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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 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.

Economic burden: 


Fluid accumulation in the tissues causing swelling.


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 heart muscle.

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 light-beam microscope.

Electrophysiologic recording: 

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, etc.).


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.


Any abnormal conditions or diseases of the structure or function of the brain, particularly chronic, degenerative conditions.

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.


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.


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.


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 the stomach

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.


(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.


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.


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 involuntary movements.

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