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

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