ASTROCYTIC PLAQUES AND TUFTS OF ABNORMAL FIBERS DO NOT COEXIST IN CORTICOBASAL DEGENERATION AND PROGRESSIVE SUPRANUCLEAR PALSY

Corticobasal degeneration (CBD) and progressive supranuclear palsy (PS P) are characterized by their unique clinical features and neuronal pa thology. Although astrocytic plaques and tufts of abnormal fibers have been suggested to be specific histopathologic markers, recent studies have revealed significant clinicopathologic overlap between CBD and P SP Based on the distinctive camera lucida profile of astrocytic inclus ions on Gallyas-Braak silver staining, we found that astrocytic plaque s and tufts of abnormal fibers did not coexist in the same patient amo ng 30 cases of clinically diagnosed CBD, PSP and atypical Parkinson's disease. Using Tau immunohistochemistry it was difficult to verify the absence of tufts of abnormal fibers. A morphometric analysis revealed that the two groups classified by the presence or absence of astrocyt ic plaques and tufts of abnormal fibers exhibited significant differen ces in the density of ballooned neurons and neurofibrillary tangles an d degeneration of the subcortical nuclei. Assessment using the NINDS n europathologic criteria revealed that the cases with astrocytic plaque s and tufts of abnormal fibers closely correspond to CBD and typical P SP, respectively. In addition, the cases lacking either of these two a strocytic inclusions had atypical PSP according to the NINDS criteria, and were associated with novel tau-positive astrocytes (spiny astrocy tes). We thus conclude that astrocytic plaques and tufts of abnormal f ibers are highly characteristic structures for CBD and typical PSP, re spectively. We emphasize the importance of strict differentiation betw een different astrocytic inclusions not only for diagnosis, but also f or further studies for elucidation of their role in the disease mechan isms of CBD and PSP.