Effects of Non-invasive Brain Stimulation on Headache Intensity and Frequency of Headache Attacks in Patients With Migraine: A Systematic Review and Meta-Analysis

Background Non-invasive brain stimulation (NIBS) techniques such as repetitive transcranial magnetic stimulation (rTMS), as well as transcranial direct current stimulation (tDCS) electrically stimulate the brain and modify brain activity to suppress pain. This method is emerging as a potential clinical intervention against migraine. Objective To quantitatively review the efficacy of rTMS and tDCS in randomized controlled trials (RCTs) in modifying headache intensity and frequency of headache attacks in patients suffering from migraine. Methods We searched 5 databases: PubMed, EMBASE, Web of Science, Cochrane Library, and Scopus for articles from January 2000 to September 2018. Any RCT regarding the efficacy on rTMS and tDCS on patients with migraine, was considered to be included. A random effects meta-analysis was performed to pool effect sizes of outcomes related to headache intensity or frequency of headache attacks. The methodological quality of the included RCTs was assessed using the Physiotherapy Evidence Database scale. Results Nine RCTs with 276 participants in total (experimental group [EG] = 149; control group [CG] = 127) were included in this review. Five included articles used rTMS (EG = 81; CG = 80), and 4 used tDCS (EG = 68; CG = 47). Meta-analysis of excitatory primary motor cortex (M1) stimulation showed significant effects on reducing headache intensity in patients with migraine (Hedges' g = -0.94; 95% CI, -1.28 to -0.59; P < .001, I-2 = 18.39%) with a large effect size. Meta-analysis of excitatory M1 stimulation showed significant effects on reducing frequency of headache attacks in patients with migraine, with a large effect size (Hedges' g = -0.88; 95% CI, -1.38 to -0.38; P = .001, I-2 = 57.15%). Excitatory dorsolateral prefrontal cortex stimulation showed a significant effect on the headache intensity in patients with migraine (Hedges' g = -1.14; 95% CI, -2.21 to -0.07; P = .04, I-2 = 61.86%) with a large effect size. However, reductions of frequency of headache attacks was not significant. Limitations Potential differential effects of rTMS and tDCS, various sham methods, and potential overlapping headache disorders among included subjects may affect the estimation of effect sizes. Conclusion Excitatory NIBS of the M1 is likely to reduce headache intensity and the frequency of headache attacks in patients with migraine.