Focal brain lesions in patients with AIDS: aetiologies and corresponding radiological patterns in a prospective study.

We report the results of a hospital-based study of 188 consecutive patients seropositive for the human immune deficiency virus type 1 (HIV-1) who presented in a 4-year period (1988-1991) with possible signs or symptoms of first-ever central nervous system disease. Confirmed diagnoses were cerebral toxoplasmosis in 47 patients (25.0%), HIV-1 encephalopathy in 19 (10.1%), progressive multifocal leucoencephalopathy (PML) in 9 (4.8%), cerebral lymphoma in 1 (0.5%), and other conditions in 9 patients (4.8%). Seventy-three subjects (38.8%) showed focal brain lesions on initial computed tomography or magnetic resonance imaging, which were assessed prospectively. Positive predictivity for toxoplasmosis was 100% if multiple lesions occurred in combination with mass effect or contrast enhancement (23 patients), or if at least one space-occupying or enhancing lesion was located in the basal ganglia or the thalamus (26 patients). Solitary lesions with mass effect or contrast enhancement were seen in 26 patients and were caused by cerebral toxoplasmosis in 22 (84.6%). Eight of the 9 PML patients presented with one or more non-enhancing, non-mass lesions, although the predictive value of this pattern was low (47.1% for PML). Thus, in our epidemiological context, certain imaging findings in HIV-1-seropositive patients were highly predictive of cerebral toxoplasmosis. This may differ from findings from other parts of the world where cerebral toxoplasmosis may be less prevalent among HIV-1-infected individuals.