Evaluation of noise-induced hearing loss by auditory steady-state and auditory brainstem-evoked responses

Analysis of Chronic Tinnitus in Noise-Induced Hearing Loss and Presbycusis

Introduction: The most frequent causes of tinnitus associated with hearing loss are noise-induced hearing loss and presbycusis. The mechanism of tinnitus is not yet clear, although several hypotheses have been suggested. Therefore, we aimed to analyze characteristics of chronic tinnitus between noise-induced hearing loss and presbycusis. Materials and Methods: This paper is a retrospective chart review and outpatient clinic-based study of 248 patients with chronic tinnitus from 2015 to 2020 with noise-induced or presbycusis. Pure tone audiometry (PTA), auditory brainstem response (ABR), distortion product otoacoustic emissions (DPOAE), transient evoked otoacoustic emissions (TEOAE), and tinnitograms were conducted. Results: PTA showed that hearing thresholds at all frequencies were higher in patients with noise-induced hearing loss than the presbycusis group. ABR tests showed that patients with presbycusis had longer wave I and III latencies (p < 0.05 each) than patients with noise-induced hearing loss. TEOAE tests showed lower values in patients with noise-induced hearing loss than presbycusis at 1.5, 2, 3, and 4 kHz (p < 0.05 each). DPOAE tests showed that response rates in both ears at 1.5, 2, and 3 kHz were significantly higher in patients with presbycusis than noise-induced hearing loss (p < 0.05 each). Discussion: This study showed that hearing thresholds were higher, the loudness of tinnitus was smaller, and the degree of damage to outer hair cells was lower in patients with presbycusis than with noise-induced hearing loss. Moreover, wave I and III latencies were more prolonged in patients with presbycusis despite their having lower hearing thresholds. These phenomena may reflect the effects of aging or degeneration of the central nervous system with age. Further studies are needed to evaluate the etiologies of tinnitus.

The Influence of Stimulus Repetition Rate on Tone-Evoked Post-Auricular Muscle Response (PAMR) Threshold

OBJECTIVES

Post-auricular muscle response (PAMR) is a large myogenic potential that can be useful in estimating behavioral hearing thresholds when the recording protocol is optimal. The main aim of the present study was to determine the influence of stimulus repetition rate on PAMR threshold.

DESIGN

In this repeated-measures study, 20 normally hearing adults aged between 18 and 30 years were recruited. Tone bursts (500, 1000, 2000, and 4000 Hz) were used to record PAMR thresholds at 3 different stimulus repetition rates (6.1/s, 11.1/s, and 17.1/s).

RESULTS

Statistically higher PAMR thresholds were found for the faster stimulus rate (17.1/s) compared with the slower stimulus rate (6.1/s) (p < 0.05). For all stimulus rates and frequencies, significant correlations were found between PAMR and pure-tone audiometry thresholds (r = 0.62 to 0.82).

CONCLUSIONS

Even though the stimulus rate effect was significant at most of the tested frequencies, the differences in PAMR thresholds between the rates were small (<5 dB). Nevertheless, based on the correlation results, we suggest the use of 11.1/s stimulus rate when recording PAMR thresholds.

Longitudinal Comparison of Auditory Steady-State Evoked Potentials in Preterm and Term Infants: The Maturation Process

Introduction  Preterm neonates are at risk of changes in their auditory system development, which explains the need for auditory monitoring of this population. The Auditory Steady-State Response (ASSR) is an objective method that allows obtaining the electrophysiological thresholds with greater applicability in neonatal and pediatric population.

Objective  The purpose of this study is to compare the ASSR thresholds in preterm and term infants evaluated during two stages.

Method  The study included 63 normal hearing neonates: 33 preterm and 30 term. They underwent assessment of ASSR in both ears simultaneously through insert phones in the frequencies of 500 to 4000Hz with the amplitude modulated from 77 to 103Hz. We presented the intensity at a decreasing level to detect the minimum level of responses. At 18 months, 26 of 33 preterm infants returned for the new assessment for ASSR and were compared with 30 full-term infants. We compared between groups according to gestational age.

Results  Electrophysiological thresholds were higher in preterm than in full-term neonates ( p  < 0.05) at the first testing. There were no significant differences between ears and gender. At 18 months, there was no difference between groups ( p  > 0.05) in all the variables described.

Conclusion  In the first evaluation preterm had higher thresholds in ASSR. There was no difference at 18 months of age, showing the auditory maturation of preterm infants throughout their development.