Cognitive dysfunction in corticobasal degeneration.

Corticobasal degeneration (CBD) was originally described as a distinct clinicopathological entity in 1967. Since then, different phenotypic presentations have emerged as possible manifestations of CBD histopathological findings. In addition, pathophysiological findings and the molecular basis have been delineated and several aspects of its cognitive manifestations have been clarified. Thus, not only the spectrum of what is currently designated as CBD has expanded, but overlap with other degenerative and even secondary disorders has made clinical diagnostic certainty even more challenging in the absence of specific and readily-available markers. Cognitive deficits in CBD are now recognized as a frequent initial presentation and may appear up to eight years before the motor symptoms, depending on the phenotypic variant. Characteristic cognitive features of CBD involve language deficits, visuospatial and executive dysfunctions, apraxia, and behavioral disorders. Semantic and episodic memories are usually preserved, while language is often impaired in the early stages.