[Progressive multifocal leukoencephalopathy. Clinical, CT scan and neuropathologic findings. Apropos of 4 cases].

Four cases of progressive multifocal leukoencephalopaty are reported, 3 of them with an ultrastructural study and 2 with a C.T. scan study. In 2 cases, there were no other associated pathological condition. In 1 case chronic alcoholism only was present; in the last case a primitive hemochromatosis with a prevailing hepatic dysfunction was evidenced. In 2 of these cases, the initial clinical picture was made of mental disorders while it was made of a progressive left hemiparesis in one case and of a brain stem syndrome in the other case. The results of neuroradiological and isotopical investigations remained negative throughout the evolution in the 4 cases except for some C.T. scan abnormalities. Indeed, in 2 cases the C.T. scan evidenced brain lesions identified as large demyelinated areas. These were low density areas non altered by contrast and unaccompanied by any mass effect. These areas were not seen when the first clinical signs were present and thus, normality of C.T. scan appears not to allow infirmation of the diagnosis of progressive multifocal leukoencephalopathy. In the 4 cases the pathological study showed characteristic lesions of the white matter. Mononucleated cells inflammatory infiltration was observed at the periphery of the demyelinizated regions. This may be related with the primitive aspect of these cases. An ultrastructural study was performed in 3 cases: viral inclusions were present not only in the nucleus of oligodendrocytes but also in their cytoplasm and in some astrocytes.