[HIV encephalopathy--clinical aspects, neuropathology and pathogenesis]

HIV encephalopathy, which is probably primarily caused by human immunodeficiency virus, is the most common neurological disorder in HIV-infected patients and is more frequent than opportunistic diseases of the central nervous system. It is characterized most often by slowly progressing cognitive impairment, psychomotoric slowing and increasing apathy. The syndrome is found almost exclusively in the late stages of HIV infection; its frequency in patients with full-blown AIDS is estimated as being between 40 and 70%. Although numerous studies have demonstrated alterations in the electrophysiological parameters, cerebral perfusion and cerebrospinal fluid in many asymptomatic patients, there are no reliable parameters that can predict the risk of developing HIV encephalopathy. Also, there is no sufficient correlation between the extent of the frequent but mostly subtle neuropathological changes and the clinical degree of the severity of the encephalopathy. The mechanisms causing cerebral injury are poorly understood. Recent studies indicate that the indirect effects of HIV infection of the brain are the most important pathogenetic factors. In particular, certain viral proteins and cytokines produced by infected macrophages or activated microglia seem to induce neuronal dysfunction and finally loss of nerve cells.