Sensitivity of current criteria for the diagnosis of behavioral variant frontotemporal dementia

Abstract

Background: Diagnosis of behavioral variant frontotemporal dementia (bvFTD) relies on criteria that are constraining and potentially ambiguous. Some features are open to clinical interpretation and their prevalence unknown. This study investigated the sensitivity of current diagnostic criteria in a large group of patients with bvFTD.

Methods: Forty-five patients with clear evidence of bvFTD as judged by progressive clinical decline (>3 years) with marked frontal features and significant frontal brain atrophy on brain MRI were included. Thirty-two have died; pathologic confirmation of frontotemporal lobar degeneration was found in all 18 coming to autopsy. We established the prevalence of core and supportive diagnostic features at presentation and with disease progression.

Results: Only 25/45 patients (56%) showed all five core features necessary for a diagnosis of bvFTD at initial presentation and 33/45 (73%) as their disease progressed. Two core features, emotional blunting and loss of insight, were never observed in 25% and 13% of cases. Executive dysfunction, hyperorality, mental inflexibility, and distractibility were the only supportive features present in >50% of cases at initial presentation. Although not a diagnostic feature, impaired activities of daily living was present in 33/45 patients (73%).

Conclusions: Strict application of the criteria misses a significant proportion of patients. Many supportive features have low prevalence and are clinically not useful. Revision of the criteria to include level of certainty (definite, probable, possible) dependent on the number of features present and the presence of ancillary information (e.g., brain atrophy, neuropsychological abnormalities, impaired activities of daily living) is encouraged.

Figure 1 Prevalence of core features (A) and speech and language supportive features (B) of clinical behavioral variant frontotemporal dementia at initial presentation and with disease progression Among the core features, loss of insight includes lack of awareness, or denial of mental symptoms; emotional blunting includes loss of empathy and sympathy; impairment in personal conduct includes inertia and passivity or overactivity such as pacing; decline in social interpersonal conduct includes disinhibited behavior, tactlessness, and loss of social graces.

Figure 2 Prevalence of behavioral supportive features (A) and physical signs (B) in patients with behavioral variant frontotemporal dementia at initial presentation and with disease progression Frequencies of the core and supportive clinical features in cases with postmortem confirmation did not differ from the cases without confirmation or from the patients who were still alive.