Assessment of Distortion Product Otoacoustic Emissions Input-Output Function in Individuals with and without Musical Abilities

Background and Aim: Musical training has shown to bring about superior performance in several auditory and non-auditory tasks compared to those without musical exposure. Distortion product otoacoustic emissions (DPOAE) input-output function can be an indicator of the non-linear functioning of the cochlea. The objective of this study was to evaluate and compare the differences in the slope of DPOAE input-output function in individuals with and without musical abilities. Methods: Twenty normal-hearing individuals were considered in the age range of 18–25 years. They were divided based on the scores obtained on the questionnaire of musical abilities, as individuals with and without musical abilities. DPOAE input-output function was done for each of the two groups. The slope of the DPOAE input-output function was compared at different frequencies between the groups. Results: The results of the Mann Whitney test revealed that the slope was significantly steeper at 2000, 3000, 4000 and 6000 Hz in individuals with musical abilities. There was no significant difference in slope at 1000 and 1500 Hz. Conclusion: The increased steepness of the slope indicates a relatively better functioning of the cochlea in individuals with musical abilities. The enhanced perception of music may induce changes in the cochlea resulting in a better appreciation of music.

Using electrocochleography to detect sensory and neural damages in a gerbil model

Hearing is one of the five sensory organs that allows us to interact with society and our environment. However, one in eight Americans suffers from sensorineural hearing loss that is great enough to adversely impact their daily life. There is an urgent need to identify what part/degree of the auditory pathway (sensory or neural) is compromised so that appropriate treatment/intervention can be implemented. Single- or two-tone evoked potentials, the electrocochleography (eCochG), were measured along the auditory pathway, i.e., at the round window and remotely at the vertex, with simultaneous recordings of ear canal distortion product otoacoustic emissions. Sensory (cochlear) and neural components in the (remote-) eCochG responses showed distinct level- and frequency-dependent features allowing to be differentiated from each other. Specifically, the distortion products in the (remote-)eCochGs can precisely localize the sensory damage showing that they are effective to determine the sensory or neural damage along the auditory pathway.

Hearing Screening of Newborns using Distortion Product Otoacoustic Emissions

Introduction The present study was devised to estimate the prevalence of neonatal hearing loss and document the importance of using DPOAE as a screening tool for identifying hearing loss in newborns. Materials and Methods This hospital based descriptive study was conducted from August 2018 to August 2019. A total of 928 newborn babies were included in the study. These newborn babies were subjected to hearing screening by distortion product otoacoustic emissions (DPOAE) at 24-72 hrs after birth. For pass cases, no further testing was done. For refer cases, repeat testing with DPOAE was done within 15-30 days. Newborns with refer result on repeat DPOAE testing were subjected to Brainstem evoked response audiometry (BERA) within 3 months to confirm hearing loss. Results Nine hundred and twenty eight newborn babies were screened by DPOAE. 851 newborns passed the first DPOAE hearing screening and 77 newborns gave refer result. 21 newborns were lost to follow-up. 56 newborns underwent repeat DPOAE testing and 5 newborns were referred for BERA. Amongst the 5 newborns who underwent BERA testing, one newborn was diagnosed with bilateral profound hearing loss. Hence, the prevalence of hearing loss of 1.08 per thousand newborn babies was estimated in this study. Conclusion Hearing screening of newborns using DPOAE followed by BERA in refer cases to confirm hearing loss is useful for early detection followed by timely intervention and rehabilitation.

Reliability of Contralateral Suppression in Evoked Distortion Product Otoacoustic Emissions

Introduction Distortion product otoacoustic emissions (DPOAE) and their suppression may be considered useful in monitoring cochlear function and the efferent auditory pathway inhibitory effect. Nonetheless, the establishment of reliable parameters of response variations is of great importance. Objectives To verify the replicability of test and retest in the research of the inhibitory effect of the efferent pathway using contralateral suppressing stimulus during DPOAE recording for clinical applicability. Methods Cross-sectional study with 48 volunteers, aged 18 to 30 years, with normal audiometric thresholds. The procedures included were audiometric and immittance measures to overrule any conductive or sensorineural conditions and DPOAE recordings without and with contralateral suppression with a 60 dBHL white noise. Distortion product otoacoustic emissions amplitudes were analyzed and compared in both conditions with Wilcoxon test, and the Spearman correlation test was used to assess test-retest reliability. Results The comparative analysis showed differences between amplitudes in test and retest conditions only in 1,500 Hz for DPOAE measures with all other tested frequencies showing no differences, and no difference was observed in all recorded frequencies in the test and retest comparison for DPOAE suppression. The degree of correlation between test and retest of DPOAE amplitude was good at 6,000 Hz and strong (r > 0.880) at the other frequencies. For DPOAE with suppression, all frequencies presented strong correlation between test and retest: 1,500 Hz (r = 0.880), 2,000 Hz (r = 0.882), 3,000 Hz (r = 0.940), and 6,000 Hz (r = 0.957). Conclusions The study found good replicability in contralateral suppression of DPOAE with potential clinical applicability, and we recommend conducting the test from 2000Hz to higher frequencies for more reliable results.

Estimation of outer hair cells function in chronic bilateral tinnitus patients with normal hearing using distortion product otoacoustic emissions

Background and Aim: It is not clear if the measurement of distortion product otoacoustic emissions (DPOAE) at frequencies above 8 kHz adds any value in determining the differences in the cochlear function between patients with and without tinnitus. This study aimed to compare DPOAE in the frequency range of 0.5−10 kHz in patients with normal hearing with and without tinnitus. Methods: This comparative cross-sectional study was conducted on 20 individuals with tinnitus and normal hearing as a study group (SG) and a control group (CG) of 20 normal-hearing individuals without tinnitus. The DPOAE was measured with F1/F2 = 1.22 and intensities of F1 = 65 dB SPL and F2 =55 dB SPL in the frequency range of 0.5−10 kHz, moreover in the frequency of tinnitus in SG and corresponding frequency in CG. Results: DPOAE level at 10 kHz did not differ significantly between SG and CG (p = 0.491). However, the mean of overall DPOAE level, DPOAE level at the frequency of tinnitus, and F2 values of 2.5, 5, and 6.298 kHz were significantly lower in SG than CG (p < 0.05). Conclusion: Measurement of DPOAE at 10 kHz did not seem to add any value in determining the differences in the cochlear function between patients with and without tinnitus. However, decreased DPOAE levels at 2.5, 5, and 6.298 kHz which were observed among patients who have tinnitus and normal hearing, indicates some outer hair cells damage that was not detectable by conventional audiometry. Keywords: Tinnitus; normal hearing; outer hair cell; distortion product otoacoustic emission

Distortion Product Otoacoustic Emissions (DPOAEs) In Tinnitus Patients

Introduction Tinnitus is the perception of sound in the absence of external sound stimulation. There is a general agreement that it is a direct consequence of irreversible and permanent cochlear damage. Objectives The present work is designed to study the distortion product otoacoustic emissions (DPOAEs) in tinnitus patients with normal hearing in comparison with normal hearing control and to study any possible correlation between DPOAEs recording and patients' complaints. Methods The present study included 80 subjects divided into 2 groups: Control group: consisted of 30 normal-hearing adults not complaining of tinnitus and Study group: consisted of 50 normal-hearing adults complaining of tinnitus. The methodology includes full audiological history, otoscopic examination, basic audiological evaluation, DPOAEs including both DP-gram and DPOAEs input/output functions. Results Basic audiological evaluation showed within normal hearing sensitivity in both groups, however, with significant higher hearing thresholds in tinnitus patients at all frequency ranges. The Tinnitus Handicap Inventory Questionnaire showed mean scores of 35.2 ± 16.9 in the study group. The DP-gram showed higher amplitudes in the control group when compared with tinnitus patients. The DPOAEs input-output functions at different frequencies (1, 2, 4 and 6kHz) also showed higher amplitudes at all frequencies and different input levels. The slope of the I/O function tends to be steeper in tinnitus cases. Conclusion Patients with tinnitus might have neural dysfunction at either the level of the cochlea, as shown in reduced DPOAE levels, and changes in the normal DP-I/O function recorded in the present work.