Relationship between frontotemporal dementia and corticobasal degeneration/progressive supranuclear palsy.

Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) were described as separate entities, but prior to that an extrapyramidal variety of Pick's disease was recognized. Subsequently a pathological overlap between these conditions and clinical overlap between frontotemporal dementia, primary progressive aphasia, corticobasal degeneration syndrome and more recently PSP was recognized. Initially only the movement disorder had been emphasized, but now the behavioral and language symptoms are considered common. The syndromes of frontotemporal dementia/Pick's disease can be produced by underlying CBD, PSP or Pick pathology as well as with neural inclusions of the motor neuron disease type. The concept of this overlap has been confirmed genetically finding a similar spectrum of pathology with different tau mutations and even with tau negative pathology, which could be a deficiency of normal tau. The overlap of CBD with PSP and both with PPA and FTD allows to consider these relatively rare conditions as part of a more commonly occurring degenerative disease than previously recognized.