Auditory Function in Vestibular Schwannoma Resections via the Retro-Sigmoid Approach

Objective: During vestibular schwannoma (VS) surgery, the final period of resection close to the eighth cranial nerve is most sensitive with regard to auditory function. This study focuses on advantageous factors of microsurgical technique.

Methods: Out of a consecutive series of 244 tumor operations, auditory function before and after surgery was analyzed in relation to tumor extension and to intra-operative auditory brainstem response (ABR) monitoring results and microsurgical procedure.

Results: There was a preponderance of large brainstem adhesive or compressive tumors (154 [63%] compared with 90 (37%) small to medium-sized tumors). Among 186 patients with some residual hearing before surgery, hearing preservation was achieved in 58 (31%) after surgery. Tumor extension was an unfavorable factor in this regard (p = 0.013). Nonetheless, tumor resection time in case of preservation of ABR and hearing was significantly longer (2:50 hours) compared with cases with ABR loss (2:05 hours) pointing to two decisive factors, repeated reaction and breaks by the surgeon and meticulous slow movements in accordance with the monitoring feedback.

Conclusion: Tumor size remains an important risk factor with regard to functional outcome, but this should not lead to exclusion from ABR trial. If ABRs are present at the start and up to the last phase of surgery, slow refined microsurgical technique with immediate response to monitoring changes can lead to successful hearing preservation.