Neurology update.

A Multicenter AIDS Cohort Study (MACS) demonstrates a 50-percent or greater decline in the incidence of HIV-related dementia, toxoplasmosis, cryptococcal meningitis, progressive multifocal leukoencephalopathy (PML), and primary CNS lymphoma since the 1996 introduction of highly active antiretroviral therapy (HAART). Although data on mortality and morbidity trends associated with these diseases are encouraging, people with HIV are still highly vulnerable to these conditions. PML is a terrifying neurological complication which has been resistant to a number of drugs, but cidofovir is currently being studied in an AIDS Clinical Trials Group (ACTG 363) and a European study group; results to date are controversial. Trial results are given for studies of other neurological complications of HIV. The relatively weak link between levels of HIV RNA in the brain and the onset of neurologic diseases suggests that indirect mechanisms may be critical determinants of neurologic damage.