Environmental dependency (ED) behaviours, such as imitation behaviour (IB) and incidental utilization behaviour (UB), are considered pathognomonic of a frontal lesion and can play a unique role in diagnosing behavioural variant frontotemporal dementia (bvFTD). However, with only few focused observations of ED behaviour reported in earlier studies, their roles in the diagnosis of bvFTD have so far remained supportive. In this observational study, conducted in the cognitive clinic of a tertiary-care hospital, we explored the hypotheses that a focused and systematic search could uncover more ED behaviours in patients with bvFTD, and that the presence of ED behaviours such as incidental UB and IB should allow us to cleanly differentiate bvFTD from AD. Forty-one bvFTD patients and 75 probable AD patients, all diagnosed using accepted criteria, were seen by a neurologist and a neuropsychologist. Information regarding ED behaviour was obtained from the caregiver's history, observations for spontaneous behaviour and induction of the behaviour in the clinic. All ED behaviours were significantly more frequent in bvFTD compared with AD. UB (78 %; 66 % incidental) and IB (59 %) occurred exclusively in bvFTD. Multi-pronged and focused clinical assessment contributed to the high frequency of ED behaviours. Nearly two-thirds of bvFTD patients, but none with AD, showed three or more ED behaviours. We concluded that ED behaviours are more common in bvFTD than is currently recognized. UB, IB or three ED behaviours, if present, could clearly differentiate bvFTD from AD. A focused search should consistently uncover ED behaviours in bvFTD patients.

BackgroundThe International Consortium (FTDC) that revised the diagnostic criteria for behavioural variant frontotemporal dementia (bvFTD) did not have an Asian representation. Whether the revised criteria are equally useful in the early detection of Asian bvFTD patients therefore remains largely unexplored. Earlier studies have indicated differences in clinical manifestations in Indian and other Asian bvFTD patients when compared to western groups. There is an urgent need for clarification, given the projected exponential rise in dementia in these countries and the imminent clinical trials on bvFTD.ObjectiveTo assess how Indian bvFTD patients fulfil the FTDC criteria, hypothesizing that our patients might present differently early in the illness.MethodIn a hospital-based retrospective observational study, we assessed 48 probable bvFTD patients, diagnosed according to the FTDC criteria, for the speed with which these criteria were fulfilled, the frequency of individual symptoms and their order of appearance during the illness.ResultsMost of our patients presented with moderate to severe dementia, in spite of having relatively short onset to diagnosis times. Patients on average took 1.4 years from onset to meet the FTDC criteria, with 90% of them presenting with four or more symptoms at diagnosis. Disinhibition was the commonest symptom and the first symptom in most patients.ConclusionWith most patients presenting with advanced and florid disease, the FTDC criteria have little additional impact in early identification of bvFTD in India. Modifying the criteria further could allow detection of Indian patients early enough for their inclusion in future clinical trials.