Nine patients with post-
stroke pain, six with brachial plexus
injuries, two with
phantom limb pain, one with
spinal cord injury, and one with brain stem injury were treated with a modified motor cortex stimulation (MCS) protocol. Preoperative pharmacological tests were performed with
phentolamine,
lidocaine,
ketamine,
thiopental,
morphine, and placebo. We placed a grid
electrode in the subdural space to decide upon the best stimulation point for
pain relief over a few weeks with the purpose of determining the placement of a Resume
electrode. In five patients, Resumes were implanted in the interhemispheric fissure to reduce lower extremity
pain. In five other patients, Resumes were placed within the central sulcus to stimulate area 4 and area 3b. In addition,
electrodes were also placed on the surface of the precentral gyrus. Fourteen of the 19 patients showed
pain reduction (6 excellent, 3 good, and 5 fair) using the MCS with our results indicating area 4 within the central sulcus to be the optimal stimulation point for
pain relief. We speculate that conventional method may sometimes fail to stimulate area 4 and that focal stimulation of the primary motor cortex within the central sulcus may improve the efficacy of this treatment. Our pharmacological tests show that patients with
ketamine sensitivity seem to be good candidates for MCS. Test stimulation with a subdural multi-grid
electrode and Resumes in the cetral sulcus were helpful in locating the best stimulation point for
pain relief.