Clusters of cognitive and behavioral disorders clearly distinguish primary progressive aphasia from frontal lobe dementia, and Alzheimer's disease.

BACKGROUND/AIMS Frontal lobe dementia (FLD) and primary nonfluent progressive aphasia (PnPA) are two forms of frontotemporal lobe degeneration. The relationship between these conditions remains unclear. Our study aimed to better define the behavioral and cognitive clusters characterizing PnPA patients. METHODS We cognitively and behaviorally evaluated three groups of newly diagnosed patients affected by Alzheimer's disease (AD, n=20), FLD (n=22) and PnPA (n=10), in order to assess the cognitive-behavioral pattern of PnPA, compared to both FLD and AD. RESULTS We found, as expected, worse performances in episodic memory in AD, of both the verbal fluency and naming tasks in PnPA, while FLD mainly showed behavioral disorders associated with an unremarkable deficit in the executive tasks. PnPA was not characterized by any significant behavioral disorders. Factor analysis-extracted three main factors ('mnesic', 'behavioral' and 'linguistic') clearly correlated to each group. A discriminant analysis based on the extracted factors correctly classified 84.6% of all patients. CONCLUSION The evidence of a characteristics cognitive profile, without any significant behavioral changes, highlights that PnPA is different from other forms of frontotemporal lobe degeneration regarding both the cognitive and behavioral patterns; thus, it should be considered independently in further studies.