Abstract

Phenocopy frontotemporal dementia (phFTD) shares core characteristics with behavioral variant frontotemporal dementia (bvFTD), yet without associated cognitive deficits and brain abnormalities on conventional magnetic resonance imaging (MRI), and without progression. Using advanced MRI techniques, we previously observed subtle structural and functional brain changes in phFTD similar to bvFTD. The aim of the current study was to follow these as well as cognition in phFTD over time, by means of a descriptive case series. Cognition, gray matter (GM) volume and white matter (WM) microstructure, and perfusion of 6 phFTD patients were qualitatively compared longitudinally (3-years follow-up), and cross-sectionally with baseline data from 9 bvFTD patients and 17 controls. For functional brain changes, arterial spin labeling (ASL) was performed to assess GM perfusion. For structural brain changes, diffusion tensor imaging was performed to assess WM microstructure and T1w imaging to assess GM volume. MRI acquisition was performed at 3T (General Electric, US). Clinical profiles of phFTD cases at follow-up are described. At follow-up phFTD patients showed clinical symptomatology similar to bvFTD, but had a relatively stable clinical profile. Longitudinal qualitative comparisons in phFTD showed some deterioration of language and memory function, a stable pattern of structural brain abnormalities and increased perfusion over time. Additionally, both baseline and follow-up cognitive scores and structural values in phFTD were generally in between those of controls and bvFTD. Although a descriptive case series does not allow for strong conclusions, these observations in a unique longitudinal phFTD patient cohort are suggestive of the notion that phFTD and bvFTD may belong to the same disease spectrum. They may also provide a basis for further longitudinal studies in phFTD, specifically exploring the structural vs. functional brain changes. Such studies are essential for improved insight, accurate diagnosis, and appropriate treatment of phFTD.

Highlights

  • Phenocopy frontotemporal dementia is a clinical syndrome predominantly affecting men [1], that is much debated, as it shares core features with behavioral variant frontotemporal dementia but does not follow its disease course

  • Psychiatric assessment ruled out a psychiatric diagnosis for this sample. As these abnormalities are similar to behavioral variant frontotemporal dementia (bvFTD)—in addition to their similar symptomatology and lack of psychiatric diagnosis—we suggested that Phenocopy frontotemporal dementia (phFTD) and bvFTD may belong to the same disease spectrum

  • In order to gain more insight into possible longitudinal brain changes in phFTD and to acquire more support for the notion that phFTD and bvFTD may belong to the same disease spectrum, we present clinical reports and qualitatively describe findings from advanced magnetic resonance imaging (MRI) and neuropsychological examination of six phFTD patients at 3years follow-up

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Summary

Introduction

Phenocopy frontotemporal dementia (phFTD) is a clinical syndrome predominantly affecting men [1], that is much debated, as it shares core features with behavioral variant frontotemporal dementia (bvFTD) but does not follow its disease course. These core features are behavioral changes, such as apathy, behavioral disinhibition, and loss of insight [2]. PhFTD patients do not show the cognitive and brain abnormalities that are typical for bvFTD. On conventional (structural) magnetic resonance imaging (MRI), phFTD patients show no or only mild abnormalities [7, 9] in the frontotemporal brain regions typically affected in bvFTD [10]. The issue of whether phFTD is a psychiatric or neurodegenerative disease could possibly be settled by observing brain abnormalities similar to bvFTD that progress over time, which have not been previously found in phFTD

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