Glossary of terms related to multiple sclerosis (MS)*

Acute

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

Antibody

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

Antigen

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

Ataxia

The incoordination and unsteadiness that results 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.

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 (eg, of the gut), and glands. The autonomic nervous system has 2 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.

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.

Central nervous system (CNS)

The part of the nervous system that includes the brain, optic nerves, and spinal cord. The nerves that leave the spinal cord and go to the rest of the body make up the peripheral nervous system.

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.

Chronic

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

Clinically isolated syndrome (CIS)

A first neurological event that is suggestive of demyelination, accompanied by multiple, clinically "silent" (asymptomatic) lesions on MRI that are typical of MS. Individuals with CIS are at high risk for developing clinically definite MS.

Demyelination

A loss of myelin in the white matter of the central nervous system.

Dysesthesia

Distorted or unpleasant sensations experienced by a person when the skin is touched. These sensations are typically caused by abnormalities in the sensory pathways in the brain and spinal cord.

Dysmetria

A disturbance of coordination caused by lesions in the cerebellum. A tendency to over- or underestimate the extent of motion needed to place an arm or leg in a certain position (eg, overreaching for an object).

Dysphagia

Difficulty in swallowing. It is a neurologic or neuromuscular symptom that may result in aspiration (whereby food or saliva enters the airway), slow swallowing (possibly resulting in inadequate nutrition), or both.

Evoked potentials (EPs)

EP tests are a useful way of confirming the diagnosis of MS. These tests measure the brain's electrical response to sensory input (eg, sound, light, or touch) and are done by placing wires on specific areas of the scalp. The doctor then compares the patient's response times with normal response times. If there is a difference in response time, this can show that there are lesions along specific nerve pathways, even when there are no symptoms. Visual EPs are considered the most useful in MS.

Finger-to-nose test

As a test of dysmetria and intention tremor, the person is asked, with eyes closed, to touch the tip of the nose with the tip of the index finger. This test is part of the standard neurologic exam.

Hemiparesis

Weakness of one side of the body, including one arm and one leg.

Hemiplegia

Paralysis of one side of the body, including one arm and one leg.

Intention tremor

Tremor that develops or becomes more pronounced as a person tries to grasp or reach for an object, or tries to move a hand or foot to a precise spot. Often the tremor only occurs during physical movement. Intention tremor is the most common and can be the most disabling form of tremor in people with MS.

Immunosuppressant

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.

Lhermitte'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.

Myelin

A soft, white coating of nerve fibers in 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.

Myelogram

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 cord.

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.

Neurologist

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

Oscillopsia

Continuous, involuntary, and chaotic eye movements that result in a visual disturbance in which objects appear to be jumping or bouncing.

Paraparesis

A weakness, but not total paralysis, of the lower extremities/legs.

Plaque

An area of inflamed or demyelinated central nervous system tissue. A plaque, or lesion, which can vary from a few millimeters to a few centimeters in diameter, generally contains inflammatory cells and other cells that contribute to brain inflammation.

Stance ataxia

An inability to stand upright due to disturbed coordination of the involved muscles, which results in swaying and a tendency to fall in one or another direction.

Trigeminal neuralgia

Lightning-like acute pain in the face caused by demyelination of nerve fibers at the site where the sensory (trigeminal) nerve root for that part of the face enters the brainstem.

Vertigo

A dizzying sensation of the environment spinning, often accompanied by nausea and vomiting.

White matter

The part of the brain that contains myelinated nerve fibers, and therefore appears white, in contrast to the cortex of the brain, which contains nerve cell bodies and appears gray.