Abstract
We studied whether the spinal cord evoked potential which was obtained from spinal cord stimulation could be applied to small animal clinical use. Five normal adult mongrel dogs and a mongrel puppy with spinal damage were used. To record the basic wave pattern, laminectomy was performed on the 12th and 13th thoracic vertebrae and the 5th and 6th lumbar vertebrae in 2 normal animals, and 2 bipolar electrodes were inserted under fluoroscopy into the exposed epidural region. In 3 other normal animals, electrodes consisting of epidural needles were inserted into the cerebellomedullary cistern and the 6th and 7th lumbar vertebrae by puncture. In the dog with spinal damage, a stimulating electrode was inserted into the cerebellomedullary cistern, and recordings were made at various points with a wide exposure of the lesion. In the normal dogs, changes in the wave pattern was observed with different positions of the stimulating or recording electrodes placed on or near the spinal cord, and with different stimulating intensity. Acute spinal pressure resulted in the changes of the wave pattern of the spinal cord evoked potential. The normal wave pattern was recorded frequently as a two-peaked negative potential. Recordings with the electrode placed on the exposed epidural cavity had the same wave patterns as those with the electrode by puncture. In clinical use recordings by puncture will be a better method because of easiness and safety. In the acute pressure experiment, the delay of latency and decrease of amplitude were observed with the intensity of pressure. In the clinical case, when the recording electrode was transferred along the spinal cord from the cranial site to the caudal site through the lesion, the decrease of amplitude was observed as the electrode approached the disordered region : a positive wave pattern was recorded at the disordered region, and then no potential was recorded if the electrode passed over the disordered region. This proves that an conduction disorder was in presence at the disordered region, suggesting the possibility of its clinical application.
