Benefits of Monitoring Motor-Evoked Potentials during Thoracoabdominal Aortic Aneurysm Repair: Technique of Choice to Assess Spinal Cord Ischemia?

Spinal cord ischemic injury following thoracoabdominal aortic aneurysm (TAAA) repair remains the most devastating complication, which still occurs in 10 to 30°I° of patients, despite protective measures such as distal aortic perfusion, cerebrospinal fluid (CSF) drainage, epidural cooling, and reattachment of intercostal arteries. One of the most important limitations of protective actions is the inability to assess the adequacy of spinal cord perfusion and cord function. We developed a technique to record motor-evoked potentials (MEPs) during thoracoabdominal aortic surgery to assess spinal cord ischemia and evaluate the subsequent protective strategies to prevent neurological deficit. Furthermore, a subpopulation was simultaneously monitored with somatosensory evoked potentials (SSEPs). The surgical protocol included left heart bypass and CSF drainage. When spinal cord ischemia was detected, distal aortic pressure and mean arterial pressure were increased. By means of sequential crossclamping, MEPs were used to identify critical intercostal or lumbar arteries. The results show that monitoring of MEPs allows accurate assessment of spinal cord ischemia. SSEP monitoring does not offer additional benefit because of delayed ischemia detection and a high incidence of false-positive and false-negative results. Surgical stragegies based on MEPs prevented neurological deficits in 97% of patients treated for type I and II TAAA.