Clinical and neuroanatomical characterization of the semantic behavioral variant of frontotemporal dementia in a multicenter Italian cohort

Background: Semantic behavioral variant frontotemporal dementia (sbvFTD) is a neurodegenerative condition presenting with specific behavioral and semantic derangements and predominant atrophy of the right anterior temporal lobe (ATL). The objective was to evaluate clinical, neuropsychological, neuroimaging, and genetic features of an Italian sbvFTD cohort, defined according to recently proposed guidelines, compared to semantic variant primary progressive aphasia (svPPA) and behavioral variant FTD (bvFTD) patients. Methods: Fifteen sbvFTD, sixty-three bvFTD, and twenty-five svPPA patients and forty controls were enrolled. Patients underwent clinical, cognitive evaluations, and brain MRI. Symptoms of bvFTD patients between onset and first visit were retrospectively recorded and classified as early and late. Grey matter atrophy was investigated using voxel-based morphometry. Results: sbvFTD experienced early criteria-specific symptoms: world, object and person-specific semantic loss (67%), complex compulsions and rigid thought (60%). Sequentially, more behavioral symptoms emerged (apathy/inertia, loss of empathy) along with non-criteria-specific symptoms (anxiety, suspiciousness). sbvFTD showed sparing of attentive/executive functions, especially compared to bvFTD and better language functions compared to svPPA. All sbvFTD patients failed at the famous face recognition test and more than 80% failed in understanding written metaphors and humor. At MRI, sbvFTD had predominant right ATL atrophy, almost specular to svPPA. Three sbvFTD patients presented pathogenic genetic variants. Conclusion: We replicated the application of sbvFTD diagnostic guidelines in an independent Italian cohort, demonstrating that the presence of person-specific semantic knowledge loss and mental rigidity, along with preserved executive functions and a predominant right ATL atrophy with sparing of frontal lobes, should prompt a diagnosis of sbvFTD.