title: Intraoperative auditory steady-state monitoring during surgery in the cerebellopontine angle for estimation of postoperative hearing classes.
abstract: OBJECTIVE Brainstem auditory evoked potentials (BAEPs) have been used for intraoperative monitoring of the auditory nerve for many years. However, BAEPs yield limited information about the expected postoperative hearing quality and speech perception. The auditory steady-state response (ASSR) enables objective audiograms to be obtained in patients under anesthesia. These ASSRs could be used for intraoperative estimation of hearing classes to improve the postoperative outcome and quality of life. Studies investigating the clinical use of ASSRs during total intravenous anesthesia are currently lacking. The work presented in this article therefore investigates the application of ASSRs for intraoperative estimation of hearing classes. METHODS In 43 patients undergoing surgery for vestibular schwannoma, ASSR measurements were performed at the beginning and end of the surgical procedure. ASSR stimuli consisted of 80-dB hearing level amplitude-modulated tones with 5-minute duration, 90-Hz modulation, and 3 different carrier frequencies: 500, 1000, and 2000 Hz. Stimulation was performed unilaterally with and without contralateral masking, using single and combined carriers. Evoked responses were recorded and analyzed in the frequency domain. ASSRs were compared with extraoperative hearing classes and BAEPs using ANOVA, correlation, and receiver operating characteristic statistics. RESULTS ASSRs yielded high and consistent area under the curve (AUC) values (mean 0.83) and correlation values (mean -0.63), indicating reliable prediction of hearing classes. Analysis of BAEP amplitude changes showed lower AUC (mean 0.79) and correlation values (0.63, 0.37, and 0.50 for Waves I, III, and V, respectively). Latencies showed low AUC values (mean 0.6) and no significant correlation. Combination of several carriers for simultaneous evaluation reduced ASSR amplitudes and respective AUC values. Contralateral masking did not show a significant effect. CONCLUSIONS ASSRs robustly estimate hearing class in patients under total intravenous anesthesia, even when using short measurement durations. The method provides a diagnostic performance that exceeds conventional BAEP monitoring and enables objective and automated evaluation. On the basis of these findings, continuous intraoperative auditory monitoring could become a promising alternative or adjunct to BAEPs.
authors.affiliation: Departments of 1 Neurosurgery and.
authors.forename: Stefan
authors.initials: S
authors.lastname: Rampp
authors.affiliation: Departments of 1 Neurosurgery and.
authors.forename: Leonhard
authors.initials: L
authors.lastname: Rensch
authors.affiliation: Departments of 1 Neurosurgery and.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Simmermacher
authors.affiliation: Otorhinolaryngology, Head and Neck Surgery, University Hospital Halle (Saale), Germany.
authors.forename: Torsten
authors.initials: T
authors.lastname: Rahne
authors.affiliation: Departments of 1 Neurosurgery and.
authors.forename: Christian
authors.initials: C
authors.lastname: Strauss
authors.affiliation: Departments of 1 Neurosurgery and.
authors.forename: Julian
authors.initials: J
authors.lastname: Prell
mesh_terms: D000328:Adult; D000368:Aged; D002530:Cerebellopontine Angle / Q000601:surgery*; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D006320:Hearing Tests; D006801:Humans; D064795:Intraoperative Neurophysiological Monitoring / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000601:surgery*; D019635:Neurosurgical Procedures; D011183:Postoperative Complications / Q000517:prevention & control; D012189:Retrospective Studies; D055815:Young Adult
keywords: ASSR = auditory steady-state response; AUC = area under the curve; BAEP = brainstem auditory evoked potential; CPA; CPA = cerebellopontine angle; EEG = electroencephalography; HL = hearing level; NPV = negative predictive value; PPV = positive predictive value; QOL = quality of life; ROC = receiver operating characteristic; VS = vestibular schwannoma; cerebellopontine angle; diagnostic technique; hearing class; intraoperative monitoring; vestibular schwannoma