Inclusion bodies [Ref : Bobbin's Thie p. 13751 Involvement of C.N.S. is a common and impoant manifestation of AIDS. In addition to the lymphoid system the nervous system is a major target of HIV infection. Macrophages and microglia cells in the central nervous system that belongs to the monocyte and macrophages lineages are the predominant types in the brain that are infected with HIV. It is widely believed that HIV is carried into the brain by infected monocytes. Ninety percent of patients demonstrate some form of neurological involvement at autopsy. C.N.S. involvement in AIDS usually produces AIDS dementia complex. The pathology associated with AIDS related congnitive motor complex sometimes called subacute encephalitis is located mainly in subcoical areas with relative sparing of cerebral coex. Between 10 and 20% of I-UV-infected patients present with neurologic signs as their first clinical manifestation of infection. In some, no other signs of AIDS develop. Between 50 and 70% of all AIDS patients eventually develop some features of what is called AIDS dementia or the AIDS related cognitive-motor complex. -This term is used to describe the characteristic pattern of cognitive, motor, and behavioral dysfunction, including mood disturbances, seen in AIDS patients. At autopsy, between 60 and 90% of AIDS patients brains show some .form of pathology. Pathologic changes directly due to HIV infection (subacute encephalitis) The pathology associated with the AIDS-related cognitive-motor complex, sometimes called subacute encephalitis, is located mainly in subcoical areas, with relative sparing of cerebral coex. Microscopic changes include : - Diffuse white matter pallor - Perivascular infiltrates of lymphocytes and macrophages - Foci of necrosis, gliosis, and/or demyelination Microglial nodules, macrophages and multinucleated cells Remember, Vasculitis is characteristically absent in CNS involvement in AIDS. The virus enters the brain, probably primarily by way of nacrophages, as HIV has been localized in CNS, mainly in macrophages, microglia and multinucleated giant cells. The virus is able to reproduce in the brain. Vacuolar myelopathy - Is sometimes seen in the spinal cord. This change consists of white matter vacuolation in posterior and lateral columns, and is mainly due to swelling within mhyelin sheaths. Peripheral nervous system pathology - PNS damage is seen in some HIV-infected patients. Inflammatory demyelinating neuropathy is the primary PNS pathology.