Pathological and Clinical Spectrum of Progressive Supranuclear Palsy: With Special Reference to Astrocytic Tau Pathology

Progressive supranuclear palsy (PSP) is a four‐repeat tauopathy with tau‐positive, argyrophilic tuft‐shaped astrocytes (TAs). We performed a pathological and clinical investigation in 40 consecutive autopsied Japanese patients with pathological diagnoses of PSP or PSP‐like disease. Unequivocal TAs were present in 22 cases, all of which were confirmed to be PSP. Such TAs were hardly detected in the other 18 cases, which instead exhibited tau‐positive, argyrophilic astrocytes, appearing as comparatively small clusters with central nuclei of irregularly shaped, coarse structures (equivocal TAs). Cluster analysis of the distribution pattern of tau‐related pathology for these 18 cases identified two subgroups, pallido‐nigro‐luysian atrophy (PNLA) Type 1 (n = 9) and Type 2 (n = 9), the former being distinguished from the latter by the presence of tau‐related lesions in the motor cortex, pontine nucleus and cerebellar dentate nucleus in addition to the severely affected PNL system. The duration from symptom onset until becoming wheelchair‐bound was significantly longer in PNLA Type 1. Immunoblotting of samples from the three disease conditions revealed band patterns of low‐molecular‐mass tau fragments at ～35 kDa. These findings shed further light on the wide pathological and clinical spectrum of four‐repeat tauopathy, representing PSP in the broad sense rather than classical PSP.