Multiple sclerosis (MS) is characterized by disseminated patches of demyelination in the brain and spinal cord. Common symptoms include visual and oculomotor abnormalities, paresthesias, weakness, spasticity, urinary dysfunction, and mild cognitive symptoms. Typically, neurologic deficits are multiple, with remissions and exacerbations gradually producing disability. Diagnosis requires clinical or MRI evidence of ≥ 2 characteristic neurologic lesions that are separated in both time and space (location in the central nervous system [CNS]). Treatment includes corticosteroids for acute exacerbations, immunomodulatory drugs to prevent exacerbations, and supportive measures.
(See also Overview of Demyelinating Disorders.)
Multiple sclerosis is believed to involve an immunologic mechanism. One postulated cause is infection by a latent virus (possibly a human herpesvirus such as Epstein-Barr virus), which, when activated, triggers a secondary autoimmune response.
An increased incidence among certain families and presence of human leukocyte antigen (HLA) allotypes (HLA-DR2) suggests genetic susceptibility.
MS is more common among people who spend their first 15 years of life in temperate climates (1/2000) than in those who spend them in the tropics (1/10,000). One explanation is that lower levels of vitamin D are associated with an increased risk of MS, and vitamin D levels correlate with the degree of sun exposure, which is lower in temperate climates. Cigarette smoking also appears to increase risk.
Age at onset ranges from 15 to 60 years, typically 20 to 40 years; women are affected somewhat more often.
Neuromyelitis optica spectrum disorder (Devic disease), previously considered a variant of MS, is now recognized as a separate disorder.
