Long-term effects of contralesional rTMS in severe stroke: Safety, cortical excitability, and relationship with transcallosal motor fibers

Issue title: ICF and Neurorehabilitation

Guest editors: Christina Brogårdh and Jan Lexell

Article type: Research Article

Authors: Demirtas-Tatlidede, Asli^{a; b; *} | Alonso-Alonso, Miguel^a | Shetty, Ravi P.^c | Ronen, Itamar^{c; d} | Pascual-Leone, Alvaro^a | Fregni, Felipe^{a; e; *}

Affiliations: [a] Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA | [b] Behavioral Neurology and Movement Disorders Unit, Department of Neurology, Istanbul University, Istanbul Medical Faculty, Istanbul, Turkey | [c] Center for Biomedical Imaging, Boston University, Boston, MA, USA | [d] Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands | [e] Laboratory of Neuromodulation, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA, USA

Correspondence: [*] Address for correspondence: Asli Demirtas-Tatlidede, MD, Department of Neurology, Istanbul University Medical Faculty, 34093, Istanbul, Turkey. Tel.: +90 212 533 8575; E-mail: aslidemirtas@yahoo.com. Address for correspondence: Felipe Fregni, MD, PhD, 125 Nashua Street, 726, Boston, MA 02114, USA. Tel.: +1 617 573 2195; E-mail: fregni.felipe@mgh.harvard.edu

Abstract: Background:Contralesional 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. Objective:This study aimed to investigate the safety of contralesional rTMS in a selected group of severe chronic stroke patients. Methods:Ten 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). Results:rTMS 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. Conclusions:Our 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.

Keywords: Severe stroke, cerebrovascular disease, repetitive transcranial magnetic stimulation (rTMS), diffusion tensor imaging (DTI), neurorehabilitation, cortical excitability

DOI: 10.3233/NRE-141191

Journal: NeuroRehabilitation, vol. 36, no. 1, pp. 51-59, 2015