Abstract
BackgroundTranscranial magnetic stimulation (TMS) has attracted plenty of attention as it has been proved to be effective in facilitating motor recovery in patients with stroke. The aim of this study was to systematically review the effects of repetitive TMS (rTMS) and theta burst stimulation (TBS) protocols in modulating cortical excitability after stroke.MethodsA literature search was carried out using PubMed, Medline, EMBASE, CINAHL, and PEDro, to identify studies that investigated the effects of four rTMS protocols—low and high frequency rTMS, intermittent and continuous TBS, on TMS measures of cortical excitability in stroke. A random-effects model was used for all meta-analyses.ResultsSixty-one studies were included in the current review. Low frequency rTMS was effective in decreasing individuals’ resting motor threshold and increasing the motor-evoked potential of the non-stimulated M1 (affected M1), while opposite effects occurred in the stimulated M1 (unaffected M1). High frequency rTMS enhanced the cortical excitability of the affected M1 alone. Intermittent TBS also showed superior effects in rebalancing bilateral excitability through increasing and decreasing excitability within the affected and unaffected M1, respectively. Due to the limited number of studies found, the effects of continuous TBS remained inconclusive. Motor impairment was significantly correlated with various forms of TMS measures.ConclusionsExcept for continuous TBS, it is evident that these protocols are effective in modulating cortical excitability in stroke. Current evidence does support the effects of inhibitory stimulation in enhancing the cortical excitability of the affected M1.
Highlights
Transcranial magnetic stimulation (TMS) has attracted plenty of attention as it has been proved to be effective in facilitating motor recovery in patients with stroke
The meta-analysis conducted by McDonnell et al suggested that the unaffected Primary motor cortex (M1) of patients with stroke was not hyperactivated during active contraction and resting, indicated by the nonsignificant differences on Active motor threshold (aMT), Resting motor threshold (rMT), and motor evoked potentials (MEPs) compared with healthy controls [1]
Our meta-analyses indicated that both HF-repetitive TMS (rTMS) and intermittent TBS (iTBS) are useful in increasing the cortical excitability of the unaffected M1
Summary
Transcranial magnetic stimulation (TMS) has attracted plenty of attention as it has been proved to be effective in facilitating motor recovery in patients with stroke. The aim of this study was to systematically review the effects of repetitive TMS (rTMS) and theta burst stimulation (TBS) protocols in modulating cortical excitability after stroke. With respect to the cortical reorganization within the unaffected M1, as suggested by neuroimaging studies, the unaffected M1 in stroke patients became overactivated during movement execution of the affected hand [5]. In view of the association between cortical excitability and motor impairment of the hemiplegic arm, noninvasive brain modulation by repetitive TMS (rTMS) has attracted plenty of attention as it is effective in facilitating motor relearning and motor recovery after stroke. LF-rTMS was shown to significantly reduce the MEPs of the unaffected M1 and the IHI from the unaffected to affected M1 [9, 10], while HF-rTMS had a direct facilitatory effect on the affected M1 [10]
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