False-negative transcranial motor-evoked potentials during scoliosis surgery causing paralysis: a case report with literature review

Case report. To report a case of false-negative intraoperative motor-evoked potentials (MEP) that developed paraplegia after surgery. Although several false-negative results have been reported with somatosensory-evoked potentials, there is no report noted with MEP. Therefore, several authors have preferred using MEPs as a gold standard in neuromonitoring. We report a case of false-negative MEP during the scoliosis surgery which is the first report showing false-negative MEPs during operation. A 15-year-old girl with severe kyphoscoliosis (Cobb angle, 140 degrees) in neurofibromatosis was operated for correction and posterior spinal fusion surgery, using pedicle screw instrumentation. Intraoperative neuromonitoring did not show any change in MEPs throughout the procedure, however, she woke-up with paraplegia. Immediate implant release could not recover her neurology functionally at last follow-up. Positive event during the operation was massive blood loss which could not show drop in MEPs as an ischemic cord injury (probable cause). Postoperative CT scan in both patients did not show any injury with pedicle screw as implants were well placed within the pedicles. Reviewing the literature, we could not find out any prospective study in animals identifying false-negative results with MEPs. From our experience of false-negative MEPs, we conclude that unwanted events with use of MEP in scoliosis or other spinal surgeries. We propose further prospective research on animals to solve this issue.