Grey and white matter brain network changes in frontotemporal dementia subtypes

Abstract

Background: Frontotemporal dementia (FTD) comprises of three clinical syndromes, behavioural-variant frontotemporal dementia (bvFTD), semantic dementia (SV-PPA), and progressive nonfluent aphasia (NFV-PPA) with unique underlying neuroanatomical deficits. To date, however, grey matter structural differences and their connecting white matter tracts in this network have been mostly characterised in comparison to controls, whereas within FTD subtype comparisons in the same patients have not been explored. Methodology: In 94 participants, including bvFTD (n = 16), SV-PPA (n = 16) and NFV-PPA (n = 16), as well as an age-matched control group (n = 46), we employed voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) to examine grey and white matter key signatures in each of the three FTD subtypes. Results: Our results showed that bvFTD had specific ventromedial prefrontal cortex and striatum grey matter atrophy along with their connecting white matter tracts compared to other FTD subtypes. By contrast, SV-PPA showed additional temporal pole grey matter damage to bvFTD and grey and white matter temporal, amygdala and insula changes compared to NFV-PPA. Finally, NFV-PPA showed mild insula grey and white matter changes compared to bvFTD but differed from SV-PPA only on anterior corpus callosum white matter changes. Conclusions: Our findings clearly indicate that not only grey matter regions of the FTD network but also their white matter connecting tracts have specific signatures for each FTD subtype. These promising findings highlight how neural network approaches can shed new light on neurodegenerative conditions and FTD in particular, which will inform future diagnostic and disease management. © Versita Sp. z o.o.