Outcomes of audiometric testing in children with auditory neuropathy spectrum disorder

Introduction: Auditory Neuropathy Spectrum Disorder (ANSD) is characterized by hearing loss ranging from normal to profound. Additionally, results are confounded by commonly fluctuating hearing thresholds in ANSD. As such, we sought to evaluate results of audiometric testing on children with ANSD and the impact of age and time on testing results. Methods: Retrospective chart review on children < 18 years of age diagnosed with ANSD at two tertiary care academic institutions. Data analyzed included initial audiogram with speech detection thresholds (SDT) and pure tone averages (PTA) as well as most recent unaided audiogram SDT and PTA. Results: 75 ANSD patients were analyzed, of which 32 (42.7%) were female, Bilateral and unilateral ANSD was seen in 55 (73.3%) and 20 (26.7%), respectively. A total of 130 ears with ANSD were assessed with 80 (61.5%) meeting inclusion criteria. Of these patients, the median age in years at first audiogram and most recent audiogram were 1.94 (0.45-13.68) and 4.22 (0.97-14.61), respectively. The median ages at which an SDT and PTA could first be acquired on the audiogram in ANSD patients were 1.94 (0.50-13.68) and 2.86 (0.45-13.68), respectively. The average SDT/PTA at the initial and most recent audiogram were 47.5/45.7 and 49.4/53.0 dB, respectively. SOT to PTA within the same audiogram exhibited strong correlation (r = 0.82, p < 0.001). Similarly, comparison of initial SDT to SDT at a later time interval showed strong correlation (r = 0.73, p < 0.001). SDT and PTA at initial audiogram and PTA at later time demonstrated lower correlation but was still statistically significant (r = 0.49, p < 0.009 and r = 0.51, p < 0.044, respectively). Individual PTA was associated with age (r = -0.56, p < 0.001). Conclusions: SDT and PTA within the same audiogram and initial SDT to SDT acquired at a later time correlate strongly in audiometric testing in children with ANSD. Although not as strong, initial SDT and PTA still correlate with PTA at a later time interval. These findings suggest that audiometric results yielding a reliable SDT and frequency specific information necessary to calculate the PTA is not typically obtained until 2-3 years old. However, once this information is obtained, the child's hearing is fairly stable but may fluctuate over time.