tDCS for Patients With Disorders of Consciousness tDCS for Patients With Disorders of Consciousness

The study covered in this summary was published on as a preprint and has not yet been peer reviewed.

Key Takeaways

  • Meta-analysis data from eight randomized controlled trials (RCT) showed that transcranial direct-current stimulation (tDCS) treatment for patients with disorders of consciousness (DoC) was more effective at improving behavioral performance compared to controls.

  • Patients who underwent more than one session of tDCS showed statistically significant improvement in behavioral performance compared to controls.

  • Subgroup analysis suggested that patients who are male or with a minimally conscious state (MCS) diagnosis were most likely to respond to tDCS treatment, and treatment effects tended to be more pronounced for patients under 65 years old.

Why This Matters

Study Design

  • This systematic review and individual patient meta-analysis identified RCT of studies utilizing tDCS as an intervention for DoC patients by searching terms “persistent vegetative state (PVS),” “unresponsive wakefulness syndrome (UWS),” “MCS” or “DoC,” and “tDCS.”

  • Studies were included if: (1) studies recruited patients diagnosed with MCS, PVS, or UWS; (2) tDCS was used as an intervention; (3) sham stimulation was used as the control; (4) pre- and post-tDCS Coma Recovery Scale Revised (CRS-R) scores were used to measure the recovery in DoC patients as the outcomes; (5) RCTs used either crossover or parallel design; and (6) the authors provided individual patient data.

  • Studies were excluded if they: (1) were published as a conference abstract, as narrative or systematic reviews, or in books; (2) were not RCT or observational studies; or (3) were not accessible in English.

  • Study-level data (first author, year of publication, study design, number of included patients, tDCS protocol including number of sessions, current intensity, stimulation duration, stimulation site, and adverse effects) and patient-level data (age, gender, diagnosis, etiology of injury, time from injury to tDCS intervention, and CRS-R score at baseline and after intervention) were extracted, and variables transformed to create a uniform database. The risk of bias in each trial was assessed by two authors independently using the Cochrane Risk Bias Tool.

  • The outcome measured was the behavioral effect of tDCS treatment measured via the absolute change in CRS-R score between pre-tDCS baseline score and post-tDCS score after all treatment sessions.

  • Statistical analysis involved a combination of a one-stage method, a generalized linear mixed-effects model to analyze all trials simultaneously, and a two-stage method. Each trial was analyzed separately followed by a random-effects meta-analysis model to account for variability between trials.

Key Results

  • Literature research and screening criteria identified eight RCT with 180 patients total that were eligible for inclusion in the meta-analysis: four studies were from Belgium, three from China, and one from Italy.

  • Among the included trials, 41 participants of two trials were in parallel-RCT design (18 were allocated to the sham-tDCS group, and 23 to the active-tDCS group) and 139 participants of six trials were in crossover-RCT design (all 139 participants were allocated to both active-tDCS group and sham-tDCS group with a washout time interval between the two groups). In total, 157 participants received sham-tDCS and 162 received active-tDCS.

  • Meta-analysis demonstrated a mean difference change in the CRS-R score of 0.89 (95% CI, 0.17 – 1.61) between tDCS and sham-control, favoring tDCS.

  • Subgroup analysis showed that patients who were male or in MCS were associated with greater improvement in CRS-R score and that five or more sessions of tDCS were more effective than one session.


  • Only the behavioral effect of tDCS was analyzed in this meta-analysis, while individual studies assessed neurophysiological effects such as electroencephalogram (EEG) power spectra, EEG complexity, EEG connectivity analyses, and event-related potential (ERP) analyses.

  • Due to the heterogeneity of individual participant data, some information from individual studies was excluded with the transformation of data necessary to create uniform database.

  • The interaction analyses in subgroup analysis may have been limited for detecting heterogeneity in treatment outcomes.


  • Xuehai Wu is supported by the Shanghai Municipal Science and Technology Major Project (No.2018SHZDZX01).

  • The authors have disclosed no relevant financial relationships.

This is a summary of a preprint research study, “Behavioral effects in disorders of consciousness following transcranial direct current stimulation: a systematic review and individual patient data meta-analysis of randomized clinical trials,” written by Zeyu Xu from the Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University; National Center for Neurological Disorders; Neurosurgical Institute of Fudan University; and Shanghai Clinical Medical Center of Neurosurgery, Shanghai, China, and colleagues on provided to you by Medscape. This study has not yet been peer reviewed. The full text of the study can be found