Motor cortex stimulation in patients with chronic central pain.

Background: Motor cortex stimulation is one of the neuromodulation methods of treating refractory central neurogenic pain.

Objectives: The aim of this study was to retrospectively evaluate the effects of motor cortex stimulation.

Material And Methods: The study group consisted of 14 consecutive patients with thalamic pain, atypical facial pain, post-brachial plexus avulsion injury pain, phantom pain and pain in syringomyelia who were treated with motor cortex stimulation at the Department of Neurosurgery of the Military Research Hospital in Bydgoszcz, Poland, from 2005 to 2013. The procedures were conducted with the use of neurosurgical navigation and intraoperative neurophysiological monitoring. The outcomes were assessed in terms of visual analog scale scores. The long-term follow-up ranged from one to six years.

Results: A statistically significant reduction in the intensity of pain was noted in patients treated with motor cortex stimulation (pre-surgery median visual analog scale=9, short-term result median visual analog scale=3, p=0.0009; long-term result median visual analog scale=5, p=0.0036). Over the long term, with follow-ups ranging from one to six years, the results were excellent (over 80% reduction in pain) in 31% of the patients and satisfactory (50-80% reduction in pain) in 23% of the patients. Unsatisfactory pain control (less than 50%) was noted in 31% of the patients and no improvement was noted in 15%. Significantly better relief of pain was observed in the early postoperative period. In this series of patients, the highest efficacy of motor cortex stimulation was observed in post-stroke or post-hemorrhagic thalamic pain (5/7 patients-71%). Long-term outcomes were not related to the age or sex of the patient, the preoperative duration of the pain, or to the position or number of implanted electrodes.

Conclusions: MCS significantly reduces the intensity of neurogenic pain. The best long-term results in the present study were achieved in patients with thalamic syndrome. No significant predictors were found for a successful final outcome. The authors consider appropriate selection of patients, accurate placement of the electrodes and frequent adjusting of the stimulation parameters to be important factors increasing the efficacy of MCS.