Neuropathology of acquired immunodeficiency syndrome.

The nervous system is involved in the acquired immunodeficiency syndrome (AIDS) by infections and infestations, by neoplasms, and by several diseases of uncertain pathogenesis. The most common pathological abnormalities are the changes associated with the HIV agent itself, the 'HIV subacute encephalitis'; the most specific change is demyelination with multinucleate giant cells. Cytomegalovirus (CMV) is the most common secondary virus, but progressive multifocal leucoencephalopathy (PML) is more frequently seen at biopsy. Toxoplasmosis is the most common cause of abscess formation, but fungal infections, especially by cryptococcus, are more often the cause of meningitis. Mycobacterial infections and other opportunistic organisms are relatively rarely seen in the CNS. A vacuolar myelopathy of unknown pathogenesis is seen in AIDS; it involves the dorsal and lateral columns and the thoracic spinal cord most prominently. Endarteritis of unknown cause with resultant infarction is seen in children. Primary CNS lymphoma accounts for a major percentage of the lymphomas seen in AIDS; they are high grade tumours, are most often multiple, and are of B-cell origin. Metastatic Kaposi's sarcoma is very rare. Several peripheral neuropathies occur in AIDS, and recently a myopathy with small rod bodies has been reported.