Translabyrinthine approach in surgical treatment of internal auditory canal lesions

The aim: to describe the microsurgical anatomy of translabyrinthine approach with a focus on the anatomy of the fundus of internal auditory canal (IAC), facial nerve, cochlea in cases of the IAC lesions; demonstrate the surgical technique on clinical cases.

Materials and methods: We performed a cadaveric dissection study in March 2022. In total, 2 heads (4 sides) were dissected focusing on anatomical landmarks and surgical feasibility. Data from dissections were reviewed and analysed for further consideration. Features of translabyrinthine approch in different temporal bone pathology were demonstrated in cases of intracanal vestibular schwannoma, petrous bone supralabyrinthine cholesteatoma, meningioma.

Results: The anatomy and features of the translabyrinthine approach in various pathologies of IAC are described. The attention is paid to the syntopy of IAC fundus (horizontal and vertical crests), facial nerve (FN), and cochlea. Removal of the lateral part of the horizontal ridge provides access to the lateral recess and the cochlear nerve. However, when expanding access in the anterior superior direction and removing the bone between the tympanic and labyrinth segments of the FN, it is possible to open the 2nd turn of the cochlea. The point 1 mm below the labyrinthine segment of FN and 1.2 1.4 mm posterior to the FN tympanic segment approaches the scala vestibule at the level of the transition of the ascending part of the basal turn to the middle cochlea. Conclusion: The pathology of IAC is diverse and is represented by neoplasms of different types and histological structure. Surgical treatment of IAC pathologies is similar and is based on the same anatomical location and the necessity to prevent similar intra and postoperative complications. The translabyrinthine approach is the standard and widest approach in the treatment of IAC pathology, which makes it possible to control the facial nerve throughout the temporal bone, to fully visualize the area of the lateral recess of the IAC fundus. To preserve the cochlear potential it is rational to use the method of introducing a test electrode into the lumen of the cochlea.

Keywords: translabyrinthine approach; internal auditory canal lesion; vestibular schwannoma; petrous bone cholesteatoma; internal auditory canal fundus
Conflicts of interest. The authors have no conflicts of interest to declare. Funding. There was no funding for this study