EP 122. The effectiveness of standard neuropsychological testing to differentiate behavioral variant of frontotemporal dementia (bvFTD) from Alzheimer’s Dementia (AD) – A retrospective clinical approach

Abstract

Objective Neuropsychological testing is crucial in diagnosing dementia syndromes. Specific patterns of neuropsychological deficits have been reported for Alzheimer‘s disease (AD) and behavioral variant of frontotemporal dementia (bvFTD). However previous studies also showed a significant overlap of neuropsychological deficits in both diseases. Whether patients with AD or bvFTD may be distinguished at initial clinical presentation by comparing their performance profile in a standard neuropsychological test battery remains indistinct. In a retrospective approach we evaluated the usefulness of a standard neuropsychological assessment for successful differential diagnosis between AD and bvFTD in early and mild disease stages. Methods We compared the cognitive profile of patients who fulfill current diagnostic criteria of AD ( N = 43) and bvFTD ( N = 30) and provide additional biomarker evidence of the underlying pathological process. Differential test performances in standard clinical tests for the domains memory, language, visuospatial skills, executive functions, praxis and emotion recognition were submitted into a stepwise discriminant analysis. Results Compared with normative sample data, both patients groups showed deterioration in all cognitive domains. Patients with AD were significantly more impaired in the domains episodic memory and visuospatial skills than patients with bvFTD. AD patients also scored lower in the subdomains processing speed , set shifting , limb imitation and pantomime of object use . Patients with bvFTD had a significantly lower performance in imitation of face postures . For successful group classification in 86.3% of our cases, the subdomains verbal short term memory , imitation of face postures , imitation of limb gestures and figure copy task were selected by a stepwise discriminant analysis. Subsequent jackknifed cross-validation of the test selection led to an accuracy of 79.5% to discriminate between the two groups. Conclusion Given that global cognitive impairment is present in patients with bvFTD as well as in patients with AD, standardized neuropsychological assessment is essential to assess the degree and profile of cognitive dysfunctions for clinical diagnosis. A test battery consisting of a memory retrieval task, a figure copy task and an apraxia tasks for limb and face imitation correctly classifies between patients with AD and bvFTD in 79.5% and supports differential diagnosis. Tests on executive function and emotion recognition are not useful to distinguish between the dementia syndromes when only assessed through standard tests without more specific and detailed assessments.