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Cochrane Database of Systematic Reviews: Plain Language Summaries [Internet]. Chichester, UK: John Wiley & Sons, Ltd; 2003-.

Cochrane Database of Systematic Reviews: Plain Language Summaries [Internet].

Direct electrical current to the brain to improve rehabilitation outcomes

This version published: 2016; Review content assessed as up-to-date: February 27, 2015.

Link to full article: [Cochrane Library]

Plain language summary

Review question

We reviewed the evidence about the effect of direct electrical current to the brain (transcranial direct current stimulation, tDCS) to reduce impairment in activities of daily living (ADLs), arm and leg function, muscle strength and cognitive abilities (including spatial neglect), dropouts and adverse events in people after stroke.

Background

Stroke is one of the leading causes of disability worldwide. Most strokes take place when a blood clot blocks a blood vessel leading to the brain. Without a proper blood supply, the brain quickly suffers damage, which can be permanent. This damage often causes impairment of ADLs and motor function among stroke survivors. Current rehabilitation strategies have limited effectiveness in improving these impairments. One possibility for enhancing the effects of rehabilitation might be the addition of non‐invasive brain stimulation through a technique known as transcranial direct current stimulation (tDCS). This technique can alter how the brain works and may be used to reduce impairment of ADLs and function. However, the effectiveness of this intervention for improving rehabilitation outcomes is still unknown.

Search date

The review is current to February 2015.

Study characteristics

We included 32 studies involving a total of 748 participants aged above 18 with acute, postacute or chronic ischaemic or haemorrhagic stroke. The mean age in the experimental groups ranged from 43 years up to 70 years and from 45 years up to 75 years in the control groups. The level of participants' impairment ranged from severe to moderate. The majority of studies were conducted in an inpatient setting. Different stimulation types (anodal, cathodal, dual) of tDCS with different stimulation durations and dosages were administered and compared with sham tDCS or an active control intervention. Sham tDCS means that the stimulation is switched off covertly in the first minute of the intervention.

Key results

This review found that tDCS might enhance ADLs, but it is still uncertain if arm and leg function, muscle strength and cognitive abilities may be improved. Proportions of adverse events and people discontinuing the treatment were comparable between groups. Included studies differed in terms of type, location and duration of stimulation, amount of current delivered, electrode size and positioning as well as type and location of stroke. Future research is needed in this area to foster the evidence base of these findings, especially regarding arm and leg function, muscle strength and cognitive abilities (including spatial neglect).

Quality of the evidence

The quality of evidence for tDCS for improving ADLs was very low to moderate. It was low for upper extremity function and low for adverse events and people discontinuing the treatment.

Abstract

Background: Stroke is one of the leading causes of disability worldwide. Functional impairment, resulting in poor performance in activities of daily living (ADLs) among stroke survivors is common. Current rehabilitation approaches have limited effectiveness in improving ADL performance, function, muscle strength and cognitive abilities (including spatial neglect) after stroke, but a possible adjunct to stroke rehabilitation might be non‐invasive brain stimulation by transcranial direct current stimulation (tDCS) to modulate cortical excitability, and hence to improve ADL performance, arm and leg function, muscle strength and cognitive abilities (including spatial neglect), dropouts and adverse events in people after stroke.

Objectives: To assess the effects of tDCS on ADLs, arm and leg function, muscle strength and cognitive abilities (including spatial neglect), dropouts and adverse events in people after stroke.

Search methods: We searched the Cochrane Stroke Group Trials Register (February 2015), the Cochrane Central Register of Controlled Trials (CENTRAL; the Cochrane Library; 2015, Issue 2), MEDLINE (1948 to February 2015), EMBASE (1980 to February 2015), CINAHL (1982 to February 2015), AMED (1985 to February 2015), Science Citation Index (1899 to February 2015) and four additional databases. In an effort to identify further published, unpublished and ongoing trials, we searched trials registers and reference lists, handsearched conference proceedings and contacted authors and equipment manufacturers.

Selection criteria: This is the update of an existing review. In the previous version of this review we focused on the effects of tDCS on ADLs and function. In this update, we broadened our inclusion criteria to compare any kind of active tDCS for improving ADLs, function, muscle strength and cognitive abilities (including spatial neglect) versus any kind of placebo or control intervention.

Data collection and analysis: Two review authors independently assessed trial quality and risk of bias (JM and MP) and extracted data (BE and JM). If necessary, we contacted study authors to ask for additional information. We collected information on dropouts and adverse events from the trial reports.

Main results: We included 32 studies involving a total of 748 participants aged above 18 with acute, postacute or chronic ischaemic or haemorrhagic stroke. We also identified 55 ongoing studies. The risk of bias did not differ substantially for different comparisons and outcomes.

We found nine studies with 396 participants examining the effects of tDCS versus sham tDCS (or any other passive intervention) on our primary outcome measure, ADLs after stroke. We found evidence of effect regarding ADL performance at the end of the intervention period (standardised mean difference (SMD) 0.24, 95% confidence interval (CI) 0.03 to 0.44; inverse variance method with random‐effects model; moderate quality evidence). Six studies with 269 participants assessed the effects of tDCS on ADLs at the end of follow‐up, and found improved ADL performance (SMD 0.31, 95% CI 0.01 to 0.62; inverse variance method with random‐effects model; moderate quality evidence). However, the results did not persist in a sensitivity analysis including only trials of good methodological quality.

One of our secondary outcome measures was upper extremity function: 12 trials with a total of 431 participants measured upper extremity function at the end of the intervention period, revealing no evidence of an effect in favour of tDCS (SMD 0.01, 95% CI ‐0.48 to 0.50 for studies presenting absolute values (low quality evidence) and SMD 0.32, 95% CI ‐0.51 to 1.15 (low quality evidence) for studies presenting change values; inverse variance method with random‐effects model). Regarding the effects of tDCS on upper extremity function at the end of follow‐up, we identified four studies with a total of 187 participants (absolute values) that showed no evidence of an effect (SMD 0.01, 95% CI ‐0.48 to 0.50; inverse variance method with random‐effects model; low quality evidence). Ten studies with 313 participants reported outcome data for muscle strength at the end of the intervention period, but in the corresponding meta‐analysis there was no evidence of an effect. Three studies with 156 participants reported outcome data on muscle strength at follow‐up, but there was no evidence of an effect.

In six of 23 studies (26%), dropouts, adverse events or deaths that occurred during the intervention period were reported, and the proportions of dropouts and adverse events were comparable between groups (risk difference (RD) 0.01, 95% CI ‐0.02 to 0.03; Mantel‐Haenszel method with random‐effects model; low quality evidence; analysis based only on studies that reported either on dropouts, or on adverse events, or on both). However, this effect may be underestimated due to reporting bias.

Authors' conclusions: At the moment, evidence of very low to moderate quality is available on the effectiveness of tDCS (anodal/cathodal/dual) versus control (sham/any other intervention) for improving ADL performance after stroke. However, there are many ongoing randomised trials that could change the quality of evidence in the future. Future studies should particularly engage those who may benefit most from tDCS after stroke and in the effects of tDCS on upper and lower limb function, muscle strength and cognitive abilities (including spatial neglect). Dropouts and adverse events should be routinely monitored and presented as secondary outcomes. They should also address methodological issues by adhering to the Consolidated Standards of Reporting Trials (CONSORT) statement.

Editorial Group: Cochrane Stroke Group.

Publication status: New search for studies and content updated (conclusions changed).

Citation: Elsner B, Kugler J, Pohl M, Mehrholz J. Transcranial direct current stimulation (tDCS) for improving activities of daily living, and physical and cognitive functioning, in people after stroke. Cochrane Database of Systematic Reviews 2016, Issue 3. Art. No.: CD009645. DOI: 10.1002/14651858.CD009645.pub3. Link to Cochrane Library. [PubMed: 26996760]

Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.

PMID: 26996760

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