Clinical comparison of progressive aphasia associated with Alzheimer versus FTD-spectrum pathology.

Objective: Recent post-mortem studies indicate that 30-40% of patients with clinically diagnosed progressive aphasia (PA) have Alzheimer's disease pathology, while the remainder have pathology in the FTD spectrum. This study aimed to compare the clinical features of patients from these two groups.
Materials and Methods: A retrospective chart review was conducted on 33 pathologically verified PA patients: n=13 AD and n=20 FTD-spectrum pathology. Demographics, global cognitive function, non-verbal memory, neuropsychiatric symptoms and structural imaging were compared between the two pathology-confirmed groups.
Results: The median survival was 6.3 years in the FTD group versus 8.1 years in the AD group, in spite of the fact that onset for AD was on average 2.0 years older than FTD. Features highly specific in predicting FTD-spectrum pathology were age of onset before 60 years, preference for sweet food, disinhibition and focal knife-edge frontotemporal atrophy, although the sensitivity for each of these was remarkably low (highest sensitivity was 45% for disinhibition). Some clinical features hypothesised to distinguish AD from FTD-spectrum pathology, such as global functional impairment within 2 years of onset and poor non-verbal memory ability, were not useful in separating the two groups.
Conclusions: If present, certain clinical and imaging features can help to identify PA with FTD-spectrum pathology, notably the presence of the neuropsychiatric features seen with behavioural presentations of FTD and knife-edge atrophy on structural imaging. The profile of non-linguistic cognitive deficits does not appear to be discriminatory, though prospective studies are needed to evaluate this issue further.