Use Of Distortion Product Otoacoustic Emissions Research Articles

Dynamic characteristics of the middle ear after stapes surgery: a distortion product otoacoustic emission study

BackgroundOtosclerosis is a primary localized disease of the bony otic capsule that is mainly localized to the stapedial footplate. Stapedotomy is the treatment of choice. The effect of stapes surgery on otoacoustic emissions is not sufficiently known.ObjectivesThe aim of the present study was to assess changes in the middle ear dynamic characteristics, and to evaluate distortion product otoacoustic emissions (DPOAEs) in otosclerosis. Moreover, the study aimed to evaluate DPOAEs before and after stapes surgery.Patients and methodsA total of 20 patients with otosclerosis and undergoing stapedotomy surgery were included in the study. Assessment was performed preoperatively, 1 week, 1 month, and 6 months postoperatively by using pure-tone average, tympanometry, and DPOAE.ResultsSignificant improvement in the air–bone gap by pure-tone average was reported at 1 week and 1 month postoperatively, whereas 6 months postoperative hearing threshold remained the same as that of 1 month postoperative. The difference between preoperative and postoperative detection of DPOAE was not significant.ConclusionConventional pure-tone audiometry remains the choice for evaluation of stapes surgery in patients of otosclerosis. The use of DPOAEs in the evaluation of a successful stapes surgery requires further studies including a larger number of patients.

Effect of Tinnitus on Distortion Product Otoacoustic Emissions Varies With Hearing Loss

The aim of this study was to measure the effect of tinnitus, while accounting for the effect of hearing loss and aging, on distortion product otoacoustic emissions (DPOAEs). DPOAEs were measured twice in both ears in 5 groups of participants: young adults with normal hearing, middle-age adults with normal hearing, adults with high-frequency sensorineural hearing loss, age-matched adults with similar hearing loss and tinnitus, and adults with normal hearing and chronic tinnitus. Multivariate analysis revealed a main effect of hearing loss and age, but no effect of tinnitus, across all 5 groups. Separate tests revealed significant effects of age and tinnitus in the normal-hearing groups and hearing loss in adults with or without tinnitus, but no effect of tinnitus in those with hearing loss. DPOAE levels in the group of adults with hearing loss and tinnitus were diminished, but those in the group with normal hearing and tinnitus were enhanced, relative to DPOAE levels in the controls. Outer hair cell function, as indexed by DPOAEs, exhibits a complex association with tinnitus, and this has implications in the use of DPOAEs as a tool both for testing for tinnitus presence and for creating a model of neural mechanisms underlying tinnitus.

Multivariate DPOAE metrics for identifying changes in hearing: Perspectives from ototoxicity monitoring

Distortion-product otoacoustic emissions (DPOAEs) provide a window into real-time cochlear mechanical function. Yet, relationships between the changes in DPOAE metrics and auditory sensitivity are still poorly understood. Explicating these relationships might support the use of DPOAEs in hearing conservation programs (HCPs) for detecting early damage leading to noise-induced hearing loss (NIHL) so that mitigating steps might be taken to limit any lasting damage. This report describes the development of DPOAE-based statistical models to assess the risk of hearing loss from cisplatin treatment among cancer patients. Ototoxicity risk assessment (ORA) models were constructed using a machine learning paradigm in which partial least squares and leave-one-out cross-validation were applied, yielding optimal screening algorithms from a set of known risk factors for ototoxicity and DPOAE changes from pre-exposure baseline measures. Single DPOAE metrics alone were poorer indicators of the risk of ototoxic hearing shifts than the best performing multivariate models. This finding suggests that multivariate approaches applied to the use of DPOAEs in a HCP, will improve the ability of DPOAE measures to identify ears with noise-induced mechanical damage and/or hearing loss at each monitoring interval. This prediction must be empirically assessed in noise-exposed subjects.

Ototoxicity caused by topical administration of gentamicin versus tobramycin in rabbits

Aim To investigate the possible differences in cochleotoxic effects in rabbits between twice-daily administration of topical gentamicin and tobramycin throughout the perforated tympanic membrane with the use of distortion-product otoacoustic emissions (DPOAEs). Materials and methods Twenty female rabbits were studied prospectively daily for 21 days. The rabbits’ ears were divided into two groups: right and left ear groups. Twice-daily for 21 days after paracentesis, 0.3% gentamicin was administered topically in the left ears, and 0.3% tobramycin was administered topically in the right ears. For 21 days, the cochlear activity of the right and left ears of all rabbits was examined every 7 days using DPOAEs. The numerical values of the distortion product (DP) intensity recorded on days 7, 14 and 21 of drug administration were compared between the two groups. Results Cochlear activity was reduced earlier in the gentamicin group in the 2–4 kHz frequencies compared to the tobramycin group in the second DPOAE measurement (day 7 of the experiment). In two rabbits in the gentamicin group, the third DPOAE measurement showed that cochlear activity was reduced in all frequencies. In six rabbits in the tobramycin group, the third DPOAE measurement showed that cochlear activity was reduced in all frequencies. There was no statistical significance between the two groups except day 7 in the 2 and 3 kHz frequencies ( p < 0.05). Conclusion We concluded that low frequencies (2 and 3 kHz) are more sensitive to the administration of topical gentamicin than to topical tobramycin. Early cessation of tobramycin drops may be minimally cochlear toxic compared to gentamicin within the first 7 days when these drugs are misused in treating chronic otitis media.

Distortion product otoacoustic emissions for assessment of intracranial hypertension at extreme altitude?

The levels of distortion product otoacoustic emissions (DPOAEs) change at frequencies between 0.75 and 1.5 kHz along with intracranial pressure (ICP) and DPOAEs are suggested for monitoring ICP changes. Elevated ICP plays a major role in high-altitude disease, but direct measurement is unlikely to be feasible at high altitudes. The aim of the presented study was to measure DPOAEs at extreme altitudes in order to determine whether information about elevated ICP can be obtained. Data are presented from DPOAE measurements at the frequencies 1, 1.5, 2, 3 and 4 kHz in 13 climbers during an ascent to Gasherbrum II (8,035 m) up to an altitude of 7,400 m. Valid DPOAE measurements could be obtained in all climbers. DPOAE levels exhibited great variability concerning both the affected frequency range and the change. As expected due to elevated ICP, DPOAE levels decreased in some of the climbers at 1 kHz. However, an even more pronounced decline of DPOAE levels was observed at 3 and 4 kHz, which cannot be explained by intracranial hypertension. Possible other reasons for DPOAE level changes at extreme altitude are hypoxia, increased serum osmolarity and unbalanced middle ear pressure. Only one climber developed severe acute mountain sickness with clinical signs of intracranial hypertension. The most pronounced decline of DPOAEs at 1 kHz was seen on that occasion, which suggests a possible use of DPOAEs for detection of intracranial hypertension and early detection of high-altitude cerebral edema.

Distortion product otoacoustic emissions during the first year in term infants: A longitudinal study

Understanding of any age-related differences in distortion product otoacoustic emissions (DPOAEs) during infancy is important for the use of DPOAEs in detection of cochlear impairment in infants. We studied DPOAEs at 10 frequencies of f 2 primary tone between 500 Hz to 10 kHz longitudinally during the first year of life in 70 ears of 35 normal term infants. On days 3–5 after birth DPOAE pass rates ranged between the highest 98.6% at f 2 frequencies 6–10 kHz and the lowest 22.9% at 750 Hz. The higher the frequency, the higher was the pass rate. At 6 months the pass rates at various frequencies were generally similar to those on days 3–5, and were greater than 91% across the frequencies of 3–10 kHz. At 12 months the pass rates were 100% or near 100% across 3–10 kHz. During the first year the pass rate was always very low at 750 Hz (<40%) and tended to decrease at 1 kHz with the increase in age. DPOAE level at f 2 frequencies ⩾4 kHz increased from birth to 6 months but then reduced slightly at 12 months. At lower frequencies the age-related DPOAE levels change was less significant. These results indicate that there are no major changes in DPOAE or cochlear function during the first year of life at most frequencies. However, the interpretation of DPOAE results in infants need to take into account the age-related difference in DPOAE pass rate at low-frequency and in DPOAE level at high-frequency.

Distortion Product Otoacoustic Emissions in Children at School Entry: A Comparison with Pure-Tone Screening and Tympanometry Results

This study examined the test performance of distortion product otoacoustic emissions (DPOAEs) when used as a screening tool in the school setting. A total of 1003 children (mean age 6.2 years, SD = 0.4) were tested with pure-tone screening, tympanometry, and DPOAE assessment. Optimal DPOAE test performance was determined in comparison with pure-tone screening results using clinical decision analysis. The results showed hit rates of 0.86, 0.89, and 0.90, and false alarm rates of 0.52, 0.19, and 0.22 for criterion signal-to-noise ratio (SNR) values of 4, 5, and 11 dB at 1.1, 1.9, and 3.8 kHz respectively. DPOAE test performance was compromised at 1.1 kHz. In view of the different test performance characteristics across the frequencies, the use of a fixed SNR as a pass criterion for all frequencies in DPOAE assessments is not recommended. When compared to pure tone plus tympanometry results, the DPOAEs showed deterioration in test performance, suggesting that the use of DPOAEs alone might miss children with subtle middle ear dysfunction. However, when the results of a test protocol, which incorporates both DPOAEs and tympanometry, were used in comparison with the gold standard of pure-tone screening plus tympanometry, test performance was enhanced. In view of its high performance, the use of a protocol that includes both DPOAEs and tympanometry holds promise as a useful tool in the hearing screening of schoolchildren, including difficult-to-test children.

Clinical relevance of distortion product emissions by means of receiver operating characteristic (ROC) analysis.

The clinical use of distortion product otoacoustic emissions (DPOAE) stems from the observation that the outer hair cells are the most vulnerable part of the cochlea, and damage to these cells is associated with hearing loss and loss of DPOAE. The purpose of this study is to evaluate the applicability of DPOAE in predicting hearing thresholds under clinical conditions. DPOAE measurements (L1 = L2 = 70 dB SPL. f2/f1 = 1.20) of 219 hearing-impaired and normal hearing ears were analyzed. Recordings were acquired for DPOAE at 2 f1-f2 varying from 635 to 4052 Hz. The detectability of DPOAE in hearing-impaired subjects exhibited a strong hearing threshold dependence. Receiver operating characteristic (ROC) analysis yielded the highest sensitivity and specificity for threshold levels of about 30 dB at low frequencies and for threshold levels of about 60 dB at high frequencies. In addition, the separability of groups with different hearing status was more reliable at high frequencies as compared to low frequencies. The DPOAE provide an objective assessment of cochlear function. However, prognosis of hearing thresholds on the basis of DPOAE measurements depends strongly on the test frequency and is associated with large errors. Hence, the clinical use of DPOAE in predicting hearing thresholds is limited.

Use of distortion-product otoacoustic emissions for auditory evaluation in Meniere's disease

Otoacoustic emissions are a relatively new tool for assessment of inner ear function. We studied 65 patients diagnosed as having Menière's disease. In order to obtain and characterize responses at different frequencies we used distortion-product otoacoustic emissions (DPOAE). In unilateral cases, the difference in response between ears on the diseased and healthy sides was evident at all frequencies. In the former the result was lower than expected for a group of normally hearing subjects, while in the latter it was better than expected according to pure tone averages. Reduction in amplitude and increment in threshold of the DPOAE in the diseased ear was a significant finding and could be correlated to the stage of the disease. In those subjects treated with Betahistine after 1 year's follow-up, DPOAE testing showed the recovery of response at low frequencies and a reduction of its threshold at all frequencies studied.

Effect of temperature elevation on rabbit cochlear function as measured by distortion-product otoacoustic emissions

Low-intensity laser stapedotomy has been shown to produce temperature elevations of 3° to 4° C within the cochlea. This study investigates the effect of temperature elevations in this range on cochlear outer hair cell function by use of distortion-product otoacoustic emissions in rabbits. Using esophageal temperature monitoring, we compared 2f 1-f 2 distortion-product otoacoustic emissions over a range of frequencies (1806 to 8691 Hz) at rabbit normothermia, normothermia plus 3° C, and normothermia after passive cooling. Cochlear temperature was found to exceed changes in esophageal temperature by as much as 1.2° C. We found that a maximum of 3° C elevation in esophageal temperature did not permanently impair outer hair cell function in the rabbit cochlea. Results of this study suggest that moderate changes in cochlear temperature, such as those produced by low-intensity CO 2 and holmium - yttrium aluminum garnet lasers, may not produce irreversible thermal damage to the cochlear outer hair cells. (Otolaryngol Head Neck Surg 1996;115:548-52.)

Test–retest reliability of distortion product otoacoustic emissions in normal-hearing and hearing-impaired adults.

Distortion product otoacoustic emissions (DPOAEs) were measured in the ears of 25 normal-hearing and 25 hearing-impaired adults to assess test–retest reliability. Primary tones with geometric mean frequencies of 1, 2, and 4 kHz (f2/f1=1.21) were utilized. Results for the normal-hearing adults indicated that test and retest DPOAE detection thresholds for each ear were highly correlated at 1 kHz (r=0.81), but only moderately correlated at 2 and 4 kHz (r=0.53 and 0.48, respectively). DPOAE amplitude at various suprathreshold input levels was also evaluated for test–retest reliability. DPOAE amplitudes at all input levels and frequencies showed at least a moderate correlation, with the strongest seen at 1 and 4 kHz with 75 dB input (r=0.85). Of the two DPOAE measures, detection threshold and amplitude, the latter appears to be most stable over successive measurements in normal ears. The data from the hearing-impaired listeners will be used to explore further the reliability and validity of the use of DPOAEs as a clinical measure. [Work supported by NIH.]