Stimulation of internal capsule for relief of chronic pain JOHN E. ADAMS, M.S., YOSHIO HOSOBUCHI, M.D., AND HOWARD L. FIELDS, M.D. Departments of Neurological Surgery and Neurology, University of California School of Medicine, San Francisco, California ~' The severe spontaneous pain associated with lesions of the central nervous system has been successfully suppressed by electrical stimulation of the posterior limb of the internal capsule. The physiological basis for this result is not understood but the authors' hypothesis is that the pain suppression is due to stimulation of parietal cor- ticofugal inhibitory fibers. KEY W o a D s ~ pain 9 electrical stimulation 9 paraplegia 9 internal capsule 9 parietal cortex 9 thalamus E LECTRICAL stimulation of specific areas in the central nervous system has shown promise in the treatment of chronic pain syndromes of both peripheral and central origin. It has been demonstrated that electrical stimulation through electrodes placed over the dorsal columns of the spinal cord can effectively ameliorate many cases of pain arising in a variety of peripheral sites, and of varying etiology: '1~ Electrical stimula- tion of subcortical sites in the brain has also been demonstrated to be effective in the treat- ment of certain severe chronic pain states. Relief has been reported from stimulation in the septal region, e caudate nucleus: and posterior diencephalon. 1~ We have recently reported control of in- tractable pain associated with facial anesthe- sia dolorosa in four patients. The stimulating electrodes were placed in the nucleus posterior ventralis medialis (PVM): Encouraged by this initial success with diencephalic stimulation in the treatment of facial anesthesia dolorosa when the thalamic somatosensory neuron was stimulated, we next explored the possibility that similar stimulation of the somatosensory neurons in the region of the posterior limb of the internal capsule might provide relief from the pain associated with lesions of the central nervous system. Method Patients with the syndrome of pain associated with cerebral pathology were ini- tially selected. Subsequently the technique was extended to patients with pain related to spinal cord injury. The operative technique for the insertion of the stimulating platinum electrodes has been previously described: The multicontact flexible electrodes* are implanted stereotaxi- *The electrodes and electronic hardware were manufactured by Medtronic Inc., Minneapolis, Minnesota. 740 J. Neurosurg. / Volume 41 / December, 1974