Objective: To assess the long-term maintenance of analgesia induced by high-frequency repetitive transcranial magnetic stimulation (rTMS) of the motor cortex contralateral to pain in a naturalistic study of patients with chronic refractory facial pain.
Methods: 55 patients were included (cluster headache, n = 19; trigeminal neuropathic pain, n = 21; atypical facial pain, n = 15). The rTMS protocol consisted of an "induction phase" of one daily rTMS session for five days per week during two consecutive weeks, followed by a "maintenance phase" of two sessions during one week, then one session in weeks 4 and 6, and a monthly session for the next five months. In a subset of patients, navigated targeting was performed and session duration was shortened from 20-min to 10-min (with the same number of 2000 pulses per session). The analgesic effect of rTMS was assessed on a 0-10 visual numerical scale from 15 to 180 days after treatment initiation.
Results: All pain measures significantly decreased from baseline to D15: the intensity of permanent pain (5.2 ± 1.6 to 3.2 ± 1.9) and paroxysmal pain (8.6 ± 1.5 to 4.5 ± 3.4), as well as the daily number of painful attacks (5.6 ± 3.1 to 2.3 ± 3.1). The percentage of responders (defined as pain score decrease ≥30%) was 73% at D15 and dropped to 40% at D180. The analgesic effect was similar regardless of the type of pain and was significantly lower when session duration was shortened, irrespective of the number of pulses.
Conclusion: This long-term maintenance rTMS protocol can be a therapeutic option in the clinical management of patients with chronic refractory facial pain, including cluster headache. However, only part of the patients respond to this technique and session duration should not be reduced.
Keywords: Chronic pain; Cluster headache; Facial pain; Trigeminal neuralgia; rTMS.
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