[Impaired visual perception in progressive multifocal leukoencephalopathy; a clinical diagnosis based on sequential computerized axial tomography (author's transl)].

Progressive multifocal leukoencephalopathy (PML) is a viral illness affecting principally cerebral white matter of patients, who have diminished immunologic resistance. A patient is presented, whose initial complaint was blurred vision. Relentless progression over a period of seven months to left hemianopsia, prosopagnosia, alexia with agraphia and eventually cortical blindness was observed. Accompanying the visual impairment was a steady deterioration of mental function. Sequential computerized axial tomography defined low density lesions in the occipital white matter with sparing of the cortical ribbon. As hemianopsia progressed to cortical blindness, the scans confirmed the evolution of bilaterial occipital lesions. The diagnosis was made clinically and established on histological and cultural grounds. Computerized tomography seems to be valuable in diagnosis and monitoring progress of PML.