MONITORING FOR SPINAL-CORD ISCHEMIA BY USE OF THE EVOKED SPINAL-CORD POTENTIALS DURING AORTIC-ANEURYSM SURGERY

Purpose: This clinical study was to evaluate changes of evoked spinal cord potentials (ESCPs) elicited by direct spinal cord stimulation and to determine their relation to spinal cord ischemia during aortic ane urysm surgery. Methods: We monitored descending ESCPs from the thoraci c spinal cord and lumbar enlargement after cervical spinal cord stimul ation (thoracic descending ESCP and lumbar descending ESCP), and segme ntal ESCP at lumbar enlargement elicited by bilateral tibial nerve sti mulation in 22 aortic aneurysm surgical operations. Results: ESCP chan ges were classified into three types: (1) decrease of amplitude in lum bar descending ESCP and segmental ESCP; (2) decrease of amplitude in s egmental ESCP atone; (3) decrease of amplitude in all ESCPs. The late negative waves of both lumbar descending ESCP and segmental ESCP were more sensitive than other components of ESCPs. Postoperative paraplegi a occurred in the two cases that showed persistent diminution of ampli tude in the late negative waves. Segmental ESCP was less reliable than lumbar descending ESCP, because it depended entirely on the adequate perfusion of the lower extremities. Conclusions: Lumbar descending ESC P was the best method for the spinal cord ischemia during aortic aneur ysm surgery. Spinal cord ischemia could be detected by diminution in t he amplitude of the late negative wave of lumbar descending ESCP. The recovery amplitude of the late negative wave after declamping correlat ed with the neurologic outcome.