Modified translabyrinthine approach and hearing preservation: imaging evaluation

Hearing preservation/rehabilitation surgery for small vestibular schwannoma: preliminary experience with the presigmoid retrolabyrinthine approach

BACKGROUND

The presigmoid retrolabyrinthine approach (PRA) for small vestibular schwannoma (VS) has unique advantages. Combination with partial labyrinthectomy further makes up its defect of high demand for anatomy.

OBJECTIVE

Aimed to describe our use of the PRA with partial labyrinthectomy in VS surgery.

METHODS

We retrospectively analyzed 10 patients diagnosed with VS who underwent PRA between September 2017 and November 2020. Their perioperative data were analyzed.

RESULTS

Six tumors were on the left and three were on the right. One case was due to neurofibromatosis type 2 with bilateral involvement and underwent internal auditory canal decompression by PRA without tumor removal; all other patients underwent total tumor resection. Four patients underwent cochlear implantation simultaneously because of hearing loss that was detected during surgery. Three patients underwent partial labyrinthectomy. Five patients achieved hearing preservation, and one experienced hearing improvement. One of the three patients who underwent partial labyrinthectomy maintained hearing. All patients' pre- and postoperative facial nerve functions were House-Brackmann grade I. After a median follow-up time of 13 months, no tumors recurred.

CONCLUSIONS

PRA for small VS is a safe and effective surgery that can achieve facial nerve and hearing preservation. Combination with partial labyrinthectomy can also preserve hearing.

Hearing Preservation in Patients Who Undergo Labyrinthectomy and Translabyrinthine Procedures: A Case Report and Systematic Review

Importance

Preservation of endolymphatic fluids, maintenance of a fluid-filled vestibule, and preservation of the cochlear nerve and its vasculature are believed to be necessary to retaining hearing after an inner-ear operation. However, some studies have reported no hearing loss despite the violation of the vestibule, questioning the importance of maintaining a fluid-filled vestibule in preserving hearing.

Objective

To report on the preservation of hearing after a complete labyrinthectomy for Meniere disease and after disruption of the vestibule.

Evidence Review

This systematic review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting guidelines. A search of PubMed, Scopus, Ovid, and Cochrane Library databases was conducted to identify English-language articles on hearing preservation after labyrinthectomy, published from 1947 through December 11, 2019. The search strategy used a combination of boolean operators and included the following Medical Subject Heading terms and keywords: hearing preservation, labyrinth surgery, labyrinthectomy, vestibule violation, vestibule disruption, translabyrinthine approach, schwannoma removal, and semicircular canal ablation. Studies that included disruption of the vestibule and hearing preservation were included.

Findings

This systematic review identified 10 studies with 10 patients who underwent surgical removal of cholesteatoma or vestibular schwannoma and displayed postoperative hearing preservation. This study also reported on 1 patient with Meniere disease who retained hearing after undergoing a complete labyrinthectomy. Among these 11 patients, the mean (range) age was 45.1 (27-55) years, and 8 patients (73%) were women. Multiple theories exist that explain the mechanism behind hearing preservation, such as sealing of the ductus reuniens or closure of the remaining vestibule.

Conclusions and Relevance

This systematic review describes a set of patients who did not experience hearing loss after a labyrinthectomy or surgical violation of the vestibule, which seems to contradict prevailing principles for retaining hearing after inner-ear surgical procedures. This finding suggests that hearing preservation is possible after labyrinthine destruction despite the absence of a fluid-filled vestibule and that other mechanisms, such as occlusion of the ductus reuniens with granulation tissue or bone dust, may be sufficient to achieve that outcome.

Comparative Analysis of Transpetrosal Approaches to the Internal Acoustic Meatus Using Three-Dimensional Radio-Anatomical Models

Background The transcrusal approach that involves partial removal of the labyrinth was recently described to approach lesions of the cerebellopontine angle. It carries the benefit of hearing preservation and was suggested to have equivalent exposure of the petroclival surface compared with the transcochlear/transotic approaches. The current study was designed to assess if the transcrusal approach could achieve as good access to the internal auditory meatus (IAM) as the more destructive translabyrinthine exposure. Methods Fifty disease-free high-resolution computed tomography scans of the temporal bone were reviewed. Surgical freedom, angle of attack, and angle of trajectory to the internal acoustic canal were measured in three-dimensional models. Results Surgical freedom and angles of attack showed steady increments with the progression of petrous bone resection from the retrolabyrinthine-transcrusal-translabyrinthine approaches. The angle of access to the IAM axis was dramatically reduced in the translabyrinthine approach compared with the transcrusal and retrolabyrinthine approaches (37.51 ± 5.7, 24.56 ± 4.6, and 3.17 ± 2.85 degrees, respectively; n = 50; average plus or minus standard deviation, p < 0.001). Conclusion Using this novel radio-anatomical system, we demonstrate the advantage of the translabyrinthine approach to the axis of the internal auditory canal. The transcrusal approach lags behind the translabyrinthine corridor and should be considered alongside the subtemporal and retrosigmoid approaches designed to spare hearing.