopamine is a chemical
in the body that allows one nerve cell to send a message or signal to another
nerve cell and helps to control movement. After dopamine finishes sending its
message, a substance called a dopamine transporter carries the dopamine back
from the nerve ending to the cell that produced it so that the dopamine can be
reused. The number of dopamine transporters is a sign of the number of nerve
endings that produce or release dopamine.
Dopaminergic: Having the effect of dopamine
or related to dopamine-producing cells
Dopaminergic dysfunction: Malfunction of
Double-blind trial: A double-blind trial is
a clinical experiment in which neither the patients nor the researchers are
aware of which patients are receiving the active treatment and which are
Dysarthria: Disordered or impaired
articulation of speech due to disturbances of muscular control, usually
resulting from damage to the central or peripheral nervous system. Dysarthria is
associated with certain neurodegenerative disorders, such as Parkinson’s disease
or Huntington’s disease; cerebral palsy; brain tumors or stroke; or certain
types of brain surgery.
Dysesthesias: Unpleasant sensations that are
produced in response to normal stimuli.
Dyskinesias: Abnormal neuromuscular
conditions characterized by disorganized or excessive movement (also known as
hyperkinesia). Forms of dyskinesia include sudden, brief, "shock-like" muscle
contractions (myoclonus); involuntary, rhythmic, oscillatory movements of a body
part (tremor); rapid involuntary jerky movements (chorea); relatively slow
writhing motions (athetosis); or abrupt, purposeless, simple or complex muscle
movements or vocalizations (motor or vocal tics).
Dyskinesias while awake (DWA): Uncontrolled,
sporadic movements of the legs and, in some cases, the arms. These movements may
be very rapid (myoclonic) or quite slow and prolonged (dystonic); they usually
disappear upon voluntary action. Some researchers suspect that these movements
may represent a wakeful form of periodic limb movements in sleep (PLMS).
Dysphagia: Difficulty in swallowing.
Dysphagia may be associated with esophageal obstruction as well as certain
neurodegenerative or motor disorders involving the esophagus.
Dyspraxia: Partial loss of the ability to
coordinate and perform certain purposeful movements and gestures in the absence
of motor or sensory impairments.
Dystonia: A neurologic movement disorder
characterized by sustained muscle contractions, resulting in repetitive,
involuntary, twisting or writhing movements and unusual postures or positioning.
Dystonia may be limited to specific muscle groups (focal dystonia), such as
dystonia affecting muscles of the neck (cervical dystonia or spasmodic
torticollis) or the eyes, resulting in closure of the eyelids (blepharospasm).
Dystonia is associated with certain underlying genetic disorders, such as
dystonia musculorum deformans, dopa-responsive dystonia, and paroxysmal
kinesigenic and paroxysmal non-kinesigenic dystonic choreoathetosis. The
condition may result from the use of certain medications, lack of oxygen during
or immediately after birth, or other causes of brain trauma.
Dystonic: Referring to dystonia; sudden
jerky or repetitive movements and muscle spasms due to impaired muscle tone and
abnormal muscle rigidity.
DYT-1 dystonia: The DYT-1 gene regulates or
"encodes" production of a protein called torsinA. Although its specific function
is not know, torrsinA appears to be related to a class of proteins that enable
cells to recover from injury or stress. The change, or mutation, that causes
DYT-1 dystonia involves one of a pair of three basic chemical "building blocks"
of DNA. These are called guanine, adenine, and guanine, or "GAG" trinucleotides
and are part of the genetic code within the DYT-1 gene. The specific mutation
that occurs in DYT-1 dystonia is an absence, or deletion, of GAG. This
relatively tiny change in the blueprint for torsinA apparently causes critical
changes in the function of the protein and may lead to the symptoms of dystonia.
Echocardiogram: An echocardiogram is a
medical test that is used to study the structure and function of the heart. A
computer captures echoes that are created from sound waves (ultrasound).
Economic burden: Economic burden involves
both direct medical costs such as expenditures for drugs, physicians, and
institutions, as well as indirect costs due to lost wages from illness,
premature death, and disability.
Edema: Fluid accumulation in the tissues
Edentulousness: lack of permanent teeth.
Effector organs: Organs that produce a
nerve-stimulated effect, such as a muscle contraction or glandular secretion.
Electrical stimulation (ES): A test in which
a small electrical charge is applied to a muscle via a needle to determine the
level of muscle responsiveness.
Electrocardiogram (ECG, EKG): A noninvasive,
diagnostic test that assesses the electrical activity of the heart muscle
(myocardium). The heart’s conduction system transmits electrical impulses that
serve to coordinate contractions of the heart. During an ECG, the electrical
activity of the cardiac conduction system is translated into recordings that
assist in evaluating any abnormal alterations. The test may be administered
while a patient is at rest or performing certain designated exercises. ECGs may
help to detect or characterize cardiac conduction defects, abnormal heart
rhythms (arrhythmias), enlargement (cardiac hypertrophy), or localized damage in
Electroencephalography (EEG): A noninvasive,
diagnostic technique that records the electrical impulses produced by brain cell
activity. An EEG reveals characteristic brain wave patterns that may assist in
the diagnosis of particular neurologic conditions, such as seizure disorders,
impaired consciousness, and brain lesions or tumors.
Electromyography (EMG): A diagnostic test
that records the electrical responses of skeletal muscles while at rest and
during voluntary action and electrical stimulation. During this test, a small
needle is inserted into a muscle to record the level of activity.
Electron microscopy: An electron microscope
beams electrons, instead of light beams, to magnify an object, providing very
detailed images that are approximately 1000 times the magnification of a typical
Electrophysiologic recordings include the study of the electrical activity
associated with a specific body function (e.g., electromyogram [muscles],
electroencephalogram [brain waves], etc.).
Electrophysiologic studies: The study of the
electrical activity associated with a specific body function (e.g., EMG, EEG,
Encephalitis: Inflammation of the brain.
Encephalitis is most commonly caused by certain viral infections or may occur
subsequent to prior infection due to immune reactions that indirectly result in
inflammation (postinfectious encephalitis). Although associated symptoms and
findings may be variable, features may include fever, headache, irritability,
listlessness (lethargy), and weakness. Some affected individuals may also
develop confusion, disturbances of speech and memory, abnormal involuntary
movements, paralysis of one side of the body, seizures, and/or coma. For those
with involvement of the protective membranes enclosing the brain and spinal cord
(meningitis), characteristic findings may include nausea, vomiting, stiffness of
the neck, abnormal sensitivity to light (photophobia), and/or other symptoms.
Encephalopathies: Any abnormal conditions or
diseases of the structure or function of the brain, particularly chronic,
Endogenous opiate system: A morphine-like
substance that is produced within the body.
Endoplasmic reticulum (ER): The ER consists of a
membrane system that branches out through the cytoplasm and includes rough ER,
which is found in eukaryotic cells and contains ribosomes, and smooth ER, which
is biochemically similar to rough ER but lacks ribosomes.
Endotoxin: An endotoxin is a poisonous
substance that is released from bacteria after the bacteria die or break apart.
Enzyme: A protein produced by cells that
accelerates the rate of or "catalyzes" a specific chemical reaction in the body
without being consumed or permanently changed in the process. A chemical
substance that is acted upon by an enzyme is called a "substrate." In many
cases, enzymes are named by adding the suffix "-ase" to the name of the
substrate upon which the enzyme exerts its action.
Epidemiological study: examination of the
distribution of disease as well as the determining factors related to specific
diseases or health-related problems in a specific population.
Ergot: A plant alkaloid produced by the
fungus Claviceps purpurea.
Ergot-derived medication: A medication that
has a chemical structure based on ergot, a plant alkaloid produced by a fungus
called Claviceps purpurea. Permax® and Parlodel® are examples of ergot-derived
medications that may be used to treat certain neurologic movement disorders.
Esophageal atony: Lack of normal muscle tone
within the esophagus, the muscular tube that transports food from the throat to
Essential tremor (ET): A common, slowly and
variably progressive neurologic movement disorder characterized by involuntary,
rhythmic, "back and forth" movements (i.e., tremor) of a body part or parts. In
ET patients, tremor is primarily a "postural" or "kinetic" tremor or may be a
combination of both types: i.e., tremor occurs while voluntarily maintaining a
fixed position against gravity (postural tremor) and/or when conducting
self-directed, targeted actions (kinetic intention tremor). In many individuals
with ET, both hands are affected, although the condition may sometimes initially
be noted in the dominant hand. ET also frequently affects the head, with tremor
occurring in a "no-no" horizontal pattern in about three quarters of patients
and the remainder affected by vertical "yes-yes" tremors. Less commonly,
patients have tremor involving the voice, tongue, or roof of the mouth (palate),
leading to impaired articulation of speech (dysarthria). Rarely, tremor may
affect the trunk or lower limbs, particularly with advanced stages of disease.
ET may appear to occur randomly for unknown reasons (sporadically) or be
transmitted as an autosomal dominant trait.
Estrogen: (1) Any of several, naturally
occurring female sex hormones that promote the development of female secondary
sexual characteristics and the proper functioning of the reproductive system;
(2) synthetically produced agents used in birth control pills (oral
contraceptives) or in the treatment of symptoms of menopause; osteoporosis,
which is a bone disorder characterized by a progressive loss of bone mass;
particular types of advanced postmenopausal breast cancer and prostate cancer;
and other conditions.
Eukaryotic: Meaning literally "true
nucleus," eukaryotic organisms include protists, plants, animals and fungi, all
of which have separate membrane-bound nuclei that contain genetic material (mDNA).
Executive function: Executive function
refers to a person’s ability to establish a goal and then make decisions and put
into action activities to meet that goal.
Exon: An exon is a region of a gene that
contains part of the code for producing the gene’s protein. Each exon codes for
a specific portion of the complete protein. Exons are separated by long regions
of DNA (called introns or sometimes "junk DNA") that have no apparent function.
Extrapyramidal system: Refers to central
nervous system structures (i.e., outside the cerebrospinal pyramidal tracts)
that play a role in controlling motor functions. The extrapyramidal system
includes substructures of the basal ganglia and the brainstem and
interconnections with certain regions of the cerebellum, cerebrum, and other
areas of the central nervous system. Extrapyramidal disturbances may result in
postural and muscle tone abnormalities as well as the development of certain
Feldenkrais: Feldenkrais is a method of
improving the body’s ability to function, learn, and change by increasing
awareness of movement, posture, and breathing.
Fibrosis: Build-up of fibrous tissue in an
abnormal place in the body.
First-degree relatives: First-degree
relatives include a person’s mother, father, brothers, sisters, sons, and
daughters who are related by blood and not through adoption or marriage.
Flexion: The act of bending (as opposed to
extending) a joint.
Food and Drug Administration (FDA): The FDA
is a federal agency charged with ensuring that the food supply in the United
States is safe and wholesome, that cosmetics are not harmful, and that
medicines, medical devices, and radiation-emitting consumer products are safe
Free radicals: Unstable molecular fragments
that can damage cells. One hypothesis holds that free radical formation in the
substantia nigra causes the loss of nigral cells (leading to Parkinson’s
Frequency: number of cycles or repetitions
within a fixed unit of time such as the number of cycles per second (Hertz or
Hz). For example, essential tremor is typically 4 to 12 Hz.
Friedreich’s ataxia: Friedreich’s ataxia is
the most common autosomal recessively inherited type of ataxia. Like the
autosomal dominant spinocerebellar ataxias, the main symptoms are loss of
coordination and unsteadiness of gait. Other systems may also be affected and
people with Friedreich’s ataxia should be monitored for heart disease and
diabetes. The affected protein is called frataxin, and is thought to be involved
in iron metabolism.
Froment’s sign: Increased resistance to
passive movements of a limb that may be detected upon voluntary activity of
another body part.
Functional Magnetic Resonance Imaging (fMRI):
A noninvasive, diagnostic scanning procedure that produces detailed,
computerized images. The use of a "contrast agent" or dye enhances the detail of
the images. Sequencing of these images may help physicians visualize the body’s
functioning, thus aiding differential diagnosis.
Gait: The style or manner of walking. Gait
disturbances may be associated with certain neurologic or neuromuscular
disorders, orthopedic conditions, inflammatory conditions of the joints (i.e.,
arthritic changes), or other abnormalities.
Gait apraxia: Loss of the ability to
consciously sequence and execute the movements required to coordinate walking.
Gait apraxia may result in unsteady walking patterns; "toe-walking"; a widely
based, jerky gait; and balance difficulties.
Gamma knife radiosurgery: a highly
specialized technique using a device that produces ionizing radiation to produce
a lesion in the target tissue. This device focuses a beam of high intensity
irradiation to a targeted area and is used as localized therapy to treat
individuals with certain brain diseases (e.g., brain tumors, certain movement
Gamma-aminobutyric acid (GABA): An amino
acid neurotransmitter that inhibits or decreases the electrical activities of
nerve cells. GABA is the primary inhibitory neurotransmitter in the brain.
Gastroesophageal reflux: Backflow of stomach
contents into the esophagus. This condition may be chronic and cause weakness of
the lower esophageal sphincter, the ring-shaped muscle located at the junction
of the esophagus and stomach.
Gastrostomy tube: A plastic tube inserted
into the stomach through a surgical incision in the abdomen. A gastrostomy tube
is used to deliver liquified food to the digestive system when swallowing
becomes dangerous or difficult.
Gene: Genes are the smallest units of
heredity. The information from all the genes, taken together, makes up the
blueprint or plan for the human body and its functions. A gene is a short
segment of DNA, which is interpreted by the body as a plan or template for
building a specific protein.
Genetic anticipation: A phenomenon in which
the onset of symptoms of a hereditary disease appears to occur at a
progressively earlier age in successive generations. Genetic anticipation has
been demonstrated in a number of hereditary disorders (such as Huntington’s
disease, dentatorubropallidoluysian atrophy, etc.) in which the gene mutation
consists of abnormally long sequences or "repeats" of particular coded
instructions (e.g., unstable expansion of CAG repeats). With other disorders in
which genetic anticipation has previously been suggested (e.g., essential
tremor), studies have indicated that increased awareness of the condition in
affected families may be responsible for earlier recognition of symptom onset.
Germline mosaicism: The presence of a gene
mutation for a disease trait in some yet not all of an individual’s sexual
reproductive cells (germ cells) within the ovaries or testes (gonads). Germline
mosaicism is sometimes suspected when parents have more than one child with a
genetic disorder transmitted as a dominant trait yet neither parent appears to
be affected by the condition.
Gliosis: A proliferation of astrocytes in
damaged areas of the central nervous system (CNS). Astrocytes are relatively
large glial cells, which are the connective tissue cells of the CNS. Astrocytes
have various functions, including accumulating in areas where nerve cells
(neurons) have been damaged. Gliosis and neuronal loss in certain brain regions
are findings seen in various neurodegenerative disorders.
Globus pallidus: A major substructure of the
basal ganglia deep within the brain. Specialized groups of nerve cells in the
globus pallidus function as an "intermediate relay system." This system
processes and transmits information from the basal ganglia by way of the
thalamus to areas of the brain that regulate complex motor functions (e.g.,
motor cortex, premotor area of frontal lobe).
Glottis: The slit-like opening between the
vocal cords; the region of the voice box (larynx) consisting of the vocal cords
and the opening between them.
Glutamate: An amino acid that is a primary
excitatory neurotransmitter in the central nervous system. This chemical agent
plays an essential role in initiating and transmitting nerve impulses, crossing
synapses to stimulate postsynaptic neurons.
Gram staining: Gram staining is a method
used to classify bacteria. In the first step of the process bacteria are stained
with gentian violet and then treated with Gram solution (named after Dr. Gram,
the inventor of the technique). After the bacteria have been decolorized with
alcohol and treated with safranine, a red organic dye, and washed in water,
those bacteria that keep the gentian violet are gram-positive and those that do
not are gram-negative.
Gray matter: Nerve tissue that primarily
consists of nerve cell bodies, dendrites, and unmyelinated axons, thus having a
gray appearance. In contrast, white matter predominantly contains myelinated
Half life: The half life of a drug is the
time it takes for the blood level to decrease by half after a drug is stopped.
Hallervorden-Spatz disease: A slowly
progressive hereditary disorder characterized by abnormal accumulations of iron
pigments in certain regions of the basal ganglia (e.g., globus pallidus and
substantia nigra). This autosomal recessive disorder typically becomes apparent
during late childhood or adolescence. Associated symptoms may include
progressive stiffness and resistance to movement (rigidity); increasing
difficulties speaking and eating; sustained muscle contractions that result in
repetitive twisting motions or unusual postures or positions (dystonia); the
presence of multiple, irregular, jerky motions that may combine to appear
flowing or writhing in nature (choreoathetosis); and/or other abnormalities.
Hallucinations: Perceptions that occur in
the absence of external stimuli and while an individual is awake. Hallucinations
may involve any of the senses, including hearing (auditory hallucinations),
vision (visual hallucinations), smell (olfactory hallucinations), taste
(gustatory hallucinations), and touch (tactile hallucinations). Hallucinations
may occur with high-dose administration of certain medications or the abuse of
particular drugs (hallucinogens) that cause increased stimulation or excitation
of the central nervous system. They may also be caused by chronic alcohol abuse;
sensory deprivation; certain types of seizures due to impairment or damage of a
limited area of the brain (e.g., temporal lobe epilepsy); psychotic illnesses
characterized by disturbances in thought, behavior, and emotional reactions
(schizophrenia); or certain organic disorders, such as Huntington’s disease.
Hashimoto’s Thyroiditis: Auto-immune
disorder that is characterized by anti-body formation to thyroid tissue. Most
commonly, anti-body production is toward the thyroid peroxidase antigen (TPA)
and to a lesser degree, against Thyroglobulin. Commonly, TSH levels, T-3 and T-4
levels are measured to be ‘normal,’ but the patient suffers from the symptoms of
hypothyroidism. Often associated with adrenal fatigue/failure, patients with
Hashimoto’s Thyroiditis develop the clinical picture that may be labeled as
"Chronic Fatigue Syndrome (CFS)" and Fibromyalgia (FMS). Treatment is best
accomplished with treatment consisting of T-3 and T-4, combined, with adrenal
replacement of DHEA, Pregnenolone, Cortisol, guided with sequential blood
analysis and clinical monitoring.
Heat pain: Heat pain arises from warm or hot
Hemichorea: Irregular, abrupt, relatively
rapid involuntary (i.e., choreic) movements that are unilateral or involve
muscle groups on one side of the body.
Hemidystonia: Hemidystonia is a form of
dystonia that affects one side of the body or is characterized by unilateral
involvement of the upper and lower limbs.
Hemizygote: Refers to a cell, organism, or
individual with only one of a pair of genes for a specific trait. This term is
often used to describe males who inherit one copy of an X-linked disease trait.
It may also refer to the state in which genetic material is deleted from one
member of a chromosomal pair.
Hereditary: Inherited; inborn; referring to the
genetic transmission of a trait, condition, or disorder from parent to
offspring. This is very different from "famililal," which may infer a genetic
condition, but it can also infer a shared-environmental factor or influence.
Heredodegenerative: Pertaining to
genetically transmitted (hereditary) neurologic disorders characterized by
progressive neuronal loss and other neurodegenerative changes (e.g., associated
gliosis). For example, the term "heredodegenerative dystonias" is used to refer
to several, usually hereditary disorders in which neurodegenerative changes may
lead to dystonia as a primary feature and other neurologic symptoms are
typically present. However, in some patients with such disorders, dystonia may
not always develop and other neurologic features may be primary findings.
Disorders that have been categorized as heredodegenerative dystonias include
ataxia-telangiectasia, Hallervorden-Spatz disease, Huntington’s disease,
Parkinson’s disease, progressive supranuclear palsy, neuroacanthocytosis, and
Hertz (Hz): cycles per second.
Heterogeneity: comprising unrelated or
differing parts or elements.
Heterozygous carriers: The term
"heterozygosity" refers to the state of having different genes that occupy the
same position (locus) on one or more paired chromosomes. "Heterozygous carriers"
describes individuals who carry a single copy of a mutated gene for a disease
trait, such as females who have a copy of a disease gene for an X-linked
disorder. Because females have two X chromosomes yet only one functioning copy
is necessary, a percentage of X chromosomes with the mutated gene may not be
expressed, typically in a random pattern (known as "random X chromosome
inactivation"). Therefore, females who are heterozygous for an X-linked disease
trait often have no disease manifestations or less severe symptoms than affected
males. However, because males have one X chromosome from the mother and one Y
chromosome from the father, males who carry an X-linked disease trait will
typically fully express the mutated gene. Rarely, females who are heterozygous
for an X-linked disease trait may manifest symptoms with about the same severity
as affected males.
Hoehn and Yahr Scale: The Hoehn and Yahr
Scale is a commonly used physician-administered rating of the global severity of
the motor symptoms of Parkinson’s disease. Scores range from 0, no signs of
disease, to 5, wheelchair bound or bedridden without assistance.
Homeopathy: Homeopathy is a system of
medicine that is based on the Law of Similars, a belief in which substances that
cause healthy people to exhibit symptoms can, conversely, be used to restore the
body to health.
Homeostasis: Homeostasis exists when an
organism’s internal state of being is in balance even when the external
environment is changing.
Homocystinuria: A metabolic abnormality
characterized by excessive amounts of the amino acid homocystine in the urine.
Homocystinuria, which may be transmitted as an autosomal recessive trait, may
result from deficient activity of certain enzymes involved in the metabolic
conversion of the amino acid methionine to cysteine. Associated symptoms and
findings often include developmental delay; dislocated lens of the eyes (ectopia
lentis); thin, weak muscles; progressive mental retardation; psychiatric
abnormalities; skeletal defects; blockage of a blood vessel by a piece of a
blood clot (thrombus) carried in the bloodstream (thromboembolism); and/or other
Huntington’s disease (HD): A hereditary,
progressive, neurodegenerative disorder primarily characterized by the
development of emotional, behavioral, and psychiatric abnormalities; gradual
deterioration of thought processing and acquired intellectual abilities
(dementia); and movement abnormalities, including involuntary, rapid, irregular
jerky movements (chorea) of the face, arms, legs, or trunk. HD may be inherited
as an autosomal dominant trait or, less commonly, appear to occur randomly for
unknown reasons (sporadically). The disorder results from abnormally long
sequences or "repeats" of certain coded instructions (i.e., unstable expanded
CAG repeats) within a gene (located on chromosome p16.3). Progressive nervous
system dysfunction associated with HD results from loss of neurons in certain
areas of the brain, including the basal ganglia and cerebral cortex.
Huntington’s Disease-like 2 (HDL2): This
rare disease strongly resembles Huntington’s disease in its inheritance and
symptoms, which include abnormal movements, personality changes, and changes in
the ability to think and process information. HDL2 is due to damage to the same
parts of the brain as in HD; however, it is caused by mutation of a different
gene, and also has an increased number of repeats. To date, almost all affected
families have been of African ancestry. The other “Huntington’s disease-like”
disorders (types 1, 3, and 4) are even rarer and have only been reported in one
Hyperglycemia: An abnormally high level of
the simple sugar glucose in the blood.
Hyperkalemic: Pertaining to hyperkalemia, a
condition characterized by unusually high concentrations of potassium in the
blood. Potassium, a positively charged ion, helps to regulate water balance,
nerve conduction, and muscle contraction. Hyperkalemia may lead to various signs
and symptoms, such as diarrhea, nausea, abdominal cramps, weakness, and, with
increasing severity, abnormal heart rhythms and muscle paralysis.
Hyperkinetic: Characterized by excessive
movement because of abnormally increased motor activity or function. Certain
movement disorders are termed "hyperkinetic" such as tics or essential tremor.
Hypertension: Hypertension, also referred to
as high blood pressure, is an abnormal increase in the pressure of blood against
the walls of the arteries. Hypertension may be essential, meaning that it has no
known cause, or may be related to another disease such as kidney disease or
Hyperthyroidism: a condition caused by the
effects of too much thyroid hormone on tissues of the body.
Hyperventilation: Abnormally rapid breathing
usually accompanied by air swallowing. Hyperventilation results in excessive
intake of oxygen and increased elimination of carbon dioxide, which may
eventually lead to a disturbance in the body’s acid-base balance.
Hypokalemic: Referring to hypokalemia, which
is characterized by abnormally low potassium levels in the blood. Potassium, the
primary positively charged ion (cation) of muscle, plays an important role in
regulating muscle contraction, nerve conduction, and other bodily functions.
Hypokalemia may result in confusion, fatigue, weakness, and, in severe cases,
paralysis and heart rhythm abnormalities.
Hypokinetic: Diminished movement and
decreased motor function. Some movement disorders are hypokinetic, such as
Hypoparathyroidism: An endocrine condition
characterized by insufficient secretion of parathyroid hormone due to injury,
disease, or congenital
abnormalities of the parathyroid glands. Parathyroid hormone
plays an essential role in regulating calcium balance in the body.
Hypoparathyroidism results in low calcium blood levels (hypocalcemia), leading
to various symptoms and findings. For example, hypoparathyroidism may cause a
condition known as tetany in which increased excitability of nerves and muscles
results in uncontrollable, painful muscle spasms and cramping; abnormal
involuntary movements resembling chorea; spasmodic closure of the larynx (laryngospasm);
and other findings. Hypoparathyroidism may also lead to seizures; abnormal
calcium deposits (calcifications) in the basal ganglia; loss of transparency of
the lenses of the eyes (cataracts); dry, scaly skin; weakened tooth enamel;
and/or other abnormalities.
Hypoxia: abnormally low levels of oxygen.
Iatrogenic: a disease or disorder that is
induced inadvertently by a physician or surgeon or by medical treatment or
Idiopathic: A disorder or condition of
spontaneous origin; self-originated or of unknown cause. The term is derived
from the prefix "idio-" meaning one’s own and "pathos" indicating disease.
Idiopathic epilepsy: Recurrent seizures of
unknown origin or cause; repeated episodes of uncontrolled electrical activity
in the brain that occur in the absence of detectable brain lesions. Also known
as essential or primary epilepsy, these conditions are often thought to have a
genetic component. This may suggest that affected individuals have an inherited
predisposition for recurrent seizures.
Immunofluorescence: This technique uses
antibodies linked to a light-emitting or fluorescent dye in order to study
foreign substances in a tissue sample.
Immunogenicity: The ability to or the degree
to which a particular substance may provoke an immune response; having the
properties of an antigen or any substance that may trigger a particular immune
reaction, such as the production of antibodies.
Implantable Pulse Generator (IPG): A device
that is placed under the skin near the collarbone as part of a surgical
procedure known as deep brain stimulation. Wire leads from electrodes implanted
in the brain are connected to the pulse generator, which then delivers
continuous high frequency electrical stimulation to the thalamus via the
implanted electrodes. This form of stimulation probably "jams" the nucleus and
therefore modifies the message in the movement control centers of the brain,
serving to suppress tremor.
Inhibition: The restraint, suppression, or
arrest of a process or the action of a particular cell or organ; the prevention
or slowing of the rate of a chemical or an organic reaction. The term
"reciprocal inhibition" refers to the restraint or "checking" of one group of
muscles upon stimulation (excitation) and contraction of their opposing
Inhibitor: A substance that blocks,
restricts, or interferes with a particular chemical reaction or other biologic
Innervate: To supply a body part, tissue, or
organ with nerves or nervous stimulation.
Insidious: Of subtle, gradual, or
imperceptible development; referring to the development of symptoms that may not
be recognized by an affected individual until the disorder in question is
Intravenous: Within a vein or veins, as in
introducing certain substances, such as fluids, nutrients, or medications,
directly into a vein.
Ion: An electrically charged atom or group
of atoms due to the loss or gain of one or more electrons. Positively charged
ions, known as cations, include potassium, calcium, sodium, hydrogen, ammonium,
and magnesium. Negatively charged ions, called anions, include chloride,
phosphate, and bicarbonate. The transfer of ions across cellular membranes plays
an essential role in vital bodily processes, including enzyme activation,
protein metabolism, acid-base balance, nerve impulse transmission, and muscle
Ischemia: Ischemia occurs when the flow of
oxygen-rich blood to tissue in the body is reduced or stopped.
Isoleucine: an essential amino acid.
Jejunostomy tube: The jejunostomy tube is
similar to a gastrostomy tube, although this tube is longer and is inserted
through the abdominal wall into the jejunum, the middle section of the small
Joint contractures: Permanent flexing or
extension of joints in fixed postures due to shortening of muscle fibers.
Contractures, abnormal fixation of the limbs, and associated deformity may
result from prolonged immobility of developing joints.
Juvenile myoclonic epilepsy: A form of
idiopathic epilepsy or recurrent seizures of unknown origin, with symptom onset
typically occurring from approximately 12 to 16 years of age. The condition is
characterized by sudden, involuntary, "shock-like" muscle jerks (myoclonus) that
primarily occur during the morning or with stress, fatigue, or alcohol
consumption. Patients may later develop generalized tonic-clonic seizures
associated with loss of consciousness and rhythmic contraction and relaxation of
all muscle groups.
Kinesigenic: Caused by sudden voluntary
movement; movement induced. More specifically, this term is often used to
describe abrupt episodes of involuntary movement that are provoked by sudden
motions or unexpected stimuli.
Lafora’s disease: A progressive myoclonic
encephalopathy (PME) that is inherited as an autosomal recessive trait.
Associated symptoms typically begin in childhood or early adolescence and
include frequent seizures characterized by loss of consciousness and rhythmic
contraction and relaxation of all muscle groups (generalized tonic-clonic
seizures); sudden, involuntary, "shock-like" muscle jerks (myoclonus); and
rapidly progressive deterioration of thought processing and acquired
intellectual abilities (dementia). Removal and microscopic examination of minute
tissue samples (e.g., muscle fibers, liver cells, etc.) reveal abnormal,
characteristic deposits of complex proteins and carbohydrates within the fluid
portion of cells (intracytoplasmic inclusions known as "Lafora bodies").
Lance-Adams syndrome: Also known as
"posthypoxic" or "postanoxic action myoclonus," this condition is characterized
by the development of chronic action myoclonus due to a temporary lack or
inadequate supply of oxygen to the brain (cerebral hypoxia or anoxia). Patients
with action myoclonus experience sudden, involuntary, "shock-like" muscle
contractions that may be triggered or aggravated by voluntary movement.
Lance-Adams syndrome is also often associated with cerebellar ataxia or lack of
coordination, postural imbalance, and other associated findings.
Lateral: Sideways; of, on, from, or toward
Leigh disease: A disorder of mitochondrial
function that typically becomes apparent during infancy. Also known as subacute
necrotizing encephalomyelopathy, the disorder may be characterized by feeding
and swallowing difficulties, vomiting, muscle weakness, low muscle tone (hypotonia),
and delayed acquisition of motor and language skills. Affected infants and
children may also develop seizures; an impaired ability to coordinate voluntary
movements (ataxia); involuntary, rapid, rhythmic eye movements (nystagmus);
tremor; dystonia; and/or other abnormalities. The disorder, which has a number
of underlying causes, may occur randomly for unknown reasons (sporadically) or
be transmitted as an autosomal recessive or X-linked trait. Leigh disease is
associated with characteristic changes of the central nervous system (CNS),
including symmetric regions of localized tissue loss (necrosis) and
neurodegenerative changes of the basal ganglia, thalamus, brainstem, spinal
cord, and other regions of the CNS.
Leucine: an essential amino acid.
Lewy body: A Lewy body is a mass of protein
found in dying nerve cells in the brain.
Lewy Body Disease: Also called diffuse Lewy
body disease, Lewy body dementia. Lewy body disease is a common cause of
dementia, accounting for approximately 15%-20% of all cases. The age of onset is
typically in the late 50s through the 70s. It is more common in men than women.
Lewy Body Disease is characterized by more daily fluctuations in symptoms than
Alzheimer’s disease, as well as more prominent psychosis. Patients are prone to
have adverse reactions to antipsychotics. Patients also have parkinsonian
features early in the disease, including slowed movements and rigidity, though
usually without tremor. The Lewy body is a protein aggregate found in dying
neurons in the brain. In Lewy body disease, the Lewy bodies are most prominently
found in the cortex, or surface of the brain, versus in the midbrain for
Lipopolysaccharide: A lipopolysaccharide is
a molecule made up of a lipid (a fat) with a polysaccharide (a complex sugar).
In most circumstances, the terms lipopolysaccharide and endotoxin can be used
Lumbar puncture: A procedure during which a
sample of fluid (i.e., cerebrospinal fluid [CSF]) is removed from the spinal
canal for diagnostic or therapeutic purposes. During the procedure, CSF is
obtained via a hollow needle inserted between two bones of the spinal column
within the lower back (i.e., usually the third and fourth lumbar vertebrae).
Laboratory analysis conducted on CSF may help to diagnose central nervous system
infections, certain tumors, or particular neurologic disorders. In some cases,
lumbar puncture may also be performed to inject certain medications into the
CSF, such as particular anticancer (chemotherapeutic) agents.
Lysosomal: Referring to lysosomes, which are
membrane-bound bodies (organelles) outside the nuclei of cells that contain
various enzymes engaged in intracellular digestion.
Lysosomal storage diseases: Inborn errors of
metabolism in which deficiency or impaired functioning of particular lysosomal
enzymes leads to an abnormal accumulation of certain substances (e.g., fats,
complex carbohydrates) within particular cells, progressively affecting multiple
bodily tissues and organs. (Lysosomes are membrane-bound, enzyme-containing
bodies within cells that engage in digestive processes; enzymes are proteins
that accelerate the rate of certain chemical reactions in the body.) Most
lysosomal storage disorders (e.g., mucolipidoses, mucopolysaccharidoses,
lipidoses, etc.) are thought to be inherited as autosomal recessive traits.
Machado-Joseph disease: Machado-Joseph
disease, also known as spinocerebellar ataxia (SCA) type III, is probably the
most common autosomal dominant SCA. This disorder was previously known as
Azorean disease, as a large number of Portuguese families from the Azores
Islands were found to be affected; however, SCA type III has now been reported
in many other ethnic groups. In addition to unsteadiness of gait (ataxia),
symptoms may involve parkinsonism, dystonia, and chorea. The affected protein is
called ataxin-3; however, its function is not yet known.
Magnetic resonance imaging (MRI): A
diagnostic scanning technique during which radio waves and an electromagnetic
field are used to help create detailed, cross-sectional images of specific
organs and tissues. MRI is often considered a particularly valuable imaging
technique for studies of the brain and spinal cord because of the MRI’s ability
to scan images from various angles and provide strong contrast between healthy
and abnormal tissues.
MAO-B inhibitors: Inhibitors of the enzyme
monoamine oxidase B. MAO-B helps break down dopamine; inhibiting it prolongs the
action of dopamine in the brain.
Mean: An average; intermediate or middle
position in value, quantity, or degree. The "arithmetic mean" is a statistical
measure derived by adding a set of values and dividing the total by the number
Mechanical pain: Mechanical pain arises from
pressure or touch.
Medially: Toward the middle; closer to or
oriented toward the midline or median plane of a body or structure. The "median
plane" refers to the imaginary plane that divides a body into symmetrical parts.
Membrane lipid peroxidation: the oxidative
deterioration of polyunsaturated fatty acids in which polyunsaturated fatty
acids are converted to lipid hydroperoxides.
Meningitis: Meningitis is an infection of
the meninges, the thin three-layer membranes that cover and protect the brain
and spinal cord.
MERFF syndrome (myoclonus epilepsy with ragged-red
fibers): A rare hereditary disorder characterized by neurologic and
muscle abnormalities due to defects of genetic material (DNA) in mitochondria,
the rod-like structures outside the nuclei of cells that serve as a primary
source of cellular energy. Removal and microscopic examination of minute samples
of muscle fibers reveal structurally abnormal mitochondria (a finding known as
"ragged-red fibers"). Associated symptoms include muscle weakness; sudden,
involuntary, "shock-like" muscle contractions induced by voluntary movements or
in response to external stimuli (action or reflex myoclonus); repeated seizures
(epilepsy); progressively impaired coordination of voluntary movements (ataxia);
and/or gradual deterioration of intellectual functioning (dementia). Some
affected individuals may also have additional abnormalities, such as hearing
loss; degeneration of the nerves (i.e., optic nerves) that convey impulses from
the retinas to the brain (optic atrophy); short stature; heart muscle disease
(cardiomyopathy); or other findings.
Metabolism: Refers to the ongoing chemical
processes of cells of the body, including catabolism and anabolism. Catabolism
or so-called "destructive metabolism" is the breakdown of complex chemical
compounds into simpler substances, typically liberating or releasing energy. In
contrast, anabolism or "constructive metabolism" refers to the "building up" or
conversion of simple substances into more complex chemical compounds, requiring
energy consumption (provided by catabolic processes).
Mini-Mental State Examination: This short
clinician-administered test measures cognitive status (the ability to think,
calculate, and reason) in adults. This test is used to measure the presence of
impaired cognition or a change in cognition over time.
Mitochondrial: Referring to mitochondria or
rod-like structures inside cells of the body whose primary functions include the
production and regulation of energy.
Monoamine: A molecule containing one amine
group. An amine is an organic compound containing nitrogen. The so-called
"biogenic monoamines" are natural, biologically active compounds that often
function as neurotransmitters, including dopamine, serotonin, noradrenaline, and
Monotherapy: A drug used alone to treat a
disease (opposite of combination therapy).
Motor fluctuations: Motor fluctuations occur
when levodopa is used to treat Parkinson’s disease. As the disease becomes
worse, the number of cells in the brain that store dopamine decreases, the
symptoms of Parkinson’s disease worsen, and levodopa is not as effective in
controlling the symptoms. When this happens, a person is said to have “off”
Multiple sclerosis (MS): A progressive
disease of the central nervous system characterized by destruction of myelin (demyelination),
the fatty substance that forms a protective sheath around certain long nerve
fibers (axons). Myelin serves as an electrical insulator, enabling the effective
transmission of nerve signals. Patients with MS may develop paresthesias, such
as numbness or tingling; muscle weakness and stiffness; impaired coordination;
abnormal reflexes; an inability to control urination (urinary incontinence);
slurred speech; visual disturbances; and/or other symptoms and findings.
Multiple System Atrophy: A neurodegenerative
disorder characterized by parkinsonism, ataxia, and dysfunction of the autonomic
Muscle tone: The low level of contraction in
a muscle not being intentionally contracted.
Mutated: Altered; a mutation is a change in
Mutation: A change in a gene, such as loss,
gain, or substitution of genetic material, that alters its function or
expression. This change is passed along with subsequent divisions of the
affected cell. Gene mutations may occur randomly for unknown reasons or may be
Myelin: The whitish, fatty substance forming
the segmented, multilayered wrappings or "sheaths" around certain long nerve
fibers or axons. Myelin sheaths electrically insulate axons, serving to speed
the transmission of nerve signals (action potentials).
Myelinated: Referring to long nerve fibers
(axons) that have myelin sheaths. Consisting of segmented, multilayered
wrappings of myelin, a whitish protein, myelin sheaths wrap around certain nerve
fibers, providing electrical insulation and serving to speed the transmission of
Myoclonic: Pertaining to myoclonus or
irregular, involuntary, shock-like contractions or spasms of a muscle or muscle
Myoclonus: A neurologic movement disorder
characterized by brief, involuntary, twitching or "shock-like" contractions of a
muscle or muscle group. These jerk-like movements may be accompanied by
periodic, unexpected interruptions in voluntary muscle contraction, leading to
lapses of sustained posture (known as "negative myoclonus"). So-called
"positive" and "negative" myoclonus are often seen in the same individuals and
may affect the same muscle groups. Myoclonus is often a nonspecific finding,
meaning that it may occur in the setting of additional neurologic abnormalities
and be associated with any number of underlying conditions or disorders. In
other patients, myoclonus appears as an isolated or a primary finding. Depending
on the underlying cause and other factors, the shock-like muscle jerks may occur
repeatedly or infrequently; may tend to appear under specific circumstances
(e.g., with voluntary movements or in response to specific external sensory
stimuli); and may affect any body region or regions.
Nasoduodenal tube: A nasoduodenal tube is a
flexible rubber tube that is inserted through the nose and into the duodenum
(the section of the small intestine closest to the stomach) via the esophagus
and stomach. It can be used to remove the contents of or decompress the small
intestine or to provide nutrition support or medication.
National Institutes of Health (NIH): The NIH
is one of the world’s foremost medical research centers and the federal focal
point for medical research in the United States. The NIH, comprising 27 separate
Institutes and Centers, is one of eight health agencies of the Public Health
Service that, in turn, is part of the U.S. Department of Health and Human
Necrosis: Cell death. Loss of cells,
tissues, or parts of a structure or organ due to the progressively degrading
actions of certain enzymes, such as the degradation of DNA within the nucleus of
dying cells. Necrosis may result from a loss of blood supply (ischemia),
infection, excessive exposure to ionizing radiation, certain chemicals, or
Neoplastic: Relating to the formation of a
neoplasm (tumor) or a new, abnormal growth characterized by uncontrolled,
progressive multiplication of cells. Neoplasms may be benign or malignant.
Nerve conduction velocity (NCV) test: A
diagnostic study during which both sensory and motor nerves are repeatedly
stimulated in order to measure the speed at which nerve impulses are conducted.
Unusually slow conduction velocities suggest damage to nerve fibers (e.g., loss
of the protective covering surrounding certain nerve fibers [demyelination] or
other disease process).
Nervous system: The nervous system of the
human body is divided into two interconnected systems: the central nervous
system, which is made up of the brain and spinal cord, and the peripheral
nervous system. The peripheral nervous system is further divided into the
somatic nervous system (made up of peripheral nerve fibers that send sensory
information to the central nervous system and motor nerve fibers that project to
skeletal muscle) and the autonomic nervous system.
Neuroacanthocytosis: Also known as
choreoacanthocytosis, this is a genetic disorder that most often becomes
apparent between the ages of 25 to 45 years. The disorder is usually transmitted
as an autosomal recessive trait. Associated symptoms may include generalized
chorea; dystonia affecting muscles of the mouth and tongue; potentially
mutilating lip- and tongue-biting; and sudden, involuntary, repetitive muscle
movements (motor tics) and vocalizations (vocal tics). Patients may also develop
personality changes and cognitive decline, seizures, parkinsonism, atrophy of
muscle tissue (amyotrophy), and difficulties speaking and swallowing.
Neuroimaging studies may reveal atrophy of certain regions of the basal ganglia
(e.g., caudate nuclei and putamen [striatum]). The disorder may be confirmed by
blood tests revealing the presence of abnormal circulating red blood cells that
have spur-like or thorny projections (acanthocytosis).
Neurochemical: Referring to the chemistry or
biochemical processes of the nervous system, such as activities involving
naturally produced chemicals (i.e., neurotransmitters) that enable nerve cells
(neurons) to communicate.
Neurodegenerative: Marked by or pertaining
to neurologic degeneration; deterioration of the structure or function of tissue
within the nervous system.
Neuroimaging: The production of detail,
contrast, and clearness in images of the brain and spinal cord (central nervous
system) through the use of computed tomography (CT) scanning, magnetic resonance
imaging (MRI), positron emission tomography (PET) scanning, or other imaging
techniques to assist in diagnosis, treatment decisions, or research.
Neuroleptic: a drug used to treat psychotic
Neuroleptic malignant syndrome: a
life-threatening neurologic disorder most often caused by an adverse reaction to
neuroleptic or antipsychotic drugs. Symptoms include high fever, sweating,
unstable blood pressure, stupor, muscular rigidity, and autonomic dysfunction.
In most cases, the disorder develops within the first 2 weeks of treatment with
the drug; however, the disorder may develop any time during the therapy period.
The syndrome can also occur in people taking anti-parkinsonism drugs known as
dopaminergics if those drugs are discontinued abruptly.
Neuron: An individual nerve cell.
Neuronal: Pertaining to a neuron or neurons.
Neuroprotective effect: Having the ability
to prevent or slow the death of neurons. The drug selegiline (Eldepryl®) may
have a neuroprotective effect, possibly by preventing formation of free
Neuroreceptor: Specific sites on the surface
of a nerve cell to which certain special substances (neurotransmitters) bind,
initiating the conduction of impulses (or signals) to other nerve cells.
Neurotoxin: a substance that interferes with
the electrical activity or functioning of nerve cells (neurons), preventing them
from communicating with each other.
Neurotransmitter: A specialized substance
(such as norepinephrine or acetylcholine) that transfers nerve impulses across
spaces between nerve cells (synapses). Neurotransmitters are naturally produced
chemicals by which nerve cells communicate.
Nigrostriatal system: Referring to the
substantia nigra, the striatum, and the connection between them.
Nocardia asteroides: Nocardia asteroides are
gram-positive bacteria that are found throughout the world in the soil.
Localized infections usually occur in the skin following contamination of a
scrape or scratch, and disseminated infections typically occur when a person
with a compromised immune system inhales the bacteria. The primary site of
disseminated infection is typically the lungs, where abscesses form, but the
infection may spread to other parts of the body, including the brain, liver, and
Nomenclature: System of names used in a
particular scientific discipline to consistently and methodically designate
certain classifications and avoid confusion or ambiguity.
Non-ergotoline medication: A dopamine
agonist medication that has action similar to that of pergolide (Permax®) and
bromocriptine (Parlodel®) but is not derived from an ergot. Examples of
nonergotoline medications that are used to treat some neurologic movement
disorders include pramipexole (Mirapex®) and ropinirole (Requip™.)
Non-kinesigenic: Not induced by movement;
provoked by factors other than sudden motions. This term often refers to abrupt
episodes of involuntary movement that occur spontaneously or may be worsened by
fatigue, stress, alcohol or caffeine intake, heat or cold, fasting, or other
Noradrenaline (norepinephrine): A
vasoconstrictor whose release triggers action within the sympathetic nervous
system, the part of the nervous system that regulates certain involuntary
responses during times of stress. Noradrenaline serves as a neurotransmitter
that stimulates receptors (alpha- and beta-adrenergic receptors) at effector
organs supplied or innervated by certain sympathetic nerve fibers
(postganglionic adrenergic fibers). In addition to its production by neurons,
noradrenaline is also secreted by the inner region of the adrenal glands
(adrenal medulla). The release of noradrenaline serves to deepen breathing,
raise blood pressure, and increase the heart rate. It also plays a role in
NREM sleep: Non-REM (nonrapid eye movement)
sleep, which is the normal period of dreamless, lighter sleep as compared to the
deeper REM sleep. NREM sleep accounts for the major portion of sleep.
Nuclear envelope: The nuclear envelope is a
membrane that surrounds the nucleus in eukaryotic cells, separating the DNA in
the nucleus from the rest of the cell.
Nucleus: The nucleus is the part of the cell
that contains the genetic material; it is surrounded by the nuclear envelope.
Obsessive-compulsive behaviors: The
performance of certain repetitive actions or rituals in response to persistent
thoughts or impulses. For example, obsessions may consist of repeated doubts,
such as wondering whether the stove was left on; a need for routine; or impulses
to perform certain inappropriate actions. Compulsions frequently include
repeated checking and rechecking, such as ensuring that the stove is indeed off;
touching particular objects in a specific pattern or sequence; repetitive hand
washing; or other repetitious behavior performed in an attempt to prevent or
relieve anxiety, distress, or a feeling of dread.
Obstructive sleep apnea: A sleep disorder
characterized by episodes of temporary cessation of breathing due to obstruction
of the airway.
Oculomotor: Relating to or causing movement
of the eyes.
Off episodes: This term refers to the times when
people with Parkinson’s disease have a decrease in the ability to move (hypomobility)
and other symptoms that cause difficulty rising from a chair, speaking, walking,
or performing their usual activities. Off episodes occur because the person’s
dose of levodopa has worn off too soon or has suddenly and unexpectedly stopped
Off time: This term refers to the times when
people with Parkinson’s disease have a decrease in the ability to move (hypomobility)
and other symptoms that cause difficulty rising from a chair, speaking, walking,
or performing their usual activities. Off episodes occur because the person’s
dose of levodopa has worn off too soon or has suddenly and unexpectedly stopped
Olivopontocerebellar atrophy (OPCA): A group
of rare hereditary disorders characterized by neurodegenerative changes of
certain brain regions, including the cerebellum and specialized groups of nerve
cells (nuclei) in the brainstem (e.g., olivary and pontine nuclei). With most
forms of the disorder, initial symptoms become apparent from adolescence to
mid-adulthood; however, a rare form has been identified that may be evident at
birth. Depending upon the type of OPCA, symptoms may include progressively
impaired coordination, postural instability, slurred speech (dysarthria), and
other associated findings (i.e., cerebellar ataxia); parkinsonism; rapid,
involuntary, rhythmic eye movements (nystagmus); and/or retinal degeneration.
Some affected individuals may also have additional symptoms and findings, such
as involuntary, rapid, jerky movements (chorea); relatively slow, writhing
motions that appear to "flow" into one another (athetosis); increased muscle
stiffness (rigidity) with associated twisting or distorted posturing of affected
muscles (dystonia); and/or other abnormalities. Most forms of OPCA are inherited
as autosomal dominant traits; however, autosomal recessive forms have also been
Opiate: Any preparation or derivative of
Opioids: Means "like or similar to opium"
and refers to medications with opium-like effects. This term is used to describe
any synthetic drug that possesses the characteristic properties of opiate
narcotics but is not derived from opium.
Organic: (1) Referring to or arising from an
organ or organs. (2) Regarding substances that arise or are derived from living
organisms. (3) Pertaining to chemicals that contain carbon.
Orthostatic hypotension: A sudden decrease
in blood pressure that occurs when the affected individual sits up or stands. In
some cases, it may occur as a side effect of certain medications.
Palate: The bony and muscular structure that
forms the roof of the mouth and separates the oral and nasal cavities.
Paranoia: Elaborate and overly suspicious
thoughts and feelings of persecution.
Parasympathetic nervous system: Part of the
nervous system that, together with the sympathetic nervous system, forms the
autonomic nervous system (ANS). The ANS controls the functioning of involuntary
structures, including the heart, glands, and smooth muscle. The parasympathetic
nervous system regulates nerve transmissions to certain effector organs under
normal conditions, as opposed to times of stress. It serves to "steady"
involuntary activities and conserve or restore energy. Parasympathetic responses
may include slowing of the heart and breathing rates, contraction of the pupils,
an increase in glandular activity, and an acceleration in the rate of
Parathyroid glands: Two pairs of endocrine
glands located in the neck at the back of the thyroid gland. The parathyroid
glands produce parathyroid hormone, which increases blood calcium levels by
causing bones to release calcium into the blood, the kidneys to conserve
calcium, and the intestines to increase calcium absorption from food. When blood
calcium levels are high, the parathyroid glands reduce their production of
parathyroid hormone, essentially reversing the process.
Paresthesias: Abnormal sensations occurring
spontaneously or in response to stimulation. Paresthesias may include prickling,
tingling, burning, or tickling feelings; numbness; "pins and needles"; or
cramp-like sensations. Various neurologic movement disorders may be
characterized by paresthesias, including restless legs syndrome (RLS),
paroxysmal kinesigenic dyskinesia (PKD), and paroxysmal non-kinesigenic
Parkinson’s disease (PD): A slowly
progressive degenerative disorder of the central nervous system characterized by
slowness or poverty of movement (bradykinesia), rigidity, postural instability,
and tremor primarily while at rest. Additional characteristic findings include a
shuffling, unbalanced manner of walking; forward bending or flexion of the
trunk; a fixed or "mask-like" facial expression; weakness of the voice;
abnormally small, cramped handwriting (micrographia); depression; or other
symptoms and findings. Such abnormalities are thought to result from progressive
loss of nerve cells within a certain region of the substantia nigra of the brain
and the associated depletion of the neurotransmitter dopamine.
Parkinsonism: A constellation of the
following symptoms: tremor, rigidity, bradykinesia (slow movements), and loss of
postural reflexes. Although classically seen in Parkinson’s disease,
parkinsonism may have other causes. In the elderly, parkinsonism may be caused
by dopamine-blocking drugs, multiple system atrophy, striatonigral degeneration,
Shy-Drager syndrome, cortico basal degeneration, diffuse Lewy body disease, and
Alzheimer’s disease with parkinsonism. In younger people, parkinsonism may be
caused by juvenile-onset dystonia/parkinsonism, Westphal variant of Huntington’s
disease, Wilson’s disease, L-dopa-responsive dystonia, Hallervorden-Spatz
disease, and progressive pallidal degeneration.
Paroxysmal: Pertaining to or occurring in
paroxysms or sudden, recurrent episodes. The term paroxysms often describes
transient episodes of abnormal involuntary movements (e.g., chorea, athetosis,
dystonia, and/or ballismus) or ataxia, which is characterized by an impaired
ability to coordinate voluntary movements.
Paroxysmal movement disorders: Certain
neurologic movement disorders characterized by abrupt, transient episodes of
abnormal involuntary movement, such as chorea, athetosis, dystonia, and/or
ballismus (i.e., the paroxysmal dyskinesias) or impaired coordination of
voluntary actions and other associated findings (i.e., paroxysmal ataxias).
Depending upon the specific disorder present, episodes may be precipitated or
worsened by different factors. As examples, in those with paroxysmal kinesigenic
dyskinesia (PKD), episodes may be triggered by sudden voluntary movements. In
non-kinesigenic dyskinesia (PNKD), episodes occur spontaneously and may be
worsened by caffeine or alcohol consumption, stress, fatigue, or other factors.
In patients with paroxysmal kinesigenic ataxias, episodes may be triggered by
sudden voluntary movements or postural changes. These disorders may be familial,
appear to occur randomly for unknown reasons (sporadically), or occur secondary
to other underlying conditions or disorders (symptomatic).
Pathogenesis: the origination and
development of a disease.
Pathophysiology: The effects of disease on
body functions; the physiology of altered function seen in disease. ("Patho-" is
a combining form denoting any disease state, and "physiology" refers to the
study of the processes and functioning of the human body).
Penetrance: The regularity or frequency with
which a specific gene yields its effect or "is expressed." For example, if a
specific gene produces a disease in all individuals who carry the gene, it is
termed 100% penetrant. If a gene produces the disease less than 100% of the
time, it is not fully penetrant.
Peptide: Peptides are short chains of amino
Pericardium: The pericardium is the
two-layered sac that surrounds and protect the heart. If the pericardium becomes
fibrotic or filled with fluid, it limits the motion of the heart and, therefore,
the ability of the heart to pump efficiently.
Periodic apnea: Episodes of the temporary
cessation of spontaneous breathing. Periodic apnea may be characterized by
absence of airflow, absence of chest wall movements, or airway obstruction that
may result from poor control of tongue movements, impaired coordination of upper
airway muscles, or other abnormalities.
Periodic limb movements in sleep (PLMS):
Repeated stereotypic movements of the limbs (usually the legs) that occur during
sleep. These movements typically consist of upward extension of the great toe
and foot as well as flexion of the ankle, knee, or hip; they occur every 15 to
40 seconds and 0.5 to 6.0 seconds, usually during NREM sleep and have a duration
of 0.5 to 6.0 seconds.
Peripheral edema: unusual fluid
accumulation, resulting in swelling of the arms or legs.
Peripheral nervous system: The peripheral
nervous system is that portion of the nervious system outside of the brain and
spinal cord (central nervous system).
Peripheral neuropathy: Inflammation,
degeneration, or damage of nerves of the peripheral nervous system (PNS). The
PNS includes nerves that extend from the brain and spinal cord (central nervous
system) to various parts of the body. Peripheral neuropathy may involve motor
nerves, causing muscle weakness, and/or sensory nerves, resulting in pain,
abnormal sensations, such as numbness or tingling, or other findings.
Peristalsis: Rhythmic, wave-like
contractions of smooth or involuntary muscle fibers that propel food through the
Phenomenology: classification based on a
Phenylalanine: an essential amino acid that
is converted in the body to tyrosine.
Phenylketonuria: an inherited disorder that,
if untreated, causes profound mental retardation as well as other medical
Phonation: The production of speech;
utterance of sounds through use of the vocal cords.
Physiatrist: a physician specializing in
physical medicine and rehabilitation.
Physiologic tremor: A form of rapid tremor
that may occasionally occur in any individual. Physiologic tremor is typically
the result of fear, anxiety, or excitement. Physiologic tremor may affect the
arms, legs, and, in some patients, the face or neck.
Pittsburgh Sleep Quality Index: This 24-item
self-administered questionnaire is designed to provide a brief clinically useful
assessment of a variety of sleep disturbances that might affect sleep quality.
Placebo: A placebo is a substance that
appears to be identical to the treatment under study but that has no effects on
the test subject. The placebo is given to members of the control group during
experimental trials that test the effects of a drug or other substance.
Placebo-controlled trial: A
placebo-controlled trial is a clinical experiment in which patients have been
randomly assigned to receive either the treatment under study or placebo, an
alternative that has no effects.
Pleura: The pleura are the two-layer
membranes that cover the outside of the lungs and line the chest cavity.
Polymerase chain reaction (PCR): A highly
sophisticated technique during which a known sequence of DNA is copied rapidly
over a short period, such as millions of copies over a few hours. PCR testing
assists in diagnosing certain genetic disorders, helps identify individuals
through analysis of a single cell or so-called "DNA fingerprinting," or
characterizes certain strains of infectious microorganisms.
Positron emission tomography (PET): An
advanced, computerized imaging technique that uses radioactively-labels
substances (e.g., glucose) to demonstrate chemical and metabolic activities in
the brain as well as track other brain functions. Brain structures are also
visualized on PET scans.
Positron emission tomography (PET) scanning:
A noninvasive, diagnostic procedure used to record the uptake and distribution
of certain substances in the tissues and organs of the body. Thus, PET assists
in evaluating various metabolic and physiological activities in the body. During
this procedure, three-dimensional, color-coded images are created based upon the
detection of positively charged particles (positrons). The positrons are
produced by certain biochemicals (e.g., glucose) carrying radioactive substances
that have been introduced into the body (via intravenous injection). PET
scanning may help to detect abnormal biochemical patterns associated with
certain neurologic conditions, such as Parkinson’s disease, brain tumors,
seizure disorders, and psychiatric abnormalities.
Postural instability: unsteadiness of gait
Postural tremor: Any tremor that is present
while an individual voluntarily maintains a position against gravity, such as
holding the arms outstretched.
Precursor: Literally a "forerunner," such as
a substance that precedes another in a biochemical reaction.
Prenatally: Before birth.
Probe: A genetic probe is a single strand of
DNA or RNA with a specific base sequence used to detect the corresponding base
sequence by hybridization—which is the process of joining two complementary
strands of DNA or one each of DNA and RNA to form a double-stranded molecule.
The single strand is either radioactively or immunologically labeled.
Progressive supranuclear palsy (PSP): A
progressive neurological disorder characterized by neurodegenerative changes of
certain brain regions, including particular areas of the basal ganglia and the
brainstem. Symptom onset most often occurs in the sixth decade of life.
Associated findings may include balance difficulties, sudden falls, stiffness
(rigidity), slowness of movement (bradykinesia), an impaired ability to perform
certain voluntary eye movements, and visual disturbances. Affected individuals
may also develop slurred speech; swallowing difficulties; personality changes;
dystonia; sudden, involuntary, "shock-like" muscle contractions (myoclonus); or
other abnormalities. The disorder usually appears to occur randomly for unknown
reasons (sporadically); however, there are some reports of families with
multiple affected members, suggesting a possible hereditary component to the
Prophylactic: Referring to preventive
treatment (i.e., prophylaxis); a medication, procedure, or device that serves as
a preventive against disease.
Prophylaxis: Protection from or the
prevention of disease; preventive (i.e., prophylactic) therapy; often refers to
the use of a drug, mechanical agent, or procedure to prevent infection with
certain microorganisms (e.g. bacteria).
Proteasome inhibitor: A proteasome inhibitor
is a chemical that interferes with, or inhibits, the action of proteasomes—the
recyclers of proteins in the cells.
Protein: Proteins are large complex
molecules made up of amino acids. Each protein starts out as a chain of amino
acids. Determined by the sequence of the base pairs in the gene that encodes it,
the protein then folds itself into its unique shape. Proteins serve many
different roles within the body, including providing structure (collagen),
allowing movement (actin and myosin), increasing the rate of a chemical reaction
(enzymes), transporting substances (hemoglobin); regulating processes within the
cells (insulin); and responding to the stimuli (receptor proteins on surface of
Psychogenic: Of mental or emotional origin;
referring to a symptom, condition, or disorder that is caused by mental,
psychological, or emotional factors rather than physical illness.
Psychosis: Refers to any mental disorder characterized
by severe distortion of thinking, comprehension, and judgment (i.e., mental
capacity); impaired contact with reality; and abnormal emotional responses and
disorganized behaviors. Symptoms may include false beliefs despite evidence to
the contrary (delusions), such as fears of persecution; the perception of
sounds, sights, or other sensations in the absence of external stimuli
(hallucinations); apparent lack of emotion (affect); abnormal thought patterns;
disorganized, incoherent speech; and/or agitated, aggressive behaviors.
Psychosis may be of physical (i.e., organic) origin, such as due to brain
damage, neurological diseases, underlying metabolic disorders, etc., or
"functional," meaning that it is produced or caused by factors other than
Pulmonary: Referring to the lungs.
Pulmonary fibrosis: Pulmonary fibrosis is a condition in
which excessive scar tissue forms in the lungs, making them stiff, decreasing
the amount of surface area that is available to provide gas exchange, and
interfering with their function.
Putamen: One of the 3 major brain regions that, together
with the caudate nuclei and the globus pallidus, comprise the basal ganglia.
Relatively similar in function and structure, the putamen and the caudate nuclei
are collectively referred to as the striatum. Specialized groups of nerve cells
within the putamen receive input from various regions of the cerebral cortex.
The messages are processed and relayed by way of the thalamus to the motor
cortex, influencing voluntary movement.
Range of motion (ROM): The extent of a
joint’s free movement. The normal ROM of the elbow, for instance, carries the
forearm through a half-circle. Passive ROM is tested while the limb is relaxed.
Active ROM is movement controlled by the patient.
Receptor: A molecule on a neuron that
receives a neurotransmitter. Reception of the neurotransmitter causes changes in
the neuron which increase or decrease its likelihood of "firing," or sending its
own signal to other neurons. Dopamine receptors are located on corpus striatum
neurons, and on nigral cells.
Reduced penetrance: Reduced expression of a
genetic disorder. The term penetrance refers to the frequency with which a
specific genetic mutation produces its typical effect in those with the genetic
abnormality. For example, if fewer than 100 percent of individuals who inherit a
gene mutation for an autosomal dominant disorder develop the disease, the
specific trait is said to have "reduced penetrance."
Reflex: Involuntary, predictable response to
a particular stimulus.
Refractory: Resistant to or not readily
yielding to treatment.
Regurgitation: In reference to the heart,
regurgitation is the backward flow of blood through a defective valve.
REM sleep: The period of sleep that is
associated with dreaming, rapid eye movements (REM), and certain involuntary
Restless legs syndrome (RLS): A neurologic
movement disorder characterized by unusual, uncomfortable sensations
(paresthesias/dysesthesias) deep within the calves and/or thighs, resulting in
an irresistible urge to move the legs, and motor restlessness in response to or
in an effort to alleviate discomfort. In some patients, the arms may also be
affected. Symptoms become obvious or worse during periods of relaxation or
inactivity; occur most frequently during the evening or the early part of the
night; and may be temporarily relieved by voluntary movements of the affected
area. Most patients experience associated sleep disturbances, including
difficulties drifting off to and remaining asleep. RLS is also often associated
with periodic limb movements of sleep (PLMS) or repeated, stereotypic, upward
extension of the great toe and foot, potentially followed by flexion of the
knee, hip, or ankle. Episodes of PLMS typically occur during periods of lighter
(i.e., non-REM) sleep.
Restorative sleep: A refreshing sleep, i.e.,
receiving a sufficient amount of rest to feel refreshed and to engage in the
activities of daily living without experiencing excessive daytime sleepiness
Retina: The nerve-rich membrane that forms
the innermost region of the eye. As light passes through other areas of the eye
(including the cornea, pupil, and lens), it is bent or refracted to focus on the
retina, which contains nerve cells that respond to light (photoreceptors).
Images formed on the retina are converted into nerve impulses that are
transmitted to the brain via the optic nerve (second cranial nerve).
Retinal: Referring to the retina, which is
the nerve-rich membrane forming the innermost region of the eye. As light passes
through the eye, it is bent (refracted) to focus on the retina, which contains
photoreceptors or specialized nerve cells that respond to light. Images formed
on the retina are converted into nerve impulses, which are then transmitted to
the brain by the optic nerve (also known as the second cranial nerve).
Retrocollis: spasmodic torticollis in which
the head is drawn directly backward.
Retroperitoneum: The retroperitoneal area is the area
behind peritoneum, the covering of the intestines. The kidneys and the adrenal
glands lie in the retroperitoneal area.
Reye syndrome: A potentially
life-threatening disease characterized by sudden inflammation and swelling of
the brain (acute encephalopathy) and rapid fat accumulation within certain
internal organs (viscera), particularly the liver, occurring subsequent to
certain viral infections, such as chickenpox or upper respiratory tract
infections (e.g., influenza B). Reye syndrome primarily occurs in children and
adolescents, although it has sometimes been reported during infancy or young
adulthood. About a week after the onset of a viral infection, patients may
develop uncontrollable vomiting, followed by a rapid onset of listlessness,
confusion, and memory loss, a state of unconsciousness (coma), seizures, and/or
other findings, potentially leading to life-threatening complications. Evidence
suggests that the use of aspirin-containing preparations (salicylates) as a
treatment for particular viral infections plays a role in the development of
Reye syndrome. Therefore, experts advise that such medications be avoided for
the treatment of viral infections during infancy, childhood, adolescence, and
Rhythmical myoclonus: Involuntary,
shock-like contractions or spasms of a muscle or muscle group that occur in a
rhythmical pattern. This usually occurs as a result of a lesion in the central
Ribonucleic acid (RNA): RNA is a chemical
that is found in the nucleus and cytoplasm of cells; it plays an important role
in protein synthesis and other chemical activities of the cell.
Ribosomes: Ribosomes are small structures
within a cell that are the site of protein synthesis.
Rigidity: Stiffness and resistance to
movement. May be a symptom of a neurologic movement disorder such as Parkinson’s
Rush Hallucination Inventory: This
standardized clinician-administered questionnaire assesses the presence or
absence of false visual (see), auditory (hear), tactile (touch), or gustatory
(taste) experiences in the setting of a clear sensorium.
Schizophrenia: a psychiatric disorder
characterized by hallucinations, delusions, disordered thinking, unusual speech
or behavior and social withdrawal that impair the affected person’s ability to
interact with others.
Scoliosis: Lateral or "sideways" curvature
of the normally vertical line of the spine. Progressive spinal deformity may be
associated with numerous neuromuscular and neurodevelopmental disorders
(neurogenic scoliosis), such as cerebral palsy, spinal muscular atrophy, and
Rett syndrome. The severity of the deformity varies, depending upon the degree
of weakness, the nature and progression of the underlying disorder, or other
Sedation: An induced state of quiet or
Seizures: Episodes of uncontrolled
electrical activity in the brain. These abnormal electrical disturbances may
lead to involuntary jerking, spasms, or rhythmic contraction and relaxation of
certain muscle groups and impaired control of involuntary functions such as
breathing or bladder or bowel control. There may also be loss of consciousness
or sensory or behavioral abnormalities.
Sensorimotor: Pertaining to both the sensory
and motor aspects of a bodily function.
Sequelae: Plural of sequela, which is any abnormal
condition that occurs subsequent to and/or is caused by disease, injury, or
Sequence: As a noun, a sequence is a series
of chemical bases—adenine (A), thymine (T), cytosine (C) and guanine (G)—in DNA
or a string of amino acids in a protein. As a verb, sequence refers to the
process of determining the order of the bases or amino acids.
Serotonin (3-[2-aminoethyl]-5-indolol): A
vasoconstrictor found in many tissues of the body that is present in relatively
high concentrations in portions of the central nervous system (e.g.,
hypothalamus, basal ganglia, etc.). Serotonin functions as a neurotransmitter,
regulating the delivery of messages between nerve cells (neurons). This
neurotransmitter is thought to play some role in regulating consciousness and
mood states. Serotonin is also present in other tissues of the body such as the
intestines and blood platelets.
Sialidosis: A lysosomal storage disease in
which deficiency of the enzyme neuraminidase leads to abnormal accumulation of
certain complex carbohydrates (sialyloligosaccharides) in particular tissues and
organs. There are different variants of the disorder, based upon age of onset,
severity, and other factors. Sialidosis type I, also known as "cherry-red-spot
myoclonus syndrome," usually becomes apparent during the second decade of life.
Associated symptoms include the development of characteristic, cherry-red
circular areas within the middle layers of the eyes; gradual loss of visual
clarity; and sudden, involuntary, "shock-like" contractions (myoclonus) of
muscles of the arms and legs. The myoclonus is progressive in nature and may be
triggered by voluntary movements (action myoclonus) or certain external stimuli,
such as sound (reflex myoclonus). Sialidosis is inherited as an autosomal
Sialorrhea: Excess production of saliva, or
increased retention of saliva in the mouth, due to difficulty swallowing.
Side effect: An effect of a drug that is not the main
or intended effect. Side effects may be of no concern, or they may be bothersome
or even dangerous, in which case they may limit the upper dose a patient can
tolerate. Side effects are also called adverse effects.
Single photon emission computed tomography (SPECT):
A noninvasive scanning procedure during which a radioactive substance known as a
radionuclide is introduced into the body to help evaluate the function and
structure of certain organs or tissues. The amount of the substance taken up by
particular tissues may depend upon the amount of blood flow within such regions.
For example, absence of radionuclide uptake in a targeted region may indicate a
lack of blood flow in certain areas. Following intravenous administration of the
radioactive compound, a specialized rotating camera detects the radiation
emanating from the radionuclides in the form of particles known as protons. The
recorded images may produce colorized, horizontal and vertical cross sections
and be reconstructed by computer to create three-dimensional images. By
evaluating the blood supply to particular tissues, SPECT may be particularly
helpful in detecting certain changes within the central nervous system or the
Sinus bradycardia: an abnormally slow heart
rate (i.e., of less than 60 beats per minute).
Sleep fragmentation: Sleep fragmentation is
a continual disruption of sleep, which often leads to excessive daytime
sleepiness. This disruption can occur as the result of a variety of factors,
including sleep disorders, the need to get up to use the bathroom, pain, and a
noisy or uncomfortable sleeping environment.
Sleep latency: The interval of time between
"settling in" to go to sleep and the onset of sleep.
Sleep maintenance: Once asleep, the ability
to remain asleep.
Spasmodic dysphonia (SD): A manifestation of
dystonia. SD involves the muscles of the larynx and surrounding muscles and
therefore involves speech. In individuals with SD, speech in blocked by
intermittent spasms of the voice box (larynx).
Spasmodic torticollis (ST): A form of
dystonia involving the muscles of the neck, and therefore called "cervical
dystonia." As a result of the abnormal involuntary contractions of the neck
muscles, the head may be rotated, tilted, flexed, extended, or any combination
of these postures. The movements may be quick, sustained, or patterned and,
therefore, may be associated with tremor.
Spasmolytic: Antispasmodic; referring to
agents that may eliminate or relieve spasms, typically of involuntary (i.e.,
smooth) muscle, such as within the arteries, the intestine, the ring-shaped
muscles around certain natural openings or passages (sphincters), the bladder,
the muscular tubes that carry urine from the kidneys to the bladder (ureters),
Spasticity: An abnormal increase in muscle tone that may be
caused by certain types of damage to the nerve pathways regulating muscles.
Spasticity is a common complication of cerebral palsy, brain injuries, spinal
cord injuries, multiple sclerosis, and stroke. Spasticity can lead to
incoordination, loss of function, pain, and permanent muscle shortening, or
Spinal cord: The cylindrical structure of
nerve tissue that, together with the brain, comprises the central nervous
system. The spinal cord is an extension of the medulla oblongata–which is part
of the lowest region of the brain (brainstem)–and is contained within a central
canal in the spinal column. The spinal cord and the brain are surrounded by a
protective, 3-layered membrane (meninges). Cerebrospinal fluid (CSF) flows
through the cavities (ventricles) of the brain, the spinal cord’s central canal,
and the space between the middle and inner layers of the meninges (subarachnoid
space). The spinal cord consists of an inner core of gray matter and surrounding
areas of white matter, composed of bundles of myelinated nerve fibers (axons)
known as spinal tracts. These include ascending tracts that carry sensory
impulses up the spinal cord to the brain and descending tracts that transmit
motor impulses from the brain down the spinal cord. Nerves emerge from both
sides of the spinal cord (i.e., spinal nerves) through the narrow gaps
(foramina) between bones of the spinal column (vertebrae). The spinal nerves,
which are attached to the spinal cord by specialized nerve bundles (spinal nerve
roots), contain both motor and sensory neurons.
Spinocerebellar ataxias (SCA): This group of
disorders, of which there are now 17 genetically identified types, are inherited
as an autosomal dominant genetic trait and appear to be mostly due to increased
numbers of repeats in the various genes involved (as in HD). All types of SCA
involve degeneration of the cerebellum, causing impaired balance, walking, and
coordination. Each type of SCA has its own typical pattern of symptoms; however,
these may vary greatly from person to person. Some forms of SCA affect eye
movements, swallowing, thinking, reflexes, or cause parkinsonism, chorea, or
dystonia. In most types of SCA, the onset of symptoms occurs during adulthood;
symptoms slowly become worse over the years.
Sporadically: Occurring intermittently,
randomly, or in isolation.
SSRIs: Selective serotonin reuptake
inhibitors. Drugs belonging to this class are antidepressant agents that
selectively inhibit the absorption of serotonin at certain nerve membranes
(e.g., presynaptic neuronal membranes). These drugs increase the concentration
of serotonin within the central nervous system and enhance serotonin’s
Stereotactic: refers to use of precise
coordinates to identify deep structures of the brain. The coordinates may be
obtained by fitting a patient’s head with a special frame and taking a CT or MRI
scan. The position of the brain structures relative to the frame permits fine
localization of the deep brain structures. Stereotactic methods are used during
brain surgery for tremor, Parkinson’s disease, and dystonia. These brain
structures are located with precise, three-dimensional coordinates.
Stereotypic: Inappropriate, persistent
repetition of particular bodily postures, actions, or speech patterns. These are
typically involuntary, rhythmic, coordinated, and purposeless movements,
postures, or vocalizations that may appear ritualistic or purposeful in nature.
Stereotypies may be associated with a variety of neurologic and behavioral
disorders, such as Tourette syndrome, obsessive-compulsive disorders, Rett
syndrome, restless legs syndrome, schizophrenia, and autism.
Stereotypical: Conforming to a repetitive
pattern as in repetition of particular movements or gestures.
Stimulus: A stimulus is something that
creates a response in a muscle, nerve, gland or other excitable tissue or organ
of the body. The plural is stimuli.
Stretch reflex: Contraction of a muscle
stimulated by rapid stretching.
Stretch-loop circuits: Pathways of
electrical impulses along specific nerve fibers (alpha motoneurons) that result
in a "stretch" reflex in a muscle.
Striatum: An area of the brain that controls
movement and balance. It is connected to and receives signals from the
Substantia nigra: A dark band of gray matter
deep within the brain where cells manufacture the neurotransmitter dopamine for
movement control. Degeneration of cells in this region may lead to a neurologic
movement disorder such as Parkinson’s disease.
Substrate: A chemical substance that is
acted upon by an enzyme is called a substrate.
Subthalamic nucleus: The subthalamic nucleus
is an oval mass of gray matter located beneath the thalamus.
Sydenham’s chorea: A usually self-limited
condition in which chorea develops in association with an inflammatory disease
caused by certain strains of streptococci bacteria. This disease, known as
rheumatic fever, is characterized by the sudden onset of fever and joint pain,
with subsequent inflammation of the heart (carditis), chest pain, skin rash, and
other symptoms. If rheumatic fever involves the nervous system, Sydenham’s
chorea may develop. This condition commonly affects children aged 5 to 15 or
women during pregnancy. Sydenham’s chorea involves involuntary, uncontrollable,
jerky movements that gradually worsen in severity, potentially affecting arm
movements, the manner of walking (gait), and speech. In most patients, the
condition spontaneously resolves in weeks or months.
Sympathetic nervous system: Part of the
nervous system that along with the parasympathetic nervous system forms the
autonomic nervous system (ANS). The ANS regulates the functioning of involuntary
structures, such as the glands, smooth muscle, and heart. The sympathetic
nervous system regulates certain involuntary responses during times of strong
emotion, such as fear or anger; exercise; or other forms of stress. These
responses, sometimes referred to as the "fright-or-flight response," include
widening of the pupils; increased heart and breathing rates; constriction of
most blood vessels, raising blood pressure; widening of those blood vessels that
supply skeletal muscles; and reduction in the rate of peristalsis.
Synapse: The junction between two neurons or
between a neuron and an effector organ. As a nerve impulse reaches a synapse,
the terminal or end of the "presynaptic" neuron’s axon releases
neurotransmitters, which diffuse across the gap and bind to receptors of the
"postsynaptic" neuron or the effector organ (i.e., muscle or gland). As the
electrical impulse is conducted across the gap, electrical changes are triggered
that serve to continue or hinder transmission of the impulse.
Synthesis: The formation of a complex
chemical compound through the union of simpler substances.
Systemic lupus erythematosus: an autoimmune
disease involving multiple organ systems that is defined clinically and
associated with antibodies directed against cell nuclei.
Tardive dyskinesia: A movement disorder that
may result from extended therapy with certain antipsychotic medications such as
haloperidol. The condition is characterized by involuntary, rhythmic movements
of the face, jaw, mouth, and tongue, such as lip pursing, chewing movements, or
protrusion of the tongue. Facial movements are sometimes accompanied by
involuntary, jerky or writhing motions (choreoathetoid movements) of the trunk,
arms, and legs. In some patients, symptoms discontinue months or years after
withdrawal of antipsychotic therapy. However, in others, the condition may not
Tardive dystonia: A form of tardive
dyskinesia characterized by chronic dystonia due to administration of
medications that block dopamine D2 receptors (dopamine receptor antagonists),
such as certain antipsychotic agents. (Dopamine receptors are molecules on the
surfaces of receiving nerve cells that are sensitive to stimulation by dopamine,
a neurotransmitter that controls movement and balance. Several types of dopamine
receptors have been identified, including D1, D2, and D3.) Dystonia is a
neurologic movement disorder characterized by sustained muscle contractions that
often result in repetitive twisting motions or unusual postures or positions.
Tardive dystonia is the most common form of secondary dystonia–i.e., dystonia
that results from certain environmental factors or "insults" that affect the
brain. In adults, tardive dystonia often initially affects facial or neck
muscles. Dystonia may remain limited to such regions or extend to affect
adjacent muscles of the trunk and arms. Children are more likely to be affected
by generalized dystonia that involves muscles of the trunk and legs.
Tauopathy: Tauopathy refers to any group of
diseases that cause dementia related to a problem with tau, a protein that is
important in maintaining the structure of brain cells.
Tay-Sachs disease: A progressive
neurodegenerative metabolic disorder that belongs to a group of diseases called
lysosomal storage diseases. Also known as GM2 gangliosidosis type I or infantile
type, Tay-Sachs disease results from deficiency of the enzyme hexosaminidase A,
which leads to an abnormal accumulation of certain fats (i.e., gangliosides) in
particular tissues, particularly nerve cells of the brain. An autosomal
recessive disorder, Tay-Sachs disease primarily affects individuals of
northeastern European Jewish (Ashkenazi Jewish) ancestry. Symptom onset
typically begins from about 3 to 6 months of age. Associated symptoms may
include an exaggerated startle response, increasing listlessness, loss of
previously acquired skills (psychomotor regression), severely diminished muscle
tone (hypotonia), and the development of characteristic, cherry-red circular
areas within the middle layers of the eyes (Tay’s sign). With disease
progression, affected infants and children may develop increasing muscle
stiffness or rigidity; seizures; sudden, involuntary, "shock-like" contractions
of multiple muscle groups in response to certain stimuli (generalized,
stimuli-sensitive myoclonus); enlargement of the brain (metabolic
megalencephaly); deafness; blindness; and dementia. Life-threatening
complications may develop between 2 to 5 years of age.
Tendon: A tough fibrous cord of tissue that
attaches muscle to bone (or other structures of the body).
Teratogenic: Possessing the ability to
disrupt normal fetal development and causing fetal abnormalities.
Thalamus: An area of the brain consisting of
2 relatively large masses of gray matter. The thalamus relays information from
most sensory organs to the outer region of the cerebrum or cerebral cortex;
receives and processes messages from the body concerning heat, cold, pain,
pressure, and touch; and influences motor activity of the cerebral cortex.
Threshold: A pain threshold is the point at
which a feeling or sensation becomes painful.
Tics: Involuntary, compulsive, stereotypic
muscle movements or vocalizations that abruptly interrupt normal motor
activities. These repetitive, purposeless motions (motor tics) or utterances
(vocal tics) may be simple or complex in nature; may be temporarily suppressed;
and are often preceded by a "foreboding" sensation or urge that is temporarily
relieved following their execution. Simple tics include abrupt, isolated
movements, such as repeated facial twitching, blinking, or shoulder shrugging,
and simple sounds, including grunting, throat clearing, or sighing. Complex tics
may involve more sustained, complex movements, such as deep knee bending or leg
kicking, or complex vocalizations, including repeating another person’s words or
phrases (echolalia) or, rarely, explosive cursing (coprolalia). Tourette
syndrome is defined as the presence of multiple motor and vocal tics for at
least one year, changes in the nature of the tics (e.g., complexity, severity,
anatomical location) during the course of the disorder, and symptom onset before
Tone: Resistance or tension in a muscle when
a limb or other body part is moved passively and in a relaxed state about a
joint. A state of muscle tension balanced by partial contraction or alternate
contraction and relaxation.
TorsinA: TorsinA is a protein that, when
defective, may cause DYT-1 dystonia. Although its exact function is not known,
TorsinA is believed to be related to a series of compounds that enable cells to
recover from stress and injury.
Toxic metabolites: Potentially harmful
substances formed as the result of normal body functions.
Toxin: A toxin is a poisonous substance that
is produced by a plant or animal.
Transient: Temporary; transitory; not
lasting or enduring.
Tremor: Rhythmic, involuntary, oscillatory
(or to-and-fro) movements of a body part.
Tropical spastic paraparesis (HTLV-1-associated
myelopathy): A rare disorder characterized by slowly progressive
weakness (paraparesis), stiffness (rigidity), and spasticity of the leg muscles
due to infection with the human T-cell lymphotropic virus-1 (HTLV-1). Modes of
transmission include sexual contact, mother-to-child transmission (e.g., via
breastfeeding), and blood transfusion.
Tryptophan: an essential amino acid.
Tyrosine: an aromatic nonessential amino
acid that is a metabolic precursor of thyroxine, the pigment melanin, and other
biologically important compounds.
Unified Parkinson Disease Rating Scale (UPDRS):
The UPDRS is the most commonly used to tool to rate the symptoms of Parkinson’s
disease. This scale is intended to be used to follow the course of Parkinson’s
disease in patients over a period of time. It is made up of three parts: (1)
Mentation (the process of thinking), Behavior, and Mood; (2) Activities of Daily
Living; and (3) Motor symptoms.
Unilateral: Affecting, pertaining to, or
confined to one side only.
Unverricht-Lundborg’s disease (Baltic myoclonic
epilepsy): A form of progressive myoclonic encephalopathy (PME)
characterized by the development of repeated seizures or episodes of
uncontrolled electrical activity of the brain (epilepsy); sudden, "shock-like"
muscle contractions that may be induced by voluntary movements or in response to
certain external stimuli (action or reflex myoclonus); and eventual impairment
of coordination, postural instability, and other associated findings (i.e.,
cerebellar ataxia). Although mental deterioration may also be associated with
the disorder, it is typically milder than that seen with Lafora’s disease
(another form of PME). Unverricht-Lundborg’s disease is thought to be inherited
as an autosomal recessive trait. Symptom onset typically begins from about age 6
to 13. The disorder is slowly progressive; however, the degree of disease
progression and disability may be extremely variable among affected family
Upper motor neurons: Nerve cells extending
from the brain to the spinal cord that control movement.
Vaginosis: Bacterial vaginosis involves the
abnormal increased growth of certain bacteria in the vagina.
Valine: an essential amino acid.
Variable expressivity: Varying manifestation
of a genetic trait. The term "expressivity" refers to the degree to which a
hereditary trait appears in an individual. Thus, in individuals with a gene
mutation for an autosomal dominant disorder that has variable expressivity, the
specific characteristics that are manifested may vary in range and degree from
mild to severe.
Vascular: Pertaining to or containing blood
Vasoconstrictor: A chemical substance whose
actions result in the narrowing of blood vessels.
Vasodilator: A chemical substance whose
actions cause an increase in the diameter of blood vessels.
Vasomotor: Pertaining to the muscles and
nerves that control blood vessel diameter, thereby regulating or modulating
Ventral intermediate (VIM) nucleus: A
specific region of the thalamus. This area of the brain is involved in the
control of movement and is the "target" area for thalamotomy and deep brain
stimulation when treating patients with tremor.
Ventriculography: Brain imaging method that
uses an injected dye and X-rays to visualize the brain’s ventricles (cavities)
Virulent: Referring to or characterized by
virulence or the degree to which an invading microorganism, such as a bacterium
or virus, is able to produce disease. Measures of virulence may be based upon
the microorganism’s ability to invade bodily tissues and the severity of the
Visual-analog scale: This linear scale
allows responses on a continuum.
White matter: Bundles of myelinated nerve
fibers or axons. These nerve fibers have a creamy white appearance due to
myelin, a whitish substance that primarily contains fats and proteins. Myelin
forms a protective, insulating sheath around certain axons, functioning as an
electrical insulator and ensuring efficient nerve conduction. The breakdown,
destruction, or loss of myelin from a nerve or nerves (demyelination), such as
seen in certain neurodegenerative diseases, results in impaired nerve impulse
Wilson disease: A rare genetic disorder of
copper metabolism, leading to an excessive accumulation of copper in certain
tissues and organs, including the liver, brain, kidneys, or corneas of the eyes.
Without prompt, appropriate treatment, the disorder may result in progressive
liver disease, degenerative changes of the brain, psychiatric abnormalities, and
other symptoms. Neurologic findings may include tremor; involuntary, rapid,
jerky movements combined with relatively slow, writhing movements (choreoathetosis);
impaired muscle tone and sustained muscle contractions, producing repetitive
movements and abnormal posturing; increasingly slurred speech; and difficulties
swallowing. Some patients may also experience increasing irritability, anxiety,
severe depression, unusual behaviors, or other psychiatric problems.
X-linked dominant trait: Human
traits, such as an individual’s specific blood group, eye color, or expression
of certain diseases, result from the interaction of one gene inherited from the
mother and one from the father. In X-linked dominant disorders, the gene
mutation for the disease trait is transmitted as a dominant gene on the X
chromosome and therefore may "override" the instructions of the normal gene on
the other chromosome, resulting in expression of the disease. Because females
have two X chromosomes yet only one functioning copy is necessary, a percentage
of X chromosomes with the mutated gene may not be expressed (random X chromosome
inactivation). As a result, females often have less severe symptoms than
affected males. In contrast, because males have one X chromosome from the mother
and one Y chromosome from the father, those who inherit an X-linked dominant
disease trait typically fully express the mutated gene on the X chromosome,
causing a more severe form of the disorder that may result in lethality before
or shortly after birth. Fathers with an X-linked dominant trait transmit the
gene to their daughters but not to their sons. Mothers with a single copy of an
X-linked dominant gene have a 50 percent risk of transmitting the gene to their
daughters as well as to their sons.
X-linked recessive trait: Human
traits, such as a person’s eye color, specific blood group, or expression of
certain diseases, result from the interaction of one gene inherited from the
mother and one from the father. In X-linked recessive disorders, the gene
mutation for the disease trait is located on the X chromosome. Because females
have two X chromosomes yet only one functioning copy is necessary, a percentage
of X chromosomes with the mutated gene may not be expressed (random X chromosome
inactivation). However, because males have one X chromosome from the mother and
one Y chromosome from the father, those who inherit an X-linked recessive
disease trait typically fully express the mutated gene on the X chromosome. Some
females who carry a single copy of the disease gene (heterozygous carriers) may
have certain symptoms associated with the disorder; however, such findings are
usually more variable and less severe than those seen in affected males. Fathers
with an X-linked recessive trait may transmit the gene to their daughters but
not to their sons. Mothers with an X-linked recessive gene have a 50 percent
risk of transmitting the gene to their daughters and their sons.
Zydis: Unlike drugs that are incorporated
into pills or capsules that must be swallowed, Zydis drugs are incorporated into
fast-dissolving freeze-dried wafers that "melt" on the tongue. The term Zydis
refers to the vehicle that is used for drug delivery and not to the drug itself.