Acute Multiple Sclerosis

Brain tissue from a 16-year-old boy with an 18-month clinical history of acute multiple sclerosis (MS) was examined byelectron microscopy. Grossly visible plaques existed; at the peripheries and in unaffected areas of white matter, many vessels were surrounded by lymphocytic infiltrates, plasmocytes, foamy macrophages, and rims of demyelination. Cellular infiltration appeared a primary event in forming MS lesions. Chronic lesions contained perivascular cuffs of foamy macrophages. In acute and chronic lesions, these cells frequently displayed intranuclear inclusions identical to those described previously in chronic relapsing MS. These cells had nucleochromatin dispersed as a fibrillar network. Individual filaments were 15 nm across, sometimes tubular and cross-striated—somewhatreminiscent of paramyxovirus nucleocapsids. Specific virologic and immunologic studies are needed before these inclusions can be positively identified as viral.