Changes In Distortion Product Otoacoustic Emissions Research Articles

Distortion Product Otoacoustic Emissions changes after administration of Sildenafil in animal model

Distortion Product Otoacoustic Emissions changes after administration of Sildenafil in animal model

Study on gene therapy for DPOAE and ABR threshold changes in adult Otof-/- mice

Objective:This study aims to analyze the threshold changes in distortion product otoacoustic emissions（DPOAE） and auditory brainstem response（ABR） in adult Otof-/- mice before and after gene therapy, evaluating its effectiveness and exploring methods for assessing hearing recovery post-treatment. Methods:At the age of 4 weeks, adult Otof-/- mice received an inner ear injection of a therapeutic agent containing intein-mediated recombination of the OTOF gene, delivered via dual AAV vectors through the round window membrane（RWM）. Immunofluorescence staining assessed the proportion of inner ear hair cells with restored otoferlin expression and the number of synapses.Statistical analysis was performed to compare the DPOAE and ABR thresholds before and after the treatment. Results:AAV-PHP. eB demonstrates high transduction efficiency in inner ear hair cells. The therapeutic regimen corrected hearing loss in adult Otof-/- mice without impacting auditory function in wild-type mice. The changes in DPOAE and ABR thresholds after gene therapy are significantly correlated at 16 kHz. Post-treatment,a slight increase in DPOAE was observeds,followed by a recovery trend at 2 months post-treatment. Conclusion:Gene therapy significantly restored hearing in adult Otof-/- mice, though the surgical delivery may cause transient hearing damage. Precise and gentle surgical techniques are essential to maximize gene therapy's efficacy.

Prospective Assessment of Otologic Adverse Events due to Teprotumumab: Preliminary Results.

To assess a series of patients receiving teprotumumab therapy and objectively quantify the rates of otologic adverse events. A prospective cohort study of adult patients receiving teprotumumab between May 2020 and January 2022. Tertiary referral center. Prior to treatment initiation, an ototoxicity-specific audiometric battery was completed, which included conventional audiometry (frequencies 250-8000 Hz), ultrahigh-frequency audiometry (9000-20,000 Hz), tympanometry, speech discrimination scores, and distortion product otoacoustic emissions (DPOAEs). Testing was then repeated after treatment completion. In total, 35 patients were recruited, with a median (range) age of 48.5 years (21-74), and 8 (22.8%) were male. The most common subjective symptom reported was a hearing decline (25.7%), followed by aural fullness (17.1%) and tinnitus (14.3%). Fourteen patients had both pre- and posttreatment audiometric data. Among them, 3 patients (21.4%) were found to have changes in standard frequency audiometry, and 10 (71.4%) had changes in high-frequency audiometry, with 2 patients having changes in both. Less than half (n = 5) of the 11 patients with changes in standard or high-frequency pure tone hearing noted subjective hearing decline. Changes in DPOAE were noted in 4 patients out of 13 (30.7%). Two patients discontinued treatment due to hearing decline. Finally, 3 patients (8.6%) were diagnosed with patulous eustachian tube (PET) by an otolaryngologist, and another 3 patients are suspected to have PET based on symptom description during ophthalmologic follow-up. In our cohort, a high incidence of otologic symptoms was found to be associated with teprotumumab usage. Subjective hearing decline, changes in ultrahigh-frequency hearing as well as eustachian tube dysfunction may be encountered and suggest the potential ototoxicity of teprotumumab.

Impact of endolymphatic hydrops on DPOAE in subjects with normal to mild hearing loss.

The increased endolymph volume affects a shift in the organ of Corti and basilar membrane in ears with endolymphatic hydrops (EH), which might affect distortion-product otoacoustic emissions (DPOAE) by altering the operating point of the outer hair cells. We investigated how changes in DPOAE are related to the distribution site of EH. Prospective study. Among 403 patients with hearing or vestibular symptoms who underwent contrast-enhanced magnetic resonance imaging (MRI) for the diagnosis of EH and subsequent DPOAE testing, subjects whose hearing levels on pure tone audiometry were ≤35dB at all frequencies were included in this study. In patients with EH on MRI, the presence and amplitude of DPOAE were evaluated between groups with hearing levels of ≤25dB at all frequencies versus hearing levels of >25dB at one or more frequencies. There were no differences in the distribution of EH between groups. The amplitude of DPOAE had no clear correlation with the presence of EH. However, in both groups, there was a significantly higher probability of the presence of a DPOAE response from 1001 to 6006Hz in cases with EH in the cochlea. Among patients whose hearing levels were ≤35dB at all frequencies, better responses on DPOAE testing were found in subjects with EH in the cochlea. Alteration of DPOAEs in the early stages of hearing impairment could indicate morphological changes in the inner ear with altered basilar membrane compliance due to EH. 4.

EFFECTS OF AGMATINE ON ACOUSTIC STARTLE REFLEX AND AUDITORY SYSTEM IN RATS

Background: A polyamine, agmatine, has been proposed as a new neurotransmitter in the brain. Objective: The aim of this study was to evaluate the effects of acute and chronic agmatine treatment on the rat auditory system. Methods: Male Wistar albino rats weighing between 280-330 grams were used. Animals were divided into four groups (n= 8 for each group). Acute and chronic agmatine (160 mg/kg) was administered to rats. Prepulse inhibition (PPI) of the acoustic startle reflex (ASR), distortion product otoacoustic emissions (DPOAEs), auditory brainstem responses (ABR) were evaluated in all groups. Results: Both acute and chronic agmatine treatments also significantly disrupted PPI. Chronic but not acute treatment with agmatine produced some DPOAE and ABR changes in rats. Conclusion: Our results suggested that chronic agmatine treatment for seven days resulted in some significant negative changes in cochlear function. Because the PPI of the ASR is also used as an indicator for psychoses, such as schizophrenia, in human and experimental animal studies, our findings also imply that the DPOAE and ABR tests may also be considered in the diagnosis and follow-up of patients with psychoses.

Limiares auditivos em frequências altas e emissões otoacústicas em pacientes com anemia falciforme

Objetivo: Verificar limiares auditivos em frequências convencionais e altas frequências e presença de emissões otoacústicas por produto de distorção em pacientes falcêmicos, analisando a variável faixa etária. Método: Coorte observacional, prospectivo, analítico, de fins diagnósticos. Realizada audiometria convencional, audiometria em frequências altas (AAF) e emissões otoacústicas por produto de distorção (EOAPD) em pacientes portadores da doença. Resultados: Foram avaliados 38 pacientes, sendo 16 (42,1%) na faixa etária de 7 a 20 anos de idade e 22 (57,9 %), de 21 a 35 anos. A alteração auditiva na audiometria convencional foi de 6,3% na faixa etária de 7 a 20 anos e 13, 6%, entre 21 e 35 anos. Não houve diferença estatisticamente significativa entre as faixas etárias (p=0,624). Na AAF, alteração em 25% das crianças e adolescentes e em 68,2% dos adultos. Os adultos apresentaram maior perda auditiva (p=0,021). Não houve diferença significativa na comparação das medidas de relação sinal/ruído das EOAPD entre as orelhas, tanto na amostra total quanto por faixa etária (p>0,05). Não houve associação significativa entre os resultados das alterações das EOAPD e a perda auditiva em frequências ultra-altas tanto nas crianças e adolescentes (p=0,250) quanto nos adultos (p=0,121). Na comparação entre as sensibilidades dos exames AAF e EOAPD, houve diferença significativa entre eles somente nos adultos (p=0,004). Conclusões: Os adultos com maior duração da exposição à doença apresentaram elevação dos limiares em AAF, bem como alteração das EOAPD.

Slow oscillatory changes of DPOAE magnitude and phase after exposure to intense low-frequency sounds.

Sensitive sound detection within the mammalian cochlea is performed by hair cells surrounded by cochlear fluids. Maintenance of cochlear fluid homeostasis and tight regulation of intracellular conditions in hair cells are crucial for the auditory transduction process but can be impaired by intense sound stimulation. After a short, intense low-frequency sound, the cochlea shows the previously described "bounce phenomenon," which manifests itself as slow oscillatory changes of hearing thresholds and otoacoustic emissions. In this study, distortion product otoacoustic emissions (DPOAEs) were recorded after Mongolian gerbils were exposed to intense low-frequency sounds (200 Hz, 100 dB SPL) with different exposure times up to 1 h. After all sound exposure durations, a certain percentage of recordings (up to 80% after 1.5-min-long exposure) showed oscillatory DPOAE changes, similar to the bounce phenomenon in humans. Changes were quite uniform with respect to size and time course, and they were independent from sound exposure duration. Changes showed states of hypo- and hyperactivity with either state preceding the other. The direction of changes was suggested to depend on the static position of the cochlear operating point. As assessed with DPOAEs, no indication for a permanent damage after several or long exposure times was detected. We propose that sensitivity changes occur due to alterations of the mechanoelectrical transduction process of outer hair cells. Those alterations could be induced by different challenged homeostatic processes with slow electromotility of outer hair cells being the most plausible source of the bounce phenomenon. NEW & NOTEWORTHY Low-frequency, high-intensity sound can cause slowly cycling activity changes in the mammalian cochlea. We examined the effect of low-frequency sound duration on the degree of these alterations. We found that cochlear changes showed a stereotypical biphasic pattern independent of sound exposure duration, but the probability that significant changes occurred decreased with increasing sound duration. Despite exposure durations of up to 1 h, no permanent or transient impairments of the cochlea were detected.

Deterioration in Distortion Product Otoacoustic Emissions in Auditory Neuropathy Patients With Distinct Clinical and Genetic Backgrounds.

Auditory neuropathy (AN) is a clinical disorder characterized by the absence of auditory brainstem response and presence of otoacoustic emissions. A gradual loss of otoacoustic emissions has been reported for some cases of AN. Such cases could be diagnosed as cochlear hearing loss and lead to misunderstanding of the pathology when patients first visit clinics after the loss of otoacoustic emissions. The purpose of this study was to investigate the time course of changes in distortion product otoacoustic emissions (DPOAEs) in association with patients' genetic and clinical backgrounds, including the use of hearing aids. DPOAE measurements from 31 patients with AN were assessed. Genetic analyses for GJB2, OTOF, and mitochondrial m.1555A> G and m.3243A> G mutations were conducted for all cases, and the analyses for CDH23 and OPA1 were conducted for the selected cases. Patients who were younger than 10 years of age at the time of AN diagnosis were designated as the pediatric AN group (22 cases), and those who were 18 years of age or older were designated as the adult AN group (9 cases). DPOAE was measured at least twice in all patients. The response rate for DPOAEs was defined and analyzed. The pediatric AN group comprised 10 patients with OTOF mutations, 1 with GJB2 mutations, 1 with OPA1 mutation, and 10 with indefinite causes. Twelve ears (27%) showed no change in DPOAE, 20 ears (46%) showed a decrease in DPOAE, and 12 ears (27%) lost DPOAE. Loss of DPOAE occurred in one ear (2%) at 0 years of age and four ears (9%) at 1 year of age. The time courses of DPOAEs in patients with OTOF mutations were divided into those with early loss and those with no change, indicating that the mechanism for deterioration of DPOAEs includes not only the OTOF mutations but also other common modifier factors. Most, but not all, AN patients who used hearing aids showed deterioration of DPOAEs after the start of using hearing aids. A few AN patients also showed deterioration of DPOAEs before using hearing aids. The adult AN group comprised 2 patients with OPA1 mutations, 2 with OTOF mutations, and 5 with indefinite causes. Four ears (22%) showed no change in DPOAE, 13 ears (72%) showed a decrease, and one ear (6%) showed a loss of DPOAE. Although the ratio of DPOAE decrease was higher in the adult AN group than in the pediatric AN group, the ratio of DPOAE loss was lower in the adult AN group. DPOAE was not lost in all four ears with OPA1 mutations and in all four ears with OTOF mutations in the adult group. DPOAE was decreased or lost in approximately 70% of pediatric and about 80% of adult AN patients. Eleven percent of pediatric AN patients lost DPOAEs by 1 year of age. Genetic factors were thought to have influenced the time course of DPOAEs in the pediatric AN group. In most adult AN patients, DPOAE was rarely lost regardless of the genetic cause.

Relationship between distortion product otoacoustic emission signal-to-noise and hearing threshold change during methylprednisolone therapy for sudden deafness

Sudden deafness is an emergency case in audiology requiring immediate treatment. According to the consensus on diagnosis and treatment of sudden hearing loss 2010 in Madrid, Spain, steroid drugs are the treatment of choice for sudden deafness with an unknown etiology. Patients recovering from sudden deafness exhibit increasing otoacoustic emissions that begin prior to hearing improvement. In this study, we evaluated a new methylprednisolone regimen (1 mg/kg daily, tapering by 20 mg every 5 days) for sudden deafness using distortion product otoacoustic emissions (DPOAE) and pure tone audiometry. Pure tone audiometry and DPOAE evaluations were conducted on 22 patients before treatment and on day 15 after therapy. Hearing threshold improved at all measured frequencies during treatment (1500–12000 Hz). There were also significant changes in DPOAE signal-to-noise ratio (SNR) at 1500, 2000, and 8000 Hz. Moreover, there were significant associations between SNR change and hearing threshold change at 8000 Hz and 10000 Hz. Thus, this new methylprednisolone regimen is highly effective for sudden deafness.

Effectiveness of earmuffs in protecting hearing during shooting practice: a case-study

Objective: This investigation was designed to determine the effectiveness of earmuffs worn by a single individual during shooting practice.Design: Single subject experimental design. Study sample: A 21-year old female recreational shooter, who practiced shooting on a regular basis while using earmuffs participated in the study. She reported occasional noise exposures of other types including car races and demolition derbies but no hearing difficulties or symptoms such as tinnitus. Her auditory sensitivity was within normal limits. On each test-day, distortion product otoacoustic emissions (DPOAEs) were recorded in a sound-attenuated booth before and after a shooting practice session conducted while using earmuffs. Data were collected across six different days, across six weeks, to allow recovery from each of the six shooting practice sessions. The participant was requested to refrain from other noisy activities in between sessions. Results: Significant changes in DPOAE signal-to-noise ratios (SNRs) were apparent following the shooting sessions, at 1184 and 4761 Hz in the left ear suggesting that the hearing protection worn by the individual was insufficient to completely protect her hearing. Conclusions: It is possible to assess the effectiveness of hearing protection worn by individual shooters using repeated measurements of DPOAEs embedded in a single case-research design.

Role of otoacoustic emissions in the early detection and prevention of ototoxicity

Introduction: Evaluating Otoacoustic Emissions (OAEs) is one of the audiological methods for ototoxicity monitoring. The absence of OAEs indicates cochlear damage. The aim of this study was to study the usefulness of OAEs in early detection and prevention of ototoxicity. Materials and Methods: A prospective, comparative study was conducted to evaluate Transient-Evoked OAEs (TEOAEs) and Distortion-Product OAEs (DPOAEs) as they relate to Pure Tone Audiometry (PTA) in cases of ototoxicity. Hearing assessments of study group of 55 individuals exposed to ototoxic drugs were evaluated and compared at regular intervals, within the group and with control group of 25 individuals using PTA, TEOAEs, and DPOAEs. The abnormal OAE responses were calculated as predictive of significant changes in PTA thresholds. Student's t-test (independent samples, two-tailed) and ANOVA used for analysis. Results: PTA thresholds in the study group remained unaffected in the first three follow-ups whereas TPOAEs and DPOAEs were both found affected at the third follow-up, in significant number of ears in the study group. Significantly lower PTA thresholds were found in study group only at the fourth follow-up. Conclusions: Changes in TEOAEs and DPOAEs precede changes in PTA thresholds in ototoxicity and have high sensitivity and specificity in predicting hearing loss in such cases.

Effect of drill-induced noise on hearing in non-operated ear.

Background:The aim of this study was to evaluate the effect of drill-generated noise on hearing loss in non-operated ear and if any, was temporary or persistent.Materials and Methods:In this prospective clinical study, 23 patients who had undergone mastoidectomy and normal contralateral hearing were enrolled. Patients were evaluated preoperatively and postoperatively (1 and 7 days) following surgery using low and high-frequency pure tone audiometry (PTA) and low and high-frequency transient evoked and distortion product otoacoustic emission (DPOAE) testing.Results:Comparing preoperative and 1-day after surgery, PTA averages were significantly different at low frequencies, but no statistical significant differences were observed at 0.25 KHz and high-frequencies. Comparing 1-day after surgery and 7 days after surgery showed that, PTA averages at 0.5, 2 and 2 KHz were significantly different with no significant differences at the other average of thresholds in low and high frequencies; PTA average at 1 KHz was significantly different with, no significant differences at the other averages of thresholds in low and high frequencies. DPOAEs showed a significant difference preoperative and 1-day after surgery, 1-day and 7 days after, but DPOAEs were not significantly different. Transiently evoked otoacoustic emissions (TEOAEs) had a significant difference preoperative and 1-day after surgery, 1-day and 7 days after but when comparing preoperative and 7 days after surgery, TEOAEs were not significantly different.Conclusions:Drill-induced noise during ear surgery (mastoidectomy) can cause reversible changes in PTA, DPOAEs and TEOAEs in the non-operated ear.

Negative Middle Ear Pressure and Composite and Component Distortion Product Otoacoustic Emissions.

Distortion product otoacoustic emissions (DPOAEs), a by-product of normal outer hair cell function, are used in research and clinical settings to noninvasively test cochlear health. The composite DPOAE recorded in the ear canal is the result of interactions of at least two components: a nonlinear distortion component (the generator component) and a linear reflection component. Negative middle ear pressure (NMEP) results in the tympanic membrane being pulled inward and increases middle ear impedance. This influences both the forward travel of stimuli used to induce distortion products and the reverse travel of the emissions back to the ear canal. NMEP may therefore limit the effectiveness of DPOAEs in clinical settings. Twenty-six normal-hearing subjects were recruited, and eight were able to reliably and consistently induce NMEP using the Toynbee maneuver. Eight interleaved measures of tympanic peak pressure (TPP) were collected for each subject at normal pressure and NMEP. DPOAEs were then collected both when middle ear pressure was normal and during subject-induced NMEP. All measures were interleaved. Two primary tones were swept logarithmically across frequency (1 second per octave) from f1 = 410 to 6560 Hz and f2 = 500 to 8000 Hz (f1/f2 = 1.22), producing 2f1 - f2 DPOAEs from 320 to 5120 Hz. DPOAEs were collected at three equal-level primary level combinations (L65, L70, L75 dB SPL). Before composite and component DPOAE analysis, analysis of the f1 DPOAE primary confirmed that subjects had successfully induced NMEP. DPOAE and component magnitudes were separately analyzed using repeated measures analysis of variances with three factors, primary level (L65, L70, L75 dB SPL), middle ear pressure (normal pressure versus NMEP), and frequency (500 to 4000 Hz). Mean subject-induced NMEP ranged from -65 to -324 daPa. Changes in the magnitude (dB) of the primary tones used to induce the DPOAE provided a reliable indicator of subject-induced NMEP. Composite DPOAE and component levels were significantly affected by NMEP for all the frequencies tested. Changes were most clearly observed for the generator component with one subject demonstrating a mean decrease of 12 dB in magnitude during NMEP. Results were subject-specific, and there was a correlation between the degree of negative TPP induced and the amount of change in DPOAE level. Mean TPPs collected during NMEP ranged from -65 to -324 daPa and significantly affected composite DPOAE, generator, and reflection component levels. Changes in the magnitude of the swept-primaries as a function of frequency were used to confirm that NMEP had been successfully induced. The patterns of change in the composite DPOAEs were clearer and easier to interpret when the components of the DPOAE were separated with evaluation of the generator component alone.

Frequency-change in DPOAE evoked by 1 s/octave sweeping primaries in newborns and adults

Distortion product otoacoustic emissions (DPOAE) in newborns and adults were evoked by sweeping primaries up and down in frequency at 1 s/octave. Sweeping up and down in frequency resulted in changes in the amplitude vs. frequency functions of the composite DPOAE and its two major components. In addition, DPOAE component phases differed slightly between the up- and down-swept conditions. The changes in amplitude vs. frequency functions were quantified using a covariate correlation technique, yielding single-valued estimates of the magnitude of the frequency changes. Separate analyses were performed for the entire DPOAE frequency range and split into low and high frequency ranges. There were consistent changes in newborn and adult composite DPOAEs and reflection components, but not generator components. Adults had significant frequency changes in the composite DPOAE for all frequency ranges and in the reflection component for the entire frequency range. Newborns had significant frequency change in the reflection component for all frequency ranges. Differences in frequency change between adults and newborns may stem from developmental changes in cochlear processing. Alignment of the component phase differences between the up- and down-swept conditions resulted in elimination of frequency-change in reconstructed composite DPOAEs.

Auditory nerve disease and auditory neuropathy spectrum disorders.

In 1996, a new type of bilateral hearing disorder was discerned and published almost simultaneously by Kaga et al. [1] and Starr et al. [2]. Although the pathophysiology of this disorder as reported by each author was essentially identical, Kaga used the term "auditory nerve disease" and Starr used the term "auditory neuropathy". Auditory neuropathy (AN) in adults is an acquired disorder characterized by mild-to-moderate pure-tone hearing loss, poor speech discrimination, and absence of the auditory brainstem response (ABR) all in the presence of normal cochlear outer hair cell function as indicated by normal distortion product otoacoustic emissions (DPOAEs) and evoked summating potentials (SPs) by electrocochleography (ECoG). A variety of processes and etiologies are thought to be involved in its pathophysiology including mutations of the OTOF and/or OPA1 genes. Most of the subsequent reports in the literature discuss the various auditory profiles of patients with AN [3,4] and in this report we present the profiles of an additional 17 cases of adult AN. Cochlear implants are useful for the reacquisition of hearing in adult AN although hearing aids are ineffective. In 2008, the new term of Auditory Neuropathy Spectrum Disorders (ANSD) was proposed by the Colorado Children's Hospital group following a comprehensive study of newborn hearing test results. When ABRs were absent and DPOAEs were present in particular cases during newborn screening they were classified as ANSD. In 2013, our group in the Tokyo Medical Center classified ANSD into three types by following changes in ABRs and DPOAEs over time with development. In Type I, there is normalization of hearing over time, Type II shows a change into profound hearing loss and Type III is true auditory neuropathy (AN). We emphasize that, in adults, ANSD is not the same as AN.

Influence of sound-conditioning on noise-induced susceptibility of distortion-product otoacoustic emissions.

Cochlear damage caused by loud sounds can be attenuated by "sound-conditioning" methods. The amount of adaptation for distortion product otoacoustic emissions (DPOAEs) measured in alert rabbits previously predicted an ear's susceptibility to a subsequent noise exposure. The present study investigated if sound-conditioning influenced the robustness of such DPOAE adaptation, and if such conditioning elicited more protection by increasing the amount of DPOAE adaptation. Toward this end, rabbits were divided into two study groups: (1) experimental animals exposed to a sound-conditioning protocol, and (2) unconditioned control animals. After base-line measures, all rabbits were exposed to an overstimulation paradigm consisting of an octave band noise, and then re-assessed 3 weeks post-exposure to determine permanent changes in DPOAEs. A major result was that prior sound-conditioning protected reductions in DPOAE levels by an average of 10-15 dB. However, DPOAE adaptation decreased with sound-conditioning, so that such conditioning was no longer related to noise-induced reductions in DPOAEs. Together, these findings suggest that sound-conditioning affected neural pathways other than those that likely mediate DPOAE adaptation (e.g., medial olivocochlear efferent and/or middle-ear muscle reflexes).

Changes in distortion product otoacoustic emission components after music exposure.

Young adults experience some type of recreational noise exposure on a daily basis; this includes using personal music (PM) systems with earphones. In most cases, this exposure is intermittent and the short-term effects of this exposure on the auditory system are becoming better understood. The purpose of this study was to examine the effects of one hour of music exposure using a PM system on distortion product otoacoustic emission (DPOAE) absolute levels and generator and characteristic frequency (CF) component levels. Young adults (n = 101) between 18-30 years with normal hearing participated listened to one hour of music through earphones. A second group of young adults (n = 21) served as controls and did not listen to music, but sat in the sound-treated room for one hour. Otoscopy, tympanometry, and a hearing screening (≤20 dB HL at 0.5, 1, 2, and 4 kHz) were completed in a randomly determined test ear. Preferred listening level, in dBA, was obtained and DPOAEs (2f1-f2) were measured between 1 and 6 kHz with stimulus levels fixed at L1,L2 = 55,40 dB SPL. Absolute DPOAE levels, along with generator and CF components levels were measured before and after each participant listened to one hour of music at their preferred level in a quiet setting. For data analyses, absolute DPOAE and generator and CF component levels were collapsed into 1/3rd octave bands centered around 1, 1.5, 2, 3, 4, and 6 kHz. Mean preferred listening level was 57.8 dBA, with males having a higher mean level of 61.1 dBA compared with females who had a mean level of 55.7 dBA. Females and males had negligible mean changes in absolute DPOAE levels at 1, 1.5, and 2 kHz, but males had 0.4-1 dB mean decreases after music at 3, 4, and 6 kHz compared to females, although not statistically significant. For DPOAE generator component data, females had small mean decreases for the two lower frequencies whereas males had mean decreases of 0.4-0.8 dB at 3, 4, and 6 kHz. Because of missing data, analyses of the CF component were limited, although females had small mean decreases at four frequencies while males had small mean decreases at two frequencies. There was no effect of listening to music on changes in DPOAEs but control participants had strong reliability (i.e., little or no change) after sitting in quiet for one hour. Young adults listened to music well below what would be considered hazardous. Because of the lower listening levels, DPOAEs showed very little change after music. Although there were no significant short-term changes in DPOAEs after music, the cumulative effect of this noise exposure is still unknown.

Noninvasive assessment of intracranial pressure using otoacoustic emissions in pediatric patients with idiopathic intracranial hypertension (IIH)

The ability to follow response to treatment with elevated intracranial pressure (ICP) and papilledema are crucial factors in the preservation of visual function in IIH. Current methods of ICP monitoring are invasive. Distortion-product otoacoustic emissions (DPOAEs), measured non-invasively through the ear canal, appear to be sensitive to ICP changes in healthy subjects.1 We evaluated whether changes in DPOAEs correlate with changes in ICP in pediatric patients.

Intracranial pressure modulates distortion product otoacoustic emissions: a proof-of-principle study.

There is an important need to develop a noninvasive method for assessing intracranial pressure (ICP). We report a novel approach for monitoring ICP using cochlear-derived distortion product otoacoustic emissions (DPOAEs), which are affected by ICP. We hypothesized that changes in ICP may be reflected by altered DPOAE responses via an associated change in perilymphatic pressure. We measured the ICP and DPOAEs (magnitude and phase angle) during opening and closing in 20 patients undergoing lumbar puncture. We collected data on 18 patients and grouped them based on small (<4 mm Hg), medium (5-11 mm Hg), or large (≥15 mm Hg) ICP changes. A permutation test was applied in each group to determine whether changes in DPOAEs differed from zero when ICP changed. We report significant changes in the DPOAE magnitudes and angles, respectively, for the group with the largest ICP changes and no changes for the group with the smallest changes; the group with medium changes had variable DPOAE changes. We report, for the first time, systematic changes in DPOAE magnitudes and phase in response to acute ICP changes. Future studies are warranted to further develop this new approach. DPOAE, distortion product otoacoustic emissionICP, intracranial pressureIIH, idiopathic intracranial hypertensionLP, lumbar punctureTBI, traumatic brain injury.

A longitudinal study of changes in distortion-product otoacoustic emissions and pure-tone thresholds in an industrial setting

In a longitudinal study of 76 noise-exposed industrial workers, 34 (68 ears) of them were available for final evaluation after 9 years of observation. Distortion-product otoacoustic emissions (DP) at 65/55 dB SPL and pure-tone audiometry were used to detect noise-induced inner ear changes. Repeated measures analyses of variance were made on the subjects and in a control group, whereas significant threshold shifts (STS) and significant emission shifts (SES) were calculated. Both hearing thresholds and DP showed a high-frequency deterioration, but there was absence of statistical correlation between elevation of hearing thresholds and decrease of DP. There was no clear pattern between individual changes in audiometric thresholds and DP, and all combinations were present: ears with only STS, ears with only SES, ears with both STS and SES and ears with absence of STS and SES. Audiometric changes were maximal at 4 and 6 kHz and DP changes at 2 and 3 kHz. Since significant individual emission changes do not necessarily follow the same pattern as the group-averaged results, the use of DP for monitoring of individual subjects is not advised. However, its use in conjunction with audiometry in hearing conservation programs is highly recommended.