Through an updated review of randomized controlled trials, this meta-analysis aims to provide a comprehensive examination of the safety and efficacy of transcranial direct current stimulation (tDCS) in patients with refractory epilepsy.

Following the PRISMA guidelines, PubMed, Ovid MEDLINE, Embase, EBSCO, Scopus, Cochrane Central, and WOS (Web of Science) were searched from inception until June 2023 to identify relevant RCTs. Search results were compiled in Rayyan. Data were extracted and analyzed with RevMan web software. Variables such as electrodes location, current intensity, number of sessions, duration of stimulation, frequency and duration of epilepsy, and complications were extracted. Pooled mean difference was calculated for change in seizure frequency (SF), and number of Interictal epileptiform discharge (IED) at four and eight weeks. Cochrane ROB-II was used to assess the quality of the included studies. 

Eight RCTs were included with a total of 242 patients. Compared to the sham group, tDCS patients had a significantly lower seizure frequency at four and eight weeks of follow-up (MD= -4.72, 95% CI [-6.80, -2.65] P < 0.05) and (MD = -3.39, 95% CI  [-6.07, -0.72], P < 0.05), respectively. The IED was observed to decline at four weeks of follow-up (MD = -5.35, 95% CI  [-7.70, -2.99], P < 0.05). The reported adverse events were not serious. It includes only mild itching and erythematous rash that resolved spontaneously.

It was found that tDCS significantly reduced SF and the number of IED. However, there was a heterogeneity in the SF at eight weeks of follow-up. Future large RCTs are needed with a standard clear informed stimulation protocol to further promote tDCS therapy in the management of refractory epilepsy.