Multiple sclerosis (MS) is a chronic autoimmune, inflammatory neurological disease of the central nervous system (CNS).
MS attacks the myelinated axons in the CNS, destroying the myelin and the axons to varying degrees.
Its course is highly varied and unpredictable. In most patients, the disease is characterized initially by episodes of reversible neurological deficits, which is often followed by progressive neurological deterioration over time - 50% of patients will need help walking within 15 years after the onset of the disease.
MS typically presents in adults 20 to 45 years of age; occasionally, it presents in childhood or late middle age. Twice as many women are affected as men.
The disease is diagnosed on the basis of clinical findings and supporting evidence from ancillary tests, such as magnetic resonance imaging (MRI) of the brain and examination of the cerebrospinal fluid (CSF).
The cause is unknown, but it appears to involve a combination of genetic susceptibility and a nongenetic trigger, such as a virus, metabolism, or environmental factors, that together result in a self-sustaining autoimmune disorder that leads to recurrent immune attacks on the CNS.
Patients may be grouped into four major categories based on the course of disease:
- Relapsing–remitting MS: the most common form, affecting about 85% of MS patients.
- Secondary progressive MS: may develop in some patients with relapsing–remitting disease.
- Primary progressive MS: affects approximately 10% of MS patients.
- Progressive-relapsing MS: a rare form, affecting fewer than 5% of patients.
There is no single diagnostic test for MS. The diagnosis is based on evidence of (1) at least two different lesions (plaques or scars) in the white matter of the CNS (the space dissemination criterion); (2) at least two different episodes in the disease course (the time dissemination criterion); and (3) chronic inflammation of the CNS, as determined by analysis of the CSF (the inflammatory criterion).
The presence of one or more of these criteria allows a general diagnosis of MS, which may be refined according to the subsequent course of the disease.
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Adapted from Goldenberg MM. Multiple sclerosis review. P T. 2012 Mar; 37(3): 175–184. Internet. Accessed on July 15, 2016.