Progressive supranuclear palsy: pathology and genetics.

Progressive supranuclear palsy (PSP) is an atypical Parkinsonian disorder associated with progressive axial rigidity, vertical gaze palsy, dysarthria and dysphagia. Neuropathologically, the subthalamic nucleus and brainstem, especially the midbrain tectum and the superior cerebellar peduncle, show atrophy. The substantia nigra shows loss of pigment corresponding to nigrostriatal dopaminergic degeneration. Microscopic findings include neuronal loss, gliosis and neurofibrillary tangles in basal ganglia, diencephalon and brainstem. Characteristic tau pathology is also found in glia. The major genetic risk factor for sporadic PSP is a common variant in the gene encoding microtubule-associated protein tau (MAPT) and recent studies have suggested that this may result in the altered expression of specific tau protein isoforms. Imaging studies suggest that there may be sensitive and specific means to differentiate PSP from other parkinsonian disorders, but identification of a diagnostic biomarker is still elusive.