Cortical Morphometry of Contralesional Inferior Frontal Gyrus and Structural Connections of Fronto-Thalamic Circuitry...

The extended Broca's system, including its connected subcortical structures, plays a central role in language production. However, the contribution of its right hemisphere homologs to language recovery after stroke remains uncertain. This study aimed to investigate structural changes in the right inferior frontal gyrus (IFG) and fronto-thalamic pathways and their associations with language outcomes in subacute poststroke aphasia. Twenty-eight patients with subacute poststroke aphasia and 35 healthy controls were enrolled and underwent language assessments and magnetic resonance imaging. Surface-based morphometry of the right IFG and microstructural analysis of fronto-thalamic tracts were performed. Compared with healthy controls, patients exhibited significantly reduced cortical thickness in the right pars triangularis and pars orbitalis (false discovery rate [FDR]-corrected p < 0.05). Among the IFG-thalamic connections, fiber density (FD) of the tracts linking the right pars triangularis to the thalamus was significantly reduced (FDR-p < 0.05). In patients, cortical thickness of the right pars orbitalis was negatively correlated with overall and single-word repetition scores (ρ = -0.535 and ρ = -0.563, respectively), and FD of the right triangular-thalamic connection was negatively correlated with single-word repetition (ρ = -0.526) and sentence comprehension scores (ρ = -0.570 to -0.514) (all FDR-p < 0.05). In conclusion, reduced cortical thickness in the right IFG and impaired fronto-thalamic connectivity may reflect contralesional adaptations in subacute poststroke aphasia, with these structural alterations potentially serving as neuroanatomical targets for prognostic evaluation and therapeutic strategies to enhance language recovery.