Efficacy of transcranial direct current stimulation for disorders of consciousness: an updated systematic review and meta-analysis based on sham-controlled randomized trials.

BACKGROUND: Transcranial direct current stimulation (tDCS) may improve behavioral signs of consciousness in patients with disorders of consciousness (DoC), but evidence from randomized controlled trials (RCTs) and previous meta-analyses has remained inconsistent. We evaluated the efficacy and safety of tDCS in patients with DoC and explored potential effect modifiers. METHODS: PubMed, Embase, Scopus, Web of Science, and the Cochrane Library were searched for RCTs comparing active tDCS with sham stimulation. For crossover trials, only first-period data were extracted. The primary outcome was the change in Coma Recovery Scale-Revised (CRS-R) score. Mean differences (MDs) with 95% confidence intervals (CIs) were pooled across studies. Subgroup analyses were performed according to baseline level of consciousness, etiology, disease duration, stimulation target, and total stimulation dose. RESULTS: Fourteen trials including 330 patients were included. Active tDCS was associated with greater improvement in CRS-R change scores than sham stimulation (MD = 1.02, 95% CI 0.43-1.60; p < 0.001). A significant subgroup interaction was observed for etiology (p < 0.001), with significant improvements in patients with traumatic brain injury and cerebrovascular accident, but not in hypoxic-ischemic brain injury. Other analyses suggested trends toward improvement in minimally conscious state, left dorsolateral prefrontal cortex stimulation, and higher total stimulation dose, without significant between-subgroup differences. No definite tDCS-related serious adverse events were reported. CONCLUSION: tDCS may improve the level of consciousness in patients with DoC, with no definite tDCS-related serious adverse events identified. Treatment response may differ by etiology, but this finding requires confirmation because multiple subgroup comparisons were performed. SYSTEMATIC REVIEW REGISTRATION: Identifier CRD420261370518.