To determine the change of incidence and prevalence of neurological disorders caused by the human immunodeficiency virus (HIV) and opportunistic infections in HIV positive patients under treatment since the introduction of highly active antiretroviral therapy (HAART).

The data of all HIV infected patients were retrospectively analysed, who were examined in the HIV outpatients clinic of the neurological department of the University Clinic Essen between 1995 and 1998 (n=563, total number of visits=735). Data from identified patients were divided into two groups according to the time of examination from 1995 to 1996 (334 visits) and from 1997 to 1998 (401 visits). The incidence and prevalence of neurological disorders were statistically compared between both time intervals.

Significantly more patients received HAART in 1997–8 (p<0.001) and mean CD4+ cell count was significantly higher in 1997–8 (p<0.001). The prevalence of HIV associated dementia and HIV associated polyneuropathy were significantly lower in 1997–8 (both: p=0.02) and the incidence of toxoplasma encephalitis decreased from 5.7% in 1995–6 to 2.2% in 1997–8 (p=0.015). Based on the small number of patients significant changes in HIV associated myopathy, progressive multifocal leukoencephalopathy, cryptoccocal meningitis, and cytomegalovirus-encephalitis could not be detected.

The prevalence of the most frequent HIV associated neurological disorders and incidence of toxoplasma encephalitis decreased since the introduction of HAART. This may be due to the improvement of immunostatus by HAART as demonstrated by the higher CD4+ cell count in the later time interval. Direct antiretroviral effects within the nervous system may be considered causative as well. The prevalence and incidence of HIV associated neurological disorders and opportunistic CNS infections decreased after introduction of HAART.