Influence of a 6-8 kHz audiometric notch on transient evoked otoacoustic emissions

Thirty-eight patients with known unilateral cochlear hearing loss at 6 and/ or 8 kHz were examined for transient evoked otoacoustic emisssions (TEOAEs) . These findings were compared with those of the contralateral "normal hear ing" ear. Statistically significant lower values of echo reproducibility an d amplitude were recorded in hearing-impaired ears, together with a more na rrow TEOAE spectrum. In addition to these findings, a globally reduced ampl itude of the cochlear response was found that was unrelated to the frequenc y impaired in pure-tone audiometry (6, 8, or 6-8 kHz). Since patients' audi ometric thresholds at such frequencies could influence test results, findin gs could possibly be due to an altered echo travelling wave across the most basal part of the cochlea or to coexisting damage in the rest of Corti's o rgan that were undetectable with standard audiometry. A significant overlap was found between the results from hearing-impaired ears and those from no rmally hearing ones. Although TEOAEs were not helpful in the present study in identifying patients with a unilateral hearing loss at 6 and/or 8 kHz wh en compared to normal contralateral ears, they are still considered to play an important role in the followup of subjects at risk for hearing damage.