Left-right difference in high frequency sensitivity : application for unilateral cochlear disorder evaluation.

Abstract

High-frequency audiometry has the potential to detect hearing impairment at its early stage. However, several problems prevent the clinical application of high-frequency audiometry. In this study, the dispersion and left-right difference in the high-frequency sensitivity were investigated in normal hearing volunteers. In our results, the difference between the left and right ears varied only slightly among individuals or age groups, while dispersion of hearing threshold values became marked with an increase in frequency. The results suggest that the measurement of left-right difference in high-frequency sensitivity may be useful for the evaluation of unilateral impairment. To investigate this usefulness, the left-right differences were measured in the patients complaining of unilateral cochlear symptom with normal hearing. Considering the results of normal hearing, we determined that abnormal left-right difference in high-frequency sensitivity was over 20 dB. In 12 patients with unilateral tinnitus, 7 showed left-right differences, and 6 had tinnitus in the ear with increased thresholds. Our results suggested a relationship between tinnitus with normal hearing and hearing impairment in the high-frequency range.