Walsh & Hoyt: Pathology

The characteristic lesion in patients with myelinoclastic diffuse sclerosis is a large, sharply outlined, asymmetric focus of demyelination with severe, selective myelinoclasia that often affects an entire lobe or cerebral hemisphere. There is typically extension across the corpus callosum and damage to the opposite hemisphere. Both hemispheres are symmetrically affected in some cases. Careful examination of the optic nerves, brainstem, cerebellum, and spinal cord often discloses typical discrete lesions consistent with MS, and histopathologic examination of both large and small foci reveals the characteristic features reminiscent of MS, including fibrillary gliosis with formation of giant multinucleated or swollen astrocytes and perivascular cuffing with inflammatory infiltrates containing plasma cells. The axons themselves may show little damage.