White Matter Asymmetry in Primary Progressive Aphasia Explored through Radiomic Analysis

Published on May 5, 2023

Imagine a beautiful garden with two types of plants: one type has asymmetrical flowers near the middle, while the other type has asymmetrical flowers towards the edges. In a similar way, researchers have used radiomic analysis to study the asymmetry of white matter (WM) in patients with primary progressive aphasia (PPA). PPA is a neurological disease that affects language abilities. By analyzing images of the brain, the researchers found that different regions of WM showed varying degrees of asymmetry in PPA patients compared to healthy individuals. Interestingly, the specific regions affected by asymmetry differed between the two main subtypes of PPA: semantic variant (svPPA) and non-fluent/agrammatic variant (nfvPPA). Moreover, the degree of asymmetry in certain WM tracts was correlated with measures of verbal fluency and language performance in PPA patients. These findings suggest that assessing WM asymmetry using radiomic analysis may serve as a useful marker for the severity of language impairments in PPA patients. To find out more about this fascinating research and its implications for understanding PPA and its diverse subtypes, check out the full article!

IntroductionPrimary Progressive Aphasia (PPA) is a neurological disease characterized by linguistic deficits. Semantic (svPPA) and non-fluent/agrammatic (nfvPPA) variants are the two main clinical subtypes. We applied a novel analytical framework, based on radiomic analysis, to investigate White Matter (WM) asymmetry and to examine whether asymmetry is associated with verbal fluency performance.MethodsAnalyses were performed on T1-weighted images including 56 patients with PPA (31 svPPA and 25 nfvPPA) and 53 age- and sex-matched controls. Asymmetry Index (AI) was computed for 86 radiomics features in 34 white matter regions. The relationships between AI, verbal fluency performance (semantic and phonemic) and Boston Naming Test score (BNT) were explored through Spearman correlation analysis.ResultsRelative 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 fasciculi. Conversely, nfvPPA patients showed an asymmetry of WM in lateral occipital regions (ILF/IFOF). A higher lateralization involving IFOF, cingulum and forceps minor was found in nfvPPA compared to svPPA patients. In nfvPPA patients, semantic fluency was positively correlated to asymmetry in ILF/IFOF tracts. Performances at BNT were associated with AI values of the middle temporal (ILF/SLF) and parahippocampal (ILF/IFOF) gyri in svPPA patients.DiscussionRadiomics features depicted distinct pathways of asymmetry in svPPA and nfvPPA involving damage of principal fiber tracts associated with speech and language. Assessing asymmetry of radiomics in PPA allows achieving a deeper insight into the neuroanatomical damage and may represent a candidate severity marker for language impairments in PPA patients.

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