P 108. Robotized-navigated low-frequency repetitive transcranial magnetic stimulation over the right motor and prefrontal cortex improved pain and fatigue in patients with macrophagic myofasciitis

Abstract

Question Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive way to modulate brain neural activities, able to modify cortical functions for clinical and therapeutic purposes. Neuromodulation induced by rTMS notably depends on the frequency of stimulation, equal or less than 1 Hz (low-frequency (LF) rTMS) or equal or more than 5 Hz (high-frequency (HF) rTMS). In patients with unilateral or asymmetric chronic neuropathic pain, HF-rTMS is known to be able to produce analgesic effects when applied to the motor cortex (precentral gyrus) contralateral to pain side. Analgesic effects of HF-rTMS have been also reported when applied to the left dominant motor cortex (M1) in patients with generalized non-neuropathic pain (fibromyalgia). Conversely, motor cortex LF-rTMS was found to be inefficacious in the same conditions. A therapeutic impact on pain syndromes was also observed following HF-rTMS delivered to the left dorsolateral prefrontal cortex (DLPFC), but LF-rTMS of the right DLPFC showed a similar efficacy, according to the theory of interhemispheric balance. In contrast, the potential analgesic effect of LF-rTMS of the right M1 has never been investigated. Methods In a randomized placebo-controlled and double-blinded study, the effects of robotized-navigated LF-TMS applied for two weeks over a target grid of the non-dominant right M1 or DLPFC were assessed in 24 right-handed patients with macrophagic myofasciitis (MFM). Symptomatic MFM represents a rare generalized pain syndrome induced by aluminium oxyhydroxide from vaccine injections. Assessments included measures of pain, fibromyalgia symptoms, quality of life, depression, anxiety, fatigue and cortical excitability. Results LF-rTMS of the right M1 but not of the right DLPFC reduced pain level for at least 4 weeks. Both M1 and DLPFC stimulation yielded significant effects on fibromyalgia symptom severity scale as well as on the cognitive and social components of fatigue. Conclusion For the first time we showed that LF-rTMS may have therapeutic effects in generalized pain, when applied to the non-dominant cortex. We also demonstrated the eligibility of a robotized-navigated rTMS procedure, allowing a precise stimulation over M1 or DLPFC regions, based on individual anatomical targeting.