Cause is unknown. Familial incidence is low. Whites are more susceptible than blacks and Asians.
Pregnancy decreases risk of exacerbations, but exacerbations increase immediately post partum.
Infection or trauma may precipitate or trigger exacerbations. Clinical Manifestations Acute onset of symptoms usually lasting for several weeks but may persist for only a few minutes or hours. Common symptoms include weakness or numbness of a limb, monocular visual loss, diplopia, vertigo, facial weakness or numbness, sphincter disturbances, ataxia, and nystagmus. A history of symptoms aggravated by a hot bath is sometimes obtained. MRI is as sensitive as CSF exam and is the neuroimaging test of choice with gadolinium enhancement, which can differentiate new lesions from old ones.