Intraoperative somatosensory evoked potential monitoring during cervical spine corpectomy surgery

Study Design. Retrospective review. Objectives. To review consecutive cases of cervical spine corpectomy surgery performed with intraoperative somatosensory-evoked potential ( SSEP) monitoring. Summary of Background Data. There is controversy about the utility of SSEP monitoring during anterior cervical spine surgery. There is no study in the literature that has specifically evaluated the utility of SSEP monitoring for cervical spine corpectomy surgery. Methods. Intraoperative SSEP tracings for 508 patients ( average age, 55.7 years; 268 male, 240 female) who underwent anterior cervical fusion with single-level or multilevel corpectomies were reviewed. Intraoperative and postoperative records were analyzed to determine if any new neurologic deficits developed when the patients woke up from anesthesia. Results. The overall incidence of a new postoperative neurologic deficit in this series of patients was 2.4% (11 with nerve root injury, 1 with quadriplegia). The incidence of significant SSEP changes was 5.3% ( 27 of 508 patients). The most common identifiable cause of SSEP changes was hypotension, and the most common neurologic deficit was deltoid (C5) weakness. One patient had irreversible SSEP changes, and he woke up with new-onset quadriplegia. The calculated sensitivity and specificity of intraoperative SSEP monitoring for detecting impending or resultant intraoperative iatrogenic neurologic injury were 77.1% and 100%, respectively. However, if the isolated nerve root injuries are removed from the analysis, then both the calculated sensitivity and the negative predictive values were 100%. Conclusions. Intraoperative SSEP monitoring can alert the surgeon to adverse iatrogenic intraoperative events with potential for neurologic injury. Most SSEP signal changes are reversible and do not result in a clinical deficit. Isolated nerve root injury appears to be the most common iatrogenic intraoperative injury during cervical spine corpectomy surgery.