Motor cortex stimulation for central and neuropathic facial pain: a prospective study of 10 patients and observations of enhanced sensory and motor function during stimulation.

OBJECTIVE: For more than a decade, motor cortex stimulation has been used to treat difficult central and peripheral neuropathic pain syndromes. This prospective study uses the McGill Pain Questionnaire, a visual analog scale (VAS) score, and an inventory of drug consumption to review the results of treating patients with trigeminal neuropathic pain via motor cortex stimulation.
METHODS: Ten patients underwent motor cortex stimulation between 1999 and 2002. Implantation was performed via intraoperative neuronavigation and cortical mapping for stimulation site targeting. Nine patients had trigeminal neuropathic pain from postherpetic neuralgia, surgical injury, or unknown cause, and one patient had pain of central origin. Patients were evaluated with multimodality scales before, immediately after, and at designated intervals after surgery. Eight patients underwent permanent implantation after a trial evaluation. In two patients, the stimulating electrodes were removed after an unsuccessful trial. One of these patients had a lateral medullary infarct leading to central pain, and in another patient, there was no explanation for the pain.
RESULTS: The average duration of pain before surgery was 6 years. Postoperatively, there was an 88% rate of immediate pain relief (>50% on VAS) and a 75% rate of pain relief at mean follow-up of 10 months (range, 3-24 mo). Mean preoperative McGill Pain Questionnaire total pain rating index was 57 (higher than that observed in causalgia) for patients who did not undergo implantation and 53 for those who underwent implantation. Mean McGill Pain Questionnaire pain rating index at mean follow-up of 10 months was 24 (55% decrease). Mean VAS preoperatively was 9 in patients with stimulator implants and 8 in those whose stimulator was removed after the trial. Immediate postoperative mean VAS score was 1. This score stabilized 3 months after surgery. Patients with implanted stimulators reduced their pain medication dose by a mean of more than 50%. Three patients with facial weakness and sensory loss regained both strength and discriminative sensation during stimulation. In another patient, dysarthria improved. In a review of the literature, 29 (76%) of 38 patients with neuropathic facial pain treated with motor cortex stimulation achieved greater than 50% pain relief.
CONCLUSION: These results provide further support for the use of motor cortex stimulation in facial neuropathic pain and document pain improvement as measured by multidimensional scales. Observations of motor and sensory improvements during stimulation suggest that stimulation alters cortical plasticity and inhibits thalamic hyperactivity.