Early Detection of Pedicle Screw-Related Spinal Cord Injury By Continuous Intraoperative Neurophysiological Monitoring (IONM)

Abstract

ABSTRACT.Pedicle screw placement has a high risk of damaging the motor and sensory pathways due to the close proximity to the spinal cord and nerve roots. Early detection and prevention of injury can be achieved by utilizing Somatosensory Evoked Potentials (SSEP) and Transcranial electrical Motor Evoked Potentials (TCeMEP) during a scoliosis surgery.A 19-year-old female presented for correction of scoliosis. After intubation, electrodes were placed for upper and lower SSEPs, EMGs and TCeMEPs. Total intravenous anesthesia was used. Baseline SSEP and TCeMEP responses were present in all limbs.Eight pedicle screws were placed. After placing the last screw, TCeMEP signals were lost bilaterally in lower extremities. Surgery was paused. After removing all the screws TCeMEP responses returned to baseline in left lower limb but remained absent in right lower limb. A wake-up test was performed which was positive in her right leg. Blood pressure was increased and bolus of steroids was given. There was no improvement in right lower limb TCeMEP responses. Surgeon was advised to stop the surgery and proceed for MRI and follow-up. SSEP signals remained stable in all four extremities. The surgical correction was cancelled. MRI revealed intramedullary spinal cord ischemic changes at Til. After extubation, patient was unable to move her right lower extremity with flaccid paralysis. She also complained about severe burning in her left lower extremity. The patient was taken for rehabilitation exercises. One week post-op, she was moving hip flexors and two weeks later had a full motor function, bilaterally.Real-time IONM was useful in early identification of spinal cord injury. Significant changes were seen in TCeMEP, without any change in SSEP. We highly recommend utilizing continuous TCeMEP and SSEP monitoring during pedicle screw placement for prevention of injury to the spinal cord. In this case, the patient would have been paralyzed post-operatively without the use of IONM.