Neural networks associated with body composition in frontotemporal dementia

BACKGROUND: Frontotemporal dementia (FTD) is associated with complex changes in eating behavior and metabolism, which potentially affect disease pathogenesis and survival. It is currently not known if body composition changes and changes in fat deposition also exist in FTD, the relationship of these changes in eating behavior and appetite, and whether these changes are centrally mediated. METHODS: Body composition was measured in 28 people with behavioral‐variant frontotemporal dementia (bvFTD), 16 with Alzheimer’s disease (AD), and 19 healthy controls, using dual energy x‐ray absorptiometry. Changes in body composition were correlated to brain grey matter atrophy using voxel‐based morphometry on high‐resolution magnetic resonance imaging. RESULTS: Behavioral‐variant FTD was characterized by changes in body composition, with increased total fat mass, visceral adipose tissue area (VAT area), and android: gynoid ratio compared to control and AD participants (all P values < 0.05). Changes in body composition correlated to abnormal eating behavior and behavioral change (P < 0.01) and functional decline (P < 0.01). Changes in body composition also correlated to grey matter atrophy involving a distributed neural network that included the hippocampus, amygdala, nucleus accumbens, insula, cingulate, and cerebellum – structures known to be central to autonomic control – as well as the thalamus, putamen, accumbens, and caudate, which are involved in reward processing. CONCLUSIONS: Changes in body composition and fat deposition extend the clinical phenomenology in bvFTD beyond cognition and behavior, with changes associated with changes in reward and autonomic processing suggesting that these deficits may be central in FTD