Evaluation of tinnitus patients with normal hearing sensitivity using TEOAEs and TEN test

This study was designed to investigate the possibility of underlying cochlear damage whether outer hair cells (OHCs) or inner hair cells (IHCs) in tinnitus suffering patients with normal hearing sensitivity, using transient evoked otoacoustic emission (TEOAEs) and threshold equalizing noise (TEN) test, if any.

Twenty patients suffering from unilateral tinnitus with normal hearing sensitivity participated in this study. Their other ear acted as control ears. They were subjected to full history taking, otoscopy, basic audiologic evaluation, TEOAEs and TEN test.

TEOAEs were abnormal in 85% of the tinnitus ears compared to 20% in control ears; this difference was statistically significant. The abnormal TEOAEs frequency bands in the tinnitus ears were statistically significant above 2000 Hz when compared to the control ears and were more common for the 4000 and 5000 Hz. This suggests that OHCs dysfunction may be important in the generation of tinnitus. TEN test demonstrated dead regions in the cochlea in 15% of the tinnitus ears only. This might be attributed to increased resistance of IHCs to damage compared to OHCs vulnerability. The affected frequency location was at 500 Hz in 5%, 3000 and 4000 Hz in 10% of tinnitus ears.

This work has shown a higher prevalence of OAE abnormalities in tinnitus patients with normal hearing in contrast to TEN test denoting the more vulnerability of OHCs to damage.