Low-Frequency rTMS of the Primary Motor Area Does Not Modify the Response of the Cerebral Cortex to Phasic Nociceptive Stimuli

Abstract

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive technique of cortical stimulation. Although the exact mechanism of action is not clearly understood, it has been postulated that rTMS action on pain depends most on stimulation sites and stimulation parameters. Most studies concern high-frequency rTMS of the primary motor cortex (M1). High-frequency rTMS over motor cortex seems to induce an analgesic effect while contrasting results were reported after low-frequency rTMS. The aim of the current study was to investigate the effects of 1 Hz rTMS stimulation over the left primary motor cortex on subjective laser pain rating and laser evoked potential (LEP) amplitudes in healthy subjects. Subjects underwent two different sessions (real and sham rTMS) according to a cross-sectional design. In each session, LEPs and laser-pain rating to stimulation of both right and left hand dorsum were collected before 1 Hz rTMS over the left M1 area (baseline), which lasted 20 min. Then, LEPs and laser-pain rating were measured immediately after rTMS (T0), after 20 min from T0 (T0+20), and after 40 min from T0 (T0+40). We could not find any modification of both laser-pain rating and LEP parameters (latencies and amplitudes) following 1 Hz rTMS. Therefore, our results show that the low-frequency rTMS of the M1 area does not change the response of the cerebral cortex to pain.

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“…Traditionally, low-frequency (LF) rTMS (defined as stimulation at frequencies below 1 Hz) has been shown to reduce cortical excitability, whereas high-frequency (HF) rTMS (stimulation at frequencies over 1 Hz) has the opposite effect (Wassermann, 1998;Wagner et al, 2007;Bai et al, 2022). Multiple studies have shown that HF-rTMS provides better pain relief than LF stimulation (Cruccu et al, 2007;Borckardt et al, 2011;Pazzaglia et al, 2018). In previous studies on the analgesic effect of rTMS on PSP, HF-rTMS (5-20 Hz) was found to be effective in relieving pain in PSP.…”

Repetitive transcranial magnetic stimulation in central post-stroke pain: a meta-analysis and systematic review of randomized controlled trials

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