Alzheimer's disease and frontal variant of frontotemporal dementia: A very brief battery for cognitive and behavioural distinction

The aim of this study was to investigate whether a brief neuropsychological battery consisting of a limited number of cognitive tests and an evaluation of the behavioural domains intended to discriminate between frontotemporal dementia (fv-FTD) and Alzheimer's disease (AD), constitutes a useful instrument for making a differential clinical diagnosis between these two pathologies. Nineteen fv-FTD and 39 AD patients were compared on cognitive tasks (assessing memory, executive functions, language and constructional praxis) and on the NPI behavioural assessment. A stepwise discriminant analysis was performed to identify the linear combination of cognitive and behavioural measures able to best discriminate between the two groups. One test for each of the investigated cognitive domains (Delayed Prose Recall, FAS verbal fluency, Boston naming test, Rey's Figure A Copy) and the four subscales of the Neuropsychiatry Inventory (NPI) which best differentiated between fv-FTD and AD patients (apathy, disinhibition, euphoria, aberrant motor behaviour) were used. The analysis selected Rey's Figure A Copy, FAS verbal fluency and NPI apathy subscale as the best discriminants between fv-FTD and AD patients. The final equation assigned 73.7% of the fv-FTD patients and 94.7% of the AD patients to the correct diagnostic group. A validation study conducted on a new independent sample of 11 fv-FTD and 22 AD patients confirmed the high sensitivity (82.6 %) and specificity (81.8%) of the diagnostic equation in assigning fv-FTD and AD patients to the correct dementia group. Although both cognitive and behavioural differences exist between FTD and AD, previous studies have aimed at differentiating the two pathologies by considering the two aspects separately and discriminant analyses were focused only on neuropsychological or neuropsychiatric evaluations. The present results emphasise the importance of rating both cognitive and behavioural clinical features of the two syndromes as objectively as possible to improve differential diagnostic accuracy.