Transcranial direct current stimulation (tDCS) for improving capacity in activities and arm function after stroke: a network meta-analysis of randomised controlled trials
Elsner et al. Journal of NeuroEngineering and Rehabilitation
Transcranial direct current stimulation (tDCS) for improving capacity in activities and arm function after stroke: a network meta-analysis of randomised controlled trials
Bernhard Elsner 0 1
Gert Kwakkel 2 4 5 6
Joachim Kugler 1
Jan Mehrholz 0 1 3
0 Physiotherapy, SRH University of Applied Health Sciences Gera , Gera , Germany
1 Department of Public Health, Dresden Medical School, Technical University Dresden , Fetscherstr. 74, 01307 Dresden , Germany
2 Department of Rehabilitation Medicine, VU University Medical Center, MOVE Research Institute Amsterdam , Amsterdam , The Netherlands
3 Wissenschaftliches Institut, Private Europäische Medizinische Akademie der Klinik Bavaria in Kreischa GmbH , Kreischa , Germany
4 Department of Physical Therapy and Human Movement Sciences, Northwestern University , Evanston, IL , USA
5 Neuroscience Campus Amsterdam, VU University Amsterdam , Amsterdam , The Netherlands
6 Neurorehabilitation, Amsterdam Rehabilitation Research Center Reade , Amsterdam , The Netherlands
Background: Transcranial Direct Current Stimulation (tDCS) is an emerging approach for improving capacity in activities of daily living (ADL) and upper limb function after stroke. However, it remains unclear what type of tDCS stimulation is most effective. Our aim was to give an overview of the evidence network regarding the efficacy and safety of tDCS and to estimate the effectiveness of the different stimulation types. Methods: We performed a systematic review of randomised trials using network meta-analysis (NMA), searching the following databases until 5 July 2016: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, CINAHL, AMED, Web of Science, and four other databases. We included studies with adult people with stroke. We compared any kind of active tDCS (anodal, cathodal, or dual, that is applying anodal and cathodal tDCS concurrently) regarding improvement of our primary outcome of ADL capacity, versus control, after stroke. PROSPERO ID: CRD42016042055. Results: We included 26 studies with 754 participants. Our NMA showed evidence of an effect of cathodal tDCS in improving our primary outcome, that of ADL capacity (standardized mean difference, SMD = 0.42; 95% CI 0.14 to 0. 70). tDCS did not improve our secondary outcome, that of arm function, measured by the Fugl-Meyer upper extremity assessment (FM-UE). There was no difference in safety between tDCS and its control interventions, measured by the number of dropouts and adverse events. Conclusion: Comparing different forms of tDCS shows that cathodal tDCS is the most promising treatment option to improve ADL capacity in people with stroke.
Stroke; Recovery of function; Transcranial direct current stimulation; Review; Meta-analysis
Background
An emerging approach for enhancing neural plasticity
and hence rehabilitation outcomes after stroke is
noninvasive brain stimulation (NIBS). Several stimulation
procedures are available, such as repetitive transcranial
magnetic stimulation (rTMS) [
1
], transcranial direct
current stimulation (tDCS) [
2–4
], transcranial
alternating current stimulation (tACS) [
5
], and transcranial
pulsed ultrasound (TPU) [
6
]. In recent years a
considerable evidence base for NIBS has emerged, especially for
rTMS and tDCS.
tDCS is relatively inexpensive, easy to administer and
portable, hence constituting an ideal adjuvant therapy
during stroke rehabilitation. It works by applying a weak
and constant direct current to the brain and has the
ability to either enhance or suppress cortical excitability,
with effect lasting up to several hours after the
stimulation [
7–9
]. Hypothetically, this technique makes
tDCS a potentially useful tool to modulate neuronal
inhibitory and excitatory networks of the affected and the
non-affected hemisphere post stroke to enhance, for
example, upper limb motor recovery [
10, 11
]. Three
different stimulation types can be distinguished.
In anodal stimulation, the anodal electrode (+)
usually is placed over the lesioned brain area and the
reference electrode over the contralateral orbit [
12
].
This leads to subthreshold depolarization, hence
promoting neural excitation [
3
].
In cathodal stimulation, the cathode (−) usually is
placed over the non-lesioned brain area and the
reference electrode over the contralateral orbit [
12
],
leading to subthreshold polarization and hence
inhibiting neural activity [
3
].
Dual tDCS means the simultaneous application of
anodal and cathodal stimulation [
13
].
However, the literature does not provide clear
guidelines, not only regarding the tDCS type, but also
regarding the electrode configuration [
14
], the amount of
current applied and the duration of tDCS, or the
question if tDCS should be applied as a standalone therapy
or in combination with other treatments, like
robotassisted therapy [
15
].
Rationale
There is so far conflicting evidence (...truncated)