Delayed response of transcranial myogenic motor-evoked potential monitoring to spinal cord ischemia during repair surgery for descending thoracic aortic aneurysm.

The efficacy of transcranial myogenic motor-evoked potential (tc-MEP) monitoring during thoracic aortic surgery has been the subject of some reports, because tc-MEP monitoring can rapidly reflect changes in spinal cord blood flow during thoracic aortic cross-clamping. In this article, we present a case in which delayed loss of tc-MEP signals was observed after cross-clamping of the descending thoracic aorta. We must be aware that tc-MEPs recorded from the lower extremities can fail to provide rapid detection of spinal cord ischemia in the upper thoracic level after cross-clamping of the descending thoracic aorta.