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Objective To analyze the intraoperative neurophysiological monitoring (IONM) data of patients with intraspinal abnormalities undergoing posterior spinal fusion and to determine how intraspinal abnormalities influence IONM results. Methods Patients with severe kyphoscoliosis and intraspinal abnormalities who underwent posterior spinal correction and fusion between September 2015 and January 2019 were retrospectively reviewed. Candidate intraspinal abnormalities included Chiari malformation, syringomyelia, split cord malformation, and tethered cord syndrome. Total intravenous anesthesia was administered, and no muscle relaxant or inhalation anesthesia was used for maintenance. IONM data, including somatosensory evoked potentials (SSEP) and motor evoked potentials (MEP), were recorded. The P37 and N50 latencies and amplitude were recorded for SSEP, whereas only the amplitude was recorded for MEP. The possible high‐risk factors for abnormal IONM results were analyzed. Results The current study included 87 patients (40 men, 47 women) with an average age of 20.2 ± 10.4 years. The etiologies were neuromuscular in 45 patients, idiopathic in four, and congenital in 38. A total of 136 intraspinal abnormalities were detected, including Chiari malformation in 33 patients, syringomyelia in 55, split‐cord malformation in 25, and tethered cord syndrome in 23. Forty patients had one intraspinal abnormality, whereas 47 patients had two or three intraspinal abnormalities. The monitorabilities were 87.4% and 97.7% for the SSEP and MEP, respectively. SSEP alerts were reported in five patients and MEP alerts in four patients, and new neurological deficits were observed in three patients postoperatively. The sensitivity and specificity were 100% and 97.3% for SSEP, and 100% and 98.8% for MEP, respectively. A significant difference in MEP amplitude between the concave and convex sides was observed, while significantly higher SSEP latency was observed on the concave side in patients with preoperative neurological deficits. There were 52 (59.8%) patients with abnormal IONM data. Preoperative neurological deficits (χ 2 = 7.715, p = 0.005) and more than one intraspinal abnormality (χ 2 = 9.186, p = 0.004) indicated a higher risk of abnormal IONM data. Conclusions IONM can be effectively used in patients with intraspinal abnormalities who undergo posterior spinal fusion. Patients with preoperative neurological deficits and more than one intraspinal abnormality have a higher risk of abnormal IONM monitoring.

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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.

Objective. To analyze the performance of intra-operative neurophysiological monitoring (IONM) including somatosensory evoked potentials (SEP) and motor evoked potentials (MEP) in patients with pre-operative neurological deficit and to identify the high-risk factors for failed IONM. Methods. Patients with pre-operative neurological deficit undergoing spinal surgery between October 2010 and August 2019 were retrospectively reviewed. The presence or absence of SEP and MEP of target muscles were separately recorded and the high-risk factors for failed IONM results were investigated. Results. A total of 136 patients (86 males, 50 females) with an average age of 43.0±17.7 years were included. The muscle strength of recorded muscles in 272 lower extremities included grade 1 in 25 muscles, grade 2 in 15, grade 3 in 41, grade 4 in 134 and grade 5 in 57. The SEP records were available in 177 (65.1%) lower extremities while MEP records were available in 199 (73.2%) lower extremities. Significantly higher success rates of SEP and MEP were obtained in lower extremities with muscle strength of grade 4-5 than those of grade 1-3 (P<0.001). Patients with spinal trauma and cervical spinal stenosis were associated with more prevalent failed IONM results. Conclusions. The overall success rates of SEP and MEP were 65.1% and 73.2%, respectively. The high-risk indicators for failed IONM results included muscle strength lower than grade 4, spinal trauma and cervical spinal stenosis.

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Prupose: To analyze the incidence and risk factors of intraoperative neurophysiological monitoring (IONM) alerts in patients undergoing three-column osteotomy.Methods: A total of 551 patients (340 males and 211 females) with an average age of 31.9 years undergoing posterior 3-column osteotomy were retrospectively reviewed. The coronal Cobb angle of main curve and sagittal global kyphosis were measured on preoperative standing whole spinal x-rays. The Frankel scores at preoperation, postoperation, and the last follow-up were recorded and applied for assessment of neurologic status. Surgical procedures and other factors associated with IONM alerts were analyzed.Results: A total of 98 (17.8%) IONM alerts were reported during surgery, including 82 somatosensory evoked potential alerts and 91 motor evoked potential alerts. Positive wake-up test was revealed in 57 patients (10.3%) even after prompt managements, and new neurologic deficits were observed in 50 patients (9.1%) at immediate postoperation. Of the 50 patients with new neurologic deficits at postoperation, the Frankel scores were A in 5 patients, B in 4, C in 9, and D in 32. The x 2 test showed that patients with congenital deformities, global kyphosis .908, vertebral column resection procedure, cervicothoracic/thoracic osteotomy, blood loss .3,000 mL, and preoperative neurologic deficit were at a higher risk of IONM alerts. Conclusions:The incidence of IONM alerts in patients undergoing 3-column osteotomy was 17.8%. Congenital deformities, global kyphosis .908, vertebral column resection, cervicothoracic/thoracic osteotomy, blood loss .3,000 mL, and preoperative neurologic deficit indicated high risk of IONM alerts.

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