THE PATHOLOGY AND NOSOLOGY OF PRIMARY PROGRESSIVE APHASIA

We present three cases of primary progressive aphasia (PPA) with Pick- variant pathology to support a hypothesis of an underlying nosologic r elatedness. Neuropathologic examination demonstrated focal brain atrop hy with corresponding neuronal loss and gliosis, accompanied by superf icial spongiosis. Specific histologic findings were ballooned neurons (Pick cells) in the atrophic areas, and in two of the cases, Pick bodi es. They were immunoreactive for tau. In contrast to classic Pick's di sease, there were no Pick bodies in the hippocampus. The intense neuro filament immunoreactivity of the perikarya of the ballooned neurons gr eatly facilitated their recognition. Based on our cases and a critical review of the literature, we hypothesize that the common underlying p athology of PPA is a variant of Pick's disease. Furthermore, we propos e the concept of ''Pick complex'' to include other neurodegenerative d iseases characterized by focal cortical degeneration, such as PPA, fro ntal lobe dementia, ALS with PPA, and corticonigral and corticobasal g anglionic degenerations.