Comparison of Frequency-Specific Hearing Thresholds between Pure-Tone Audiometry and Auditory Steady-State Response

Introduction: Hearing assessment in difficult to assess persons gives inconsistent response in free field hearing and pure-tone audiometry (PTA). We have been performing brainstem evoked response audiometry (BERA) as an objective assessment in such cases. BERA has limitations that it is not frequency specific, measures thresholds in higher frequencies only, signal intensity levels cannot be higher than 90 dB and presents the data in waveform which needs to be interpreted by experienced audiologist to deduce correct information. All these limitations can be negated with use of auditory steady-state response (ASSR) which can present intensity levels till 120 dB, is frequency specific, even for lower frequencies and has automated response and deduction analysis. The aim of our study was to compare pure-tone thresholds with ASSR thresholds in normal hearing and hearing loss subjects with an objective to validate the ASSR as a tool for objective hearing assessment. Materials and Methods: In this prospective cross-sectional study of 70 adults (n = 140 ears) of both genders, with and without hearing complaints, Group 1 consisted of 24 individuals of normal hearing, Group 2 consisted of 25 individuals of sensorineural hearing loss, and 21 individuals with conductive hearing loss in Group 3. The patients were evaluated with PTA and ASSR test. The mean pure tone and ASSR thresholds for each frequency were calculated and analyzed using the SPSS IBM software. Results: The mean difference of ASSR with PTA was noted at 9.92 dB in the right ear and 10 dB in the left ear. A high significant correlation was noted between ASSR and PTA with P (0.0005) across all the three groups. The relationship between the PTA and ASSR measurement for measuring average hearing threshold levels is described by the equation: PTA = ASSR mean x 0.99-9.92. Conclusion: ASSR is an excellent tool to predict accurate level of frequency-specific hearing threshold. It has constant relationship with pure tone thresholds. ASSR can predict true hearing thresholds in "difficult to assess" patients such as children and malingerers. This can also be used in the prediction of disability assessment objectively.