Bihemispheric Motor Cortex Transcranial Direct Current Stimulation Improves Force Steadiness in Post-Stroke Hemiparetic Patients: A Randomized Crossover Controlled Trial

Abstract

Post-stroke patients usually exhibit reduced peak muscular torque (PT) and/or force steadiness during submaximal exercise. Brain stimulation techniques have been proposed to improve neural plasticity and help to restore motor performance in post-stroke patients. The present study compared the effects of bihemispheric motor cortex transcranial direct current stimulation (tDCS) on PT and force steadiness during maximal and submaximal resistance exercise performed by post-stroke patients vs. healthy controls. A double-blind randomized crossover controlled trial (identification number: TCTR20151112001; URL: http://www.clinicaltrials.in.th/) was conducted involving nine healthy and 10 post-stroke hemiparetic individuals who received either tDCS (2 mA) or sham stimulus upon the motor cortex for 20 min. PT and force steadiness (reflected by the coefficient of variation (CV) of muscular torque) were assessed during unilateral knee extension and flexion at maximal and submaximal workloads (1 set of 3 repetitions at 100% PT and 2 sets of 10 repetitions at 50% PT, respectively). No significant change in PT was observed in post-stroke and healthy subjects. Force steadiness during knee extension (~25–35%, P < 0.001) and flexion (~22–33%, P < 0.001) improved after tDCS compared to the sham condition in post-stroke patients, but improved only during knee extension (~13–27%, P < 0.001) in healthy controls. These results suggest that tDCS may improve force steadiness, but not PT in post-stroke hemiparetic patients, which might be relevant in the context of motor rehabilitation programs.

Transcranial Direct-Current Stimulation in Combination With Exercise: A Systematic Review

“…The use of cathodal stimulation had its beneficial effect diagnosed in the improvement of the motor control in people affected by stroke. 24 In this study, cathodal tDCS was used associated with muscular control of the elbow flexors in post-stroke subjects, classified as having a moderate level of impairment. The study showed that the subjects presented significant results in the increase of the control of the effort of the muscle group related to the brain region injured by the stroke.…”

“…With the cathodal current, the focus is to decrease the excitability of the region opposite the lesion that may already be excited. 22,11,24 Regarding the intensity and duration of the stimulations, the studies presented three types of stimulation, with a current of 2mA for 40, 20, 15 or 10 minutes, 17,12,8,15,4 with 1mA for 20, 15 and 10 minutes 16,10,27,7 and with 1.5mA for 20 minutes. 14 Despite the discrepancies, Nitsche and Paulus 3 affirm that, after one hour of tDCS for 20 minutes at 2mA, it is possible to verify changes in cortical excitability.…”

Transcranial Direct Current Stimulation Does Not Affect Lower Extremity Muscle Strength Training in Healthy Individuals: A Triple-Blind, Sham-Controlled Study

“…In contract, among other tDCS studies, this first triple-blind study provides cogent evidence that the enhancement of knee torque was not seen with anodal tDCS combined with muscle strength training during each training session, compared to the sham tDCS with muscle strength training (Figure 4). However, the acute effects are inconsistent across studies (Tanaka et al, 2009, 2011; Montenegro et al, 2015, 2016; Angius et al, 2016; Washabaugh et al, 2016) and seem dependent on tDCS protocols, training tasks, muscle groups, and subject populations. In this context, computational modeling would be useful to understand the different spatial distributions of the electric field induced by different tDCS protocols (electrode configuration, size, or current intensity; Laakso et al, 2015, 2016).…”

“…The application of anodal tDCS to the primary motor cortex of the lower extremity transiently increases corticospinal excitability in healthy individuals (Jeffery et al, 2007; Tatemoto et al, 2013) and improves motor function in healthy individuals and patients with stroke (Tanaka et al, 2009, 2011; Madhavan et al, 2011; Sriraman et al, 2014; Chang et al, 2015; Montenegro et al, 2015, 2016; Angius et al, 2016; Washabaugh et al, 2016). Thus, anodal tDCS has a potential to become a new adjunct therapeutic strategy for the rehabilitation of leg motor function and locomotion following a stroke.…”

“…Several studies have examined the effect of a single session of tDCS on lower leg muscle strength, although the evidence is inconsistent (Tanaka et al, 2009, 2011; Montenegro et al, 2015, 2016; Angius et al, 2016; Washabaugh et al, 2016). Its effects seem dependent on tDCS protocols, training tasks, muscle groups, and subject populations.…”