CONCENTRIC SCLEROSIS (BALO) - MORPHOMETRIC AND IN-SITU HYBRIDIZATION STUDY OF LESIONS IN 6 PATIENTS

Brain tissues from 6 patients with concentric sclerosis (Balo) were ex amined by in situ hybridization, immunocytochemistry, morphometry, and histological methods. The patients were 24 to 48 years old and had pr ogressive cerebral symptoms and signs that lasted 15 to 100 days. Larg e demyelinative lesions, most frequent in the frontal white matter, co ntained alternating bands of demyelinated and partly myelinated white matter that were arranged in concentric or mosaic patterns. In the are as of demyelination, axons were relatively well preserved and there we re perivascular inflammatory infiltrates. In 2 specimens, lesions cont ained regions with the characteristic appearance of actively demyelina ting multiple sclerosis plaques. Oligodendroglial densities were highe st in normal-appearing white matter, lower in partially myelinated are as, and lowest in demyelinated areas, which also contained many hypert rophic astrocytes closely associated with oligodendroglia. Messenger R NA levels for myelin-related proteins followed the same pattern; they were lowest in demyelinated areas, higher in partially myelinated area s, and highest in normal-appearing white matter beyond lesion margins. Our findings suggest that concentric sclerosis is a variant of multip le sclerosis, that oligodendroglial loss is important in the pathogene sis of demyelination, and that partially myelinated areas probably rep resent stages of ongoing myelin breakdown rather than remyelination of previously demyelinated areas.