OBJECTIVE We aimed to define the prewarning sign of brainstem auditory evoked potentials (BAEPs) associated with cerebellar retraction (CR) during microvascular decompression surgery for hemifacial spasm. METHODS A total of 241 patients with a latency prolongation of 1 ms or an amplitude decrement of 50% of wave V were analyzed. According to BAEPs before significant changes during CR, patients were classified into Groups A (latency prolongation of wave I [≥0.5 ms] without prolongation of the I-III interpeak interval [<0.5 ms]) and B (no latency prolongation of wave I [<0.5 ms] with prolongation of the I-III interpeak interval [≥0.5 ms]). BAEPs and postoperative hearing loss (HL) were compared between the two groups. RESULTS Group B comprised 160 (66.4%) patients. With maximal changes in wave V, latency prolongation (≥1 ms) with amplitude decrement (≥50%) was more common in Group B (p < 0.018). At the end of the operation, wave V loss was observed in 11 patients, including 10 patients from Group B. Five patients developed postoperative HL; all were from Group B. CONCLUSIONS Latency prolongation of wave III during CR was associated with serious BAEPs changes and postoperative HL. SIGNIFICANCE Latency prolongation of wave III is a significant prewarning sign.

中文翻译：

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面肌痉挛微血管减压手术中脑干听觉诱发电位听力损失的预警信号

目的：我们旨在确定在面肌痉挛微血管减压手术期间与小脑回缩（CR）相关的脑干听觉诱发电位（BAEP）的预警信号。方法 共分析了 241 名潜伏期延长 1 ms 或波幅下降 50% 的患者。根据 CR 期间显着变化前的 BAEP，将患者分为 A 组（I 波潜伏期延长 [≥0.5 ms]，I-III 波峰间间隔无延长 [<0.5 ms]）和 B（I 波潜伏期延长 [≥0.5 ms]） [<0.5 ms]，I-III 峰间间隔延长 [≥0.5 ms]）。比较两组的BAEPs和术后听力损失（HL）。结果 B 组包括 160 (66.4%) 名患者。随着波 V 的最大变化，潜伏期延长 (≥1 ms) 和振幅下降 (≥50%) 在 B 组中更为常见 (p < 0.018)。手术结束时V波消失11例，其中B组10例。术后HL 5例；全部来自 B 组。结论 CR 期间波 III 的潜伏期延长与严重的 BAEP 变化和术后 HL 相关。意义 III 波的潜伏期延长是一个重要的预警信号。