The Neuropathology o f Diseases o f the White Matter JUSTIN PARR

The diseases of white matter compose essentially three nosological entities of a heterogeneous group. The clinical and neuropathological attention has been directed to the deficiency of myelin in more or less specific patterns and distribution as the primary characteristic, and the unique natural history and the respective cellular pathology as the modifiers which define each disease. Basically, 13 diseases are cited. Current research investigations are concerned with theoretical hypotheses based on the pathology of the human diseases, etiologically proven naturally occurring animal diseases and experimentally produced animal demyelinative diseases of central and peripheral nervous system. Hypersensitivity mecha­ nisms evoked by an immune response of the delayed type, circulating anti­ bodies, and the possibility of viruses initiating an immune response as causa­ tive by direct or indirect effects are the key subjects today. The data are most exciting and the research efforts are challenging. Direct evidence is lacking for any of the hypotheses of etiology of the human disorders of white matter except perhaps for the leukodystrophies and progressive multifocal leukoencephalopathy.