We have presented a patient (48 year-old male) in whom the evoked spinal potential monitor detected impending spinal ischemia after aortic cross-clamping, which allowed surgical intervention to be modified so as to restore the decaying evoked spinal potential. The patient received replacement of the dissecting aneurysm in the thoracic descending aorta with clamping of the aorta at the sites immediately proximal and distal to the aneurysm and initiation of femoro-femoral venoarterial bypass under normothermia. The evoked spinal potential was recorded via the T12/L1 epidural electrode in response to transdural electric stimulation of the spinal cord at the C7/T1 level. As the evoked spinal potential gradually decreased in amplitude without latency prolongation after aortic cross-clamping, the distal clamp was moved from the T6 vertebral level to the T4. The reduced spinal potential then returned to the baseline amplitude. This episode was repeated twice from surgical necessity. The patient was free from any neurological disorders postoperatively.