A comparison of interaural asymmetry, audiogram slope, and psychometric measures of tinnitus, hyperacusis, anxiety and depression for patients with unilateral and bilateral tinnitus.

Objective: To evaluate differences in tinnitus impact, hyperacusis and hearing threshold level (HTL) between patients with unilateral and bilateral tinnitus. For patients with unilateral tinnitus, to compare audiological variables for the tinnitus ear and the non-tinnitus ear. To assess whether the presence of unilateral tinnitus increases the likelihood of interaural hearing asymmetry (relative to bilateral tinnitus) that warrants referral for an MRI scan.
Design: Retrospective cross-sectional.
Study Sample: Data regarding HTLs and responses to self-report questionnaires were collected from the records of 311 patients attending a tinnitus clinic.
Results: 38.5% had unilateral tinnitus and the ears with tinnitus had higher HTLs and greater HTL slopes than the ears without tinnitus. There was no significant difference in tinnitus impact and hyperacusis between patients with unilateral and bilateral tinnitus. 40% of patients with unilateral tinnitus and 13% of patients with bilateral tinnitus had a between-ear difference in HTL ≥15 dB at two adjacent frequencies (2AF15 asymmetry). Unilateral tinnitus increased the risk of 2AF15 asymmetry by a factor of 4.4.
Conclusions: Unilateral tinnitus increases the risk of having interaural asymmetry in HTLs that warrants referral for an MRI scan.