Cortical degeneration in progressive supranuclear palsy. A comparison with cortical-basal ganglionic degeneration

We report 3 patients with progressive supranuclear palsy (PSP) who developed limb apraxia, focal dystonia, and arm levitation late in the course of the disease. Neuropathological examination revealed cortical degeneration in addition to the characteristic pathological findings of PSP. Semiquantitative comparative histological and immunohistological studies of the neocortex of these patients as well as 5 cases of classical PSP and 4 cases of cortical-basal ganglionic degeneration (CBGD) revealed a distinctive form of cortical degeneration in PSP. The cortical degeneration was often circumscribed and confined to premotor and motor cortex. It was characterized by neuronal loss and gliosis. Swollen neurons were only rarely observed in neocortex of PSP cases in contrast with CBGD, where they were abundant. Neuronal and glial tau as well as tau immunoreactive threads were seen in both PSP and CBGD, but were more abundant in CBGD. The appearance of tau reactive astrocytes also differed in both disorders; tufted astrocytes were seen exclusively in PSP, while typical annular astrocytic plaques were confined to CBGD. These observations indicate that cortical degeneration occurs in PSP and may be associated with atypical clinical manifestations that lead to diagnostic difficulties.