Factors Associated with Hearing Outcomes After a Middle Fossa Approach in 131 Consecutive Patients with Vestibular Schwannomas

Introduction: The middle fossa approach is an effective option for the treatment of small (Koos grade 1 and 2) vestibular schwannomas (VS) when the goal is hearing preservation. We evaluated the rates of hearing preservation and examined the factors associated with improved hearing outcomes after the middle fossa approach for VS.

Methods: In this retrospective, single-center cohort study evaluating the clinical outcomes after resection of small VS using the middle fossa approach, consecutive adult patients (>18 years) who had surgery between January 2000 and December 2021 were included. Clinical and imaging characteristics were analyzed, including baseline hearing status, duration of surgery, anesthetic parameters, and imaging characteristics of the tumors.

Results: Among the 131 included patients, 102 had pre- and postoperative audiology assessments recorded. The mean follow-up was 26 months (range 1-180 months). Eighty-five patients had serviceable hearing preoperatively, defined as American Academy of Otorhinolaryngology-Head and Neck Surgery (AAO-HNS) class A/B, of which 78% retained class A/B hearing on last follow-up. Binary logistic regression demonstrated that the preoperative hearing AAO-HNS class (OR 0.19; 95%CI 0.05-0.77; p=0.02), overlap between fundus and cochlea (OR 0.32; 95% CI 0.11-0.96; p=0.04), and duration of anesthesia (OR 0.98; 95%CI 0.97-0.99; p=0.03) were independent predictors of hearing outcomes. Additionally, 75% of patients with high diffusion-weighted imaging (DWI) signal in the tumor (p=0.009) and 67% of patients with tumor originating at the modiolus of the cochlea had poor hearing outcomes (p=0.004).

Conclusion : The hearing preservation rates after microsurgical resection of small VS using the middle fossa approach are high, with 78% of patients maintaining AAO-HNS class A/B hearing. Poor hearing status at baseline, longer anesthesia, and large overlap between the fundus of the internal auditory canal and the cochlea were independently associated with unfavorable hearing outcomes. The imaging characteristics can be used to stratify patients’ risk of hearing loss.