Cortical evoked potentials in spinal surgery

Few complications of surgery are as devastating as paraplegia in a patient who has been operated on for correction of a spinal abnormality. Early warning of potential damage to the spinal cord is highly desirable. This is possible with cortical evoked potentials. It measures electroencephalographic activity after peripheral nerve stimulation, and may be used during surgery without interrupting the procedure.In this report, 42 patients were studied by means of cortical evoked potentials. Findings in 35 patients were unremarkable. Six showed changes that made the test valuable; four of these six patients had changes that were ominous. In three of the four, the changes were appreciated and corrections were made to avoid paralysis. In one, changes were not appreciated and the patient became paralyzed. In one case, improvement in conduction was evident when the deformity of the spine was corrected. In another case, the latency was momentarily prolonged when a feeder artery to the cord was ligated.Although this technique requires special training and equipment, its value justifies the trouble and expense. Certainly its common use in spinal surgery is inevitable.