Ohashi Masayuki, Watanabe Kei, Furutani Kenta, Hirano Toru, Katsumi Keiichi, Shoji Hirokazu, Mizouchi Tatsuki, Endo Naoto
Division of Orthopaedic Surgery, Department of Regenerative and Transplant Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata City, Niigata, Japan.
Division of Anesthesiology, Niigata University Graduate School of Medical and Dental Sciences, Niigata City, Niigata, Japan.
Spinal Cord Ser Cases. 2017 Sep 21;3:17053. doi: 10.1038/scsandc.2017.53. eCollection 2017.
Transcranial motor evoked potential (TcMEP) monitoring is the gold standard for intra-operative neurological monitoring (IOM) of motor pathways during complex spine surgery because of its high sensitivity and specificity. However, although it is very low, the rate of false-negatives in TcMEP monitoring is not zero. Therefore, over-reliance on TcMEP monitoring can cause potentially preventable motor deficits.
We report a case of motor deficits due to nerve root stretch after surgical correction of a congenital lumbar kyphoscoliosis in a 56-year-old woman. TcMEPs did not show any significant changes during surgery, whereas free-run electromyography (EMG) demonstrated a long-lasting train activity in the left quadriceps femoris muscle (QF) after correction at the osteotomy area. According to the normal findings on TcMEP monitoring, we did not release the correction. Postoperatively, a significant decrease (grade 2-) in the manual muscle test for the left QF and iliopsoas muscle and hypesthesia of the left anterior thigh was revealed. Fortunately, muscle strength was fully recovered without revision surgery at 6 months postoperatively; however, numbness in the left anterior thigh persisted at 2 years after surgery.
Our report suggests that the possibility of false-negative TcMEPs should be kept in mind, especially during surgery with a risk of nerve root injury. When abnormal findings in the free-run EMG, including long-lasting train activity, are observed, surgeons should consider performing appropriate responses, such as the release of the correction, even when no substantial changes are seen in the TcMEPs.
经颅运动诱发电位（TcMEP）监测因其高敏感性和特异性，是复杂脊柱手术中运动通路术中神经监测（IOM）的金标准。然而，尽管TcMEP监测的假阴性率很低，但并非为零。因此，过度依赖TcMEP监测可能会导致潜在的可预防的运动功能障碍。
我们报告一例56岁女性先天性腰椎后凸侧弯手术矫正后因神经根牵拉导致运动功能障碍的病例。手术过程中TcMEP未显示任何显著变化，而自由运行肌电图（EMG）显示在截骨区域矫正后左股四头肌（QF）出现持续的成串活动。根据TcMEP监测的正常结果，我们未放松矫正。术后，左QF和髂腰肌的徒手肌力测试显著下降（2-级），左大腿前部感觉减退。幸运的是，术后6个月肌力完全恢复，无需翻修手术；然而，术后2年左大腿前部麻木仍持续存在。
我们的报告表明，应牢记TcMEP出现假阴性的可能性，尤其是在有神经根损伤风险的手术中。当观察到自由运行EMG出现异常结果，包括持续的成串活动时，即使TcMEP未出现实质性变化，外科医生也应考虑采取适当措施，如放松矫正。
