Hearing Preservation Following Vestibular Schwannoma Microsurgery

Aim: The aim of the study was to conduct a comprehensive analysis of the factors influencing the success rate of hearing preservation in patients undergoing microsurgical removal of vestibular schwannoma (VS). Materials and methods:A total of 81 consecutive patients with serviceable hearing underwent surgical removal of unilateral vestibular schwannoma via retrosigmoid-transmeatal approach between 2008 and 2010. Patient, tumor and audiometric parameters together with intraoperative findings were prospectively analyzed. Data were statistically processed including a regression analysis of independent variables. Results: Serviceable hearing was preserved in 17 patients (useful hearing in nine and non-useful in eight cases). We observed improvement of hearing from non-useful to useful level in two patients. Average size of VS was smaller in the preserved hearing group (p < 0.001) where lower stage tumors prevailed (p = 0.001). Extent of internal auditory canal filling did not correlate with the result. Preoperative hearing level (p < 0.001) and the type of brainstem auditory evoked response (p = 0.03) arose as significant prognostic factors. Employment of intraoperative BERA was crucial for the outcome (p < 0.001) but success rate of its preservation was not correlated with the result. Identification of the cochlear nerve (p < 0.001), employment of endoscopic technique (p < 0.001), soft consistency of the tumor (p = 0.05) and the lack of adhesions to the neurovascular structures (p < 0.001) proved to be crucial factors affecting the preservation of hearing. Neither hypervascularity nor the presence of cystic component affected outcome. Conclusions: Apart from the experience of the surgical team, size of the tumor, preoperative hearing level and possibility of intraoperative hearing monitoring represented the main factors for hearing preservation. Early identification of the cochlear portion of the CN VIII is key. For this, the use of endoscopic technique seems to be beneficial. Soft consistency of tumor and lack of adhesions to the neurovascular structures represent crucial intraoperative factors.