New criteria for frontotemporal dementia syndromes: clinical and pathological diagnostic implications

Abstract

Objective: To assess the impact of new clinical diagnostic criteria for frontotemporal dementia (FTD) syndromes, including primary progressive aphasias (PPA), on prior clinical diagnosis and to explore clinicopathological correlations.

Methods: 178 consecutive neuropathologically ascertained cases initially diagnosed with a FTD syndrome were collected through specialist programmes: the Cambridge Brain Bank, UK, and Sydney Brain Bank, Australia. 135 cases were reclassified using the revised diagnostic criteria into behavioural variant (bvFTD), semantic variant PPA (sv-PPA), non-fluent/agrammatic variant PPA (nfv-PPA) and logopenic variant PPA (lv-PPA). Pathological diagnoses included FTLD-tau, FTLD-TDP, FTLD-FUS, FTLD-UPS, FLTD-ni and Alzheimer's disease (AD). Statistical analyses included χ(2) tests, analyses of variance and discriminant statistics.

Results: Comparison of the original and revised diagnosis revealed no change in 90% of bvFTD and sv-PPA cases. By contrast, 51% of nfv-PPA cases were reclassified as lv-PPA, with apraxia of speech and sentence repetition assisting in differentiation. Previous patterns of pathology were confirmed, although more AD cases occurred in FTD syndromes (10% bvFTD, ∼15% sv-PPA and ∼30% nfv-PPA) than expected. AD was the dominant pathology (77%) of lv-PPA. Discriminant analyses revealed that object agnosia, phonological errors and neuropsychiatric features differentiated AD from FTLD.

Conclusions: This study provides pathological validation that the new criteria assist with separating PPA cases with AD pathology into the new lv-PPA syndrome and found that a number of diagnostic clinical features (disinhibition, food preferences and naming) did not assist in discriminating the different FTD syndromes.

Keywords: Alzheimer's Disease; Aphasia; Behavioural Disorder; Dementia; Neuropathology.