Multiple sclerosis (MS) is an autoimmune disorder that affects the central nervous system. It is a demyelinating disease that damages myelin covering nerves in the brain and spinal cord. In general, the age of onset is between 20 and 50 years, although onset can occur in childhood; women are more likely to be affected than men.

Patients may initially present with optic neuritis or transverse myelitis, although there is a wide range of symptoms depending on where lesions occur. Attacks can include motor, sensory, visual, or autonomic symptoms. There may be relapses and remissions (relapsing-remitting multiple sclerosis [RRMS]) or steady accumulation of disease and disability (progressive MS). Over 80% of patients initially follow a relapsing-remitting course, characterized by recurrent neurologic deficits, followed by partial or complete recovery. Some of these patients may later develop a steady accumulation of deficits (secondary progressive MS). About 10%-15% of patients have a progressive course from the onset characterized by gradual onset of neurologic symptoms and continued clinical deterioration. There is no cure, and permanent neurologic deficits and cognitive decline usually occur as the disease progresses.