• Asli Demirtas-Tatlidede, Miguel Alonso-Alonso, Ravi P Shetty, Itamar Ronen, Alvaro Pascual-Leone, and Felipe Fregni.
• Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA Behavioral Neurology and Movement Disorders Unit, Department of Neurology, Istanbul University, Istanbul Medical Faculty, Istanbul, Turkey.
• NeuroRehabilitation. 2015 Jan 1; 36 (1): 51-9.

BackgroundContralesional hemispheric repetitive transcranial magnetic stimulation (rTMS) may improve motor function in mild to moderate stroke and effects are considered to be mediated through transcallosal motor fibers.ObjectiveThis study aimed to investigate the safety of contralesional rTMS in a selected group of severe chronic stroke patients.MethodsTen sessions of 1 Hz rTMS were applied to contralesional primary motor cortex (M1) using neuronavigated stimulation and changes in motor impairment were evaluated before, during and after rTMS applications and at 4-weeks follow-up. Neurophysiological response to stimulation was assessed through cortical excitability evaluations. The relationship between functional and neurophysiological response to rTMS and microstructural integrity of transcallosal motor fibers were searched using diffusion tensor imaging (DTI) based fractional anisotropy (FA).ResultsrTMS was well-tolerated with high compliance and no dropouts; no seizures or motor worsening occurred. Transcallosal FA values revealed a positive linear relationship with the mild motor improvement detected after rTMS while higher FA values were observed in subjects with better motor outcome. Cortical excitability showed a significant change in contralesional short-interval intracortical inhibition indicating altered plasticity following rTMS.ConclusionsOur results suggest that noninvasive neuromodulation of the contralesional hemisphere may present a possibility to assist adaptive neuroplastic changes in severe chronic stroke. Implementation of DTI-derived measures of transcallosal microstructural integrity may allow for individually-tailored interventions to guide processes of interhemispheric neuroplasticity. Further research is warranted to establish the clinical value of these findings in neurorehabilitation settings for subjects with chronic severe stroke.

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