Stroke & TMS

The use of transcranial magnetic stimulation (TMS) in stroke research has increased dramatically over the last decade with two emerging and potentially useful functions identified. Firstly, the use of single pulse TMS as a tool for predicting recovery of motor function after stroke, and secondly, the use of repetitive TMS (rTMS) as a treatment adjunct aimed at modifying the excitability of the motor cortex in preparation for rehabilitation. This review discusses recent advances in the use of TMS in both prediction and treatment after stroke. Prediction of recovery after stroke is a complex process and the use of TMS alone is not sufficient to provide accurate prediction for an individual after stroke. However, when applied in conjunction with other tools such as clinical assessment and MRI, accuracy of prediction using TMS is increased. rTMS temporarily modulates cortical excitability after stroke. Very few rTMS studies are completed in the acute or sub-acute stages after stroke and the translation of altered cortical excitability into gains in motor function are modest, with little evidence of long term effects. Although gains have been made in both of these areas, further investigation is needed before these techniques can be applied in routine clinical care.

The random effects meta-analysis model on the 18 qualified studies identified the significant positive effects relating to NIBS in terms of functional balance and postural control poststroke. The moderator-variable analyses revealed that these treatment effects were only significant in rTMS across patients with acute, subacute, and chronic stroke whereas tDCS did not show any significant therapeutic effects. The meta-regression analysis showed that a higher number of rTMS sessions was significantly associated with more improvements in functional balance and postural control poststroke.

Conclusions
Our systematic review and meta-analysis confirmed that NIBS may be an effective option for restoring functional balance and postural control for patients with stroke.

Amanda McIntyre, Spencer Thompson, Amer Burhan, Swati Mehta, Robert Teasell, Repetitive Transcranial Magnetic Stimulation for Depression Due to Cerebrovascular Disease: A Systematic Review, Journal of Stroke and Cerebrovascular Diseases, Volume 25, Issue 12, 2016, Pages 2792-2800, ISSN 1052-3057, https://doi.org/10.1016/j.jstrokecerebrovasdis.2016.08.043.

INTRODUCTION
Modern approaches to therapeutic exercise in stroke rehabilitation can accelerate the recovery of motor control and function but still do not typically lead to complete recovery in patients with moderate to severe stroke.1,2 As a result, clinical neuroscientists have turned to technology coupled with therapeutic task practice to facilitate further neural recovery.3 This article discusses the emerging use of neuromodulation in the form of noninvasive electromagnetic brain stimulation. Transcranial magnetic stimulation (TMS) presently has few clinical applications. However, TMS could potentially have wide use in stroke rehabilitation if clinicians can identify effective stimulation parameters. As shown in this review, there are several different therapeutic stimulation parameters under investigation, and each may ultimately have a clinical role depending on the neurologic condition.

KEY POINTS
It is likely that transcranial magnetic brain stimulation will be used for the clinical treatment of stroke and stroke-related impairments in the future. The anatomic target and stimulation parameters will likely vary for any clinical focus, be it weakness, pain, or cognitive or communicative dysfunction. Biomarkers may also be usefulfor identifyingpatients who will respond best,with a goal to enhance clinical decision making. Combination with drugs or specific types of therapeutic exercise may be necessary to achieve maximal response.

Julio C. Hernandez-Pavon, Richard L. Harvey, Noninvasive Transcranial Magnetic Brain Stimulation in Stroke, Physical Medicine and Rehabilitation Clinics of North America, Volume 30, Issue 2, 2019, Pages 319-335, ISSN 1047-9651, ISBN 9780323677806, https://doi.org/10.1016/j.pmr.2018.12.010.

Highlights

• tDCS and rTMS improved force production capabilities post stroke.

• Increasing cortical activity in the affected hemisphere enhanced force production.

• Reducing cortical activity in the unaffected hemisphere increased force production.

• Force production capability improved in each of three recovery stages.

Abstract

Background
Non-invasive brain stimulation (NIBS) facilitates motor improvements post stroke. Transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) are representative NIBS techniques frequently used in stroke motor rehabilitation. Our primary question is: Do these two techniques improve force production capability in paretic limbs?

Objective
The current systematic review and meta-analysis investigated the effects of tDCS and rTMS on paretic limb force production in stroke survivors.

Methods
Our comprehensive search identified 23 studies that reported changes in force production following tDCS or rTMS interventions. Each used random assignment and a sham control group. The 23 qualified studies in our meta-analysis generated 29 comparisons: 14 tDCS and 15 rTMS comparisons.

Results
Random effects models indicated improvements in paretic limb force after tDCS and rTMS rehabilitation. We found positive effects on force production in the two sets of stimulation protocols: (a) increasing cortical activity in the ipsilesional hemisphere and (b) decreasing cortical activity in the contralesional hemisphere. Moreover, across acute, subacute, and chronic phases, tDCS and rTMS improved force production.

Conclusion
Cumulative meta-analytic results revealed that tDCS and rTMS rehabilitation protocols successfully improved paretic limb force production capabilities.

Nyeonju Kang, Jeffery J. Summers, James H. Cauraugh, Non-Invasive Brain Stimulation Improves Paretic Limb Force Production: A Systematic Review and Meta-Analysis, Brain Stimulation, Volume 9, Issue 5, 2016, Pages 662-670, ISSN 1935-861X, https://doi.org/10.1016/j.brs.2016.05.005.

Highlights

• Noninvasive brain stimulation improved deficits in functional balance and postural control poststroke.

• The treatment effects on postural imbalance were significant following repetitive transcranial magnetic stimulation (rTMS).

• The improvements after rTMS appeared in patients with history of acute, subacute, and chronic stroke.

• A higher number of rTMS sessions significantly increased the treatment effects.

Abstract

Objectives
The postural imbalance poststroke limits individuals’ walking abilities as well as increase the risk of falling. We investigated the short-term treatment effects of noninvasive brain stimulation (NIBS) on functional balance and postural control in patients with stroke.

Data Sources
We started the search via PubMed and the Institute for Scientific Information’s Web of Science on March 1, 2019 and concluded the search on April 30, 2019.

Study Selection
The meta-analysis included studies that used either repetitive transcranial magnetic stimulation (rTMS) or transcranial direct current stimulation (tDCS) for the recovery of functional balance and postural control poststroke. All included studies used either randomized controlled trial or crossover designs with a sham control group.

Data Extraction
Three researchers independently performed data extraction and assessing methodological quality and publication bias. We calculated overall and individual effect sizes using random effects meta-analysis models.

Data Synthesis
The random effects meta-analysis model on the 18 qualified studies identified the significant positive effects relating to NIBS in terms of functional balance and postural control poststroke. The moderator-variable analyses revealed that these treatment effects were only significant in rTMS across patients with acute, subacute, and chronic stroke whereas tDCS did not show any significant therapeutic effects. The meta-regression analysis showed that a higher number of rTMS sessions was significantly associated with more improvements in functional balance and postural control poststroke.

Conclusions
Our systematic review and meta-analysis confirmed that NIBS may be an effective option for restoring functional balance and postural control for patients with stroke.

Nyeonju Kang, Ru Da Lee, Joon Ho Lee, Moon Hyon Hwang, Functional Balance and Postural Control Improvements in Patients With Stroke After Noninvasive Brain Stimulation: A Meta-analysis, Archives of Physical Medicine and Rehabilitation, Volume 101, Issue 1, 2020, Pages 141-153, ISSN 0003-9993, https://doi.org/10.1016/j.apmr.2019.09.003.

Highlights

• rTMS is an effective neurorehabilitative strategy for enhancing motor recovery in the early stage after stroke.

• Effects of high- versus low-frequency rTMS on motor regions reflect different neuroplastic mechanisms supporting motor recovery.

• Functional reorganization of the ipsilesional M1 after stroke plays a critical role in long-term motor recovery.

Abstract

Background
Repetitive transcranial magnetic stimulation (rTMS) can modulate cortical excitability, and may be beneficial for motor recovery after stroke. However, the neuroplasticity effects of rTMS have not been thoroughly investigated in the early stage after stroke.

Objective
To comprehensively assess the effects of high- and low-frequency repetitive transcranial magnetic stimulations on motor recovery in early stroke patients, using a randomized controlled trial based on clinical, neurophysiological and functional imaging assessments.

Methods
Sixty hospitalized, first-ever ischemic stroke patients (within 2 weeks after stroke) with motor deficits were randomly allocated to receive, in addition to standard physical therapy, five consecutive sessions of either: (1) High-frequency (HF) rTMS at 10 Hz over the ipsilesional primary motor cortex (M1); (2) Low-frequency (LF) rTMS at 1 Hz over the contralesional M1; (3) sham rTMS. The primary outcome measure was a motor impairment score (Upper Extremity Fugl-Meyer) evaluated at baseline, after rTMS intervention, and at 3-month follow-up. Cortical excitability and functional magnetic resonance imaging (fMRI) data were obtained within 24 h before and after rTMS intervention. Analyses of variance were conducted to compare the recovery effects among the three rTMS groups, assessed using clinical, neurophysiological and fMRI tests.

Results
Motor improvement was significantly larger in the two rTMS groups than in the control group. The HF-rTMS group showed significantly increased cortical excitability and motor-evoked fMRI activation in ipsilesional motor areas, whereas the LF-rTMS group had significantly decreased cortical excitability and motor-evoked fMRI activation in contralesional motor areas. Activity in ipsilesional motor cortex significantly correlated with motor function, after intervention as well as at 3-month follow-up.

Conclusion
HF- and LF-rTMS can both improve motor function by modulating motor cortical activation in the early phase of stroke.

Juan Du, Fang Yang, Jianping Hu, Jingze Hu, Qiang Xu, Nathan Cong, Qirui Zhang, Ling Liu, Dante Mantini, Zhiqiang Zhang, Guangming Lu, Xinfeng Liu, Effects of high- and low-frequency repetitive transcranial magnetic stimulation on motor recovery in early stroke patients: Evidence from a randomized controlled trial with clinical, neurophysiological and functional imaging assessments, NeuroImage: Clinical, Volume 21, 2019, 101620, ISSN 2213-1582, https://doi.org/10.1016/j.nicl.2018.101620.