Evidence-Based Guidelines and Secondary Meta-Analysis for the Use of Transcranial Direct Current Stimulation in Neurological and Psychiatric Disorders

Abstract

Background Transcranial direct current stimulation (tDCS) has shown promising clinical results, leading to increased demand for an evidence-based review on its clinical effects. Objective We convened a team of tDCS experts to conduct a systematic review of clinical trials with more than one session of stimulation testing: Pain, Parkinson’s Disease Motor Function and Cognition, Stroke Motor Function and Language, Epilepsy, Major Depressive Disorder, Obsessive-Compulsive Disorder, Tourette Syndrome, Schizophrenia and Drug Addiction. Methods Experts were asked to conduct this systematic review according to the search methodology from PRISMA guidelines. Recommendations on efficacy were categorized into: Levels A (definitely effective), B (probably effective), C (possibly effective) or no recommendation. We assessed risk of bias for all included studies to confirm whether results were driven by potentially biased studies. Results Although most of the clinical trials have been designed as proof-of-concept trials, some of the indications analyzed in this review can be considered as definitely effective (Level A) such as depression, probably effective (Level B) such as neuropathic pain, fibromyalgia, migraine, post-operative patient-controlled analgesia and pain, Parkinson´s disease (motor and cognition), stroke (motor), epilepsy, schizophrenia and alcohol addiction. Assessment of bias showed that most of the studies had low risk of biases and sensitivity analysis for bias did not change these results. Effect sizes vary from 0.01 to 0.70 and were significant in about 8 conditions, with largest effect size being in postoperative acute pain, and smaller in stroke motor recovery (nonsignificant when combined with robotic therapy). Conclusion All recommendations listed here are based on current published Pubmed-indexed data. Despite high level of evidence in some conditions, it needs to be underscored that effect sizes and duration of effects are often limited; thus, real clinical impact needs to be further determined with different study designs.

Age as a Mediator of tDCS Effects on Pain: An Integrative Systematic Review and Meta-Analysis

“…The international scientific community recognizes the importance of producing high-quality evidence of clinical efficacy regarding neuromodulatory techniques, including the tDCS. Aligned to this perspective, a recent meta-analysis points to benefits of tDCS usage in the treatment of many disorders, e.g., neuropathic pain, Parkinson's disease (motor), epilepsy, depression, schizophrenia, chronic and subacute stroke (motor without robotics), and post-stroke aphasia (Fregni et al, 2020). We can also include the primary chronic pain as a prototypical condition in this disease setting the fibromyalgia.…”

Transcranial Direct Current Stimulation as an Add-on Treatment to Cognitive-Behavior Therapy in First Episode Drug-Naïve Major Depression Patients: The ESAP Study Protocol

“…For power spectrum, band power, and intraband mean and median analysis of the EEG frequency ranges, we will use the Fast Fourier transformation analysis, which will allow us to determine and measure the amplitude of the predominant EEG frequency, and properties in the time and frequency domains. For these two EEG analysis, we will define the following frequency bands: delta (1-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), and beta (13-30 Hz) and four frequency sub-bands: low-alpha (9-10 Hz), high-alpha (10-12 Hz), low-beta (13-20 Hz), and highbeta (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), which can be obtained by decomposing the raw signal being generated in different areas of the brain.…”

“…Although tDCS per se showed promising results in treating MDD, the previous trial highlights that the effects of tDCS can be enhanced by combining it with other interventions. Overall, tDCS seems to decrease MDD symptoms by a pooled effect size of 0.36 (22). Moreover, according to a recent individual patient data meta-analysis, tDCS seems to be less effective in high-resistant patients, suggesting that tDCS may be a promising add-on therapy to therapies such as the cognitive behavioral therapy (CBT) (23) or cognitive control therapy (24,25).…”

Neural mechanism underlying task-specific enhancement of motor learning by concurrent transcranial direct current stimulation

“…There are previous reports on the use of tDCS in alleviating neurologic disorders, including stroke ( 4, 15 ). Meta-analyses of published reports ( 16, 17 ) have shown a large variability in the clinical efficacy of tDCS that may be attributed to differences in the tDCS protocol and stroke condition. We thus examined the effect of tDCS on motor learning in a relatively defined mouse model of stroke.…”

“…The timing of tDCS relative to the targeted task performance has been addressed in previous studies of healthy human subjects and stroke patients, but conflicting results have been reported, as summarized by various meta-analyses ( 16, 17 ). For examples, online but not offline anodal tDCS of M1 during motor sequence task was found to enhance motor learning, while online cathodal tDCS had no or opposite effects ( 18, 19 ).…”