Background: Improvement in sensory detection thresholds was found associated with neuropathic pain relief produced by epidural motor cortex stimulation with surgically implanted electrodes.
Objective: To determine the ability of repetitive transcranial magnetic stimulation (rTMS) of the motor cortex to produce similar sensory changes.
Methods: In 46 patients with chronic neuropathic pain of various origins, first-perception thresholds for thermal (cold, warm) and mechanical (vibration, pressure) sensation were quantified in the painful zone and in the painless homologue contralateral territory, before and after rTMS of the motor cortex corresponding to the painful side. Ongoing pain level was also scored before and after rTMS. Three types of rTMS session, performed at 1Hz or 10Hz using an active coil, or at 10Hz using a sham coil, were compared. The relationships between rTMS-induced changes in sensory thresholds and in pain scores were studied.
Results: Subthreshold rTMS applied at 10Hz significantly lowered pain scores and thermal sensory thresholds in the painful zone but not mechanical sensory thresholds. Pain relief correlated with post-rTMS improvement of warm sensory threshold in the painful zone.
Conclusions: Thermal sensory relays are potentially dysfunctioning in chronic neuropathic pain secondary to sensitisation or deafferentation-induced disinhibition. By acting on these structures, motor cortex stimulation could relieve pain and concomitantly improve innocuous thermal sensory discrimination.
- motor cortex stimulation
- neuropathic pain
- quantitative sensory testing
- thermal sensation
- transcranial magnetic stimulation