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Repetitive transcranial magnetic stimulation (rTMS) is a procedure increasingly used to treat patients with central neuropathic pain, but its efficacy is still under debate. Patients with medically refractory chronic central neuropathic pain were included in 2 randomized phases (active/sham), separated by a wash-out period of 8 weeks. Each phase consisted of 4 consecutive rTMS sessions and a final evaluation session, all separated from one another by 3 weeks. High-frequency (20 Hz) rTMS was delivered over the primary motor cortex (M1) contralateral to the patient's pain using a neuronavigated robotic system. Patients and clinicians assessing outcomes were blinded to treatment allocation during the trial. The primary outcome measured the percentage of pain relief (%R) from baseline. Secondary outcomes were VAS score, Neuropathic Pain Symptom Inventory, analgesic drug consumption, and quality of life (EQ-5D). Thirty-six patients performed the entire study with no adverse effects. The analgesic effect for the main criterion (%R) was significantly higher in the active (33.8% confidence interval [CI]: [23.88-43.74]) than in the sham phase (13.02% CI: [6.64-19.76]). This was also the case for the secondary outcome VAS (-19.34% CI: [14.31-25.27] vs -4.83% CI: [1.96-8.18]). No difference was observed for quality of life or analgesic drug consumption. Seventeen patients (47%) were identified as responders, but no significant interaction was found between clinical and technical factors considered here and the analgesic response. These results provide strong evidence that 3 weeks spaced high-frequency rTMS of M1 results in a sustained analgesic effect and support the clinical interest of this stimulation paradigm to treat refractory chronic pain.

The intensity of experimental pain is known to be dependent on stimulation duration. However, it remains unknown whether this effect arises largely from the actual stimulus duration or is substantially influenced by the subject's perception of the stimulus duration. In the present study, we questioned this issue by misleading the perception of the duration of pain in a population of 36 healthy volunteers stimulated with a thermode. To this aim, time was signified by a clock with rotating hands in which imperceptible differences in speed rotation had been introduced. Subjects were therefore immersed in 2 comparative conditions in which time was manipulated to provide the illusion of either long or short duration of the painful stimulus. In a first condition ("full-length" clock), participants were instructed that pain would last for a complete revolution of the clock's hands, whereas in the second condition ("shortened" clock), revolution was reduced by 25%. Although the intensity and the real duration of stimulation were identical in both conditions, the intensity of pain was significantly reduced when the perception of time was misleadingly shortened by the manipulated clock. This study suggests that the perceived duration of a noxious stimulation may influence the perceived intensity of pain. The perceived duration of the length of a noxious stimulation influences (decreases) the intensity of perceived pain.