Functional Cortical Reorganization after Low-Frequency Repetitive Transcranial Magnetic Stimulation plus Intensive Occupational Therapy for Upper Limb Hemiparesis: Evaluation by Functional Magnetic Resonance Imaging in Poststroke Patients

Abstract

Background Low-frequency repetitive transcranial magnetic stimulation of the nonlesional hemisphere combined with occupational therapy significantly improves motor function of the affected upper limb in poststroke hemiparetic patients, but the recovery mechanism remains unclear. Aims To investigate the recovery mechanism using functional magnetic resonance imaging. Methods Forty-seven poststroke hemiparetic patients were hospitalized to receive 12 sessions of 40-min low-frequency repetitive transcranial magnetic stimulation over the nonlesional hemisphere and daily occupational therapy for 15 days. Motor function was evaluated with the Fugl–Meyer Assessment and Wolf Motor Function Test. The functional magnetic resonance imaging with motor tasks was performed at admission and discharge. The laterality index of activated voxel number in Brodmann areas 4 and 6 on functional magnetic resonance imaging was calculated (laterality index range of −1 to +1). Patients were divided into two groups based on functional magnetic resonance imaging findings before the intervention: group 1: patients who showed bilateral activation ( n = 27); group 2: patients with unilateral activation ( n = 20). Results Treatment resulted in improvement in Fugl–Meyer Assessment and Wolf Motor Function Test in the two groups ( P < 0.01). The treatment also resulted in a significant increase in laterality index in group 1 ( P < 0.05), suggesting a shift in activated voxels to the lesional hemisphere. Patients of group 2 showed a significant increase in lesional hemisphere activation ( P < 0.05). Conclusions The results of serial functional magnetic resonance imaging indicated that our proposed treatment can induce functional cortical reorganization, leading to motor functional recovery of the affected upper limb. Especially, it seems that neural activation in the lesional hemisphere plays an important role in such recovery in poststroke hemiparetic patients.