The fine structure of plaques fibromyéliniques in ulegyria and in status marmoratus

Summary A 12 year old boy with a history of perinatal injury resulting in encephaloclastic porencephaly is described. Electron microscopic examination of the plaques fibromyéliniques in areas of ulegyria and status marmoratus revealed that they mainly consist of fibrillated processes, apparently of astrocytic origin, surrounded by myelin lamellae. Hypermyelinization of some of these processes was also present. These observations suggest excessive regenerative activity on the part of myelin-forming glial cells.This work was supported by Neuropathology Training Grant 5T01-NB-05500-3 and Research Grant NB A1 07380-01A1 from the National Institute of Neurological Diseases and Stroke, U. S. Public Health Service, Bethesda, Maryland.