Objectives

Trochlear nerve (CN-IV) mapping method has not been confirmed to date. The compound muscle action potential (CMAP) of CN-IV cannot be recorded because of the low mapping sensitivity and anatomical characteristics of the superior oblique muscle (SOM). The aim of this study was to evaluate the effectiveness of a novel needle electrode (NNE), for the intraoperative mapping of CN-IV.

Materials and methods

The NNEs were inserted in the target extraocular muscles in 19 patients. We compared the CMAP amplitude of the NNE with that of the conventional needle electrode (CNE). Furthermore, we investigated the dissimilarity between the CMAP of the CN-IV and other extraocular cranial nerves (ECNs) and the correlation between the readings of the CN-IV mapping and its postoperative functional outcome.

Results

The CMAP of CN-IV has been measured in nine patients (47.4%). The CMAP of CN-IV was distinguishable from other ECNs. The CMAP of the NNE was found to be three times higher than that of the CNE. Although the NNE has shown the potential to record the CN-IV’s CMAP, 4 cases ended up having a CN-IV postoperative dysfunction.

Conclusions

For the first time, we confirmed the possibility of intraoperative mapping the CN-IV using an NNE inserted into the SOM. The NNE can also be useful for other neurophysiological monitoring methods.

中文翻译：

---

一种用于术中第四颅神经神经生理学标测的新型针电极。

目标

滑车神经（CN-IV）映射方法迄今尚未得到证实。CN-IV 的复合肌肉动作电位 (CMAP) 不能被记录，因为上斜肌 (SOM) 的映射敏感性和解剖学特征较低。本研究的目的是评估一种新型针电极 (NNE) 在 CN-IV 术中标测中的有效性。

材料和方法

19 名患者将 NNE 插入目标眼外肌。我们将 NNE 的 CMAP 振幅与传统针电极 (CNE) 的 CMAP 振幅进行了比较。此外，我们研究了 CN-IV 和其他眼外颅神经 (ECN) 的 CMAP 之间的差异以及 CN-IV 映射读数与其术后功能结果之间的相关性。

结果

已在 9 名患者（47.4%）中测量了 CN-IV 的 CMAP。CN-IV 的 CMAP 与其他 ECN 不同。发现 NNE 的 CMAP 是 CNE 的三倍。尽管 NNE 已显示出记录 CN-IV 的 CMAP 的潜力，但 4 例最终出现了 CN-IV 术后功能障碍。

结论

我们第一次确认了使用插入 SOM 的 NNE 在术中映射 CN-IV 的可能性。NNE 还可用于其他神经生理学监测方法。