• Go Yoshida, Hiroki Ushirozako, Masaaki Machino, Hideki Shigematsu, Shigenori Kawabata, Kei Yamada, Tsukasa Kanchiku, Yasushi Fujiwara, Hiroshi Iwasaki, Muneharu Ando, Shinichirou Taniguchi, Tsunenori Takatani, Nobuaki Tadokoro, Masahito Takahashi, Kanichiro Wada, Naoya Yamamoto, Masahiro Funaba, Akimasa Yasuda, Jun Hashimoto, Shinji Morito, Kenta Kurosu, Kazuyoshi Kobayashi, Kei Ando, Katsushi Takeshita, Yukihiro Matsuyama, and Shiro Imagama.
• Department of Orthopedic Surgery, Hamamatsu University School of Medicine, Hamamatsu, Japan.
• Spine. 2022 Nov 15; 47 (22): 159015981590-1598.

Study DesignA prospective, multicenter study.ObjectiveThis study clarified the uses and limitations of transcranial motor-evoked potentials (Tc-MEPs) for nerve root monitoring during adult spinal deformity (ASD) surgeries.Summary Of Background DataWhether Tc-MEPs can detect nerve root injuries (NRIs) in ASD surgeries remains controversial.Materials And MethodsWe prospectively analyzed neuromonitoring data from 14 institutions between 2017 and 2020. The subjects were ASD patients surgically treated with posterior corrective fusion using multichannel Tc-MEPs. An alert was defined as a decrease of ≥70% in the Tc-MEP's waveform amplitude from baseline, and NRI was considered as meeting the focal Tc-MEP alerts shortly following surgical procedures with postoperative nerve root symptoms in the selected muscles.ResultsA total of 311 patients with ASD (262 women and 49 men) and a mean age of 65.5 years were analyzed. Tc-MEP results revealed 47 cases (15.1%) of alerts, including 25 alerts after 10 deformity corrections, six three-column osteotomies, four interbody fusions, three pedicle screw placements or two decompressions, and 22 alerts regardless of surgical maneuvers. Postoperatively, 14 patients (4.5%) had neurological deterioration considered to be all NRI, 11 true positives, and three false negatives (FN). Two FN did not reach a 70% loss of baseline (46% and 65% loss of baseline) and one was not monitored at target muscles. Multivariate logistic regression analysis revealed that risk factors of NRI were preexisting motor weakness ( P <0.001, odds ratio=10.41) and three-column osteotomies ( P =0.008, odds ratio=7.397).ConclusionsNerve root injuries in our ASD cohort were partially predictable using multichannel Tc-MEPs with a 70% decrease in amplitude as an alarm threshold. We propose that future research should evaluate the efficacy of an idealized warning threshold (e.g., 50%) and a more detailed evoked muscle selection, in reducing false negatives.Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.

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