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Abductor muscle   
A muscle used to pull a body part away from the midline of the body (e.g., the abductor leg muscles are used to spread the legs).

ACTH (adrenocorticotropic hormone)
ACTH is extracted from the pituitary glands of animals or made synthetically. ACTH stimulates the adrenal glands to release glucocorticoid hormones. These hormones are anti-inflammatory in nature, reducing edema and other aspects of inflammation. Data from the early 1970s indicate that ACTH may reduce the duration of MS exacerbations. In recent years it has been determined that synthetically produced glucocorticoid hormones (e.g., cortisone, prednisone, prednisolone, methylprednisolone, betamethasone, dexamethasone), which can be directly administered without the use of ACTH, are more potent, cause less sodium retention and less potassium loss, and are longer-acting than ACTH.

Activities of daily living (ADLs)   
Activities of daily living include any daily activity a person performs for self-care (feeding, grooming, bathing, dressing), work, homemaking, and leisure. The ability to perform ADLs is often used as a measure of ability/disability in MS.

Having rapid onset, usually with recovery; not chronic or long-lasting.

Acute attack
See Exacerbation.

Adductor muscle   
A muscle that pulls inward toward the midline of the body (e.g., the adductor leg muscles are used to pull the legs together).

See Activities of daily living.

Adrenocorticotropic hormone (ACTH)   

Advance (medical) directive   
Advance directives preserve the person’s right to accept or reject a course of medical treatment even after the person becomes mentally or physically incapacitated to the point of being unable to communicate those wishes. Advance directives come in two basic forms: (1) a living will, in which the person outlines specific treatment guidelines that are to be followed by health care providers; (2) a health care proxy (also called a power of attorney for health care decision-making), in which the person designates a trusted individual to make medical decisions in the event that he or she becomes too incapacitated to make such decisions. Advance directive requirements vary greatly from one state to another and should therefore be drawn up in consultation with an attorney who is familiar with the laws of the particular state.

Affective release   
Also called pseudo-bulbar affect or pathological laughing and weeping; a condition in which episodes of laughing and/or crying occur with no apparent precipitating event. The person’s actual mood may be unrelated to the emotion being expressed. This condition is thought to be caused by lesions in the limbic system, a group of brain structures involved in emotional feeling and expression.

Afferent pupillary defect   
An abnormal reflex response to light that is a sign of nerve fiber damage due to optic neuritis. A pupil normally gets smaller when a light is shined either into that eye (direct response) or the other eye (indirect response). In an afferent pupillary defect (also called Marcus Gunn pupil), there is a relative decrease in the direct response. This is most clearly demonstrated by the “swinging flashlight test.” When the flashlight is shined first in the abnormal eye, then in the healthy eye, and then again in the eye with the pupillary defect, the affected pupil becomes larger rather than smaller.

See Ankle-foot orthosis.

Ankle-foot orthosis (AFO)   
An ankle-foot orthosis is a brace, usually plastic, that is worn on the lower leg and foot to support the ankle and correct foot drop. By holding the foot and ankle in the correct position, the AFO promotes correct heel-toe walking. See Foot drop.

Protein produced by certain cells of the immune system, which is produced in response to bacteria, viruses, and other types of foreign antigens. See Antigen.

Refers to the action of certain medications commonly used in the management of neurogenic bladder dysfunction. These medications inhibit the transmission of parasympathetic nerve impulses and thereby reduce spasms of smooth muscle in the bladder.

Any substance that triggers the immune system to produce an antibody; generally refers to infectious or toxic substances. See Antibody.

Inhalation of food particles or fluids into lungs.

Aspiration pneumonia   
Inflammation of the lungs due to aspiration.

Assistive devices   
Any tools that are designed, fabricated, and/or adapted to assist a person in performing a particular task, e.g., cane, walker, shower chair.

Assistive technology   
A term used to describe all of the tools, products, and devices, from the simplest to the most complex, that can make a particular function easier or possible to perform.

The incoordination and unsteadiness that result from the brain’s failure to regulate the body’s posture and the strength and direction of limb movements. Ataxia is most often caused by disease activity in the cerebellum.

A wasting away or decrease in size of a cell, tissue, or organ of the body because of disease or lack of use.

Autoimmune disease   
A process in which the body’s immune system causes illness by mistakenly attacking healthy cells, organs, or tissues in the body that are essential for good health. Multiple sclerosis is believed to be an autoimmune disease, along with systemic lupus erythematosus, rheumatoid arthritis, scleroderma, and many others. The precise origin and pathophysiologic processes of these diseases are unknown.

Autonomic nervous system   
The part of the nervous system that regulates involuntary vital functions, including the activity of the cardiac (heart) muscle, smooth muscles (e.g., of the gut), and glands. The autonomic nervous system has two divisions: the sympathetic nervous system accelerates heart rate, constricts blood vessels, and raises blood pressure; the parasympathetic nervous system slows heart rate, increases intestinal and gland activity, and relaxes sphincter muscles.

The extension or prolongation of a nerve cell (neuron) that conducts impulses to other nerve cells or muscles.  Axons are generally smaller than 1 micron (1 micron = 1/1,000,000 of a meter) in diameter, but can be as much as a half meter in length.

Pertaining to the axon.

Axonal damage   
Injury to the axon in the nervous sytem, generally as a consequence of trauma or disease. This damage may involve temporary, reversible effects or permanent severing of the axon. Axonal damage usually results in short-term changes in nervous system activity, or permanent inability of nerve fibers to send their signals from one part of the nervous system to another or from nerve fibers to muscles. The damage can thus result in a variety of symptoms relating to sensory or motor function.

A type of lymphocyte (white blood cell) manufactured in the bone marrow that makes antibodies.

Babinski reflex   
A neurologic sign in MS in which stroking the outside sole of the foot with a pointed object causes an upward (extensor) movement of the big toe rather than the normal (flexor) bunching and downward movement of the toes. See Sign.

Bell’s palsy   
A paralysis of the facial nerve (usually on one side of the face), which can occur as a consequence of MS, viral infection, or other infections. It has acute onset and can be transient or permanent.

An attempt to eliminate bias in the interpretation of clinical trial outcomes. It indicates that at least one party involved in the clinical trial is unaware of which patients are receiving the experimental treatment and which are receiving the control substance. Trials may be either single-blind (patients do not know which treatment they are receiving) or doubled-blind (neither the examining physicians nor the patients know which treatment each patient is receiving).

Blood-brain barrier   
A semipermeable cell layer around blood vessels in the brain and spinal cord that prevents large molecules, immune cells, and potentially damaging substances and disease-causing organisms (e.g., viruses) from passing out of the blood stream into the central nervous system (brain and spinal cord). A break in the blood-brain barrier may underlie the disease process in MS.

That part of the central nervous system that is contained within the cranium (skull).

The part of the central nervous system that houses the nerve centers of the head as well as the centers for respiration and heart control. It extends from the base of the brain to the spinal cord.

Brainstem auditory evoked potential (BAEP)   
A test in which the brain’s electrical activity in response to auditory stimuli (e.g., clicking sounds) is recorded by an electroencephalograph and analyzed by computer. Demyelination results in a slowing of response time. This test is sometimes useful in the diagnosis of MS because it can confirm the presence of a suspected lesion or identify the presence of an unsuspected lesion that has produced no symptoms. BAEPs have been shown to be less useful in the diagnosis of MS than either visual or somatosensory evoked potentials. See Visual evoked potential; Somatosensory evoked potential.

A hollow, flexible tube, made of plastic or rubber, which can be inserted through the urinary opening into the bladder to drain excess urine that cannot be excreted normally.

Central nervous system   
The part of the nervous system that includes the brain, optic nerves, and spinal cord.

A part of the brain situated above the brainstem that controls balance and coordination of movement.

Cerebrospinal fluid (CSF)   
A watery, colorless, clear fluid that bathes and protects the brain and spinal cord. The composition of this fluid can be altered by a variety of diseases. Certain changes in CSF that are characteristic of MS can be detected with a lumbar puncture (spinal tap), a test sometimes used to help make the MS diagnosis. See Lumbar puncture.

The large, upper part of the brain that acts as a master control system and is responsible for initiating thought and motor activity.  Its two hemispheres, united by the corpus callosum, form the largest part of the central nervous system.

Pertaining to the cerebrum.

Of long duration, not acute; a term often used to describe a disease that shows gradual worsening.

Chronic progressive
A former “catch-all” term for progressive forms of MS. See Primary-progressive MS, Secondary-progressive MS, and Progressive-relapsing MS.

Clinical finding   
An observation made during a medical examination indicating change or impairment in a physical or mental function.

Clinically isolated syndrome (CIS)
A first neurologic event that is suggestive of demyelination, accompanied by multiple, clinically “silent” (asymptomatic) lesions on MRI that are typical of MS. Individuals with this syndrome are at high risk for developing clinically definite MS.

Clinical trial   
Rigorously controlled studies designed to provide extensive data that will allow for statistically valid evaluation of the safety and efficacy of a particular treatment. See also Double-blind clinical study; Placebo.

A sign of spasticity in which involuntary shaking or jerking of the leg occurs when the toe is placed on the floor with the knee slightly bent. The shaking is caused by repeated, rhythmic, reflex muscle contractions.

High level functions carried out by the human brain, including comprehension and use of speech, visual perception and construction, calculation ability, attention (information processing), memory, and executive functions such as planning, problem-solving, and self-monitoring.

Cognitive impairment   
Changes in cognitive function caused by trauma or disease process. Some degree of cognitive impairment occurs in approximately 50–60 percent of people with MS, with memory, information processing, and executive functions being the most commonly affected functions. See Cognition.

Cognitive rehabilitation   
Techniques designed to improve the functioning of individuals whose cognition is impaired because of physical trauma or disease. Rehabilitation strategies are designed to improve the impaired function via repetitive drills or practice, or to compensate for impaired functions that are not likely to improve. Cognitive rehabilitation is provided by psychologists and neuropsychologists, speech/language pathologists, and occupational therapists. While these three types of specialists use different assessment tools and treatment strategies, they share the common goal of improving the individual’s ability to function as independently and safely as possible in the home and work environment.

Combined (bladder) dysfunction   
A type of neurogenic bladder dysfunction is MS (also called detrusor-external sphincter dyssynergia—DESD). Simultaneous contractions of the bladder’s detrusor muscle and external sphincter cause urine to be trapped in the bladder, resulting in symptoms of urinary urgency, hesitancy, dribbling, and incontinence.

Computerized axial tomography (CT scan)   
A non-invasive diagnostic radiology technique for examining soft tissues of the body. A computer integrates X-ray scanned “slices” of the organ being examined into a cross-sectional picture.

Condom catheter   
A tube connected to a thin, flexible sheath that is worn over the penis to allow drainage of urine into a collection system; can be used to manage male urinary incontinence.

A condition in which bowel movements happen less frequently than is normal for the particular individual, or the stool is small, hard, and difficult or painful to pass.

A shortening of muscle fibers that results in the movement of a joint.

A permanent shortening of the muscles and tendons adjacent to a joint, which can result from severe, untreated spasticity and interferes with normal movement around the affected joint. If left untreated, the affected joint can become frozen in a flexed (bent) position.

Controlled study
A clinical trial that compares the outcome of a group of randomly-assigned patients who receive the experimental treatment to the outcome of a group of randomly-assigned patients who receive a standard treatment or inactive placebo.

An organized working together of muscles and groups of muscles aimed at bringing about a purposeful movement such as walking or standing.

Corpus callosum   
The broad band of nerve fiber tissue that connects the two cerebral hemispheres of the brain.

The outer layer of brain tissue.

Any of the natural or synthetic hormones associated with the adrenal cortex (which influences or controls many body processes). Corticosteroids include glucocorticoids, which have an anti-inflammatory and immunosuppressive role in the treatment of MS exacerbations. See also Glucocorticoids; Immunosuppression; Exacerbation.

A glucocorticoid steroid hormone, produced by the adrenal glands or synthetically, that has anti-inflammatory and immune-system suppressing properties. Prednisone and prednisolone also belong to this group of substances.

Cranial nerves   
Nerves that carry sensory, motor, or parasympathetic fibers to the face and neck. Included among this group of twelve nerves are the optic nerve (vision), trigeminal nerve (sensation along the face), vagus nerve (pharynx and vocal cords). Evaluation of cranial nerve function is part of the standard neurologic exam.

CT scan   
See Computerized axial tomography.

A diagnostic procedure in which a special viewing device called a cystoscope is inserted into the urethra (a tubular structure that drains urine from the bladder) to examine the inside of the urinary bladder.

A surgically created opening through the lower abdomen into the urinary bladder. A plastic tube inserted into the opening drains urine from the bladder into a plastic collection bag. This relatively simple procedure is done when a person requires an indwelling catheter to drain excess urine from the bladder but cannot, for some reason, have it pass through the urethral opening.

Messenger chemicals produced by various cells, particularly those of the immune system, to influence the activity of other cells.

Reprinted with permission from Rosalind C. Kalb (ed.), Multiple Sclerosis: The Questions You Have—The Answers You Need, 3rd Edition. New York: Demos Medical Publishing, Inc., 2004

  Last updated October 2004