Environmental dependency behaviours in frontotemporal dementia: have we been underrating them?

Abstract

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.

Utilization Behavior: What Is Known and What Has to Be Known?

“…Other interesting relationships have been highlighted, in two recent studies [3, 4] between the UB and the fronto-temporal dementia (FTD). In the former study, the UB was reported in 80% of patients with FTD, in contrast with 0% of subjects suffering from Alzheimer's disease (AD).…”

“…In the latter study [4], the authors showed that careful evaluation of environmental dependency behaviors, considered pathognomonic sign of frontal lesion, could clearly differentiate the behavioral variant of FTD from probable AD. In particular, UB (78% overall UB; 66% incidental UB) and IB (59%) occurred exclusively in behavioral variant of FTD (bvFTD).…”

“…What is surprising about the UB is that the patient does not detect any discrepancy between his actions and his intentions, so he will claim that “he wanted to do that.” The UB is often concomitant with another frontal sign, the imitation behavior (IB) and, together, they are the core symptoms of the EDS, that is, a more complex kind of dependence in which is the whole context that elicits scripts of behavior from the patient (see paragraph §3 for further details). Actually, there are still a lot of controversies about the UB, particularly referring to its neuroanatomical basis, its cognitive accounts, and its clinical value for both neurological (e.g., FTD onset [3, 4]) and psychiatric disorders (e.g., UB and attention deficit with hyperactivity disorder (ADHD) relationships [5, 6]). Only recent studies [7, 8] reported systematic neuroimaging evaluation about the individual differences of the UB phenomenology, with still unclear results.…”

“…The UB has been associated with lesions of different brain areas [1, 11–15] as if with various (and often very different) conditions, from neurodegenerative diseases [3, 4, 16] to neuropsychiatric disorders [5, 6, 17]. …”

Neurological signs of possible diagnostic value in the cognitive disorders clinic: Table 1

“…Imitation behaviour may be exclusive to behavioural variant frontotemporal dementia 24. Environmental dependency behaviours may result from a frontoparietal network dysfunction 25…”