Threshold Mismatches between Pure-Tone Audiometry and Auditory Steady State Response in Non-Auditory Neuropathy Adults

Abstract

Background and Objectives To evaluate mismatches between pure-tone audiometry (PTA) and auditory steady-state response (ASSR) tests in non-auditory neuropathy adults and investigate brain lesions that may explain the mismatches, especially in cases where the ASSR threshold was worse than the estimated PTA threshold.Subjects and Method PTA, speech audiometry, auditory brainstem response, ASSR, and neuroimaging tests were carried out on individuals selected. Among them, medical records of 30 subjects (16 males, 14 females; mean age=54.4±13.2 years) with significant mismatches between PTA and estimated ASSR thresholds were analyzed retrospectively. All neuroimaging tests were reviewed to identify any neurologic abnormalities.Results Pathologic brain lesions were found in 19 cases (63.3%) in the study group, all of which showed significant mismatch in hearing threshold between PTA and ASSR. Seven case of ischemic brain lesions (23.3%), five tumorous lesions (16.6%), and four brain vessel anomalies (13.3%) were found. Brain hemorrhage due to trauma were found in two cases (6.6%) as well as one case (3.3%) of unruptured aneurysm. Central auditory pathway disorder was suspected in two cases. The 11 cases showing normal results in the imaging studies included one mental retardation, one brain concussion, and seven cases (23.3%) with no specific causes. Six tinnitus cases included two subjects showing discrepancies between frequency matching in the tinnitogram.Conclusion In adults with a mismatch between PTA thresholds and estimated ASSR thresholds, especially for those with moderate to profound hearing loss, additional neuroimaging tests and other audiologic tests may reveal other possible causes of hearing loss.