Hearing Preservation Surgery via Retrosigmoid Approach with Retrolabyrinthine Meatotomy in Small Vestibular Schwannoma

Objectives Vestibular schwannomas (VS) extending into the internal auditory canal (IAC) are currently considered as an unfavorable condition for hearing preservation surgery (HPS) via retrosigmoid (RS) approach due to the poor direct visualization of the facial and cochlear nerves course through the IAC and the fundus during microsurgery. Design The operative steps are described in a surgical instructional video. Setting The surgery took place at a tertiary-care center. Participants Patient is a 45-year-old man who was incidentally diagnosed with an extrameatal VS extending for 9 mm into the left cerebellopontine angle (CPA). Hearing function at diagnoses was excellent, with pure tone average (PTA) = 15 dB and speech discrimination score (SDS) = 100% (class A according to the Tokyo classification) and minimal impairments on auditory brainstem response (ABR). Given these preoperative features in small VS, hearing was the main function to look into in the treatment planning. Initial observation or HPS were proposed. Results The patient underwent surgical excision for HPS via RS approach combined with retrolabyrinthine meatotomy (RLM). RLM enables the complete exposure of the IAC to the fundus, after drilling the bony surface of the posterior IAC wall, under guidance of the anatomical landmarks, namely, the endolymphatic duct, the blue lines of the posterior, and superior semicircular canals, and common crus. Nor intra-, neither postoperative complications occurred. Histologic examination confirmed the diagnosis of VS. A 3-month short-term follow-up revealed a class B hearing function with PTA = 30 dB, SDS = 100%, and normal facial nerve status. Conclusions RLM via RS approach proved to be effective for HPS, enabling the full course of the facial and cochlear nerves through the IAC to be directly exposed.The link to the video can be found at: https://youtu.be/KC1S4pxpLCk.

Retrolabyrinthine Meatotomy as Part of Retrosigmoid Approach to Expose the Whole Internal Auditory Canal: Rationale, Technique, and Outcome in Hearing Preservation Surgery for Vestibular Schwannoma

BACKGROUND Vestibular schwannoma extending to the fundus of the internal auditory canal is currently considered an unfavorable condition for hearing preservation surgery via a retrosigmoid approach because the lateral end of the canal is hard to view directly during microsurgery. OBJECTIVE To present an improved retrolabyrinthine meatotomy (RLM) technique that enables the full length of the cochlear and facial nerves to be inspected up to their orifices on the fundus. Long-term results are briefly reported. METHODS A consecutive series of 100 cases with various degrees of fundus involvement underwent surgery via a retrosigmoid approach and RLM. The follow-up ranged from 4 to 14 yr. Outcomes on hearing and facial nerve function were recorded, and preoperative MRI findings of the tumor on the fundus were correlated with the surgical findings and the long-term radicality of the tumor resection. RESULTS Residual tumor on the fundus was identified in 3 cases, all belonging to the group with tumors adhering to the fundus. The functional results were in line with the best reported outcomes of this surgery. CONCLUSION RLM via a retrosigmoid approach seemed adequate for the purposes of hearing preservation surgery and enabled the full course of the facial and cochlear nerves through the internal auditory canal to be exposed to direct view. Tumors adhering to the vestibular quadrant of the fundus were more difficult to remove, and there were a few cases of local residual tumor.