Teaching Case

HIV-positive woman presented with progressive ataxia, dysarthria and hyperthermia. Antitoxoplasma therapy was started but had no effect. Subsequently she was admitted to the emergency department with a bipyramidal syndrome. CT and MRI were performed prior to brain biopsy.

A 32-year-old HIV-positive woman presented with progressive ataxia, dysarthria and hyperthermia. Antitoxoplasma therapy was started but had no effect. Subsequently she was admitted to the emergency department with a bipyramidal syndrome. CT and MRI were performed prior to brain biopsy. Histological examination of the tissue sample, obtained by stereotactic biopsy from the right cerebellar hemisphere showed progressive multifocal leukoencephalopathy (PML).

Progressive Multifocal Leukoencephalopathy (PML) is an uncommon demyelinating disease that occurs in immuno-compromised patients (lymphoma, leukemia, carcinomatosis, AIDS). The incidence of PML in adult AIDS-patients has been estimated to be up to 4%. PML is caused by central nervous system infection by group B Human Papovaviruses (Jacob-Creutzfeldt virus, simian virus 40), destroying principally oligodendroglia, thus resulting in extensive demyelination. The clinical manifestations are those of multiple, progressively enlarging lesions of the cerebral and cerebellar fiber systems: motor system abnormalities, visual loss, dementia and ultimately death, which occurs four to six months after onset. The typical distribution of PML is bilateral, asymetric with a predilection for the white matter of the posterior centrum semiovale. The lesions initially tend to be focal and circumscribed; later they become confluent and large. CT scan shows focal, non-enhancing regions of low attenuation without mass effect. MRI, the most sensitive imaging modality for white matter disease, reveals patchy, poorly defined areas of hyperintensity in the white matter on T2- weighted images; hypointense, mostly non-enhancing on T1-weighted images. In AIDS-patients PML increasingly occurs in unusual locations: primary involvement of the cortex, the basal ganglia, the thalamus, the cerebellum and the brainstem is observed in up to 50% of AIDS-patients with proven PML. The lesions may also behave slightly different from the classical pattern, showing discrete contrast enhancement. Hemorrhagic transformation with spontaneous hyperintensity on T1-weighted images is a rare finding. Thus, imaging studies may help to identify and distinguish PML from lymphoma and toxoplasma abscesses, which both appear as focal mass lesions with ring enhancement.