Subtle Peripheral Auditory Dysfunction in Patients With Listening Difficulties

Objectives: This study aimed to investigate the potential contribution of subtle peripheral auditory dysfunction to listening difficulties (LiD) using a threshold-equalizing noise (TEN) test and distortion-product otoacoustic emissions (DPOAE). We hypothesized that a subset of patients with LiD have undetectable peripheral auditory dysfunction. Design: This case-control study included 61 patients (12 to 53 years old; male/female, 18/43) in the LiD group and 22 volunteers (12 to 59 years old; male/female, 10/12) in the control group. The participants were selected based on normal hearing thresholds (<25 dB for an average of 0.5, 1, 2, and 4 kHz) and speech-recognition scores of 90% for monosyllabic words. The test battery consisted of pure-tone audiometry, speech-recognition tests, DPOAE testing, and the TEN test. For the TEN test, the difference between the detection threshold and TEN level was calculated as the signal-to-TEN ratio (STR). Results: The LiD group showed significantly higher STR values across all tested frequencies. A cutoff value of 1.143 for the average STR across seven frequencies yielded an odds ratio of 3.599 with 69.7% sensitivity and 88.6% specificity. DPOAE revealed significantly lower distortion-product levels and signal to noise ratios for the LiD group, especially at 6 kHz. Among the patients with LiD, 80.0%, 71.4%, and 57.2% had positive results for the TEN test, DPOAE, and both, respectively. All participants in the control group, except one 59-year-old, had negative results for the TEN and DPOAE tests. Conclusions: The study findings suggest that subtle peripheral auditory dysfunction, which is undetected by standard audiometry, may contribute to LiD symptoms in some patients. The combination of TEN test results, DPOAE findings, and developmental disorder status may simplify the diagnosis of LiD. This approach may be efficient for screening and may reduce the duration of evaluation relative to the more complex methods currently in use. However, further multicenter studies are required to validate these findings and refine the diagnostic approach for LiD.