• Kazuyoshi Kobayashi, Shiro Imagama, Go Yoshida, Muneharu Ando, Shigenori Kawabata, Kei Yamada, Tsukasa Kanchiku, Yasushi Fujiwara, Shinichirou Taniguchi, Hiroshi Iwasaki, Nobuaki Tadokoro, Masahito Takahashi, Kanichiro Wada, Naoya Yamamoto, Hideki Shigematsu, Masahiro Funaba, Akimasa Yasuda, Sho Kobayashi, Hiroki Ushirozako, Toshikazu Tani, and Yukihiro Matsuyama.
• Department of Orthopedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
• Spine. 2021 Jun 15; 46 (12): E694-E700.

Study DesignProspective multicenter observational study.ObjectiveTo evaluate transcranial motor-evoked potentials (Tc-MEPs) baseline characteristics of lower limb muscles and to determine the accuracy of Tc-MEPs monitoring based on preoperative motor status in surgery for high-risk spinal disease.Summary Of Background DataNeurological complications are potentially serious side effects in surgery for high-risk spine disease. Intraoperative spinal neuromonitoring (IONM) using Tc-MEPs waveforms can be used to identify neurologic deterioration, but cases with preoperative motor deficit tend to have poor waveform derivation.MethodsIONM was performed using Tc-MEPs for 949 patients in high-risk spinal surgery. A total of 4454 muscles in the lower extremities were chosen for monitoring. The baseline Tc-MEPs was recorded immediately after exposure of the spine. The derivation rate was defined as muscles detected/muscles prepared for monitoring. A preoperative neurological grade was assigned using the manual muscle test (MMT) score.ResultsThe 949 patients (mean age 52.5 ± 23.3 yrs, 409 males [43%]) had cervical, thoracic, thoracolumbar, and lumbar lesions at rates of 32%, 40%, 26%, and 13%, respectively. Preoperative severe motor deficit (MMT ≤3) was present in 105 patients (11%), and thoracic ossification of the posterior longitudinal ligament (OPLL) was the most common disease in these patients. There were 32 patients (3%) with no detectable waveform in any muscles, and these cases had mostly thoracic lesions. Baseline Tc-MEPs responses were obtained from 3653/4454 muscles (82%). Specificity was significantly lower in the severe motor deficit group. Distal muscles had a higher waveform derivation rate, and the abductor hallucis (AH) muscle had the highest derivation rate, including in cases with preoperative severe motor deficit.ConclusionIn high-risk spinal surgery, Tc-MEPs collected with multi-channel monitoring had significantly lower specificity in cases with preoperative severe motor deficit. Distal muscles had a higher waveform derivation rate and the AH muscle had the highest rate, regardless of the severity of motor deficit preoperatively.Level of Evidence: 3.Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.

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