Auditory Function in the Early Postoperative Phase

Objective: In surgical resection of vestibular schwannomas, preserved auditory brainstem responses (ABRs) at the end of surgery are no guarantee for hearing.

Design: Electrophysiological and auditory functions in the early postoperative phase and their relation to intraoperative changes should be characterized.

Methods: In a prospective study from April 2010 to November 2011, 35 patients (median age 47 years; 19 male, 16 female) were investigated by continuous intraoperative and by intermittent postoperative ABR monitoring at defined intervals at the day of surgery and on the first, second, and fifth days thereafter. ABR quality was graded by presence of components I, III, and V, and postsurgical ABR development was classified into Class A (stable), Class B (intermittent fluctuations with return to baseline), and Class C (repeated fluctuations with permanent change of ABR quality).

Results: Preservation rate was 37%. In 21 patients, postoperative ABR monitoring was indicated; 7 of these patients (33%) belonged to Class A, 6 (29%) belonged to Class B, and 8 patients (38%) to Class C. Critical ABR changes (Classes B and C) started 2 to 4 hours after surgery and correlated with severe intraoperative fluctuation and delayed ABR recovery. In Class C patients, ABR development to complete loss as well as recovery to good ABR quality could be observed in single cases up to day 5 with correct correlation to hearing function.

Conclusions: At the end of surgery, the definite statuses of the auditory pathway and of ABR are not yet reached; both undergo further change leading to recovery or degeneration.