Figure 1.

Major demyelinating diseases of the central nervous system (CNS). The major demyelinating inflammatory CNS disorder is multiple sclerosis (MS), a progressive autoimmune disease of unknown etiology. There are other idiopathic inflammatory-demyelinating diseases (IIDDs) such as optic neuritis, neuromyelitis optica and transverse myelitis. Another IIDD is acute disseminated encephalomyelitis (ADEM), an inflammatory autoimmune disorder with a likely infectious etiology. Acute hemorrhagic leukoencephalitis (AHL), a variant of ADEM, is possibly elicited by an infectious trigger. Other demyelinating CNS diseases have an identified etiology, such as viral infections, for instance, subacute sclerosing panencephalitis (SSPE) or progressive multifocal leukoencephalopathy (PML), immunological mechanisms, toxins, metabolic disorders or ischemia.