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 11 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.