Demyelinating Diseases

• Multiple Sclerosis – most common

  • Mostly in whites in northern latitudes, 20-40 YOA, female > male

  • Autoimmune or postviral

  • Formation of plaques in white matter that exhibit demyelination, inflammation, and gliosis

    • Gitter cells will be present

    • Plaques are separated from one another and come and go with time (get better during periods of remission)

    • Axons seem to be spared

  • Intermittent but progressive disease

    • Early C/S: paresthesias, incoordination, and mild sensory and motor symptoms of extremities

    • Late C/S: ataxia, paraplegia, and mental dysfunction

  • Variants

    • Neuromyelitis optica (Devic’s disease)

      • Demyelinating disease of spinal cord and optic tract

      • Permanent damage to axons

    • Acute MS – more accelerated form in younger patients

    • Balo concentric sclerosis – fuhgedaboudit

• Progressive multifocal leukoencephalopathy

  • Caused by JC virus (a papovirus); may rarely come from SV40

  • Opportunistic – seen in AIDS and other immunocompromised patients

  • Oligodendrocytes are affected and show intranuclear inclusions

  • Causes focal demyelinating plaques that mimic those seen in MS (plaques tend to be larger and more separated, giving a “moth-eaten” appearance)

  • See also a bizarre reactive gliosis (very atypical-looking astrocytes that aren’t infected with the virus)

  • Progressive neurologic signs and symptoms, no effective treatment

• Perivenous encephalomyelitis

  • Severe disease centered around blood vessels

  • Probably from immune-mediated reactions

  • Acute disseminated encephalomyelitis

    • Perivenous demyelination

    • Rapidly progressive and can be fatal (most patients do recover and may have neurological sequellae)

    • Usually follows a viral infection and may be an immune reaction against myelin

  • Acute necrotizing hemorrhagic encephalomyelitis

    • Similar to ADE with acute vasculitis

    • May be related to immune complex deposition; poorly understood

Category: Pathology Notes