Does tinnitus exist in normal hearing patients?

The correlation between tinnitus and hearing threshold was often evaluated. Many authors reported that a big percentage of tinnitus patients suffered from hearing loss. But the auditory evaluation in tinnitus patients with normal hearing threshold was often little accurate. In 2008 Ami and colleagues suggested that reduced outer hair cell activity, as detected by reduced DPOAE levels, may manifest as tinnitus even before there is a shift on hearing threshold. In order to investigate the correlations between tinnitus and hearing threshold and between tinnitus and outer hair cell activity, we analyzed 150 tinnitus patients. All subjects were submitted to audiometric evaluation, including pure tone audiometry (PTA; 250 - 16,000 Hz), immittance, high-definition distortion product otoacoustic emissions (DPOAE; 10 p./octave). In particular the focus was on normal hearing subjects: normal hearing was defined as PTA maximum threshold 20dB HL for frequencies between 250 and 16,000 Hz in both ears; type A tympanogram and counter-lateral stapedial reflex recordable at the threshold (90 dB). First analyzes showed that an important percentage of tinnitus patients has a PTA threshold at 15dB HL for frequencies between 250 and 8,000 Hz, further statistical analyses will be performed on DPOAE and on PTA between 8kHz and 16 kHz.