The effects of five sessions of continuous theta burst stimulation over contralesional sensorimotor cortex paired with paretic skilled motor practice in people with chronic stroke

Article type: Research Article

Authors: Neva, J.L.^a | Brown, K.E.^b | Wadden, K.P.^b | Mang, C.S.^{b; c} | Borich, M.R.^d | Meehan, S.K.^e | Boyd, L.A.^{a; f; *}

Affiliations: [a] Department of Physical Therapy, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada | [b] Graduate Studies in Rehabilitation Sciences, University of British Columbia, Vancouver Canada | [c] Division of Physical Medicine and Rehabilitation, Department of Clinical Neurosciences, Hotchkiss Brain Institute, University of Calgary, Calgary, Canada | [d] Department of Rehabilitation Medicine, Division of Physical Therapy, School of Medicine, Emory University, Atlanta, GA, USA | [e] School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA | [f] The Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada

Correspondence: [*] Corresponding author: Lara A. Boyd, PT, Ph.D., Professor, University of British Columbia, 212 2177 Wesbrook Mall Vancouver, British Columbia, Canada V6T 2B5. Tel.: +1 604 822 7392; Fax: +1 604 822 1860; E-mail: lara.boyd@ubc.ca.

Abstract: Background:In individuals with chronic stroke, impairment of the paretic arm may be exacerbated by increased contralesional transcallosal inhibition (TCI). Continuous theta burst stimulation (cTBS) can decrease primary motor cortex (M1) excitability and TCI. However, contralesional cTBS shows inconsistent effects after stroke. Variable effects of cTBS could stem from failure to pair stimulation with skilled motor practice or a focus of applying cTBS over M1. Objective:Here, we investigated the effects of pairing cTBS with skilled practice on motor learning and arm function. We considered the differential effects of stimulation over two different brain regions: contralesional M1 (M1c) or contralesional primary somatosensory cortex (S1c). Methods:37 individuals with chronic stroke participated in five sessions of cTBS and paretic arm skilled practice of a serial targeting task (STT); participants received either cTBS over M1c or S1c or sham before STT practice. Changes in STT performance and Wolf Motor Function Test (WMFT) were assessed as primary outcomes. Assessment of bilateral corticospinal, intracortical excitability and TCI were secondary outcomes. Results:cTBS over sensorimotor cortex did not improve STT performance and paretic WMFT-rate beyond sham cTBS. TCI was reduced bi-directionally following the intervention, regardless of stimulation group. In addition, we observed an association between STT performance change and paretic WMFT-rate change in the M1c stimulation group only. Conclusions:Multiple sessions of STT practice can improve paretic arm function and decrease TCI bilaterally, with no additional benefit of prior cTBS. Our results suggest that improvement in STT practice following M1c cTBS scaled with change in paretic arm function in some individuals. Our results highlight the need for a better understanding of the mechanisms of cTBS to effectively identify who may benefit from this form of brain stimulation.

Keywords: Stroke, transcranial magnetic stimulation, skilled motor practice, motor function, transcallosal inhibition, continuous theta burst stimulation

DOI: 10.3233/RNN-190916

Journal: Restorative Neurology and Neuroscience, vol. 37, no. 3, pp. 273-290, 2019