Cerebellar functional reorganization after intermittent theta burst stimulation over vermis on balance recovery in subacute stroke patients.

BACKGROUND

This study aims to investigate whether intermittent theta-burst stimulation (iTBS) over the cerebellar vermis enhances balance recovery in subacute stroke, and examine the underlying neural mechanisms.

METHODS

Fifty-two patients with subacute stroke and balance impairment were randomized to receive either three weeks of iTBS (n = 26) or sham stimulation (n = 26). The primary outcome was the Berg Balance Scale (BBS). Secondary outcomes included additional motor function measures and surface electromyography (sEMG). Clinical assessments were conducted at baseline and at weeks 1, 2, 3, and 6 after treatment onset. sEMG and resting-state functional MRI were acquired before and after the intervention. Seed-based functional connectivity (FC) of the cerebellar vermis was analyzed using a 2 × 2 mixed-effects ANOVA. Associations between changes in BBS (ΔBBS) and FC alterations were examined using Pearson correlation analyses. Patients were further stratified into subgroups based on the direction of FC change (increase vs. decrease) to characterize distinct clinical and neural response patterns.

RESULTS

Compared with the sham group, patients receiving iTBS showed significantly greater improvements in balance, accompanied by increased sEMG activation of trunk and proximal lower-limb muscles, with effects sustained at follow-up. FC analyses revealed enhanced connectivity between Vermis X and bilateral occipitotemporal cortices, which was positively correlated with balance improvement (ΔBBS). Subgroup analyses identified distinct clinical and neural profiles: the FC-increase subgroup demonstrated sustained functional gains and enhanced cerebello-frontal connectivity, whereas the FC-decrease subgroup exhibited short-term improvement and reduced intracerebellar connectivity.

DISCUSSION: These findings indicate that cerebellar vermis-targeted iTBS facilitates balance recovery after subacute stroke through reorganization of cerebello-visual networks. Subgroup-specific patterns further highlight heterogeneous intracerebellar and cerebello-frontal plasticity, supporting the notion of patient-specific network pathways underlying the therapeutic effects of cerebellar stimulation.