Progress in PSP and CBD

Abstract

While progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) are neurodegenerative disorders with shared clinical and pathologic features, there are notable differences that warrant their continued separation as clinicopathologic entities. They are both hypokinetic extrapyramidal disorders, but unlike idiopathic Parkinson’s disease, neither PSP nor CBD are responsive to levodopa. Extrapyramidal signs are usually symmetrical in PSP and asymmetrical in CBD, but there are exceptions. Focal cortical signs, such as apraxia and aphasia, are common in CBD, but not in PSP. A frontal type dementia is more common in CBD than PSP. PSP has downward gaze palsy early in the disease, and this is a means of differentiating PSP and CBD. Pathologically, both PSP and CBD are associated with neuronal and glial filamentous inclusions composed of tau protein, but the morphology of neuronal and glial lesions and their distribution differ in PSP and CBD. Pathology of the cortical gray and white matter are prominent in CBD, but usually mild in PSP, while deep gray matter lesions are more marked in PSP than CBD. PSP and CBD are both associated with accumulation of insoluble tau protein in the brain, with more in supratentorial areas in CBD than PSP. They are usually nonfamilial or sporadic “tauopathies,” but genetic studies suggest that polymorphisms in the tau gene are similar in PSP and CBD. The present review describes some recent progress in the neuropathology, genetics and biochemistry of PSP and CBD.