Association Between Contralesional Resting Motor Threshold and Recovery of Upper Limb Motor Function in Patients with Subacute Stroke Receiving High-Frequency rTMS over the Ipsilesional Primary Motor Cortex

Background/Objectives: High-frequency repetitive transcranial magnetic stimulation (rTMS) of the ipsilesional primary motor cortex is used to improve upper limb motor function after stroke. However, treatment responses vary among individuals. Contralesional corticospinal excitability and interhemispheric interactions may contribute to motor recovery. This study investigated the association between contralesional resting motor threshold (RMT) and improvement in upper limb motor function in patients receiving ipsilesional high-frequency rTMS combined with rehabilitation. Methods: This single-center retrospective observational study included 42 patients with poststroke upper limb hemiparesis. All patients received ipsilesional high-frequency rTMS combined with rehabilitation for 8 weeks. RMTs and Fugl-Meyer Assessment for Upper Extremity (FMA-UE) were evaluated at baseline. FMA-UE was reassessed after treatment. High-frequency rTMS was applied at 10 Hz, 1000 pulses per day, 6 days per week. Associations between contralesional RMT and change in FMA-UE score were assessed using Spearman’s rank correlation and multiple linear regression adjusted for baseline FMA-UE. Subgroup analyses were performed according to whether ipsilesional RMT could be determined within the predefined limit of 60% maximum stimulator output (MSO). Results: Contralesional RMT was positively correlated with change in FMA-UE score (ρ = 0.33, p = 0.033). Baseline-adjusted regression showed a positive association (B = 0.337, p = 0.029). However, sensitivity analyses indicated that these associations were not robust. Conclusions: Contralesional RMT may be associated with upper limb motor recovery in patients with subacute stroke receiving high-frequency rTMS combined with rehabilitation. Further studies are needed to clarify its clinical significance.