Progressive supranuclear palsy with asymmetric tau pathology presenting with unilateral limb dystonia

We report an autopsy case of a 77-year-old Japanese man with a 7-year history of progressive unilateral left limb dystonia and arm levitation. Brain computed tomography showed fronto-temporal atrophy. The patient was diagnosed as having corticobasal degeneration. Histopathologically, the cerebral cortices, especially of the parasagittal region, and subcortical nuclei revealed numerous Gallyas/tau-positive cytoplasmic inclusions characteristic of progressive supranuclear palsy (PSP). Grumose degeneration was evident in the dentate nucleus. Astrocytic plaques were not present, but a small number of ballooned neurons were found in the fronto-temporal regions. The involvement by the PSP lesions was quite asymmetric in the affected areas, including the frontal cortices, basal ganglia, red nuclei, and inferior olivary nuclei, being more prominent on the side contralateral to the side of limb dystonia. The apparent unilateral dominance of PSP pathology may be relevant to the asymmetric clinical presentation of this patient.