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Immune system   
A complex network of glands, tissues, circulating cells, and processes that protect the body by identifying abnormal or foreign substances and neutralizing them.

Immune-mediated disease
A disease in which components of the immune system--t cells, antibodies, and others--are responsible for the disease either directly (as occurs in autoimmunity) or indirectly (for example, when damage to the body occurs secondary to an immune assault on a foreign antigen such as a bacteria or virus).

Immunocompetent cells   
White blood cells (B- and T-lymphocytes and others) that defend against invading agents in the body.

See Antibody.

The science that concerns the body’s mechanisms for protecting itself from abnormal or foreign substances.

In MS, a form of treatment that slows or inhibits the body’s natural immune responses, including those directed against the body’s own tissues. Examples of immunosuppressive treatments in MS include mitoxantrone, cyclosporine, methotrexate, and azathioprine.

As defined by the World Health Organization, an impairment is any loss or abnormality of psychological, physiological, or anatomical structure or function. It represents a deviation from the person’s usual biomedical state. An impairment is thus any loss of function directly resulting from injury or disease.

The number of new cases of a disease in a specified population over a defined period of time. The incidence of MS in the United States is approximately 10,000 newly-diagnosed people per year.

Also called spontaneous voiding; the inability to control passage of urine or bowel movements.

Indwelling catheter   
A type of catheter (see Catheter) that remains in the bladder on a temporary or permanent basis. It is used only when intermittent catheterization is not possible or is medically contraindicated. The most common type of indwelling catheter is a Foley catheter, which consists of a flexible rubber tube that is inserted in the bladder to allow the urine to flow into an external drainage bag. A small balloon, inflated after insertion, holds the Foley catheter in place.

A tissue’s immunologic response to injury, characterized by mobilization of white blood cells and antibodies, swelling, and fluid accumulation.

The supply or conduction of nervous impulses to a muscle or body part.

Intention tremor   
Rhythmic shaking that occurs in the course of a purposeful movement, such as reaching to pick something up or bringing an outstretched finger in to touch one’s nose.

A group of immune system proteins, produced and released by cells infected by a virus, which inhibit viral multiplication and modify the body’s immune response. Three interferon beta medications have been approved by the U.S. Food and Drug Administration (FDA) for treating relapsing forms of MS: IFN beta-1b (Betaseron®); IFN beta-1a (Avonex®); and IFN beta-1a (Rebif®).

Interferon gamma
A naturally-occurring substance in the body, produced primarily by activated T cells, which promotes inflammation and is thought to be involved in MS exacerbations. Once tried as a treatment for MS, it was found to make the disease worse. Interferon beta works to counteract the effects of interferon gamma.

Intermittent self-catheterization (ISC)   
A procedure in which the person periodically inserts a catheter into the urinary opening to drain urine from the bladder. ISC is used in the management of bladder dysfunction to drain urine that remains after voiding, prevent bladder distention, prevent kidney damage, and restore bladder function.

Internuclear ophthalmoplegia   
A disturbance of coordinated eye movements in which the eye turned outward to look toward the side develops nystagmus (rapid, involuntary movements) while the other eye simultaneously fails to turn completely inward. This neurologic sign, of which the person is usually unaware, can be detected during the neurologic exam.

Intrathecal space   
The space surrounding the brain and spinal cord that contains cerebrospinal fluid.

Within a vein; often used in the context of an injection into a vein of medication dissolved in a liquid.

See Plaque.

White blood cell.

L-Hermitte's sign   
An abnormal sensation of electricity or “pins and needles” going down the spine into the arms and legs that occurs when the neck is bent forward so that the chin touches the chest.

Living will   
See Advance (medical) directive.

Loftstrand crutch
A type of crutch with an attached holder for the forearm that provides extra support.

Lumbar puncture   
A diagnostic procedure that uses a hollow needle (canula) to penetrate the spinal canal at the level of third–fourth or fourth–fifth lumbar vertebrae to remove cerebrospinal fluid for analysis. This procedure is used to examine the cerebrospinal fluid for changes in composition that are characteristic of MS (e.g., elevated white cell count, elevated protein content, the presence of oligoclonal bands).

A type of white blood cell that is part of the immune system. Lymphocytes can be subdivided into two main groups: B-lymphocytes, which originate in the bone marrow and produce antibodies; T-lymphocytes, which are produced in the bone marrow and mature in the thymus. Helper T-lymphocytes heighten the production of antibodies by B-lymphocytes; suppressor T-lymphocytes suppress B-lymphocyte activity and seem to be in short supply during an MS exacerbation.

A white blood cell with scavenger characteristics that has the ability to ingest and destroy foreign substances such as bacteria and cell debris.

Magnetic resonance imaging (MRI)   
A diagnostic procedure that produces visual images of different body parts without the use of X-rays. Nuclei of atoms are influenced by a high frequency electromagnetic impulse inside a strong magnetic field. The nuclei then give off resonating signals that can produce pictures of parts of the body. An important diagnostic tool in MS, MRI makes it possible to visualize and count lesions in the white matter of the brain and spinal cord.

Marcus Gunn pupil   
See Afferent pupillary defect.

Minimal Record of Disability (MRD)   
A standardized method for quantifying the clinical status of a person with MS. The MRD is made up of five parts: demographic information; the Neurological Functional Systems (developed by John Kurtzke), which assign scores to clinical findings for each of the various neurologic systems in the brain and spinal cord (pyramidal, cerebellar, brainstem, sensory, visual, mental, bowel and bladder); the Expanded Disability Status Scale (developed by John Kurtzke), which gives a single composite score for the person’s disease; the Incapacity Status Scale, which is an inventory of functional disabilities relating to activities of daily living; the Environmental Status Scale, which provides an assessment of social handicap resulting from chronic illness. The MRD has two main functions: to assist doctors and other professionals in planning and coordinating the care of persons with MS, and to provide a standardized means of recording repeated clinical evaluations of individuals for research purposes. See Expanded Disability Status Scale (EDSS).

Monoclonal antibodies   
Laboratory-produced antibodies, which can be programmed to react against a specific antigen in order to suppress the immune response.

Motor neurons   
Nerve cells of the brain and spinal cord that enable movement of various parts of the body.

Motor point block   
See Nerve block.

See Magnetic resonance imaging.

Multiple Sclerosis Functional Composite (MSFC)
A three-part, standardized, quantitative assessment instrument for use in clinical trials in MS, that was developed by the Task Force on Clinical Outcomes Assessment appointed by the National MS Society’s Advisory Committee on Clinical Trials of New Agents in Multiple Sclerosis. The three components of the MSFC measure leg function/ambulation (Timed 25-Foot Walk), arm/hand function (9-Hole Peg Test), and cognitive function (Paced Auditory Serial Addition Test (PASAT)).

Muscle tone   
A characteristic of a muscle brought about by the constant flow of nerve stimuli to that muscle, which describes its resistance to stretching. Abnormal muscle tone can be defined as: hypertonus (increased muscle tone, as in spasticity); hypotonus (reduced muscle tone); flaccid (paralysis); atony (loss of muscle tone). Muscle tone is evaluated as part of the standard neurologic exam in MS.

A soft, white coating of nerve fibers in the central nervous system, composed of lipids (fats) and protein. Myelin serves as insulation and as an aid to efficient nerve fiber conduction. When myelin is damaged in MS, nerve fiber conduction is faulty or absent. Impaired bodily functions or altered sensations associated with those demyelinated nerve fibers are identified as symptoms of MS in various parts of the body.

Myelin basic protein   
One of several proteins associated with the myelin of the central nervous system, which may be found in higher than normal concentrations in the cerebrospinal fluid of individuals with MS and other diseases that damage myelin.

An inflammatory disease of the spinal cord. In transverse myelitis, the inflammation spreads across the tissue of the spinal cord, resulting in a loss of its normal function to transmit nerve impulses up and down, as though the spinal cord had been severed.

An X-ray procedure by which the spinal canal and the spinal cord can be visualized. It is performed in conjunction with a lumbar puncture and injection of a special X-ray contrast material into the spinal canal.

A bundle of nerve fibers (axons). The fibers are either afferent (leading toward the brain and serving in the perception of sensory stimuli of the skin, joints, muscles, and inner organs) or efferent (leading away from the brain and mediating contractions of muscles or organs).

Nerve block   
A procedure used to relieve otherwise intractable spasticity, including painful flexor spasms. An injection of phenol into the affected nerve interferes with the function of that nerve for up to three months, potentially increasing a person’s comfort and mobility.

Nervous system  
Includes all of the neural structures in the body: the central nervous system consists of the brain, spinal cord, and optic nerves; the peripheral nervous system consists of the nerve roots, nerve plexi, and nerves throughout the body.

Refers to the relationship between the body’s nervous system and endocrine system, whereby certain cells in the body release hormones in response to a neural stimulus.

Related to activity of the nervous system, as in “neurogenic bladder.”

Neurogenic bladder   
Bladder dysfunction associated with neurologic malfunction in the spinal cord and characterized by a failure to empty, failure to store, or a combination of the two. Symptoms that result from these three types of dysfunction include urinary urgency, frequency, hesitancy, nocturia, and incontinence.

Physician who specializes in the diagnosis and treatment of conditions related to the nervous system.

Study of the central, peripheral, and autonomic nervous system.

The basic nerve cell of the nervous system. A neuron consists of a nucleus within a cell body and one or more processes (extensions) called dendrites and axons.

A psychologist with specialized training in the evaluation of cognitive functions. Neuropsychologists use a battery of standardized tests to assess specific cognitive functions and identify areas of cognitive impairment. They also provide remediation for individuals with MS-related cognitive impairment. See Cognition and Cognitive impairment.

The need to urinate during the night.

Rapid, involuntary movements of the eyes in the horizontal or, occasionally, the vertical direction.

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