Primary progressive aphasia: a review of the neurobiology of a common presentation of Pick complex.

Primary progressive aphasia (PPA) is an identifiable and distinct form of clinical presentation of focal degenerative disease. The underlying pathology is often considered heterogeneous, but we propose that, in fact, this syndrome has a characteristic underlying neurobiology related to Pick's disease and frontotemporal dementia. The authors reviewed the literature of PPA andfound 58 cases with autopsy. The majority of the cases had related underlying pathology, termed "Pick complex," a form of non-Alzheimer's dementia. This includes Pick's disease, corticobasal degeneration, dementia lacking distinctive histology, and motor neuron disease inclusions. Several of the cases described with focal Alzheimer's pathology do not fulfill the criteria of PPA, but have Alzheimer's disease with a major aphasic component.