Monitoring of Spinal Cord Function During Descending Thoracic and Thoracoabdominal Aneurysm Repair

Abstract

Monitoring of spinal cord function is gradually being accepted as a useful adjunct during surgery for aneurysms of the descending and thoracoabdominal aorta. The most common type of monitoring used clinically involves somatosensory evoked potentials (SSEP), but motor evoked potentials (MEP) and direct spinal cord measurements are also feasible. SSEP measurements involve stimulating the posterior tibial nerve of the foot and recording the response via cortical electrodes; median nerve stimulation is used as a control to allow identification of situations in which an abnormal SSEP indicates a problem in the cortical response rather than a peripheral nerve or lower spinal cord injury. SSEPs are not reliable or cannot be recorded if there is peripheral nerve ischemia or during hypothermia, and the response can be affected by anesthetics, but in contrast to MEP, SSEPs can be used even in patients who are awake postoperatively.