STUDY DESIGN: Retrospective case series. OBJECTIVE: Analyze patients who underwent posterior vertebral column resection (PVCR) above the conus medullaris with intraoperative spinal cord monitoring (SCM) data loss. SUMMARY OF BACKGROUND DATA: PVCR is a powerful technique for treating severe spinal deformity but carries a high risk for major spinal cord deficits. METHODS: We assessed clinical, radiographic, and electrophysiologic monitoring and operative records of 90 consecutive adult and pediatric patients (mean age, 24.8 years; range, 7.5-76.8) who underwent PVCR above the conus medullaris for severe spinal deformity performed from 2002 to 2010 by one surgeon at one institution. RESULTS: Fifteen of 90 patients (16.7%) (10 male/5 female; mean age, 15 years) lost SCM (n = 13) or had data degradation meeting warning criteria (n = 2). Diagnoses were kyphoscoliosis (n = 8), angular kyphosis (n = 3), global kyphosis (n = 2), and severe scoliosis (n = 2). Seven were revisions. The average pre-/postoperative scolioses were 99 degrees (range, 32 degrees -152 degrees ) and 43 degrees (range, 6 degrees -76 degrees ), respectively. The average pre-/postoperative kyphoses were +100 degrees (range, 60 degrees -170 degrees ) and +54 degrees (range, 28 degrees -100 degrees ), respectively. SCM fluctuated during osteotomy on nine occasions, stabilizing with elevation of blood pressure in addition to anterior spinal cord decompression in four, correction of subluxation in one, and traction reduction in one. Seven patients had SCM changes during rod compression. Three required partial release of correction, two larger cage insertion, one subluxation correction, and one pedicle screw removal. One experienced changes during rod placement/removal, and another, as a result of hypothermia. Data returned in all after prompt intervention (mean, 10.1 minutes; range, 1-60) and all awoke with intact lower extremity function. CONCLUSION: The prevalence of SCM changes during PVCR above the conus medullaris was 16.7%, mostly during osteotomy and rod/screw compression. Data returned with prompt intervention and all had intact lower extremity motor function postoperatively. These SCM "saves" strongly emphasize the importance of multimodality neurophysiologic monitoring during high-risk cases, minimizing postoperative complications.