Bihemispheric changes associated with cognition in patients with chronic brainstem stroke.

Objective: We aimed to identify brain changes associated with preserved cognitive function in patients with chronic brainstem stroke.

Methods: Twelve patients with chronic brainstem stroke and 24 age-matched healthy controls were included in this retrospective study. All participants underwent T1-weighted, diffusion tensor, and resting-state functional MRI. Gray matter density, fractional anisotropy, and mean diffusivity maps from diffusion tensor imaging and seven cognition-related independent component maps from resting-state functional MRI were used to identify differences in brain volume, structural connectivity, and functional connectivity. Independent t-tests were used to determine the statistical significance of changes in gray matter density, fractional anisotropy, mean diffusivity, and inter-network functional connectivity maps.

Results: Bilateral cerebellum volumes and structural connectivity of the diffuse bilateral cerebral hemispheres were significantly lower in the patient than in the control group. However, patients exhibited increased gray matter volume and increased structural connectivity of the temporal lobe in the contra-lesional hemisphere and basal forebrain, compared with healthy controls. Furthermore, the intra-network functional connectivity in the frontal and temporal lobes was significantly higher in patients than in controls (PFWE < 0.05).

Conclusion: In the patient group, the brain regions mainly associated with the cholinergic system exhibited increased volume, structural connectivity, and functional connectivity. In contrast, the regions connected with the brainstem via cortico-ponto-cerebellar fibers exhibited decreased volume or structural connectivity. Cognitive function may be preserved in patients with brainstem stroke due to significant increases in frontal and temporal inter-network connectivity.