Relationship between motor function improvements and white matter structure after low-frequency repetitive...

This is a second paper on partly the same patient group and the same intervention, but with a different anatomical outcome measurement. An intervention that combines low-frequency repetitive transcranial magnetic stimulation and intensive occupational therapy may improve brain function in poststroke patients with motor paralysis. The aim of this study was to clarify whole-brain white matter structural changes after repetitive transcranial magnetic stimulation and occupational therapy. We recruited 25 patients hospitalized for 15 days with poststroke upper extremity paralysis to receive 12 sessions of low-frequency repetitive transcranial magnetic stimulation over the nonlesioned hemisphere and occupational therapy. Focal repetitive transcranial magnetic stimulation was applied over the primary motor area for the fingers of the nonlesioned hemisphere. Imaging analysis was carried out using diffusion tensor imaging to assess changes in white matter after the intervention. Graph-theoretical analysis was carried out to quantify the characteristics of brain white matter networks. We found a significant increase in global betweenness centrality (corrected P<0.05) and characteristic path length (corrected P<0.05) in the postintervention group. In addition, the global clustering coefficient (corrected P<0.05), small-worldness (corrected P<0.05), and global strength (corrected P<0.05) decreased in the postintervention group. Graph theory analysis suggested that our intervention increased the characteristic path length and led to more complicated neural circuits, indicating that synaptic connections may have increased across the entire network through structural plasticity following our intervention. Our results show novel findings on the relationship between stroke neurorehabilitation and cerebral nerve structure.