Department of Otorhinolaryngology, Faculty of Dentistry, Medical University of Warsaw, Warsaw, Poland.
Department of Otolaryngology, Central Clinical Hospital of the Ministry of Interior and Administration in Warsaw, Warsaw, Poland.
Otolaryngol Pol. 2023 Jul 21;77(4):39-47. doi: 10.5604/01.3001.0016.3300.
<b>Introduction:</b> The facial nerve (FN) follows a complex route in the temporal bone. Successful temporal bone surgery requires knowledge of its course which can be achieved using imaging methods such as computed tomography. This investigation aims to analyze the FN course in its mastoid portion and second genu and the frequency of its atypical course.</br></br> <b>Material and methods:</b> This is a retrospective study that enrolled 104 CT scans of temporal bones of patients followed up in the outpatient clinic of the Otorhinolaryngology Department of Dentistry Faculty of the Medical University of Warsaw between 2020 and 2022. FN courses were classified as straight, bulging, or letter "S"-like. Other parameters estimated: </br> • position of the second genu according to the prominence of the lateral semicircular canal (classified as lateral, medial, or middle) and its distance from a line adjacent to the lateral semicircular canal was measured;</br> • the distance between the short process of the incus and the outermost point of the second genu;</br> • the course of the mastoid portion of FN and the location of SG in comparison to the tympanic portion of n. VII. The course was later classified as lateral, medial, or middle.</br></br> <b>Results:</b> Among the 104 assessed temporal bones, the course of the mastoid portion of FN was classified as bulging in 47 cases (45.2%). Straight and letter "S"-like courses were present in 41 (39.4%) and 16 (15.4%) cases, respectively. Deviation of the second genu according to the prominence of the lateral semicircular canal was medial in 86 cases (82.7%), and middle in 4 cases (3.8%). In the rest, second genu was paramedian to the prominence of the later circular canal. The mean distance between the short process of the incus and the outermost point of SG was 4.9 mm (0.73 mm). The mastoid portion was located laterally, medially, and in the middle of the tympanic portion plane in, respectively, 4.8%, 83.7%, and 11.5%. The second genu was located laterally, medially, and in the middle of the tympanic portion plane in 1.9%, 73.1%, and 25%, respectively. In conclusion, seven temporal bones (6.7%) of five patients presented with a lateral displacement of FN in relation to the established anatomical landmarks.</br></br> <b>Conclusions:</b> Although the atypical course of FN, including the lateral displacement of the mastoid portion, is rare, screening for it is crucial before surgical exploration.
<b>引言：</b>面神经（FN）在颞骨中走行复杂。成功的颞骨手术需要了解其走行，这可以通过 CT 等影像学方法来实现。本研究旨在分析面神经乳突段和第二膝状神经节（SG）的走行及其异常走行的频率。</br></br> <b>材料和方法：</b>这是一项回顾性研究，纳入了 2020 年至 2022 年期间在华沙医科大学牙科学院耳鼻喉科门诊随访的 104 例颞骨 CT 扫描。面神经走行分为直、膨出或“S”形。还估计了其他参数：</br> • 根据外半规管隆起，将第二膝状神经节的位置分为外侧、内侧或中间，并测量其与毗邻外半规管的线之间的距离；</br> • 锤骨短突与第二膝状神经节最外点之间的距离；</br> • 面神经乳突段的走行和 SG 在与 VII 颅神经鼓部的位置关系。然后将走行分类为外侧、内侧或中间。</br></br> <b>结果：</b>在评估的 104 例颞骨中，面神经乳突段的走行有 47 例（45.2%）为膨出。直和“S”形走行分别为 41 例（39.4%）和 16 例（15.4%）。根据外半规管隆起，第二膝状神经节的偏离情况为内侧 86 例（82.7%），中间 4 例（3.8%）。其余的，第二膝状神经节位于外半规管隆起的旁正中位。锤骨短突与 SG 最外点之间的平均距离为 4.9 毫米（0.73 毫米）。乳突段位于鼓部平面的外侧、内侧和中间，分别占 4.8%、83.7%和 11.5%。第二膝状神经节位于鼓部平面的外侧、内侧和中间，分别占 1.9%、73.1%和 25%。总之，5 名患者的 7 例（6.7%）颞骨面神经相对于既定的解剖标志出现外侧移位。</br></br> <b>结论：</b>尽管面神经的异常走行，包括乳突段的外侧移位，较为罕见，但在手术探查前进行筛查至关重要。
