弥散张量成像面神经追踪技术在听神经瘤手术中的应用

Identification of the facial nerve in the operation of vestibular schwannoma using diffusion tensor tractography

目的探讨弥散张量成像纤维束追踪（DTT）技术在听神经瘤手术中追踪面神经的方法及准确性。方法回顾性分析首都医科大学附属北京天坛医院神经外科2013年9月至2015年9月行手术治疗的19例听神经瘤患者的临床资料。术前磁共振扫描后在工作站上以DTT技术追踪面神经，感兴趣区域（ROI）分别定位于内听道及面神经从脑干端发出的位置。各向异性指数（FA）设置为0．15。当有明显纤维束经过脑干端ROI和内听道端ROI时即定义为重建出的面神经。术中运用多模态神经导航、神经电生理监测、术者肉跟所见3种方式联合验证面神经追踪的准确性。术后不同时间点对面神经功能分级进行评估。结果19例患者中，有18例术前成功追踪出面神经纤维束的位置及走行，其中有16例术中经电生理监测及术者判断证实与面神经位置相符合，2例不相符合，其中1例为囊性，另1例为囊实性。所有病例术中均完整保留面神经，面神经以位于肿瘤腹侧中1／3为主。其中18例患者术后6个月House-Brackmann面神经功能分级为Ⅰ-Ⅲ级。结论术前DTT技术配合术中多模态神经导航可辅助术者在术前及术中对面神经位置做出判断，从而在很大程度上减少面神经损伤的机会。

Objective To explore the method and accuracy of diffuse tensor tractography of facial nerve in the operation of vestibular schwannoma （VS）. Methods We prospectively collected data of 19 patients with vestibular schwannoma who underwent diffuse tensor tractography （DTT） to identify the location and running course of the facial nerve. The seed of ROI was set in the internal auditory meatus and brainstem. The value of FA was set to 0.15. The fibers were considered to represent the facial nerve which connected the internal auditory meatus and brainstem. We intraoperatively evaluated the consistency between tractography and surgerical findings using navigation system,intraoperative facial nerve monitoring and visual inspections byneurosurgeons. Facial nerve function was evaluated at different time postoperatively according to the House-Brackmann （H-B） facial nerve grading system. Results The facial nerve of all patients were preserved, most of which were displaced anteroinferiorly. We successfully reconstructed the fibers that represent the facial nerve in 18 cases. In 16 of 18 cases, location of the tractography was entirely consistent with intraoperative findings. In the other two cases of vestibular schwannoma with cyst, the tractography image did not match intraoperative findings. No patient had severe facial paralysis 6 months post surgery. Seventeen patients were graded i-m according to H-B grade 6 months after the operation. Conclusions DTT with intraoperative neuronavigation seems to be a useful tool to identifyfacial nerve in the VS resection and could helpfacilitate facial nerve preservation.