High-frequency rTMS over the dorsolateral prefrontal cortex on chronic and provoked pain: A systematic review and meta-analysis

Background: High-frequency rTMS over the dorsolateral prefrontal cortex (DLPFC) has demonstrated mixed effects on chronic and provoked pain. Objectives/Methods: In this study, a meta-analysis was conducted to characterise the potential analgesic effects of high-frequency rTMS over the DLPFC on both chronic and provoked pain. Results: A total of 626 studies were identified in a systematic search. Twenty-six eligible studies were included for the quantitative review, among which 17 modulated chronic pain and the remaining investigated the influence on provoked pain. The left side DLPFC was uniformly targeted in the chronic pain studies. While our data identified no overall effect of TMS across chronic pain conditions, there was a significant short-term analgesia in neuropathic pain conditions only (SMD =-0.87). In terms of longlasting analgesia, there was an overall pain reduction in the midterm (SMD =-0.53, 24.6 days average) and long term (SMD =-0.63, 3 months average) post DLPFC stimulation, although these effects were not observed within specific chronic pain conditions. Surprisingly, the number of sessions was demonstrated to have no impact on rTMS analgesia. In the analysis of provoked pain, our data also indicated a significant analgesic effect following HF-rTMS over the DLPFC (SMD =-0.73). Importantly, we identified a publication bias in the studies of provoked pain but not for chronic pain conditions. Conclusions: Overall, our findings support that HF-DLPFC stimulation is able to induce an analgesic effect in chronic pain and in response to provoked pain. These results highlight the potential of DLPFC-rTMS in the management of certain chronic pain conditions and future directions are discussed to enhance the potential long-term analgesic effects. (c) 2021 Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The study found that high-frequency rTMS stimulation of the DLPFC has significant short-term analgesic effects on neuropathic pain. There is also an overall pain reduction in the midterm and long term, as well as significant analgesic effect on provoked pain following HF-rTMS over the DLPFC.