In 1958 Aström et al described a unique demyelinating process occurring in three patients with Hodgkin's disease and chronic lymphatic leukemia, which they called progressive multifocal leukoencephalopathy.1 Pathologically there were multiple foci of demyelination of different age and size with relative sparing of axis cylinders. The white matter of posterior cerebrum was most extensively involved, but lesions were also seen elsewhere in the cerebrum and in the cerebellum, brain stem, and basal ganglia. Enlarged oligodendrocytes, some with eosinophilic intranuclear inclusions, and bizarre giant astrocytes, some with multiple and mitotic nuclei, were described. Clinically, there were progressive focal neurological signs and dementia, with death occurring in two to six months. The cerebrospinal fluid (CSF) was usually normal and the electroencephalogram diffusely and nonspecifically abnormal.
Richardson has extensively reviewed the cases of progressive multifocal leukoencephalopathy,2,3 and to date over 50 cases have been reported. Most have been associated with an