Multiple Sclerosis: Glossary of Terms

Glossary of terms
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  • Atrophy: A shrinkage or reduction in volume. Often used in describing brain or spinal cord shrinkage with disease.
  • Axon: A nerve fiber that carries information from the nerve cell to other nerve cells or muscle fibers.
  • Brainstem: The back part of the brain above the base of the skull. Many nerves to the face come from this area.
  • Central nervous system: The brain and spinal cord. The central nervous system is different from the peripheral nervous system, which consists of the nerves and muscles outside of the spinal cord.
  • Cerebrospinal fluid (CSF): A clear, colorless fluid that circulates in and around the brain and spinal cord. The CSF cushions the brain from hitting the inside of the skull and may be important in removing chemicals from the brain.
  • Demyelination: A process in which the myelin that covers many nerve fibers is stripped off by disease.
  • Dysfunction: A medical term that describes abnormal function in a tissue or organ, usually based on disease.
  • Evoked potentials: Tests that check nerve conduction in brain, spinal cord, and other nerves. They may show slowing in people with MS.
  • Exacerbation: An episode usually lasting days to weeks, not caused by fever or illness, where there are new or worsened neurological symptoms in patients with MS. Note that exacerbation = attack = relapse = flare; they are all terms for the same thing.
  • Gadolinium: A dye made of a heavy material (gadolinium) sometimes used in MRI. It is injected into a vein and helps better define the tissues of the body on MRI.
  • Inflammation: A process where white blood cells, as well as chemical messengers, go to an area of the body to stimulate healing or to attack viruses or foreign material in the body.
  • Lesion: A localized area of abnormality. In MS, it is usually an area in the brain or spinal cord. This is not a specific term but is just a description of a finding usually seen on MRI or sometimes CT scanning.
  • Lumbar puncture (LP): Also called a spinal tap. An LP is a test where fluid is taken from the central nervous system, usually by placing a needle in the lower back. It tests for abnormalities in the cerebrospinal fluid.
  • Magnetic resonance imaging (MRI): The key way that doctors are able to look at the brain and spinal cord. This test is done in a very powerful magnet that shows the appearance of the inner tissues of the body.
  • Myelin: The material that is produced by oligodendrocytes in the central nervous system. Myelin wraps around the axons of many of the nerves. It helps speed nerve activity and insulates electrical conduction in the nerves.
  • Oligoclonal bands: Abnormal bands of proteins seen in certain spinal fluid tests that indicate activity of the immune system in and around the spinal fluid pathways.
  • Oligodendrocyte: The cell in the central nervous system that makes myelin.
  • Primary progressive MS: A form of MS, patients do not have attacks but instead have a slowly worsening disease over time.
  • Progression of MS: In some patients with MS the course is progressive, so that patients gradually worsen over months or years independent of their exacerbations.
  • Relapsing-remitting MS: Refers to a form of MS where patients experience relapses of symptoms and signs (exacerbations), with complete or partial improvement between attacks (remitting).
  • Secondary progressive MS: A form of MS in which patients may continue to have attacks, but also show a gradually progressive worsening of their function over time. The worsening is separate from any attacks.
  • Spinal cord: The major part of the nervous system that carries information up and down the spine from the brain to the nerves and from the nerves to the brain. It is affected in many people with MS.
  • Ventricles: Normal fluid-filled spaces in the brain. They contain the cerebrospinal fluid. Many MS lesions touch the surface of the brain where it contacts the ventricles. (A periventricular location is an ‘around the ventricle’ location).
  • White matter lesions: Refers to localized changes in the white matter; in MS, these are plaques or lesions. There are other white matter lesions in patients with other disorders.​

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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or healthcare provider. Please consult your healthcare provider for advice about a specific medical condition.

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