Intra‐Operative Neurophysiological Monitoring in Patients with Thoracic Spinal Stenosis: Its Feasibility and High‐Risk Factors for New Neurological Deficit

OBJECTIVE: Considering the high risk of postoperative neurological complications for patients with thoracic spinal stenosis (TSS), intra‐operative neurophysiological monitoring (IONM) has been used for detecting possible iatrogenic injury timely. However, the IONM waveforms are often unreliable. This article is designed to determine the test performance of somatosensory evoked potentials (SEP) and motor evoked potentials (MEP) during surgical thoracic decompression in patients with TSS, and to investigate the risk factors associated with deteriorated neurologic function at immediate postoperation. METHODS: Patients undergoing posterior spinal fusion from February 2009 to December 2020 were retrospectively reviewed. Patients were divided into the deteriorated neurologic function (DNF) group and the improved/intact neurological function (INF) group based on the postoperative neurological status. Demographic parameters such as gender, age, height, weight, etiology and IONM data were compared between groups. Demographics and IONM data between DNF and INF groups were compared by independent t or nonparametric tests. The incidence of abnormal SEP was analyzed by Chi‐square test. RESULTS: A total of 108 patients (63 males, 45 females) with an average age of 53.5 ± 14.0 years were included. The SEP and MEP records were available in 94 and 98 patients, with the overall success rates being 87.0% and 90.7%, respectively. The sensibilities and specificities were 100% and 88.2% for SEP, 100% and 98.8% for MEP, respectively. There were 17 patients in DNF group and 91 patients in INF group. High weight (79.1 ± 14.6 vs 69.7 ± 15.7 kg, P = 0.024), high inter‐side difference of MEP amplitude (899.1 ± 997.5 vs 492.3 ± 512.4 μV, P = 0.013) and high incidence of abnormal SEP (94.1% vs 64.8%, P = 0.024) were observed in the DNF group. Fourteen (82.4%) patients in the DNF group showed improvement in neurological status during follow‐up. CONCLUSIONS: The overall success rates were 87.0% for SEP and 90.7% for MEP in patients with TSS.