Evolution of Cochlear Patency During Follow-up After Translabyrinthine Vestibular Schwannoma Resection

Introduction: As cochlear implantation is increasingly considered as an option for hearing restoration after translabyrinthine resection of vestibular schwannomas, additional study is warranted to evaluate how cochlear fibrosis and ossification progresses after the bony labyrinth is disrupted.

Methods: An IRB-exempt retrospective cohort review of adult patients who underwent translabyrinthine approach for vestibular schwannoma resection between 2015-2024 at a tertiary academic center was performed. Heavily-T2-weighted MRI was used to evaluate cochlear fluid signal diminution (fibrosis) or loss (ossification) at latest available follow-up interval. Preoperative tumor dimensions, laterality, and patient age were assessed for their contribution to fibrosis or ossification. A Kaplan-Meier survival function was generated to estimate progression to fibrosis or ossification over time.

Results: 66 patients (48.5% male, averaging 58.6 yrs of age) underwent unilateral vestibular schwannoma resection. Tumors were 53.0% right-sided, averaging 21.7mm in their greatest dimension and 22.4mm in their IAC dimensions. Average imaging follow up was 29.3 months. The survival function goodness-of-fit was p(x≤χ²) = 0.920846. At 12 months, 11.5% of patients demonstrated cochlear fibrosis, and 4.9% had ossification. Half of patients had radiographic fibrosis by 37 months, and half developed ossification by 49 months. There was no significant association between patient age (p=0.54), tumor dimensions (p=0.94), or laterality (p=0.49, χ²=0.49) on risk of developing fibrosis or ossification.

Conclusions: Post-translabyrinthine-resection cochlear fibrosis and ossification progress independently of tumor size or patient age, with half of patients expected to have patent cochleae at three years postoperative follow-up.