Shim Hyok Ki, Lee Jae Meen, Kim Dong Hwan, Nam Kyoung Hyup, Choi Byung Kwan, Han In Ho
Department of Neurosurgery and Medical Research Institute, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea.
J Korean Neurosurg Soc. 2021 Jan;64(1):78-87. doi: 10.3340/jkns.2020.0111. Epub 2020 Dec 24.
Intraoperative neurophysiological monitoring (IONM) has been widely used during spine surgery to reduce or prevent neurologic deficits, however, its application to the surgical management for cervical myelopathy remains controversial. This study aimed to assess the success rate of IONM in patients with cervical myelopathy and to investigate the factors associated with successful baseline monitoring and the effect of increasing the stimulation intensity by focusing on motor evoked potentials (MEPs).
The data of 88 patients who underwent surgery for cervical myelopathy with IONM between January 2016 and June 2018 were retrospectively reviewed. The success rate of baseline MEP monitoring at the initial stimulation of 400 V was investigated. In unmonitorable cases, the stimulation intensity was increased to 999 V, and the success rate final MEP monitoring was reinvestigated. In addition, factors related to the success rate of baseline MEP monitoring were investigated using independent t-test, Wilcoxon rank-sum test, chi-squared test, and Fisher's exact probability test for statistical analysis. The factors included age, sex, body mass index, diabetes mellitus, smoking history, symptom duration, Torg-Pavlov ratio, space available for the cord (SAC), cord compression ratio (CCR), intramedullary increased signal intensity (SI) on magnetic resonance imaging, SI length, SI ratio, the Medical Research Council (MRC) grade, the preoperative modified Nurick grade and Japanese Orthopedic Association (JOA) score.
The overall success rate for reliable MEP response was 52.3% after increasing the stimulation intensity. No complications were observed to be associated with increased intensity. The factors related to the success rate of final MEP monitoring were found to be SAC (p<0.001), CCR (p<0.001), MRC grade (p<0.001), preoperative modified Nurick grade (p<0.001), and JOA score (p<0.001). The cut-off score for successful MEP monitoring was 5.67 mm for SAC, 47.33% for the CCR, 3 points for MRC grade, 2 points for the modified Nurick grade, and 12 points for the JOA score.
Increasing the stimulation intensity could significantly improve the success rate of baseline MEP monitoring for unmonitorable cases at the initial stimulation in cervical myelopathy. In particular, the SAC, CCR, MRC grade, preoperative Nurick grade and JOA score may be considered as the more important related factors associated with the success rate of MEP monitoring. Therefore, the degree of preoperative neurological functional deficits and the presence of spinal cord compression on imaging could be used as new detailed criteria for the application of IONM in patients with cervical myelopathy.
术中神经电生理监测（IONM）已在脊柱手术中广泛应用，以减少或预防神经功能缺损，然而，其在脊髓型颈椎病手术治疗中的应用仍存在争议。本研究旨在评估脊髓型颈椎病患者IONM的成功率，并通过关注运动诱发电位（MEP）来研究与成功的基线监测相关的因素以及增加刺激强度的效果。
回顾性分析2016年1月至2018年6月期间88例行脊髓型颈椎病手术并接受IONM的患者的数据。研究初始刺激电压为400V时基线MEP监测的成功率。在无法监测的病例中，将刺激强度增加至999V，并重新研究最终MEP监测的成功率。此外，使用独立t检验、Wilcoxon秩和检验、卡方检验和Fisher精确概率检验对与基线MEP监测成功率相关的因素进行统计分析。这些因素包括年龄、性别、体重指数、糖尿病、吸烟史、症状持续时间、Torg-Pavlov比值、脊髓可用空间（SAC）、脊髓压迫率（CCR）、磁共振成像上脊髓内信号强度增加（SI）、SI长度、SI比值、医学研究委员会（MRC）分级、术前改良Nurick分级和日本矫形外科学会（JOA）评分。
增加刺激强度后，可靠MEP反应的总体成功率为52.3%。未观察到与强度增加相关的并发症。发现与最终MEP监测成功率相关的因素为SAC（p<0.001）、CCR（p<0.001）、MRC分级（p<0.001）、术前改良Nurick分级（p<0.001）和JOA评分（p<0.001）。成功MEP监测的截断值为SAC 5.67mm、CCR 47.33%、MRC分级3分、改良Nurick分级2分和JOA评分12分。
增加刺激强度可显著提高脊髓型颈椎病患者初始刺激时无法监测病例的基线MEP监测成功率。特别是，SAC、CCR、MRC分级、术前Nurick分级和JOA评分可被视为与MEP监测成功率相关的更重要因素。因此，术前神经功能缺损程度和影像学上脊髓压迫的存在可作为IONM在脊髓型颈椎病患者中应用的新的详细标准。
