Distortion Product Otoacoustic Emissions Amplitudes Research Articles

Early Diagnosis of Hearing Loss in Patients Under Methadone Maintenance Treatment.

Background and Objective: Methadone maintenance treatment (MMT) as the most effective treatment for opioid addictions could induce both reversible and permanent hearing loss. Therefore, early detection of methadone-induced hearing loss is necessary to prevent irreversible cochlear damage. The present study aims to identify the early onset of hearing loss in patients who underwent MMT and to compare them with the age and gender matched normal hearing peers.Methods: This was an analytic cross-sectional study conducted on patients (n = 27 males; age range: 18–53 years old) who received 3 months MMT course (MMT group) and a control group consisting of age and gender matched healthy individuals (n = 27 males). Before MMT, all patients underwent conventional audiometry (250–8,000 Hz) and those with normal hearing threshold participated into the study. One month after MMT termination, the patients were assessed for possible hearing loss using conventional pure tone audiometry (PTA), extended high frequency (EHF) audiometry, and distortion product otoacoustic emissions (DPOAEs).Results: Our results demonstrated that the mean EHF thresholds in the MMT patients were significantly greater than the age- and gender-matched healthy controls across all frequencies (p < 0.001). However, there was no statistically significant difference in conventional PTA thresholds between both groups (p > 0.05). DPOAE amplitudes significantly reduced at higher frequencies (3,000–8,000 Hz) in the MMT group, compared to the healthy control group. In contrast to the conventional PTA audiometry, the EHF and DPOAE assessments identified hearing impairments in 11 (40.74%), and 14 (51.85%) of the MMT patients, respectively. The main mechanisms proposed for methadone induced hearing loss are cochlear ischemia following vasospasm or vasculitis, direct effect of opioids on opioid receptors present in cochlear stria vascularis of inner ear, blood-labyrinth selective transport of opioidproteins and receptors, and genetic polymorphism and mutations.Conclusion: The EHF and DPOAE tests have the potential to detect earlier changes in auditory function than conventional frequency audiometry in the MMT patients.

Hearing complaints in HIV infection originate in the brain not the ear.

Evidence suggests damage to brain auditory pathways, rather than inner ear damage, underlies the hearing difficulties HIV+ individuals report. But, antiretroviral therapy (ART) may affect the hearing system and also lead to hearing complaints. Longitudinal study of HIV+ and HIV- individuals in Dar es Salaam Tanzania. A subset of this cohort started ART while in the study allowing the effects of ART to be studied directly. The ability to hear quiet sounds (pure-tone audiometry), cochlear outer hair cell function [distortion-product otoacoustic emissions (DPOAEs)], and gaps-in-noise detection thresholds (a central auditory processing test) were assessed at each visit. Visits were scheduled for 6-month intervals, but the number and spacing of visits varied. In the group that started ART while in the study, 107 HIV+ individuals had audiometric thresholds, 98 had DPOAEs, and 98 had gap measurements suitable for analysis. Data were analyzed using a linear mixed model with time and starting ART as fixed effects and individual participant repeated measures as random effects. Starting ART did not affect audiometric or gap detection thresholds. The slope of the DPOAE amplitude vs. time relationship was more negative after starting ART but did not differ from the HIV- group. Gap thresholds were higher in the HIV+ group. ART did not affect audiometric thresholds significantly suggesting common ART drugs are not major ototoxins. The gap detection results from the study show effects on central auditory processing in HIV+ individuals, supporting the origin of HIV-related hearing complaints in the central auditory system.

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.

571-P: Analysis of Hearing Loss Characteristics in Prediabetic Patients

Objective: The goal was to study auditory function in prediabetes. Pure Tone Audiometry (PTA), Distortion Product Otoacoustic Emission (DPOAE) and Auditory Brainstem Response (ABR) were used to detect whether there is early hearing deterioration in the prediabetes. Methods: 168 participants underwent the Oral Glucose Tolerance Test (OGTT). 58 prediabetes patients younger than 60 years old, and 50 controls, age and sex matched, were enrolled. All subjects underwent PTA, DPOAE and ABR examinations. All relevant parameters including air and bone conduction pure tone audiometry, DPOAE amplitude and ABR latencies were collected. Results: (1) There were 25 cases with hearing loss in prediabetes (43%), while 6 cases in the control group (12%) by PTA; the difference was statistically significant (P &amp;lt;0.001). The hearing thresholds at each frequency (0.25kHz, 0.5kHz, 1kHz, 2kHz, 4kHz and 8kHz) in the prediabetes were higher than those in controls but only statistically significant at 4kHz and 8kHz (P &amp;lt; 0. 001). Air- and bone-conduction pure-tone thresholds synchronization increased. The difference between air conduction and bone conduction checked by PTA was less than 10dB. (2) DPOAE amplitude at each frequency in the prediabetes group was lower than control group; there were statistically significant differences at 1, 1.5, 2, 3, 4, 6 kHz (P &amp;lt; 0. 001). (3) There were no significant differences of neuron response latencies in ABR measurements between prediabetes and the control group. Conclusions: (1) Loss of auditory function began in the prediabetes stage. Sub-clinical presentations were more pronounced in the prediabetes stage. (2) Bilateral symmetry sensorineural hearing loss, especially at high frequencies, is very characteristic in prediabetic patients. (3)The preliminary findings are that DPOAE is needed to detect the usually slight hearing loss in prediabetes whereas PTA was less sensitive and did not detect such losses. (4) The damage is mainly cochlear, not in the central nervous system. Disclosure Y. Meng: None. X. Zhuang: None. B. Lu: None. X. Wu: None. Funding Capital Health Research and Development of Special Fund (2016-2-7022, 2019-1-1091); Science and Technology Plan of Beijing Municipal Education Commission (KM201610025020)

The influence of distributed source regions in the formation of the nonlinear distortion component of cubic distortion-product otoacoustic emissions.

Distortion product otoacoustic emissions (DPOAEs) are evoked by two stimulus tones with frequency f1 and f2 of ratio f2/f1 in the range between approximately 1.05 and 1.4. This study theoretically and experimentally analyzes the cubic 2f1-f2 DPOAE for different stimulus levels of one of the tones while the other is constant. Simulations for f2/f1 of 1.2 and moderate stimulus levels (30-70 dB sound pressure level) indicate that cubic distortion products are generated along a relatively large length of the basilar membrane, the extent of which increases with stimulus level. However, apical from the place of maximum nonlinear force, the wavelets generated by these distributed sources mutually cancel. Therefore, although the spatial extent of the primary DPOAE sources broadens with increasing stimulus level (up to 1.5 oct), the basilar-membrane region contributing to the DPOAE signal is relatively narrow (0.6 oct) and level independent. The observed dependence of DPOAE amplitude on stimulus level can be well-approximated by a point source at the basilar-membrane place where the largest distortion product (maximum of the nonlinear force) is generated. Onset and offset of the DPOAE signal may contain amplitude overshoots (complexities), which are in most cases asymmetrical. Two-tone suppression was identified as the main cause of these onset and offset complexities. DPOAE measurements in two normal-hearing subjects support the level dependence of the steady-state DPOAE amplitude and the asymmetry in the onset and offset responses predicted by the theoretical analysis.

Is There a Safe Level for Recording Vestibular Evoked Myogenic Potential? Evidence From Cochlear and Hearing Function Tests.

There is a growing concern among the scientific community about the possible detrimental effects of signal levels used for eliciting vestibular evoked myogenic potentials (VEMPs) on hearing. A few recent studies showed temporary reduction in amplitude of otoacoustic emissions (OAE) after VEMP administration. Nonetheless, these studies used higher stimulus levels (133 and 130 dB peak equivalent sound pressure level [pe SPL]) than the ones often used (120 to 125 dB pe SPL) for clinical recording of VEMP. Therefore, it is not known whether these lower levels also have similar detrimental impact on hearing function. Hence, the present study aimed at investigating the effect of 500 Hz tone burst presented at 125 dB pe SPL on hearing functions. True experimental design, with an experimental and a control group, was used in this study. The study included 60 individuals with normal auditory and vestibular system. Of them, 30 underwent unilateral VEMP recording (group I) while the remaining 30 did not undergo VEMP testing (group II). Selection of participants to the groups was random. Pre- and post-VEMP assessments included pure-tone audiometry (250 to 16,000 Hz), distortion product OAE, and subjective symptoms. To simulate the time taken for VEMP testing in group I, participants in group II underwent these tests twice with a gap of 15 minutes. No participant experienced any subjective symptom after VEMP testing. There was no significant interear and intergroup difference in pure-tone thresholds and distortion product OAE amplitude before and after VEMP recording (p > 0.05). Furthermore, the response rate of cervical VEMP was 100% at stimulus intensity of 125 dB pe SPL. Use of 500 Hz tone burst at 125 dB pe SPL does not cause any temporary or permanent changes in cochlear function and hearing, yet produces 100% response rate of cervical VEMP in normal-hearing young adults. Therefore, 125 dB pe SPL of 500 Hz tone burst is recommended as safe level for obtaining cervical VEMP without significantly losing out on its response rate, at least in normal-hearing young adults.

Protective Effect of Melatonin on Cisplatin-induced Ototoxicity in Rats.

Cisplatin is a highly effective chemotherapeutic agent that is used to treat solid tumors; however, its severe side effects remain a limitation. In particular, the high incidence of cisplatin-induced ototoxicity has attracted interest. Melatonin has been shown to decrease the toxic effects of cisplatin due to its antioxidant activity, and could increase the efficacy of cancer chemotherapy. The aim of this study was to determine the effect of melatonin against ototoxicity in rats treated with cisplatin. Rats were randomly divided into four groups (saline, melatonin, cisplatin+saline, and melatonin+cisplatin). Distortion-product otoacoustic emission (DPOAE) measurements were carried out on days 1 and 8. There was a decrease in DPOAE amplitudes in the animals that received cisplatin (10 mg/kg); however, the group treated with cisplatin+melatonin presented DPOAE amplitudes comparable to those of the control groups. Melatonin can be used as an adjuvant tumor treatment due to its ability to decrease cisplatin-induced ototoxicity.

Prenatal masculinization of the auditory system in infants: The MIREC-ID study

Sex differences in inner-ear function are detectable in infants, notably through the measurement of otoacoustic emissions (OAEs). Prevailing theories posit that prenatal exposure to high levels of androgens in boys may weaken OAEs, and that this phenomenon may predominantly affect the right ear/left hemisphere (Geschwind-Galaburda (GG) hypothesis). Yet, actual tests of these models have been difficult to implement in humans. Here we examined the relationship between markers of fetal androgen exposure collected at birth (anogenital distances (AGD); penile length/width, areolar/scrotal/vulvar pigmentation) and at 6 months of age (2nd to 4th digit ratio (2D:4D)) with two types of OAEs, click-evoked OAEs (CEOAEs) and distortion-product OAEs (DPOAEs) (n = 49; 25 boys; 24 girls). We found that, in boys, scrotal pigmentation was inversely associated with the amplitude and reproducibility of CEOAEs in the right ear at 4 kHz, with trends also present in the same ear for mean CEOAE amplitude and CEOAE amplitude at 2 kHz. Penile length was inversely associated with the mean amplitude of DPOAEs in both the right and left ears, as well as with DPOAE amplitude in the right ear at 2 kHz and the reproducibility of CEOAEs in the left ear at 2.8 kHz. Finally, AGD-scrotum in boys was positively associated in boys with the amplitude of DPOAEs in the left ear at 2.8 kHz. Unexpectedly, there were no sex differences in the amplitude or reproducibility of OAEs, nor, in girls, any associations between androgenic markers and auditory function. Nonetheless, these findings, reported for the first time in a sample of human infants, support both the prenatal-androgen-exposure and GG models as explanations for the masculinization of auditory function in male infants.

SENS-401 Effectively Reduces Severe Acoustic Trauma-Induced Hearing Loss in Male Rats With Twice Daily Administration Delayed up to 96 hours.

SENS-401 (R-azasetron besylate) is effective against severe acoustic trauma-induced hearing loss. SENS-401 has calcineurin inhibiting properties and attenuates cisplatin-induced hearing loss in a rat model. Cisplatin-induced and acoustic trauma-induced hearing loss share common apoptotic pathways. The dose-response relationship of SENS-401 (6.6 mg/kg BID, 13.2 mg/kg BID, 26.4 mg/kg QD) and treatment time-window (13.2 mg/kg BID starting 24, 72, and 96 h posttrauma) versus placebo for 28 days were evaluated in a male rat model of severe acoustic trauma-induced hearing loss (120 dB SPL, 2 h) using auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAE) measures followed by cochlear outer hair cell (OHC) counting with myosin-VIIa immunolabeling. All SENS-401 doses improved ABR threshold shift and recovery, reaching statistical significance (p < 0.05) for ABR threshold recoveries after 28-days treatment. DPOAE amplitude loss and recovery improved markedly for 13.2 mg/kg BID SENS-401, reaching significance after 14 days (p < 0.05). Significant improvements in ABR threshold shifts/recovery and DPOAE amplitude loss occurred with up to 96-hours delay in initiating SENS-401 (p < 0.05), and in DPOAE amplitude recovery with up to 72-hours delay (p < 0.05). Significantly more surviving OHCs were present after SENS-401 treatment compared with placebo after 24 to 96-hours delay posttrauma, with up to 5.3-fold more cells in the basal cochlea turn. In vivo data support the otoprotective potential of twice daily oral SENS-401. Improvements in hearing loss recovery make SENS-401 a promising clinical candidate for acoustic trauma-induced hearing loss, including when treatment is not initiated immediately.

A nanoliter resolution implantable micropump for murine inner ear drug delivery

Advances in protective and restorative biotherapies have created new opportunities to use site-directed, programmable drug delivery systems to treat auditory and vestibular disorders. Successful therapy development that leverages the transgenic, knock-in, and knock-out variants of mouse models of human disease requires advanced microsystems specifically designed to function with nanoliter precision and with system volumes suitable for implantation. Here we present results for a novel biocompatible, implantable, scalable, and wirelessly controlled peristaltic micropump. The micropump configuration included commercially available catheter microtubing (250 μm OD, 125 μm ID) that provided a biocompatible leak-free flow path while avoiding complicated microfluidic interconnects. Peristaltic pumping was achieved by sequentially compressing the microtubing via expansion and contraction of a thermal phase-change material located in three chambers integrated adjacent to the microtubing. Direct-write micro-scale printing technology was used to build the mechanical components of the micropump around the microtubing directly on the back of a printed circuit board assembly (PCBA). The custom PCBA was fabricated using standard commercial processes providing microprocessor control of actuation and Bluetooth wireless communication through an Android application. The results of in vitro characterization indicated that nanoliter resolution control over the desired flow rates of 10–100 nL/min was obtained by changing the actuation frequency. Applying 10× greater than physiological backpressures and ± 3 °C ambient temperature variation did not significantly affect flow rates. Three different micropumps were tested on six mice for in vivo implantation of the catheter microtubing 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. There were systematic increases in distortion product threshold shifts during the 20-min perfusions; the mean shift was 15 dB for the most basal region. A biocompatibility study was performed to evaluate material suitability for chronic subcutaneous implantation and clinical translational development. The results indicated that the micropump components successfully passed key biocompatibility tests. A micropump prototype was implanted for one month without development of inflammation or infection. Although tested here on the small murine cochlea, this low-cost design and fabrication methodology is scalable for use in larger animals and for clinical applications in children and adults by appropriate scaling of the microtubing diameter and actuator volume.

Characterization of the early pathology of cochlear stereocilia in four inbred mouse strains with progressive hearing loss.

Inbred strains of mice offer promising models for understanding the genetic basis of age-related hearing loss (AHL). NOD/LtJ, A/J, DBA/2J and C57BL/6J mice are classical models of age-related hearing loss and exhibit early onset of pathology of AHL. This study was carried out to characterize the early pathology of cochlear stereocilia in the four mouse strains with age-related hearing loss. The structural features of stereocilia in NOD/LtJ, A/J, DBA/2J and C57BL/6J mice were observed by scanning electron microscopy (SEM) at age 2, 4, 6 or 8, and 10 or 12 weeks. Meanwhile, auditory-evoked brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) amplitudes of the mice were measured at various intervals (3, 4, 6, 8, 10 and 12 weeks of age). The ABR thresholds in NOD/LtJ, A/J and DBA/2J mice increased with age from 3 to 12 weeks. DPOAE amplitudes in NOD/LtJ, A/J, DBA/2J mice were very low at 4 weeks and became negative at 8 weeks at f2 frequency of 17 672 Hz. In addition to the progressive hearing loss, the four mouse strains displayed early onset (at 2 weeks of age) and progressive degeneration of stereocilia in hair cells. Early degeneration of stereocilia contributes to the functional impairment of hair cells and hearing loss in NOD/LtJ, A/J, DBA/2J and C57BL/6J mice.

Lead Induced Ototoxicity and Neurotoxicity in Adult Guinea Pig.

Lead exposure causes or aggravates hearing damage to human or animal, but the detailed effects of lead exposure on auditory system including injury sites of the cochlea in mammal remain controversy. To investigate the effect of chronic lead exposure on auditory system, 40 adult guinea pigs with normal hearing were randomly divided into five groups. They were fed 2 mmol/L lead acetate in drinking water for 0, 15, 30, 60, and 90 days (n = 8), respectively. Lead concentrations in blood, cochlea, and brainstem were measured. Auditory function was measured by auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE). The morphology of cochlea and brainstem was observed, and expression of autophagy-related protein in brainstem was also assessed. The blood lead concentration reached a high level at the 15th day and kept stable, but the lead level in brainstem and cochlear tissue increased obviously at the 60th day and 90th day of lead exposure, respectively. There was no significant difference in the morphology of hair cells and stria vascularis (SV) among these five groups, but the number of spiral ganglion neuron (SGN) gradually decreased after 60 days. The differences of ABR thresholds and DPOAE amplitudes were not statistically significant among each group, but I wave latency, III latency, and I-III wave interval of ABR were delayed with the prolonging of time of lead exposure. The expressions of autophagy-related protein ATG5, ATG6, and LC3B in brainstem were increased after 30 days. These results suggest that the key target of lead toxicity was the auditory nerve conduction pathway including SGNs and brainstem, rather than cochlear hair cells and SV. Autophagy may play a very important role in lead toxicity to auditory nervous system.

Effect of levodopa on cochlear mechanics and efferent auditory system of Parkinson's disease individuals.

To evaluate the effect of levodopa on cochlear dynamics and on the medial olivocochlear efferent pathway of idiopathic Parkinson's disease (PD) individuals. Individuals with and without PD, followed at a University Hospital, were submitted to Distortion Product Otoacoustic Emissions (DPOAE) and DPOAE Inhibitory Effect (OAEIE) in the presence of contralateral noise. Correlation measures between DPOAE and OAEIE results with Hoehn&Yahr (H&Y) stage, daily dose of levodopa and PD diagnosis period were established. Furthermore, electroacoustic measures were compared between individuals without and those with PD, stratified by dose of levodopa daily administered. Weak negative correlation between DPOAE amplitude and daily dose of levodopa was found, as well positive correlations between EIEOA with daily dose of levodopa and time of PD diagnosis, respectively. Higher DPOAE amplitude was found in individuals with PD using daily doses of levodopa ≤ 600 milligrams when compared to individuals without PD and those with PD using higher doses. EIEOA was lower in individuals using doses ≤ 600 milligrams, when compared to the other groups. Daily doses of levodopa up to 600 mg / day increase the cochlear mechanical-transducer responses in 2 and 3 kHz frequencies, while the action of olivocochlear efferent systems is reduced in this region.

Assessment of hearing in individuals with allergic rhinitis

Background: Allergic rhinitis is an allergic inflammation of nasal airways. It occurs when allergen, such as pollen, dust, or animal dander is inhaled by an individual with a sensitized immune system. Researchers have found that AR causes conductive hearing loss in adults. Although symptoms related to the inner ear structures were not studied till Singh et al., (2011) who reported a positive correlation between AR and sensorineural hearing loss. Aims and Objectives: The present study aimed to develop an audiologic profile in individuals with allergic rhinitis. Material and Methods: Fifteen individuals with allergic rhinitis and 15 individuals without any history of allergic rhinitis were subjected for pure-tone audiometry, distortion product otoacoustic emission, auditory brainstem response, tympanometry, auditory reflex thresholds, and Eustachian tube function tests. All these tests were repeated after 1 month on the same individuals. Results: Results indicated poorer pure-tone thresholds with reduced DP amplitude compared to normals. This can be attributed to the changes in outer hair cell function due to allergens (Singh et al., 2011). None of the individuals exhibited any middle ear or Eustachian tube dysfunction. As the pure-tone thresholds or distortion product otoacoustic emission amplitude did not improve overmedication, the effects on inner ear function might not be seasonal. Conclusion: It can be concluded from the present study that individuals with AR are more prone to sensorineural hearing loss.

Age-related changes of otoacoustic emission

The aim of the study was to assess age-related changes of the transient evoked otoacoustic emissions (TEOAE) and distortion product otoacoustic emissions (DPOAE) as well as to evaluate age-related changes of DPOAE suppression in adult subjects with normal hearing and presbycusis. Only women participated in the study: 26 young women with normal hearing (20-31 years old) were included into the first group; the second group consisted of 28 elderly (60-74 years old) with normal hearing; the third group included 28 elderly women with presbycusis (mild-to-moderate hearing loss). Age-related decrease of prevalence and amplitude of OAEs was proved to be significant; no significant differences of these data for left and right ears were revealed. Contralateral suppression of DPOAE was noted more often and was the greatest in young listeners and was presented in all frequency range, meanwhile the suppression was minimal and rarely noted in patients with presbycusis. The DPOAE amplitude enhancement in the contralateral noise condition was recorded in all groups of listeners, more often in aged patients both with normal hearing and hearing loss. These results may indicate age-related changes of medial olivocochlear complex, which take place not only in patients with hearing loss but in normal hearing subjects as well.. The findings were confirmed by the results of acoustic reflex measurements obtained in this study.

Abnormalities of Otoacoustic Emissions in Myasthenia Gravis: Association With Serological and Electrophysiological Features.

Objective: To investigate whether otoacoustic emissions (OAEs) are impaired in patients with myasthenia gravis (MG) and whether such dysfunction is associated with serological and electrophysiological features of MG.Methods: We tested 15 patients with MG (30 ears) and 10 healthy age- and sex-matched subjects (20 ears) for transiently evoked OAE (TEOAE) and distortion product OAE (DPOAE).Results: Compared with controls, MG patients revealed a significant reduction in the amplitude of TEOAEs (p < 0.05) and DPOAEs at higher frequencies between 2,026 and 4,053 Hz (p < 0.05). In the subgroup analysis, TEOAE and DPOAE amplitudes were significantly lower in the acetylcholine receptor (AChR) antibody-positive group (p < 0.05) as well as in the repetitive nerve stimulation (RNS)-positive (p < 0.05) group. In particular, the OAE alteration significantly correlated with anti-AChR antibody titers. No significant difference of the OAEs was found between thymomatous and non-thymomatous MG or between purely ocular and generalized MG.Conclusions: Our study confirms that OAEs reveal subclinical dysfunction of the cholinergic neurotransmission of cochlear outer hair cells and correlate well with electrophysiological and serological characteristics of MG patients. Our findings imply that the measurement of OAEs might increase the diagnostic accuracy and help to monitor the severity of MG.

The use of distortion product otoacoustic emissions (DPOAE) records to estimate effect of vitamin B complex on changing severity of tinnitus.

IntroductionPatients that are complaining from tinnitus but have normal hearing comprise an uncommon group and there is rare literature about them. Deficiency in B-complex vitamins has been shown to result in tinnitus and supplementation may improve the symptom which means manipulation of cochlear status. Distortion Product Otoacoustic emissions (DPOAEs) used frequently to assess cochlear status.ObjectivesThe uses of DPOAE changing amplitude as a parameter to estimate effect of vitamin B complex on changing the severity of tinnitus in patients with tinnitus only in comparison to patients have tinnitus with Sensory Neural Hearing Loss (SNHL) and a control group.MethodsProspective observational cohort study was performed in AL-Karama Teaching Hospital as a secondary medical care center, from 01/01/2012 to 31/12/2016. A three groups had been evaluated clinically and by OAE device (ECHOLAB) to study the DPOAE changing amplitude before and after one month of supplementation of B-complex vitamins to 25 patients in study group (1) have (tinnitus only) and also to 25 patients in study group (2) have (Tinnitus + SNHL) but leaving control group who were a 25 medical staff (No Tinnitus and nor SNHL) without treatment.ResultsIt has been found that among Study group 1 (patients had Tinnitus only), Study group 2 (patients had Tinnitus + SNHL) and the control group: 16 patients (44%), P-value = 0.000 HS; 28 patients (78%) P-value = 0.000 HS; and 0% respectively, they had low Amplitude of DPOAE recorded by OAE device (ECHOLAB). After one month from treatment with Neurobine ampules for study group 1& 2 but not control group (whom receive no treatment), those who got clinical improvement + increase Amplitude of DPOAE (i.e. subjective + objective changes) after treatment were 10 patients (28%) P-value = 0.000 HS in study group1, and two patients (5%) P-value 0.321 NS in study group 2, and there was no changes (zero) among control group.ConclusionsThe uses of DPOAE changing amplitude could be used as a parameter to estimate effect of vitamin B complex on changing the severity of Tinnitus in patients with tinnitus only or those have Tinnitus with SNHL. The supplementation of vitamin B complex could improve the tinnitus severity especially in patients with tinnitus without SNHL.

Long‑term treatment with salicylate enables NMDA receptors and impairs AMPA receptors in C57BL/6J mice inner hair cell ribbon synapse.

Salicylate is widely used to produce animal models of tinnitus in mice and/or rats. The side effects on auditory function, including hearing loss and tinnitus, are considered the results of the auditory nerve dysfunction. A recent study indicated that chronic treatment with salicylate for several weeks reduces compressed action potential amplitude, which is contradictory to the studies reporting excessive activation of N-methyl-D-aspartate receptors (NMDAR) in tinnitus-induced animals. The specific aims of the experiment were to detect the effect of salicylate on the inner hair cells (IHCs), ribbon synapse, as well as the association between the hearing threshold and the number of mismatched ribbon synapses. In the present study, mice were injected intraperitoneally with a low dose of salicylate (200 mg/kg) for 14 days. The auditory brainstem response and otoacoustic emission were measured to assess auditory function of the mice. The postsynaptic regions of IHC were identified with two types of immunostaining targets: Postsynaptic density protein 95 and Glu2/3. The number of spheres was counted and the synapses were reconstructed in 3-dimensional images. Increases in distortion product otoacoustic emissions amplitudes of the salicylate group were detected, however, an elevation in the hearing threshold was also observed. A mismatch between pre-and post-ribbon synapses was observed. In addition, the cochlear components, including the numbers of outer hair cells and IHCs, were unlikely to be affected by salicylate. IHC ribbon synapses were more susceptible to salicylate stimuli. Furthermore, mismatch of pre- and post-ribbon synapses may indicate a competitive inhibition between NMDAR and α-amino-3-hydroxy-5-methyl-4-isoxa-zole-propionate receptors and dysfunction of ribbon synapses.

No Reliable Association Between Recreational Noise Exposure and Threshold Sensitivity, Distortion Product Otoacoustic Emission Amplitude, or Word-in-Noise Performance in a College Student Population.

The purpose of this study was to evaluate the relationship between recreational sound exposure and potentially undiagnosed or subclinical hearing loss by assessing sound exposure history, threshold sensitivity, distortion product otoacoustic emission (DPOAE) amplitudes, and performance on the words-in-noise (WIN) test. Survey data were collected from 74 adult participants (14 male and 60 female), 18 to 27 years of age, recruited via advertisements posted throughout the University of Florida campus. Of these participants, 70 completed both the survey and the additional functional test battery, and their preferred listening level was measured in a laboratory setting. There were statistically significant relationships between hearing thresholds and DPOAE amplitude. In contrast, performance on the WIN was not reliably related to threshold sensitivity within this cohort with largely normal hearing. The two most common exposures included bars or dance clubs, followed by music player use. There were no statistically significant relationships between individual or composite measures of recreational sound exposure, including preferred listening level, years of music player use, number of reported sound exposures, previous impulse noise exposure, or previous noise-induced change in hearing, and functional measures including threshold, DPOAE amplitude, and WIN measures. Some subjects were highly consistent in listening level preferences, while others were more variable from song to song. No reliable relationships between common recreational sound exposure or previous noise-induced changes in hearing were found during analysis of threshold sensitivity, DPOAE amplitude, or WIN performance in this cohort. However, the study sample was predominantly female and Caucasian, which limits generalizability of the results.

Assessing ototoxicity due to chronic lead and cadmium intake with and without noise exposure in the mature mouse

ABSTRACTExposure to heavy metals may lead to hearing impairment. However, experimental studies have not explored this issue with and without noise exposure in mature animals with environmentally relevant doses. The aim of this study was to investigate ototoxicity produced by lead (Pb) and cadmium (Cd) and noise, singly and in combination, in the adult CBA/CaJ mouse. Metals were delivered via drinking water (0.03 mM, 1 mM, and 3 mM Pb; or 30, 100, and 300 μM Cd) for 12 weeks, resulting in environmentally- and occupationally relevant mean (± standard deviations) blood levels of Pb (2.89 ± 0.44, 38.5 ± 4.9, and 60.1 ± 6.6 μg/dl, respectively) and Cd (1.3 ± 0.23, 6.37 ± 0.87, 27.2 ± 4.1 μg/L, respectively). Metal treatment was also combined with a noise exposure consisting of a 105 dB broadband (2–20 kHz) stimulus for 2 hr or a sham exposure. Auditory performance was determined by comparing auditory brainstem responses (ABR) and distortion product otoacoustic emissions (DPOAE) at baseline and after 11 weeks of metal treatment. Metal-exposed animals did not develop significant auditory deficits and did not exhibit morphological damage to cochlear hair cells. In contrast, noise-exposed animals, including those exposed to combinations of metals and noise, demonstrated significant hair cell loss, reduced DPOAE amplitudes, and ABR threshold shifts of 42.2 ± 13 dB at 32 kHz (105 dB noise alone). No significant potentiation or synergistic effects were found in groups exposed to multiple agents. This study establishes a highly reproducible adult mouse model that may be used to evaluate a variety of environmental exposure mixtures.