Otolaryngology Department, Kafrelsheikh University, Kafr el-Sheikh, Egypt.
Radiology Department, Tanta University, Tanta, Egypt.
Eur Radiol. 2023 Jan;33(1):144-151. doi: 10.1007/s00330-022-08953-7. Epub 2022 Jun 23.
The facial recess, an essential landmark for the posterior tympanotomy approach, is limited by the facial nerve and the chorda tympani, with a complicated relationship. This study tried to find the most appropriate radiological method to evaluate the chorda-facial angle (CFA). We also checked the effect of this angle on the round window accessibility during cochlear implantation.
It was a retrospective study that included cochlear implant surgeries of 237 pediatric patients, from September 2016 to April 2021. Two physicians evaluated the CFA in the para-sagittal cut of the preoperative HRCT. The round window accessibility was assessed in the unedited surgery videos.
The CFA ranged from 21° to 35° with a mean of 27.14 ± 3.5°. It was detected in all cases with a high agreement between the two CT reviewers' measurements. The CFA differed significantly between the accessible group and the group with difficult accessibility (p value < 0.001). Spearman's correlation coefficient revealed a strong correlation between the CFA and the intraoperative round accessibility. 25.5° was the best cutoff point; below this angle, difficult accessibility into the RW was expected, with high sensitivity, specificity, and accuracy CONCLUSIONS: Our study on a relatively large number of cases provided a precise, valid, reliable, and applicable method to evaluate the CFA in the HRCT scan. We found a significant-close relation between the CFA and the round window accessibility; the difficulty increased with a need for posterior tympanotomy modification when the angle decreased.
• Radiological detection of the chorda-facial angle was always problematic, without a previous straightforward method in the literature. • We used the para-sagittal cut of the high-resolution CT scans to evaluate the CFA. This cut was beneficial to seeing the chorda tympani nerve in every examined case. There was a high agreement between the two CT reviewers' measurements. • Preoperative evaluation of the CFA in the HRCT accurately predicted the round window accessibility. Patients with CFA less than 25.5 were expected to have difficult accessibility into the round window during cochlear implantation.
面神经和鼓索神经对面神经管后入路的定位至关重要，二者关系复杂。本研究旨在寻找评估鼓索面神经角（CFA）的最佳影像学方法。同时，我们还研究了该角度对面神经管后入路人工耳蜗植入术中圆窗可达性的影响。
这是一项回顾性研究，纳入了 2016 年 9 月至 2021 年 4 月期间进行的 237 例儿童人工耳蜗植入术。两位医师在术前高分辨率 CT 的矢状旁切位评估 CFA。圆窗可达性则在未经编辑的手术视频中进行评估。
CFA 的范围为 21°至 35°，平均为 27.14°±3.5°。在所有病例中均能检测到该角度，两位 CT 阅片医师的测量结果具有高度一致性。可及组与不可及组之间的 CFA 存在显著差异（p 值＜0.001）。Spearman 相关系数显示 CFA 与术中圆窗可达性之间存在强相关性。25.5°是最佳截断点；低于该角度时，预计 RW 难以触及，此时具有较高的敏感度、特异度和准确度。
我们的研究纳入了相对较多的病例，提供了一种精确、有效、可靠且适用的 HRCT 扫描中 CFA 评估方法。我们发现 CFA 与圆窗可达性之间存在密切关系；当角度减小，需要进行后鼓室切开术修正时，可达性难度增加。
鼓索面神经角的影像学检测一直存在问题，文献中尚无直接明确的方法。
我们使用高分辨率 CT 扫描的矢状旁切位评估 CFA。该切位有利于观察到每例检查患者的鼓索神经。两位 CT 阅片医师的测量结果具有高度一致性。
HRCT 中 CFA 的术前评估可准确预测圆窗可达性。CFA 小于 25.5°的患者在进行人工耳蜗植入时预计 RW 可达性较差。
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