Amplitude Of Otoacoustic Emissions Research Articles

Prevention of Noise-Induced Hearing Loss Using Investigational Medicines for the Inner Ear: Previous Trial Outcomes Should Inform Future Trial Design.

Significance:Noise-induced hearing loss (NIHL) is an important public health issue resulting in decreased quality of life for affected individuals, and significant costs to employers and governmental agencies.Recent Advances:Advances in the mechanistic understanding of NIHL have prompted a growing number of proposed, in-progress, and completed clinical trials for possible protections against NIHL via antioxidants and other drug agents. Thirty-one clinical trials evaluating prevention of either temporary or permanent NIHL were identified and are reviewed.Critical Issues:This review revealed little consistency in the noise-exposed populations in which drugs are evaluated or the primary outcomes used to measure NIHL prevention. Changes in pure-tone thresholds were the most common primary outcomes; specific threshold metrics included both average hearing loss and incidence of significant hearing loss. Changes in otoacoustic emission (OAE) amplitude were relatively common secondary outcomes. Extended high-frequency (EHF) hearing and speech-in-noise perception are commonly adversely affected by noise exposure but are not consistently included in clinical trials assessing prevention of NIHL.Future Directions:Multiple criteria are available for monitoring NIHL, but the specific criterion to be used to define clinically significant otoprotection remains a topic of discussion. Audiogram-based primary outcome measures can be combined with secondary outcomes, including OAE amplitude, EHF hearing, speech-in-noise testing, tinnitus surveys, and patient-reported outcomes. Standardization of test protocols for the above primary and secondary outcomes, and associated reporting criterion for each, would facilitate clinical trial design and comparison of results across investigational drug agents. Antioxid. Redox Signal. 36, 1171–1202.

Inner hair cell dysfunction in Klhl18 mutant mice leads to low frequency progressive hearing loss.

Age-related hearing loss in humans (presbycusis) typically involves impairment of high frequency sensitivity before becoming progressively more severe at lower frequencies. Pathologies initially affecting lower frequency regions of hearing are less common. Here we describe a progressive, predominantly low-frequency recessive hearing impairment in two mutant mouse lines carrying different mutant alleles of the Klhl18 gene: a spontaneous missense mutation (Klhl18lowf) and a targeted mutation (Klhl18tm1a(KOMP)Wtsi). Both males and females were studied, and the two mutant lines showed similar phenotypes. Threshold for auditory brainstem responses (ABR; a measure of auditory nerve and brainstem neural activity) were normal at 3 weeks old but showed progressive increases from 4 weeks onwards. In contrast, distortion product otoacoustic emission (DPOAE) sensitivity and amplitudes (a reflection of cochlear outer hair cell function) remained normal in mutants. Electrophysiological recordings from the round window of Klhl18lowf mutants at 6 weeks old revealed 1) raised compound action potential thresholds that were similar to ABR thresholds, 2) cochlear microphonic potentials that were normal compared with wildtype and heterozygous control mice and 3) summating potentials that were reduced in amplitude compared to control mice. Scanning electron microscopy showed that Klhl18lowf mutant mice had abnormally tapering of the tips of inner hair cell stereocilia in the apical half of the cochlea while their synapses appeared normal. These results suggest that Klhl18 is necessary to maintain inner hair cell stereocilia and normal inner hair cell function at low frequencies.

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.

A Wirelessly Controlled Scalable 3D-Printed Microsystem for Drug Delivery.

Here we present a 3D-printed, wirelessly controlled microsystem for drug delivery, comprising a refillable microreservoir and a phase-change peristaltic micropump. The micropump structure was inkjet-printed on the back of a printed circuit board around a catheter microtubing. The enclosure of the microsystem was fabricated using stereolithography 3D printing, with an embedded microreservoir structure and integrated micropump. In one configuration, the microsystem was optimized for murine inner ear drug delivery with an overall size of 19 × 13 × 3 mm3. Benchtop results confirmed the performance of the device for reliable drug delivery. The suitability of the device for long-term subcutaneous implantation was confirmed with favorable results of implantation of a microsystem in a mouse for six months. The drug delivery was evaluated in vivo by implanting four different microsystems in four mice, while the outlet microtubing was implanted into the round window membrane niche for infusion of a known ototoxic compound (sodium salicylate) at 50 nL/min for 20 min. Real-time shifts in distortion product otoacoustic emission thresholds and amplitudes were measured during the infusion, demonstrating similar results with syringe pump infusion. Although demonstrated for one application, this low-cost design and fabrication methodology is scalable for use in larger animals and humans for different clinical applications/delivery sites.

Hidden or subclinical cochleopathy in idiopathic subjective tinnitus: extended high frequency audiometry and otoacoustic emission

Introduction Tinnitus patients with apparently normal hearing represent a challenge to models of tinnitus generation which rely on compromised cochlear function. Although it is known that any cochlear changes even subclinical can cause tinnitus, our rational was to apply an objective measure that can aids in the quantification of these cochlear changes. Objective The of study was designed to evaluate possible hidden or subclinical cochlear dysfunction in idiopathic subjective tinnitus patients with normal hearing using extended high frequency audiometry and otoacoustic emissions. Methods Forty seven subjects enrolled in this study divided into control group (20 normal hearing adults without tinnitus) and a study group (27 normal hearing adult patients complaining of tinnitus). Extended high frequency (EHF) audiometry and otoacoustic emissions (OAEs) in addition to tinnitus matching study were done for all subjects. Study group further subdivided according to tinnitus pitch matching into low- and high-pitched tinnitus groups. Results The data of this study showed that patients with normal hearing sensitivity in the conventional frequency range (up to 8 kHz) and reporting tinnitus, present alterations of the auditory system in the affected side. This affection manifested as elevated EHF audiometry thresholds at 9000, 10,000, 11,200, 14,000 and 16,000 Hz. Most tinnitus patients had pitch matching frequency at high frequency range between (3000 and 8000 Hz). Transient evoked OAEs and distortion product OAEs amplitude was lower in tinnitus patients relative to controls. Conclusion The ultrahigh frequency hearing loss is not hidden – but – exists and awaits identification with appropriate testing.

The influence of combined exposure to noise and whole-body vibration on hearing loss under simulated heavy equipment driving conditions

Noise-induced hearing loss (NIHL) is a serious problem in occupational environments; however, there is little information about hearing loss due to combined exposure to noise and vibration. This study aimed to investigate the combined effects of exposure to noise and whole-body vibration (WBV) on hearing responses under simulated heavy equipment driving conditions. A repeated measures study was designed to evaluate the changes in distortion product otoacoustic emissions (DPOAE) amplitudes as hearing responses to 40 min of noise and/or WBV exposure. Thirty healthy males with an average age of 30.17 (±3.94) years, exposed to noise level of 85 dB(A) and two WBV levels (0.87 and 1.3 m/s2) in six experimental scenarios. The findings revealed that there was a significant change in DPOAE amplitudes after single noise exposure and combined noise and WBV exposure (p < 0.05); however, there was no significant difference in WBV exposure alone (p > 0.05). The changes in DPOAE amplitudes were greater in combined exposure to noise and WBV (1.3 m/s2) in all sessions. The statistical analysis showed the effect sizes of the combined exposure to noise and WBV were more than the sum of the exposure to each one alone. It can be concluded that some synergic effects can occur in DPOAE amplitudes in the combined noise and WBV exposure under heavy equipment driving conditions. These findings can help the occupational health experts adapt the existing physical agents' exposure limits to the realistic conditions of the occupational settings.

Effects of primary arterial hypertension on cochlear function

Background Hypertension (HT) is one of the most common chronic diseases. The existing literature on HT and hearing contains conflicting results, and no consensus has been reached yet. Objectives This study aimed to investigate cochlear function in hypertensive and normotensive groups. Methods This study was conducted on 34 patients with primary HT and 17 healthy adults. The Cochlear function was assessed with conventional audiometry (0.125–8 kHz), ultra-high frequency audiometry (10–16 kHz), the transient evoked otoacoustic emission (TEOAE) test, and the distortion product otoacoustic emission (DPOAE) test. Results Hearing thresholds at 8, 10, 12.5, 14, and 16 kHz were significantly poorer in the HT group than in the control group (p < .05). There was no significant difference in the mean conventional thresholds between the groups. Compared to the control group, the patient group exhibited statistically significant lower amplitudes of TEOAE and DPOAE. Conclusion This study demonstrated significantly poorer high-frequency hearing and lower otoacoustic emission amplitudes for adults with HT. Impairment in hearing thresholds associated with HT begins at ultra-high frequencies in the cochlea. HT may be a potential risk factor for the development of hearing loss; therefore, individuals with HT should be screened for auditory function.

Otoacoustic emissions and contralateral suppression in tinnitus sufferers with normal hearing

BackgroundThe general consensus on the role of hearing loss in generating tinnitus is not relevant in tinnitus patients with normal hearing thresholds. One source of tinnitus may be related to damage to outer hair cells (OHC) of the cochlea. If the OHC of the human cochlea are to be involved in the generation of tinnitus, testing of Otoacoustic emissions (OAE) could provide a reliable means of recording OHC dysfunction. We investigated the role of OHC and cochlear efferent system in tinnitus development in normal hearing ears through studying of Distortion Product Otoacoustic Emissions (DPOAE) and Transient Evoked Otoacoustic Emissions (TEOAE) amplitudes, contralateral suppression amplitudes and suppression value in 15 normal hearing tinnitus patients and 15 control subjects.ResultsMean f2 DPOAE amplitudes and contralateral suppression were significantly lower in tinnitus group compared to controls for all frequencies from 1001 to 6348 Hz. Suppression values of DPOAEs revealed lower but not significant difference between tinnitus and control groups for all frequencies except 1587 and 6348 Hz. TEOAE amplitudes and contralateral suppression were significantly lower in tinnitus groups for all frequencies from 1000 to 4000 Hz compared to the control group. Suppression value of TEOAEs revealed no significant difference between the two groups for all frequencies except 3000 and 4000 Hz were significantly lower in the tinnitus group compared to the control group.ConclusionsNormal hearing manifested by pure tone audiometry in non-vascular tinnitus sufferers does not exclude OHC and/or cochlear efferent pathology.

Search for Electrophysiological Indices of Hidden Hearing Loss in Humans: Click Auditory Brainstem Response Across Sound Levels and in Background Noise.

Recent studies in animals indicate that even moderate levels of exposure to noise can damage synaptic ribbons between the inner hair cells and auditory nerve fibers without affecting audiometric thresholds, giving rise to the use of the term "hidden hearing loss" (HHL). Despite evidence across several animal species, there is little consistent evidence for HHL in humans. The aim of the study is to evaluate potential electrophysiological changes specific to individuals at risk for HHL. Participants forming the high-risk experimental group consisted of 28 young normal-hearing adults who participated in marching band for at least 5 years. Twenty-eight age-matched normal-hearing adults who were not part of the marching band and had little or no history of recreational or occupational exposure to loud sounds formed the low-risk control group. Measurements included pure tone audiometry of conventional and high frequencies, distortion product otoacoustic emissions, and electrophysiological measures of auditory nerve and brainstem function as reflected in the click-evoked auditory brainstem response (ABR). In experiment 1, ABRs were recorded in a quiet background across stimulus levels (30-90 dB nHL) presented in 10 dB steps. In experiment 2, the ABR was elicited by a 70 dB nHL click stimulus presented in a quiet background, and in the presence of simultaneous ipsilateral continuous broadband noise presented at 50, 60, and 70 dB SPL using an insert earphone (Etymotic, ER2). There were no differences between the low- and high-risk groups in audiometric thresholds or distortion product otoacoustic emission amplitude. Experiment 1 demonstrated smaller wave-I amplitudes at moderate and high sound levels for high-risk compared to low-risk group with similar wave III and wave V amplitude. Enhanced amplitude ratio V/I, particularly at moderate sound level (60 dB nHL), suggesting central compensation for reduced input from the periphery for high-risk group. The results of experiment 2 show that the decrease in wave I amplitude with increasing background noise level was relatively smaller for the high-risk compared to the low-risk group. However, wave V amplitude reduction was essentially similar for both groups. These results suggest that masking induced wave I amplitude reduction is smaller in individuals at high risk for cochlear synaptopathy. Unlike previous studies, we did not observe a difference in the noise-induced wave V latency shift between low- and high-risk groups. Results of experiment 1 are consistent with findings in both animal studies (that suggest cochlear synaptopathy involving selective damage of low-spontaneous rate and medium-spontaneous rate fibers), and in several human studies that show changes in a range of ABR metrics that suggest the presence of cochlear synaptopathy. However, without postmortem examination by harvesting human temporal bone (the gold standard for identifying synaptopathy) with different noise exposure background, no direct inferences can be derived for the presence/extent of cochlear synaptopathy in high-risk group with high sound over-exposure history. Results of experiment 2 demonstrate that to the extent response amplitude reflects both the number of neural elements responding and the neural synchrony of the responding elements, the relatively smaller change in response amplitude for the high-risk group would suggest a reduced susceptibility to masking. One plausible mechanism would be that suppressive effects that kick in at moderate to high levels are different in these two groups, particularly at moderate levels of the masking noise. Altogether, a larger scale dataset with different noise exposure background, longitudinal measurements (changes due to recreational over-exposure by studying middle-school to high-school students enrolled in marching band) with an array of behavioral and electrophysiological tests are needed to understand the complex pathogenesis of sound over-exposure damage in normal-hearing individuals.

Impact of Acamprosate on Chronic Tinnitus: A Randomized-Controlled Trial.

Tinnitus is a common and distressing otologic symptom, with various probable pathophysiologic mechanisms, such as an imbalance between excitatory and inhibitory mechanisms. Acamprosate, generally used to treat alcoholism, is a glutaminergic antagonist and GABA agonist suggested for treating tinnitus. Thus, we aimed to evaluate the efficacy and safety of acamprosate in the treatment of tinnitus. The current randomized-controlled trial study included 20 subjects with chronic tinnitus. After performing psycho-acoustic, psychometric and electrophysiological evaluations, all studied tinnitus subjects were randomly divided into two groups of acamprosate and placebo. The first group received oral acamprosate (two tablets of 333 mg/d, three times a day), whereas the second group was given placebo treatment (two tablets, three times a day). After the first 30 days, all evaluations were repeated for the studied groups just in the same manner before the study. Subsequently, the final results of each evaluation were compared together with the baseline values. Nine studied subjects randomly received acamprosate, whereas eleven others received a placebo. There was no significant improvement in the psycho-acoustic tests, except a decrease was observed in the pitch match of tinnitus (P = .039). For those subjects who were receiving acamprosate, a significant reduction was observed in tinnitus handicap inventory (P = .006), tinnitus questionnaire scores (P = .007), and the visual analog scores (P = .007) compared to the placebo group. There was a significant reduction in Action Potential latency (P = .048) as well as an increase in the amplitude of distortion product otoacoustic emissions at 4 kHz (P = .048). The study results indicated a subjective relief of tinnitus as well as some degree of the electrophysiological improvement at the level of the cochlear and the distal portion of the auditory nerve among the subjects who received the acamprosate. IRCT2013121115751N1.

Effects of subchronic inhalation exposure to an organophosphorus insecticide compound containing dichlorvos on wistar rats’ otoacoustic emissions

IntroductionConsidering that previous studies suggest that pesticides may cause hearing disorders in humans, as well as the lack of studies proving the specific mechanisms of injury and the difficulty of separating concomitant etiological factors of the hearing damage, such as noise and vibration, it is important to develop studies using animal models to elucidate the effects of exposure to those substances isolated from other hearing damage etiologies. ObjectiveTo evaluate if the exposure to a dichlorvos based organophosphorus insecticide may induce ototoxicity. Methods36 male Wistar rats were assigned to 3 groups (12 rats/group): control (exposed to water), positive control (treated with cisplatin to induce hearing damage) and experimental (exposed to dichlorvos based organophosphorus insecticide). The amplitude of distortion product otoacoustic emissions in the frequencies of 4, 6, 8, 10 and 12kHz was evaluated before and after exposure, as well as systemic toxicity signs, body mass gain and plasma cholinesterase. Open field and plus maze tests were performed in 24 rats: experimental (n=8), control (n=8) and positive control group (n=8 introduced new rats to induce anxiolytic activity) to evaluate the locomotor activity and anxiety, respectively. ResultsThere was no significant change in body mass gain and plasma cholinesterase in the dichlorvos based organophosphorus insecticide group, however, the animals showed transient piloerection, depression and dyspnea during exposure. The behavior was not affected in any group. The frequencies of 8 and 10kHz were significantly affected bilaterally in the insecticide group, which also showed a significant difference of the control in 10kHz on the right and 8 and 10kHz on the left ear. ConclusionSubchronic inhalation exposure to dichlorvos based organophosphorus insecticide induced ototoxicity in the cochlear function of rats without relevant systemic toxicity.

Is the Level of Noise in a School Environment be Harmful to the Hearing of Teachers?

Introduction The excessive noise observed in the school environment can cause damages or losses to the learning process as well as risks to the health of teachers and students, such as physical, mental and social impairments, including, among them, hearing loss. Objective To assess otoacoustic emissions in teachers and determine whether classroom noise reduces distortion-product otoacoustic emissions (DPOAEs) amplitude and signal-to-noise ratio (SNR). Method Sixty-seven teachers were evaluated using otoacoustic emissions testing in two situations: after hearing rest and after the working day. Results Signal amplitude ( p = 0.044 [2 kHz]; p = 0.01 [4 kHz]) and SNR for frequencies of 2 kHz ( p = 0.008) and 4 kHz ( p = 0.001) decreased significantly between time points. Mean classroom noise was associated with the magnitude of the difference in signal amplitude at 2 kHz ( p = 0.017) and 4 kHz ( p = 0.015), and SNR at 4 kHz ( p = 0.023). Conclusions There was a decrease in the amplitude and in the SNR after exposure to the noise in the classroom environment. The high levels of sound pressure that teachers are exposed to on a daily basis can cause a temporary change in the outer hair cells of the Corti organ, and these changes may become permanent over time.

Effect of Auditory Predictability on the Human Peripheral Auditory System.

Auditory perception is facilitated by prior knowledge about the statistics of the acoustic environment. Predictions about upcoming auditory stimuli are processed at various stages along the human auditory pathway, including the cortex and midbrain. Whether such auditory predictions are processed also at hierarchically lower stages—in the peripheral auditory system—is unclear. To address this question, we assessed outer hair cell (OHC) activity in response to isochronous tone sequences and varied the predictability and behavioral relevance of the individual tones (by manipulating tone-to-tone probabilities and the human participants’ task, respectively). We found that predictability alters the amplitude of distortion-product otoacoustic emissions (DPOAEs, a measure of OHC activity) in a manner that depends on the behavioral relevance of the tones. Simultaneously recorded cortical responses showed a significant effect of both predictability and behavioral relevance of the tones, indicating that their experimental manipulations were effective in central auditory processing stages. Our results provide evidence for a top-down effect on the processing of auditory predictability in the human peripheral auditory system, in line with previous studies showing peripheral effects of auditory attention.

The characteristic of otoacoustic emissions in full-term neonates according to ABO blood groups

IntroductionPrevious research has suggested that individuals with different blood groups show varied incidences of noise-induced hearing loss. The reduced otoacoustic emissions amplitudes indicate the higher possibilities of outer hair cell damage for noise exposure. ObjectiveThe objective is to analyze the characteristics of otoacoustic emissions, including the occurrence of spontaneous otoacoustic emission and the amplitudes of distortion product otoacoustic emission at certain frequencies in full term neonates with different ABO blood groups. MethodsA total of 80 selected full-term female neonates who passed the initial newborn hearing screen were enrolled into the study, with equal number of participants in four ABO blood groups (Blood Group A, Blood Group B, Blood Group AB, Blood Group O). Measurements of spontaneous otoacoustic emission and distortion product otoacoustic emission were performed in both ears for all participants. Results(1) The blood group O participants showed significantly fewer spontaneous otoacoustic emission occurrences than the other three blood groups (A=70%, B=80%, AB=67%, O=25%, p< 0.05). (2) The blood group O participants showed lower DPOAE amplitudes at 1257 Hz (M = 4.55 dB, SD = 8.36), 1587 Hz (M = 11.60 dB, SD = 6.57), 3174 Hz (M = 7.25 dB, SD = 5.99), 5042 Hz (M = 13.60, SD = 6.70) than participants with the other three blood groups in left ears (p < 0.05). In right ears, the blood group O participants showed reduced amplitudes at 1257Hz (M=6.55dB, SD=8.36), 1587Hz (M=13.60dB, SD=6.57), 3174Hz (M=7.65dB, SD=6.43), 5042Hz (M=13.65dB, SD=6.50) than participants from non-O blood groups (p<0.05). ConclusionFemale individuals with blood group O have lower otoacoustic emissions values than individuals with the other three blood groups. We need to further investigate the possible relationships between ABO blood group and cochlear function, including the potential influences of noise damage on cochlear outer hair cells.

Effect of chronic suppurative otitis media on distortion product otoacoustic emission input-output functions in conventional and ultra-high frequencies.

Detection and valid measurements of distortion product otoacoustic emissions are not influenced by cochlear status alone, but also by middle-ear status. There is a need to understand the use of ultra-high frequency distortion product otoacoustic emissions in cases of abnormal distortion product otoacoustic emission findings for conventional frequencies related to the middle-ear condition. The present study investigated distortion product otoacoustic emission input-output functions in conventional and ultra-high frequencies in: 37 adults with chronic suppurative otitis media (clinical group) and 37 adults with normal hearing sensitivity (control group). There were significant reductions in distortion product otoacoustic emission amplitude and mean signal-to-noise ratio in the clinical group compared to the control group, especially for conventional frequencies. There was a significant reduction in the rate of ears with measurable distortion product otoacoustic emissions in the clinical group, especially for conventional frequencies. The effect of chronic suppurative otitis media was more pronounced in the conventional frequency range compared to the smaller effect seen in the ultra-high frequency range.

Dysfunction of the auditory system in sickle cell anaemia: a systematic review with meta-analysis.

To describe the occurrence of both peripheral and central auditory system dysfunction in sickle cell anaemia (SCA) patients and discuss the different mechanisms hypothesised to be responsible for these alterations. An electronic search was conducted using PubMed Central® (MEDLINE), LILACS® and Scopus® databases. This systematic review was performed in accordance with the PRISMA statement. Original observational studies that utilised audiological tests for auditory system evaluations in SCA were included. A total of 183 records were found in the databases searched. Twenty-one of these studies met the inclusion criteria. Pooled prevalence of sensorineural hearing loss (SNHL) was 20.5% (CI: 10.3-33%). Retrocochlear involvement was detected with the auditory brainstem response, which assesses integrity of the cochlea, 8th cranial nerve and brainstem structures. In addition, the increase in otoacoustic emission amplitudes in SCA patients indicates changes in cochlear micromechanics and precedes the expression of a detectable cochlear pathology. The prevalence of the SNHL is higher than in the general population. Dysfunction of the auditory system may be present in SCA patients, with the most probable mechanism being the presence of circulatory disturbances resulting from the chronic inflammatory state of the disease.

Efficacy of 2 Different Intratympanic Steroid Regimen on Prevention of Cisplatin Ototoxicity: An Experimental Study

Ototoxicity is the general name of cochlear and vestibular organ injury resulting from encountering various therapeutic agents and chemical substances. Cisplatin is commonly used in the treatment of many cancers. In this study, the efficacy of intratympanic steroids was compared for preventing cisplatin ototoxicity. In this study, 32 (64 ears) rats were used by separating into 4 groups. Cisplatin was administered intraperitoneally to the first group (n = 8). Methylprednisolone and then cisplatin were administered intratympanically to the second group (n = 8). On the third group (n = 8), dexamethasone and then cisplatin were administered intratympanically. To the fourth group (n = 8), 0.9% NaCl and then cisplatin were given intratympanically. Otoacoustic emission (OAE) measurements and auditory brainstem responses (ABRs) tests were performed on all groups before and 72 hours after the procedure. Pretreatment of ABR-IV values were 4.29 ± 0.19 milliseconds in group 2 and 4.27 ± 0.16 milliseconds in group 3, whereas posttreatment ABR-IV values were 4.95 ± 0.35 milliseconds in group 2 and 4.65 ± 0.26 milliseconds in group 3. The ABR-IV values were measured significantly shorter in the rats given dexamethasone and methylprednisolone, according to control and cisplatin groups (P < .001). Pretreatment of ABR I-IV interval values were 2.98 ± 0.34 milliseconds and 3.03 ± 0.42 milliseconds in group 1 and group 4, respectively, and ABR I-IV interval values in group 1 and group 4 posttreatment were 3.49 ± 0.39 milliseconds and 3.5 ± 0.39 milliseconds in group 1 and group 4, respectively. Auditory brainstem responses I-IV interval was significantly longer in the cisplatin and control group than in the rats given dexamethasone and methylprednisolone (P < .001). After cisplatin treatment, OAE amplitudes decreased significantly in group 1 and group 4 for all frequencies, while OAE values were protected in methylprednisolone and dexamethasone group (P < .001). In conclusion, it has been shown that both agents have protective effects on cisplatin ototoxicity, with dexamethasone slightly more than methylprednisolone.

Comparison of the protective efficacy between intratympanic dexamethasone and resveratrol treatments against cisplatin-induced ototoxicity: an experimental study

The main aim of this study was to compare the efficacy of intratympanic administration of dexamethasone and resveratrol in preventing cisplatin ototoxicity by measuring acoustic brainstem response (ABR) and distortion product otoacoustic emission (DPOAE). Forty rats (80 ears) were divided into five groups. Cisplatin was administered intraperitoneally to the first group (n = 8). Group 2 (n = 8) received cisplatin after resveratrol had been administered intratympanically. Group 3 (n = 8) received cisplatin after dexamethasone had been administered intratympanically. Group 4 (n = 8) received cisplatin after sodium chloride (NaCl) had been given intratympanically. Group 5 (n = 8) received cisplatin after dimethylsulfoxide (DMSO) had been given intratympanically. ABR and DPOAE tests were performed on all groups before and 72h after the procedure. ABR threshold values in rats that received dexamethasone and resveratrol were found to be less affected than those observed in the other post-cisplatin groups. ABR-IV and ABR-I-IV interval values were significantly reduced in rats that had been given dexamethasone and resveratrol compared to the other groups. After cisplatin treatment, otoacoustic emission (OAE) amplitudes were significantly decreased in Groups 1, 4, and 5 for all frequencies, while OAE values were sustained in the resveratrol and dexamethasone groups (Groups 2 and 3). At OAE frequency 5652, dexamethasone was more significantly associated with protective than resveratrol was, while no significant difference was found between the two groups at other OAE frequencies. In conclusion, intratympanic dexamethasone and intratympanic resveratrol treatments may provide a significant protection against cisplatin-induced ototoxicity.

Distributed sources as a cause of abrupt amplitude decrease in cubic distortion-product otoacoustic emissions at high stimulus intensities.

The amplitudes of distortion-product otoacoustic emissions (DPOAEs) may abruptly decrease even though the stimulus level is relatively high. These notches observed in the DPOAE input/output functions or distortion-product grams have been hypothesized to be due to destructive interference between wavelets generated by distributed sources of the nonlinear-distortion component of DPOAEs. In this paper, simulations with a smooth cochlear model and its analytical solution support the hypothesis that destructive interference between individual wavelets may lead to the amplitude notches and explain the cause for onset and offset amplitude overshoots in the DPOAE signal measured for intensity pairs in the notches.

Comparison of Otoacoustic Emissions in Asymptomatic Diabetes Mellitus and Normal Hearing Control Groups

Background: Diabetes mellitus (DM) is a chronic metabolic disorder. Previous studies reported the hearing impairment of diabetes patients as a progressive bilateral symmetrical sensorineural hearing loss (SNHL) of gradual onset which predominantly affected the higher frequencies, and found that diabetic patients had unsatisfactory hearing thresholds than nondiabetics in the same age group. For the use of evoked otoacoustic emissions (EOAEs) as a clinical test of hearing, EOAEs are sound which can be recorded in the outer ear canal and give objective information about preneural, mechanical elements of the cochlear function.&#x0D; Objective: To compare the otoacoustic emissions of asymptomatic DM patients with a normal hearing control group.&#x0D; Methods: All subjects received a routine audiologic evaluation which consisted of pure-tone air-bone conduction tests, tympanograms, and stapedius acoustic reflex tests. OAEs were measured in 30 asymptomatic diabetic patients with a mean age of 55.73 years and an age-matched 30 subjects normal hearing control group with a mean age of 50.87 years.&#x0D; Results: The pure-tone thresholds at 3, 4, 6, and 8 kHz; transient-evoked otoacoustic emissions (TEOAEs) amplitudes at 1, 1.5, 2, and 3 kHz; and the distortion product otoacoustic emissions (DPOAEs) amplitudes at 1, 1.5, 2, 3, 4, and 6 kHz were significantly different (P &lt; .05) between the asymptomatic and control groups.&#x0D; Conclusions: This study suggested that diabetic patients had a significant hearing impairment. SNHL is gradually progressive and is a common condition in DM patients and their thresholds for hearing are higher at higher frequencies.