High Frequency Repetitive Transcranial Magnetic Stimulation Therapy For Chronic Neuropathic Pain: A Meta-analysis

Background: Increasing evidence supports an analgesic effect of repetitive transcranial magnetic stimulation (rTMS) for neuropathic pain (NP). However, the optimal parameters of rTMS (stimulation frequency and treatment sessions) for achieving long-term analgesic effects remain unknown. This study analyzed the current findings in the literature. Objective: The aim of this study was to assess the optimal parameters of rTMS for NP, including the rTMS sessions needed for inducing acute as well as long-term analgesic effects. Study Design: A meta-analysis of the analgesic effect of high frequency rTMS (HF-rTMS) for neuropathic patients. Setting: This meta-analysis examined all studies involving the analgesic efficacy of HF-rTMS for NP. Methods: PubMed, Embase, and the Cochrane library were searched for clinical studies of rTMS treatment on NP published before December 31, 2014. Crude standardized mean differences (SMD) with 95% confidence interval (CI) were calculated for pain intensity after different treatment sessions (from 1 to 10) and follow-up of one or 2 months after rTMS treatment using random effect models. Results: Twenty-five studies (including 32 trials and 589 patients) were selected for the meta-analysis according to the inclusion and exclusion criteria. All 3 HF-rTMS treatments (5, 10, and 20 Hz) produced pain reduction, while there were no differences between them, with the maximal pain reduction found after one and 5 sessions of rTMS treatment. Further, this significant analgesic effect remained forone month after 5 sessions of rTMS treatment. Limitations: There are limitations of this meta-analysis. For example, the long-term analgesic effects of different HF-rTMS and low frequency (LF) rTMS sessions, including the single session of rTMS on different NP of varying origins have yet not been evaluated; the full degree of pain relief is still unclear for many rTMS studies. Conclusions: HF-rTMS stimulation on primary motor cortex is effective in relieving pain in NP patients. Although 5 sessions of rTMS treatment produced a maximal analgesic effect and may be maintained for at least one month, further large-scale and well-controlled trials are needed to determine if this enhanced effect is specific to certain types of NP such as post-stroke related central NP.