Comparison of the intraoperative findings with CT and MRI data for intratemporal lesions of the facial nerve

This article analyzes the literature on intratemporal lesions of the facial nerve of various etiologies. Also, the CT and MRI findings in the lesions are described in detail. We analyzed and compared the data of radiation diagnostics with intraoperative findings.

Purpose of the study. To compare the radiation diagnostics data with intraoperative findings in patients with facial nerve lesions.

Material and methods. Totally, 115 patients with facial nerve lesions of different etiologies examined and surgically treated in the Department of Ear Diseases, FSBI NMRC FMBA of Russia, from 2014 to 2020. The first group included 72 (62.6%) patients with benign tumors of the temporal bone; facial nerve schwannoma — 23 (20.0%), and paraganglioma — 49 (42.6%). The second group included 32 (27.8%) patients with chronic purulent otitis media complicated by cholesteatoma. The third group included 11 (9.6%) patients with facial nerve injury; 3 temporal bone fractures (2.6%), and 8 iatrogenic lesions (7.0%). The study included only patients of the first and second groups. There was no discrepancy between CT and MRI data and intraoperative findings in the third group. In addition, there was no difficulty in determining the tactics of surgical treatment in temporal bone fractures with the facial nerve channel damage. Therefore, patients in this group were not included in this study.

Results and discussion. We found that contrast-enhanced CT and MRI allow to clearly determine the prognosis and tactics of surgical treatment in patients with intratemporal lesions of the facial nerve. Data obtained with the temporal bones CT with 3D modeling and MRI of the brain in different modes help to determine the volume and size of a tumor and the extent of damage to vital structures, as well as the possibility of their preservation and recovery. In 5 cases, according to CT data, the defect of the bone wall of the middle cranial fossa was not visualized at the preoperative stage, but was detected intraoperatively. In some cases, according to CT data before the operation, the defect of the bone wall of the middle cranial fossa was 3 mm, while intraoperatively it reached more than 5 mm. Difficulties may arise when differentiating meningioma from hemangioma, when a lesion spreads to the middle cranial fossa. We managed to compare and to correlate the data on process dissemination according to MRI and CT findings intraoperatively, which largely simplified the work of otosurgeon, reducing the risks of intraoperative injury to vital structures of the middle and inner ear. The data compared in this study matched in 95%.

Conclusions. Comparison of CT and MRI data with intraoperative data showed that a detailed assessment of the findings from CT with 3D reconstruction, as well as contrast-enhanced MRI in different modes allows us to accurately determine the tumor size and extent of the spread, the relationship with the underlying structures, the degree of wall destruction, and involvement of vital structures in the process (internal jugular vein, internal carotid artery, brain, labyrinth, facial nerve). Detailed study of the obtained data helped to determine the prognosis and tactics of surgical treatment.

Key words: facial nerve, schwannoma, paraganglioma, chronic purulent otitis media, cholesteatoma, computed tomography, magnetic resonance imaging

Conflicts of interest. The authors have no conflicts of interest to declare.

Funding. There was no funding for this study.