Hearing loss in vestibular schwannomas: analysis of cochlear function by means of distortion-product otoacoustic emissions

Objective: We investigated cochlear function in a group of patients affected by vestibular schwannoma (VS), by means of recording distortion-product otoacoustic emissions (DPOAEs). Methods: Between January 1996 and January 2007, we observed 183 patients affected by unilateral VS. DPOAEs, compared to the corresponding hearing thresholds, were subjectively classified into three categories: "compatible" with hearing function, "cochlear" and "retro-cochlear". We also related the responses to some clinical variables (tumor size, intracanalicular tumor and radiologic appearance of the internal auditory canal). Statistical analysis was performed. Results: In 137 cases (74.9%), DPOAEs were as expected based on audiometry responses, while in I I patients (6%) a "cochlear" DP-gram was recorded and in 35 patients (19.1%) DPOAEs evidenced a "retro-cochlear" pattern. In eight cases we detected acoustic responses despite a profound hearing loss. No statistically significant data merged from the comparison between "cochlear" and "retro-cochlear" responses and the clinical variables. Conclusion: Our results confirm that sensorineural hearing loss due to VS can be of sensory and/or neural origin. DPOAEs still remain just a complementary auditory test; nevertheless, in case of severe or profound unilateral hearing loss, recorded acoustic responses may be suspicious for the presence of a vestibular schwannoma. (C) 2009 Elsevier Ireland Ltd. All rights reserved.