OBJECT Surgery of tumours in the cerebellopontine angle (CPA) can lead to loss of facial nerve function. Different methods of intra-operative nerve monitoring (IOM) (including free-running EMG, direct nerve stimulation and transcranial motor evoked potentials (TcMEP)) have been used to predict facial nerve outcome during surgery. Recent research has shown TcMEP threshold increase and the occurrence of A-trains on the EMG to have great potential in doing so. This study compares these two methods and correlates them to House-Brackmann (HB) scores post-op in patients with tumours in the cerebellopontine angle. METHOD Forty-three patients (one was operated twice) with large CPA tumours treated surgically in the Radboud University Medical Center between 2015 and 2019 were included in this study. During surgery, TcMEP threshold increases and A-train activity were measured. Because our treatment paradigm aims at facial nerve preservation (accepting residual tumour), TcMEP threshold increase of over 20 mA or occurrence of A-trains were considered as warning signs and used as a guide for terminating surgery. HB scores were measured post-op, at 6 weeks, 6 months and 1 year after surgery. Spearman's correlation was calculated between the IOM-values and the HB scores for a homogeneous subgroup of 30 patients with vestibular schwannoma (VS) without neurofibromatosis type II (NF-II) and all patients collectively. RESULTS TcMEP threshold was successfully measured in 39 (90.7%) procedures. In the homogeneous VS non-NFII group, we found a statistically significant moderate-to-strong correlation between TcMEP threshold increase and House Brackmann score immediately post-op, at 6 weeks, 6 months and 1 year after surgery (Spearman's rho of 0.79 (p < 0.001), 0.74 (p < 0.001), 0.64 (p < 0.001) and 0.58 (p = 0.002), respectively). For A-trains, no correlation was found. Similar results were found when including all patients with CPA tumours. A threshold increase of < 20 mA was a predictor of good facial nerve outcome. CONCLUSION These results show that TcMEP threshold increases are strongly correlated to post-operative HB scores, while A-trains are not. This suggests TcMEP threshold increases can be a valuable predictor for facial nerve outcome in patients with large tumours when facial nerve preservation is prioritized over total resection. In this study, we found no use for A-trains to prevent facial nerve deficits.

中文翻译：

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在预测CPA肿瘤手术中的面神经结局时，TcMEP阈值变化优于A-train检测。

目的小脑桥脑角（CPA）的肿瘤手术会导致面神经功能丧失。术中使用了不同的术中神经监测（IOM）方法（包括自由运行的EMG，直接神经刺激和经颅运动诱发电位（TcMEP））来预测手术期间的面神经结局。最近的研究表明，TcMEP阈值增加以及EMG上A列车的出现具有巨大的潜力。本研究比较了这两种方法，并将它们与小脑桥脑角肿瘤患者术后的House-Brackmann（HB）评分相关。方法本研究纳入2015年至2019年间在Radboud大学医学中心接受手术治疗的43例CPA大肿瘤患者（其中1例进行了两次手术）。手术期间 TcMEP阈值增加和A火车活动进行了测量。因为我们的治疗范例旨在保留面部神经（接受残余肿瘤），所以TcMEP阈值增加超过20 mA或发生A株被视为警告信号，并被用作终止手术的指南。术后，术后6周，6个月和1年测量HB评分。Spearman的相关性是在30例无II型神经纤维瘤病（NF-II）的前庭神经鞘瘤（VS）患者和所有患者的IOM值和HB分数之间计算的。结果TcMEP阈值已通过39（90.7％）程序成功测量。在同质VS非NFII组中，我们发现术后6周，6个月和1年手术后即刻TcMEP阈值升高与House Brackmann评分之间存在统计学上显着的从中到强相关性（Spearman的rho值为0.79（p <0.001），0.74（p <分别为0.001），0.64（p <0.001）和0.58（p = 0.002）。对于A火车，没有发现相关性。当包括所有患有CPA肿瘤的患者时，发现了相似的结果。阈值增加<20 mA是面部神经预后良好的预测指标。结论这些结果表明，TcMEP阈值升高与术后HB评分密切相关，而A训练则不相关。这表明，当保留面部神经优先于全切除术时，TcMEP阈值升高可能是大肿瘤患者面部神经结局的重要预测指标。在这个研究中，