The value of somatosensory evoked potential combined with EMG monitoring in cervical spine surgery

Objective To analyze the sensitivity and specificity of SEP and EMG combined monitoring for cervical sur-gery. Methods Data of 90 patients (58 males and 32 females, age 28-76 years, averaged 52±20 years) who had undergone neuro-logical monitoring during cervical spine surgery from Dec. 2014 to May 2016 (24 cervical OPLL cases and 42 cervical myelopathy cases through anterior approach, 24 cervical OPLL through posterior approach) were retrospectively analyzed. SEP monitoring of bilateral median nerves and tibial nerves, combined with EMG monitoring of bilateral deltoid and biceps muscles were performed for all the patients. The neurological status was evaluated by JOA score before the surgery and 3 months after the surgery. The sen-sitivity, specificity, false positive rate, false negative rate, positive predictive value and negative predictive value of SEP, EMG and EMG+SEP techniques were calculated. Results The JOA score improved after the surgery in 81 of 90 patients. In 4 cases of ante-rior cervical decompression and fixation for cervical OPLL and 1 case of cervical spondylotic myelopathy, temporary abnormal change was detected in SEP monitoring. In one patient, temporary single side neurological deterioration was detected, whose JOA was 13 preoperatively, which decreased to 8 instantly after surgery and increased to 14 at 3-month follow-up. There were 8 pa-tients (4 cases of OPLL with anterior approach, 2 cases of OPLL with posterior approach, 2 cases of cervical spondylotic myelopa-thy with anterior approach) had abnormal EMG change without SEP abnormal change during the surgery. 4 patients had tempo-rary C5 nerve palsy after surgery. The JOA was 14-15 preoperatively, which declined to 10-11 instantly after surgery and in- creased to 13-15 at 3-month follow-up. The sensitivity, specificity, false positive rate, false negative rate, positive predictive value and negative predictive value was 55.5%, 100%, 0, 44.4%, 100%, and 95.3% for SEP, while 44.4%, 95.1%, 4.9%, 55.5%, 50% and 93.9% for EMG and 100%, 95.1%, 4.9%, 0%, 69.2% and 100% for EMG+SEP. Conclusion SEP combined with EMG moni-toring increased the sensitivity in neurological monitoring for cervical spine surgery, which can prevent severe neurological deterio-ration, especially C5 nerve palsy. Key words: Cervical vertebrae; Ossification of posterior longitudinal ligament; Spinal cord compression; Evoked poten-tials, somatosensory; Electromyography