White Matter Hyperintensities in Behavioral Variant Frontotemporal Dementia and Semantic Variant Primary Progressive Aphasia

Background and Objectives: White matter hyperintensities (WMH) in patients with cerebrovascular risk factors (CVRF), are often linked to cerebral vascular changes, but can be caused by genetic variants selectively targeting white matter. In addition, WMH can be present in neurodegenerative disorders such as frontotemporal lobar degeneration (FTLD) and are linked to some FTLD genetic variants. This study aims to investigate WMH burden in patients with behavioral variant frontotemporal dementia (bvFTD) and semantic variant primary progressive aphasia (svPPA) versus controls and to evaluates the influence of CVRF. Methods: This cross-sectional retrospective analysis examined individuals meeting research diagnostic criteria for bvFTD and svPPA with high-quality structural MRI at the UCSF Memory and Aging Center between September 2008 and December 2021. WMH burden and spatial distribution were assessed by disease group compared to age- and sex-matched controls and associations with CVRF evaluated. Results: hexanucleotide repeat expansions (HRE) and WMH in bvFTD patients. Discussion: bvFTD and svPPA are associated with elevated WMH burden independent of CVRF. In bvFTD, WMH are primarily distributed within the frontal lobes, while svPPA shows widespread distribution across lobes. Study limitations include its retrospective, single-center design and limited power for genetic subgroup analyses.