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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, hyperprolactinemia, or high levels of the hormone prolactin.

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 the activity of the enzyme carbonic anhydrase. This zinc-containing enzyme is present in red blood cells and 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 the 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.


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.


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.


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 vertebrae).


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.


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.


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.


A rhythm of biological functions occurring in a 24-hour periodic cycle (e.g., sleeping, eating, etc.).


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 disorders.


The simultaneous contraction of agonist and antagonist muscles.

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 blood vessels.

COMT inhibitors: 

Drugs that block catechol-O-methyltransferase, an enzyme that breaks down dopamine. COMT inhibitors include entacapone (Comtan®) and tolcapone (Tasmar®).


Existing at birth.


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.


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).


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.”


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.


Cytokines are small proteins that regulate the body’s immunity, inflammation, and blood-cell production responses.


The cytoplasm is the part of the cell that surrounds the nucleus.