Primary Progressive Aphasia (PPA) is a neurological disease characterized by linguistic deficits. Semantic (svPPA) and non-fluent/agrammatic (nfvPPA) variants are the two main subtypes of PPA. 

Analyses were performed on 3 Tesla T1-MRI. We included 31 svPPA, 25 nfvPPA and 53 age- and sex-matched controls. Asymmetry Index (AI) was computed for 86 radiomics features in 34 WM regions. Between-group comparisons in AIs were performed using analysis of variance. Correlation analyses investigated the relationships between performance at verbal fluency tasks (semantic and phonemic) and at Boston Naming Test and AIs.

Relative to controls, WM asymmetry in svPPA patients involved regions adjacent to middle temporal cortex as part of the inferior longitudinal (ILF), fronto-occipital (IFOF) and superior longitudinal (SLF) fasciculi. Conversely, nfvPPA patients showed an asymmetry of WM in lateral occipital brain regions (ILF/IFOF). A higher lateralization of radiomics features involving IFOF, cingulum and forceps minor was found in nfvPPA compared to svPPA patients. Correlation analysis highlighted a positive relationship between semantic fluency and AI in WM adjacent to the lateral occipital gyrus in nfvPPA patients. Performances at Boston Naming Test were significantly associated with AI in WM regions located close to the middle temporal and parahippocampal gyri in svPPA patients.

Radiomics depicted distinct pathways of WM asymmetry in svPPA and nfvPPA involving damage of fiber tracts associated to linguistic functions. Assessing asymmetry of radiomics in PPA allows achieving a deeper insight into the neuroanatomical damage and a possible marker to evaluate the language severity changes related to drug therapy or rehabilitation speech treatments.