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Transcranial muscle motor evoked potentials (Tc-mMEPs), a key component of intraoperative neurophysiologic monitoring (IONM), effectively reflect the changes in corticospinal tract integrity and are closely related to the occurrence of the postoperative motor deficit (PMD). Most institutions have applied a specified (fixed) alarm criterion for the heterogeneous groups in terms of etiologies or lesion location. However, given the high risk of PMD in ossification of the posterior longitudinal ligament (OPLL) surgery, it is essential to determine a tailored cutoff value for IONM. We aimed to establish the intraoperative cutoff value of Tc-mMEPs reduction for predicting PMD in OPLL according to lesion levels. Retrospective analysis using a review of electrical medical records. In this study, we included 126 patients diagnosed with OPLL, who underwent surgery and IONM. The occurrence of PMD immediately and 1 year after operation, as well as the decrement of intraoperative Tc-mMEPs amplitude. We analyzed OPLL surgery outcomes using Tc-mMEPs monitoring. Limbs with acceptable baseline Tc-mMEPs in the tibialis anterior or abductor hallucis were included in the final set. PMD was defined as a ≥1 decrease in Medical Research Council score in the legs, and it was evaluated immediately and 1year after operation. The reduction ratios of Tc-mMEPs amplitude compared with baseline value were calculated at the two time points: the maximal decrement during surgery and at the end of surgery. Receiver operating characteristic curve analysis was used to determine the cutoff value of Tc-mMEPs amplitude decrement for predicting PMDs. In total, 203 limbs from 102 patients with cervical OPLL and 42 limbs from 24 patients with thoracic OPLL were included. PMD developed more frequently in thoracic lesions than in cervical lesions (immediate, 9.52% vs 2.46%; 1 year, 4.76% vs 0.99%). The Tc-mMEPs amplitude cutoff point at the end of surgery for PMD (both immediate and 1-year) was a decrease of 93% in cervical and 50% in thoracic OPLL surgeries. Similarly, the Tc-mMEPs amplitude cutoff point at the maximal decrement during surgery for PMD (both immediate and 1 year) was a reduction of 97% in cervical and 85% in thoracic OPLL surgeries. The thoracic lesion exhibited a lower cutoff value than the cervical lesion for both immediate and long-term persistent PMD in OPLL surgery (Tc-mMEPs at the end of surgery measuring 93% vs 50%; and Tc-mMEPs at the maximal decrement measuring 97% vs 85% for cervical and thoracic lesions, respectively). To enhance the reliability of monitoring, considering the application of tailored alarm criteria for Tc-mMEPs changes based on lesion location in OPLL could be beneficial. [ABSTRACT FROM AUTHOR]

• Postoperative voiding dysfunction is not an uncommon neurological complication after lumbar spinal surgery. • Intraoperative bulbocavernosus reflex (BCR) loss is correlated with postoperative voiding dysfunction. • Intraoperative BCR monitoring may enhance safety during posterior lumbar fusion surgery. To assess the utility of intraoperative bulbocavernosus reflex (BCR) monitoring in posterior lumbar fusion surgery. We retrospectively evaluated 153 patients undergoing posterior lumbar fusion with intraoperative BCR monitoring. Voiding function was assessed at discharge and two follow-ups. BCR was preserved in 151 patients and completely disappeared in two patients at the end of surgery. For patients in whom BCR was preserved, voiding difficulties at discharge and 1-month and 6-month follow-ups were noted in 16 (10.6%), 9 (6.0%), and 0 (0.0%) patients, respectively. However, patients with BCR loss experienced voiding difficulties at all three time-points. Statistical analysis showed a significant difference in voiding between those with preserved and disappeared BCRs at 6 months postoperatively. BCR disappeared during surgery but recovered before the end of surgery in six patients. Among these patients, one experienced transient voiding difficulties postoperatively but with good recovery. However, the other five patients did not experience postoperative voiding difficulties. BCR had low sensitivity for voiding dysfunction at discharge, but had high accuracy at 6-month follow-up examinations. BCR loss was associated with new voiding dysfunction. Intraoperative BCR monitoring is a potentially useful tool for enhancing safety during posterior lumbar fusion by predicting postoperative voiding dysfunction. [ABSTRACT FROM AUTHOR]

Highlights • The associated factors for baseline mMEP recording failure were different based on lesion locations. • Preoperative motor power showed a close correlation with the failure rate of baseline mMEP generation. • Baseline mMEP generation failure in thoracic lesion could indicate risk for postoperative deficits. Abstract Objective To identify factors associated with the failure to generate baseline muscle motor evoked potentials (mMEPs) during spinal surgery, and to determine the association between baseline mMEP generation and postoperative outcomes. Methods A total of 345 patients who underwent spine surgery with intraoperative mMEP monitoring were included, and we retrospectively reviewed their demographic/clinical parameters, and mMEP recording results according to lesion locations. Results Multivariable logistic regression analysis revealed that preoperative Medical Research Council grade of the weakest muscle <3 was significantly associated with failure of baseline mMEP generation in both cervical and thoracic lesions. In addition, high intramedullary T2 signal intensity on spine MRI for cervical lesions and male sex for thoracic lesions were also significantly associated with baseline mMEP generation failure. Moreover, the failure of baseline mMEP generation was a significantly associated factor for poor functional outcome in patients with thoracic lesions. Conclusion Sex, radiological abnormality, and preoperative functional status were associated with baseline mMEP generation failure during spine surgery with different patterns according to lesion location. Moreover, baseline mMEP generation failure in thoracic lesion could be associated with risk of postoperative deficits. Significance The risk of baseline mMEP recording failure could be evaluated based on preoperative clinical parameters. [ABSTRACT FROM AUTHOR]

Abstract: Objective: The aim of the study is to evaluate the efficacy of muscle motor evoked potentials (mMEPs) in individual leg muscles for spinal surgery monitoring. Methods: Data were obtained from 209 patients who underwent spine surgery with intra-operative mMEP monitoring in the tibialis anterior (TA) and abductor hallucis (AH) muscles. The mMEP generation, pattern-specific mMEP loss and recovery, and the accuracy of individual mMEP changes in predicting postoperative motor deficit were assessed. Results: Generation rate of mMEPs was higher in the AH than in the TA (p <0.001). The mMEP in the TA was more sensitive in detecting mMEP loss than in the AH (p <0.001); however, mMEP in the AH was more sensitive in detecting mMEP recovery (p <0.001). The mMEPs in the TA had high sensitivity in predicting sustained postoperative motor deficits. By contrast, mMEPs in the AH showed a high positive predictive value. Conclusions: Although mMEPs were generated at a high rate in the AH, mMEP in the TA can play an important complementary role in intra-operative mMEP monitoring, because mMEP in the TA can be more sensitive to potential neural damage. Significance: Using a combination of muscles with individual sensitivities and clinical significances will improve intra-operative mMEP monitoring strategies. [Copyright &y& Elsevier]