Somatosensory evoked potential monitoring in anterior thoracic vertebrectomy

Object. Spine surgeons have used intraoperative cortical and subcortical so matosensory evoked potential (SSEP) monitoring to detect changes in spinal cord function when intraoperative procedures can be performed to prevent ne urological deterioration. However, the reliability of SSEP monitoring as ap plied to anterior thoracic vertebral body resections has not been rigorousl y assessed. Methods. The authors retrospectively reviewed hospital charts and operating room records obtained between August 1993 and December 1998 and found that SSEP monitoring was used in 44 surgical procedures involving an anterior a pproach for thoracic vertebral body resections. There were no patients in whom SSEP changes did not return to baseline duri ng the surgical procedure. Patients in four cases, despite their stable SSE P recordings throughout the procedure, were noted immediately postoperative ly to have experienced significant neurological deterioration. The false-ne gative rate in SSEP monitoring was 9%. Sensitivity was determined to be 0%. Conclusions. It is important to recognize high false-negative rates and low sensitivity of SSEP monitoring when it is used to record spinal cord funct ion during anterior approaches for thoracic vertebrectomies. The insensitiv ity of SSEPs for motor deterioration during anterior thoracic vertebrectomi es is likely due to the limitation of SSEPs. which monitor only posterior c olumn function whereas motor paths are conveyed in the anterior and anterol ateral spinal cord. The authors believe that SSEPs can not be relied on to detect reversible spinal damage during anterior thoracic vertebrectomies.