Demyelination is a degenerative process that erodes away the myelin sheath that normally protects nerve fibers. Demyelination exposes these fibers and appears to cause problems in nerve impulse conduction that may affect many physical systems. Demyelinization is seen in a number of diseases, particularly multiple sclerosis, transverse myelitis, Devic's disease, progressive multifocal leukoencephalopathy, Optic neuritis.
Optic neuritis and transverse myelitis are separate items and should not be counted as demyelinating disease, but separately.