Multiple sclerosis (MS) is an immune-mediated inflammatory disease that attacks myelinated axons in the central nervous system (CNS), destroying the myelin and the axon in variable degrees. In most cases, the disease follows a relapsing-remitting pattern, with short-term episodes of neurologic deficits that resolve completely or almost completely. A minority of patients experience steadily progressive neurologic deterioration.
The cause of MS is not known, but it likely involves a combination of genetic susceptibility and a nongenetic trigger (eg, viral infection, low vitamin D levels) that together result in a self-sustaining autoimmune disorder that leads to recurrent immune attacks on the CNS (see Etiology). Geographic variation in the incidence of MS (see Epidemiology) supports the probability that environmental factors are involved in the etiology.
MS is diagnosed on the basis of clinical findings and supporting evidence from ancillary tests, such as magnetic resonance imaging (MRI) of the brain and cerebrospinal fluid examination. (See Workup.) Traditionally, MS could not be diagnosed after only a single symptomatic episode, as diagnosis required the occurrence of repeat attacks suggesting the appearance of lesions separated in time and space; however, recent guidelines allow diagnosis of MS even with a first clinical episode.
A common misconception is that any attack of CNS demyelination means a diagnosis of acute MS. When a patient has a first attack of demyelination, the physician should not rush to diagnose MS, because the differential diagnosis includes a number of other diseases. For example, MS must be distinguished from other neuroinflammatory disorders (see DDx.)
Treatment consists of immunomodulatory therapy for the underlying immune disorder and management of symptoms, as well as nonpharmacologic treatments, such as physical and occupational therapy (see Treatment). In the United States, various disease-modifying agents for MS are currently approved for use in relapsing MS
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