Central spinal cord lesion for treatment of intractable pain

$27 SOMATOSENSORY EVOKED POTENTIALS RECORDED FROM WITHIN THE 27 51ide ANTERO-LATERAL QUADRANT OF THE HUMAN SPINAL CORD. Mot 14:00 J. Campbell and S. Lipton. Centre for Pain Relief, Walton Theoire C Hospital, Liverpool England. Aim of Investigation: The procedure of percutaneous cervical cordotomy requires that an electrode be placed within the antero-lateral quadrant. of the spinal cord in order to make a radio-frequency lesion in that area. It was felt that this might offer a rare opportunity to record from within the human spinal cord. This study examines the potentials recorded from this electrode after stimulation of peripheral nerves. Methods: An insulated stainless steel electrode with a 3 nm~. bared tip was introduced into the cervical antero-lateral quadrant of the cord down the centre of a spinal needle. The electrode position was checked both by radiographs and electrical stimulation. The mediafi nerve was stimu]ated electrically at the wrist both ipsilaterally and contralatera]ly. Recordings were obtained from the eordotomy electrode using the spinal needle as the indifferent electrode. Results: Several consistent components of the evoked potential have been identified, some only appearing at high stimulus intensities. The early components are small, starting with a P;3. The ipsilateral response displays a large sharp positive peak at approximately 16 ms. This reaches its maximum amplitude at a stimulus intensity of ].3 x motor threshold. Very high amplitude waves with latencies of between 35 and 65 ms. have been seen in a minority of patients. These displayed exponential habituation which was not seen in the early components. Conclusions: It is possible to record somatosensory evoked potentials from within the human spinal cord using a cordotomy electrode. This technique allows new electrophysiological data to be collected using an existing clinical procedure. CENTRAL SPINAL CORD LESION FOR TREATMENT OF INTRACTABLE PAIN{ ] 28 S l i d e P. L. Gildenberg and Richard M. Hirshberg*, Department of I ' Neurosurgery, The University of Texas Medical School at HousJ Mon 14:15 I T h e a t r e C ! ton, Houston, Texas 77030, USA Patients with intractable cancer pain of the lower body have been successfully treated by making lesions of the spinal cord at various levels in the region of the central canal. The spinal cord is exposed surgically and the lesion made under direct vision, usually with a blunt probe, but in a few patients with a radiofrequency electrode. Satisfactory results have been obtained with lesions between the first cervical level and the thoracolumbar junction, depending on the location of the patients' pain. Eighteen patients have been operated to date. The procedure has been found particularly successful for patients with pain of visceral origin, such as patients with cancer of the rectum or colon, has been found helpful in patients with metastasis of lumbar spine or pelvis, and has been successful in patients with midline pain. An interesting impression is that some of the patients have more intense narcotic withdrawal symptoms following this procedure than had been observed after cordotomy or thalamotomy.