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DOI: 10.1055/s-0034-1384101
How to Prevent Hearing Loss in Vestibular Schwannoma Surgery—Surgical Conclusions from ABR Monitoring
Background: In vestibular schwannoma surgery, functional preservation of the cochlear nerve is far more difficult than of the facial nerve. In the present study, intra- and postoperative auditory brainstem responses (ABR) were analyzed to identify implications for the surgical strategy for hearing preservation. Methods: In a prospective study from 2010 to 2012, 46 patients were investigated by intraoperative and repeated postoperative ABR monitoring. ABR were classified by a quality classification system (Class 1 = normal, 2 = delayed, 3 = deformed, 4 = only Wave I or V, and 5 = lost) and ABR development and surgical maneuvers were correlated with hearing outcome. Results: In 30 patients, at least temporary reproducible ABRs were present at the end of surgery. In 73% of cases, ABR quality changed during the first 5 days, most often between ABR classes 2 and 4 corresponding to forgoing intraoperative ABR changes. Particularly, critical surgical phases were the opening of the internal auditory canal and the tumor dissection at the auditory nerve. Recovery from very bad ABR was possible in the early postoperative phase, but only in tumors with limited brainstem contact. Conclusion: Intraoperative critical ABR changes continue in the early postoperative phase. Secondary hearing loss may occur during the 1st week. Vice versa, ABR recovery is possible. Permanent ABR and hearing preservation are dependent on ABR quality during the most critical steps.