Sensitised audiological measures of auditory dysfunction in tinnitus patients with normal hearing thresholds

Substantial evidences show that tinnitus is associated with hearing loss. However, approximately 10% of tinnitus patients attending an ENT/Audiology clinic for their problems have hearing within normal audiometric thresholds. The general consensus on the roles of hearing loss in triggering tinnitus seems not applicable in this minority group. The absence of any grossly abnormal audiometric findings to explain their tinnitus leaves the clinician with a diagnostic dilemma and presents difficulties in dealing with the patients. The aim of this study was therefore to scrutinize auditory functioning in a sample of tinnitus subjects with normal hearing thresholds and non-tinnitus normally hearing control participants. Five tests were applied: Audioscan, Transient Evoked Otoacoustic Emission (TEOAE), Distortion Product Otoacoustic Emission (DPOAE), Threshold Equalising Noise (TEN) test and Contralateral Suppression of TEOAE (CSTEOAE). Optimal parameters for these tests have been defined and subsequently used to detect subtle auditory deficit in tinnitus patients with normal hearing thresholds. Twenty-seven tinnitus patients with hearing thresholds within normal limit participated in this study. A total of 27 non-tinnitus volunteers with similar thresholds were recruited as controls. Significant more Audioscan notches were found in tinnitus patients than in controls, particularly at 3001 to 8000 Hz region. Moreover, abnormal TEOAE was significantly more in tinnitus patients than in controls. No significant difference was observed in DPOAE, TEN and CSTEOAE test. Only one patient was found with abnormal TEN test and no TEOAE suppression, which led to the discovery of a large vestibular schwannoma. VI In summary, these results confirm the possible existence of subtle auditory deficit in tinnitus patients with normal hearing thresholds. However, combination of cochlear and retrocochlear abnormality may also possible. The presence of tinnitus without concomitant hearing loss in this group suggests that it may be an early sign of diseases that are only diagnosed after the onset of hearing loss.EThOS - Electronic Theses Online ServiceGBUnited Kingdo