Prevalence of FTD clinical diagnostic features in patients with TDP‐43 pathology

Abstract

AbstractBackgroundFrontotemporal dementia (FTD) is a heterogeneous syndrome which includes three main clinical subtypes, behavioural variant FTD (bvFTD) and the non‐fluent and semantic variants of primary progressive aphasia (nfvPPA, svPPA). The pathology underlying clinical FTD, referred to as frontotemporal lobar degeneration (FTLD), is also heterogenous with transactive response DNA binding protein Mw 43 (FTLD‐TDP) present in ∼50%. In this study we investigate the proportion of FTLD‐TDP cases that fulfil diagnostic criteria for each of the clinical FTD subtypes.MethodWe retrospectively reviewed charts of patients with autopsy proven FTLD‐TDP. Patients with additional pathology, (e.g. Alzheimer’s disease, AD), were excluded. We extracted clinical data regarding behaviour, language and cognition, and compared these against the current FTD clinical diagnostic criteria.ResultFifteen of 24 patients (62.5%) with autopsy‐confirmed FTLD‐TDP pathology met diagnostic criteria for possible bvFTD (n=9), nfvPPA (n=3) or svPPA(n=3). The clinical diagnosis of the nine patients who did not match criteria for any of the three FTD syndromes included FTD with motor neuron disease (n=5), AD type dementia (n=3), progressive supranuclear palsy (n=1), corticobasal syndrome (n=1) and FTD with Parkinsonism linked to chromosome 17 (n=1). Patients with motor neuron disease developed 1 (n=2) or 2 (n=3) diagnostic features of bvFTD.Among the bvFTD diagnostic features, executive dysfunction was the commonest (79.2%), followed by apathy (37.5%) and disinhibition (33.3%). 70.8% of all patients and 42.9% of bvFTD patients developed clinical features of aphasia. Cognitive screening tests revealed a high prevalence of impaired short‐term recall (79.2%) and language dysfunction (83.3%) irrespective of the clinical diagnosis.ConclusionbvFTD is the commonest presentation of FTLD‐TDP; however, a significant proportion of patients do not match diagnostic criteria for FTD. Additionally, the high prevalence of impaired short‐term recall suggests it may not be practical to use this as an exclusionary criteria for FTD. We recognize the selection bias in our sample which was derived exclusively from a dementia clinic population.