Effect of Real-Ear Adjusted Stimuli on Vestibular Evoked Myogenic Potential Variability in Children and Young Adults.

OBJECTIVES: There is large variability in cervical and ocular vestibular evoked myogenic potential (c- and oVEMP) amplitudes. One potential source of variability is differences in ear canal shape and size. Real ear-to-coupler difference (RECD) values are used to measure the acoustic environment of an individual's ear canal. RECD may be a useful measure to calibrate air conducted VEMP stimuli, which are elicited at high intensities and may put patients at risk of unsafe sound exposure. A recommendation for avoiding unsafe exposure is to use a 125 dB SPL stimulus for individuals with an equivalent ear canal volume (ECV) ≥ 0.9 mL and a 120 dB SPL stimulus for individuals with a smaller ECV. The purpose of this project was to determine if using a stimulus calibrated in the ear using RECD values significantly reduces intra-subject and inter-subject VEMP amplitude variability. We hypothesized that using a RECD-calibrated stimulus would significantly reduce inter-subject amplitude variability but not significantly reduce intra-subject variability. We further hypothesized that an RECD-adjusted VEMP stimulus would better protect against delivering unsafe sound exposure compared to the method of using ECV alone. DESIGN: Eleven children (4 to 9 years), 10 adolescents (10 to 18 years), and 10 young adults (20 to 40 years) with normal hearing, tympanometry, vestibular and neurological function participated. On all subjects, RECD was measured twice per ear to account for test-retest reliability. cVEMP and oVEMP were then recorded bilaterally with a 500 Hz tone burst at a traditional and an adjusted VEMP intensity level. The traditional intensity level was 125 dB SPL for individuals with ≥ 0.9 mL ECV and 120 dB SPL for individuals with ≤ 0.8 mL ECV. The adjusted intensity level was calculated by subtracting the average 500 Hz RECD measured values from the 500 Hz normative RECD value. This value was applied as a correction factor to a 125 dB SPL stimulus. Peak to peak amplitudes were recorded and used to calculate asymmetry ratios. RESULTS: Young children had significantly smaller ECVs compared to adolescents and young adults. Young children had larger RECDs; however, this was not significant in post hoc analyses. The method of calibration had no significant effect on intra-subject variability for cVEMP [ F (1, 27)= 0.996, p = 0.327] or oVEMP [ F (1, 25)= 1.679, p = 0.206]. The method of calibration also had no significant effect on inter-subject amplitude variability for cVEMP [ F (1, 120)= 0.721, p = 0.397] or oVEMP [ F (1, 120)= 0.447, p = 0.505]. Both methods of calibration adequately protected against unsafe exposure levels. However, there were subjects with ECVs ≥ 0.9 mL who approached unsafe exposure levels from the ECV-calibrated stimulus, suggesting there may be rare cases in which a 125 dB SPL stimulus is unsafe, even for patients with larger ECVs. CONCLUSIONS: The calibration method made no significant difference in intra- or inter-subject variability, indicating that the acoustic environment of the outer ear is not significantly contributing to VEMP amplitude variability. The RECD-adjusted stimulus is effective in protecting against unsafe exposure levels for two trials of both c- and oVEMPs. There may be instances where more than two trials of each test are required, which increases the effective stimulation level. Clinicians should be cautious when delivering VEMPs and not unnecessarily expose patients to unsafe levels of sound.

Acoustic particle motion detection in the snapping shrimp (Alpheus richardsoni).

Many crustaceans produce sounds that might be used in communication. However, little is known about sound detection in crustaceans, hindering our understanding of crustacean acoustic communication. Sound detection has been determined only for a few species, and for many species, it is unclear how sound is perceived: as particle motion or sound pressure. Snapping shrimp are amongst the loudest and most pervasive marine sound sources. They produce snaps during interactions with conspecifics, and they also interact with soniferous heterospecifics. If they can hear, then sound could facilitate key behavioral interactions. We measured the auditory sensitivity of the snapping shrimp, Alpheus richardsoni, using auditory evoked potentials in response to a shaker table that generated only particle motion and an underwater speaker that generated both particle motion and sound pressure. Auditory detection was most sensitive between 80 and 100 Hz, and auditory evoked potentials were detected up to 1500 Hz. Snapping shrimp responded to both the shaker table and the underwater speaker, demonstrating that they detect acoustic particle motion. Crushing the statocyst reduced or eliminated hearing sensitivity. We conclude that snapping shrimp detect acoustic particle motion using the statocyst, they might detect conspecifics and heterospecifics, and hearing could facilitate key behavioral interactions.

Forward and Reverse Middle Ear Transmission in Gerbil with a Normal or Spontaneously Healed Tympanic Membrane.

Tympanic membranes (TM) that have healed spontaneously after perforation present abnormalities in their structural and mechanical properties; i.e., they are thickened and abnormally dense. These changes result in a deterioration of middle ear (ME) sound transmission, which is clinically presented as a conductive hearing loss (CHL). To fully understand the ME sound transmission under TM pathological conditions, we created a gerbil model with a controlled 50% pars tensa perforation, which was left to heal spontaneously for up to 4 weeks (TM perforations had fully sealed after 2 weeks). After the recovery period, the ME sound transmission, both in the forward and reverse directions, was directly measured with two-tone stimulation. Measurements were performed at the input, the ossicular chain, and output of the ME system, i.e., at the TM, umbo, and scala vestibuli (SV) next to the stapes. We found that variations in ME transmission in forward and reverse directions were not symmetric. In the forward direction, the ME pressure gain decreased in a frequency-dependent manner, with smaller loss (within 10 dB) at low frequencies and more dramatic loss at high frequency regions. The loss pattern was mainly from the less efficient acoustical to mechanical coupling between the TM and umbo, with little changes along the ossicular chain. In the reverse direction, the variations in these ears are relatively smaller. Our results provide detailed functional observations that explain CHL seen in clinical patients with abnormal TM, e.g., caused by otitis media, that have healed spontaneously after perforation or post-tympanoplasty, especially at high frequencies. In addition, our data demonstrate that changes in distortion product otoacoustic emissions (DPOAEs) result from altered ME transmission in both the forward and reverse direction by a reduction of the effective stimulus levels and less efficient transfer of DPs from the ME into the ear canal. This confirms that DPOAEs can be used to assess both the health of the cochlea and the middle ear.

Cognitive performance and long-latency auditory evoked potentials: a study on aging.

OBJECTIVE: To evaluate the relationship between cognitive performance and long-latency auditory evoked potentials in an elderly population. METHODS: The sample consisted of adults between 20 and 58 years of age and elderly adults between 60 and 70 years of age. The screening procedures adopted were an inspection of the external auditory canal, tonal and vocal audiometry, tympanometry, brain stem auditory evoked potential, the Montreal Cognitive Assessment test, and long-latency auditory evoked potential. RESULTS: The latency and amplitude values of cortical components by age group showed significant differences under the following conditions: (i) signals evoked by the speech stimulus /da/ and by the pure-tone stimulus at 2,000 Hz for the N2 amplitude (p=0.008 and p=0.001, respectively) , which were both higher for adults, and (ii) signals evoked by the speech stimulus /da/ for N1 latency (p=0.018) and by the pure-tone stimulus at 2,000 Hz for P2 latency (p=0.017), which were both higher in the elderly population. The cognitive component (P300) showed a significant difference when evoked by speech stimuli, with higher latency in the elderly population (p=0.013). When correlated with cognitive processes, the latency and amplitude of cortical potentials showed direct and medium-strength correlations between abnormal scores obtained on the Montreal Cognitive Assessment test and P2 amplitude (p<0.001 and r=0.452). CONCLUSION: There is a relationship between long-latency potentials and cognitive performance in the elderly, which was observed by the increase in the P2 amplitude and the impairment of the process of sound decoding.

Refining Measurements of Power Absorbance in Newborns: Probe Fit and Intrasubject Variability.

OBJECTIVES: Because unresolved debris in the ear canal or middle ear of newborns may produce high false positive rates on hearing screening tests, it has been suggested that an outer/middle ear measure can be included at the time of hearing screening. A potential measure is power absorbance (absorbance), which indicates the proportion of power in a broadband acoustic stimulus that is absorbed through the outer/middle ear. Although absorbance is sensitive to outer/middle dysfunction at birth, there is large variability that limits its accuracy. Acoustic leaks caused by poor probe fitting further exacerbate this issue. The objectives of this work were to: (1) develop criteria to indicate whether a change in absorbance occurs in association with probe fit; (2) describe the variability in absorbance due to poor fitting; and (3) evaluate test-retest variability with probe reinsertions, excluding poor fits. DESIGN: An observational cross-sectional design was used to evaluate changes in absorbance due to probe fit and probe reinsertion. Repeated measurements were recorded in 50 newborns (98 ears) who passed TEOAE screenings and were <48 hours of age. One absorbance measurement was chosen as the baseline that served as a best-fit reference in each ear. Changes in absorbance, called absorbance probe-fit Δ, were calculated relative to the baseline in each ear. Correlations were assessed between the absorbance probe-fit Δ and low-frequency absorbance, impedance magnitude, impedance phase, and equivalent volume, to determine which measures predicted poor fits. Criteria were derived from the strongest of these correlations and their performance was analyzed. Next, measurements with poor/leaky fits were identified, and the changes in absorbance that they introduced were analyzed. Excluding the poor fits, test-retest differences in absorbance, called reinsertion Δ, were determined. Variability was assessed using the SDs associated with absorbance, absorbance probe-fit Δ, and reinsertion Δ. RESULTS: Based on the analysis of 12 moderate-strong correlations, the following criteria were adopted to identify measurements with poor fits: (1) impedance phase-based criterion (500 to 1000 Hz) > -0.11 cycles and (2) absorbance-based criterion (250 to 1000 Hz) > 0.58. Poor-fit measurements introduced statistically significant increases in absorbance up to 0.1 for 1000 to 6000 Hz, and up to 0.4 for frequencies <1000 Hz. Reinsertion Δ were ≤0.02, and were significant for 500 to 5000 Hz. The SDs of absorbance probe-fit Δ were greatest and similar to overall absorbance SD in the low frequencies. Separately, the SDs of reinsertion Δ were also greatest and similar to low-frequency absorbance SD. CONCLUSIONS: Poor probe fits introduced the greatest inflation in absorbance for frequencies < 500 Hz, and a smaller but significant inflation for higher frequencies, consistent with controlled experiments on acoustic leaks in adults. Importantly, inflation of absorbance in diagnostically sensitive 1000 to 2000 Hz may impact its clinical performance. Test-retest with probe reinsertion contributed significantly to absorbance variability, especially in the low frequencies, consistent with reports in adults, even though changes were smaller than those associated with poor probe fit. The results indicate that variability in absorbance was reduced by minimizing acoustic leaks. Pending further validation, the probe-fit criteria developed in this work can be recommended to ensure proper probe fit.

Cognitive performance and long-latency auditory evoked potentials: a study on aging

OBJECTIVE: To evaluate the relationship between cognitive performance and long-latency auditory evoked potentials in an elderly population. METHODS: The sample consisted of adults between 20 and 58 years of age and elderly adults between 60 and 70 years of age. The screening procedures adopted were an inspection of the external auditory canal, tonal and vocal audiometry, tympanometry, brain stem auditory evoked potential, the Montreal Cognitive Assessment test, and long-latency auditory evoked potential. RESULTS: The latency and amplitude values of cortical components by age group showed significant differences under the following conditions: (i) signals evoked by the speech stimulus /da/ and by the pure-tone stimulus at 2,000 Hz for the N2 amplitude (p=0.008 and p=0.001, respectively) , which were both higher for adults, and (ii) signals evoked by the speech stimulus /da/ for N1 latency (p=0.018) and by the pure-tone stimulus at 2,000 Hz for P2 latency (p=0.017), which were both higher in the elderly population. The cognitive component (P300) showed a significant difference when evoked by speech stimuli, with higher latency in the elderly population (p=0.013). When correlated with cognitive processes, the latency and amplitude of cortical potentials showed direct and medium-strength correlations between abnormal scores obtained on the Montreal Cognitive Assessment test and P2 amplitude (p<0.001 and r=0.452). CONCLUSION: There is a relationship between long-latency potentials and cognitive performance in the elderly, which was observed by the increase in the P2 amplitude and the impairment of the process of sound decoding.

Audiological evaluation of patients with cleidocranial dysplasia (CCD).

OBJECTIVE: The description of clinical manifestation of hearing problems in cleidocranial dysplasia (CCD) remains limited and incomplete, since CCD constitutes a rare congenital disorder. The study aims to provide a complex panel analysis of the auditory system in patients suffering from the disease. PATIENTS AND METHODS: The study group consisted of 4 children with CCD (aged: 12-15), who underwent orthodontic treatment. A full panel analysis of their auditory systems was performed, including high-frequency audiometry and a new method of middle ear assessment - WBT (Wideband Tympanometry). RESULTS: A slight conductive hearing loss was diagnosed in 3 out of 4 patients. While high frequency audiometry has shown a deterioration of hearing in 3 patients, in one case, the obtained thresholds were within the normal range. A decrease of absorbance in low frequencies has been observed in one or both ears. Only one patient has had a shift of maximum absorbance towards high frequencies in the left ear. CONCLUSIONS: The presented manuscript is the first with a complete evaluation of the auditory system comprising 4 cases of children in a similar age group. All of the examined patients presented an air-bone gap indicating conductive disorders.

Effect of different blood groups on tympanometric findings and acoustic reflex thresholds.

PURPOSE: The blood group can have an effect on the auditory system, and it is suggested that it could be an indicator of noise-induced hearing loss. There could be changes in the immittance findings, too, in adults having different blood groups. The present study attempted to determine if there are any differences in tympanometric results (admittance, peak pressure, gradient, resonance frequency, and ear canal volume) and acoustic reflex thresholds (ART) at 500, 1000, 2000 and 4000 Hz between individuals with different blood groups (A positive, B positive, O positive and AB positive). METHODS: Eighty normal hearing adults between the age of 18 and 27 years were considered for the study. They were divided into 20 participants, each with blood groups A, B, AB, and O. The immittance findings were recorded from all the participants of the study. RESULTS: The results showed that the resonance frequency was slightly higher in blood group O compared to other blood groups. Also, the acoustic reflex thresholds were slightly elevated at all frequencies (ipsilateral and contralateral) for individuals with blood group O. CONCLUSIONS: The results of the study suggest possible reduced outer hair cells in persons with blood group O. This could have resulted in elevated acoustic reflex thresholds.

An audiological profile of a cohort of school-aged children with HIV and AIDS attending an antiretroviral clinic in South Africa.

BACKGROUND: Recent estimates reveal that there are approximately 280 000 children between the ages of birth and 14 years who are living with the human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS) in South Africa. These children are living with a compromised immune system, are vulnerable to opportunistic infections and subsequent hearing loss. However, there is limited research on the nature and extent of this sensory impairment amongst school-aged children. OBJECTIVE: This study aimed to determine an audiological profile of a cohort of school-aged children attending an antiretroviral (ARV) clinic, describing the occurrence of hearing loss and nature in terms of degree, type, configuration and symmetry. METHODS: A non-experimental descriptive exploratory study was conducted, where 30 children aged between 6 and 12 years underwent diagnostic audiological assessments. Audiological procedures included case history, medical record review, otoscopic examination, immittance audiometry, pure-tone audiometry, speech audiometry, distortion product otoacoustic emissions (DPOAEs) and neurological auditory brainstem response (ABR) testing. The results were analysed descriptively using SPSS version 22 software. RESULTS: The results indicated abnormal otoscopic findings in half the participants, and consequently type C tympanograms were the most common. Of the 28 participants who could be assessed with pure-tone audiometry, 15 (54%) showed a hearing loss. A bilateral rising mild, conductive hearing loss was predominant. Thirteen (43%) of the participants could not be tested using DPOAE because of outer and middle-ear pathology. Neurological ABR testing revealed an abnormality in 18 (60%) of the participants suggesting the sensitivity of the ABR to detect subtle neurological changes. CONCLUSION: Half the children in this study showed hearing loss, which has serious implications for the holistic management of the children within the health and educational contexts. Therefore, there is a need for audiological monitoring of children with HIV and AIDS.

Causality-constrained measurements of aural acoustic reflectance and reflection functions.

Causality-constrained procedures are described to measure acoustic pressure reflectance and reflection function (RF) in the ear canal or unknown waveguide, in which reflectance is the Fourier transform of the RF. Reflectance calibration is reformulated to generate causal outputs, with results described for a calibration based on a reflectance waveguide equation to calculate incident pressure and source reflectance in the frequency domain or source RF in the time domain. The viscothermal model RF of each tube is band-limited to the stimulus bandwidth. Results are described in which incident pressure is either known from long-tube measurements or calculated as a calibration output. Calibrations based on constrained nonlinear optimizations are simpler and more accurate when incident pressure is known. Outputs measured by causality-constrained procedures differ at higher frequencies from those using standard procedures with non-causal outputs. Evanescent-mode effects formulated in the time domain and incorporated into frequency-domain calibrations are negligible for long-tube calibrations. Causal reflectance and RFs are evaluated in an adult ear canal and time- and frequency-domain results are contrasted using forward and inverse Fourier transforms. These results contribute to the long-term goals of improving applications to calibrate sound stimuli in the ear canal at high frequencies and diagnose conductive hearing impairments.

Electrode impedance changes over time in MED El cochlear implant children recipients: Relation to stimulation levels and behavioral measures.

Objective: Electrode impedance measures resistance encountered by electric current passing through wires, electrodes and biological tissue. This study was designed mainly to evaluate changes in electrode impedance values and psycho-electric parameters changes (i.e. threshold levels, comfortable levels, and dynamic range) in cochlear implant patients over time. Methods: It was a prospective study encompassing 20 patients implanted by MED-EL device programd using behavioral programs. Electrical stimulation levels and electrode impedance values were examined at 0, 1, 3 and 6 months after the first fitting session. Results: Electrode impedance values were reduced from the time of activation to the 6 months visit. Most comfortable levels increased and dynamic range widened until the 6 months visit. There was an inverse correlation between impedance values and most comfortable level as well as dynamic range, over time. Conclusion: Frequent monitoring of electrode impedance (for device and electrodes problems) and electric stimulation levels (for better performance, mapping and habituation) during the first 6 months of implant use is recommended.

Effect of Middle-Ear Pathology on High-Frequency Ear Canal Reflectance Measurements in the Frequency and Time Domains.

The effects of middle-ear pathology on wideband acoustic immittance and reflectance at frequencies above 6-8 kHz have not been documented, nor has the effect of such pathologies on the time-domain reflectance. We describe an approach that utilizes sound frequencies as high as 20 kHz and quantifies reflectance in both the frequency and time domains. Experiments were performed with fresh normal human temporal bones before and after simulating various middle-ear pathologies, including malleus fixation, stapes fixation, and disarticulation. In addition to experimental data, computational modeling was used to obtain fitted parameter values of middle-ear elements that vary systematically due to the simulated pathologies and thus may have diagnostic implications. Our results demonstrate that the time-domain reflectance, which requires acoustic measurements at high frequencies, varies with middle-ear condition. Furthermore, the extended bandwidth frequency-domain reflectance data was used to estimate parameters in a simple model of the ear canal and middle ear that separates three major conductive pathologies from each other and from the normal state.

A comparison of ear-canal-reflectance measurement methods in an ear simulator.

Ear-canal reflectance has been researched extensively for diagnosing conductive hearing disorders and compensating for the ear-canal acoustics in non-invasive measurements of the auditory system. Little emphasis, however, has been placed on assessing measurement accuracy and variability. In this paper, a number of ear-canal-reflectance measurement methods reported in the literature are utilized and compared. Measurement variation seems to arise chiefly from three factors: the residual ear-canal length, the ear-probe insertion angle, and the measurement frequency bandwidth. Calculation of the ear-canal reflectance from the measured ear-canal impedance requires estimating the ear-canal characteristic impedance in situ. The variability in ear-canal estimated characteristic impedance and reflectance due to these principal factors is assessed in an idealized controlled setup using a uniform occluded-ear simulator. In addition, the influence of this measurement variability on reflectance-based methods for calibrating stimulus levels is evaluated and, by operating the condenser microphone of the occluded-ear simulator as an electro-static speaker, the variability in estimating the emitted pressure from the ear is determined. The various measurement methods differ widely in their robustness to variations in the three principal factors influencing the accuracy and variability of ear-canal reflectance.

On the calculation of reflectance in non-uniform ear canals.

Ear-canal reflectance is useful for quantifying the conductive status of the middle ear because it can be measured non-invasively at a distance from the tympanic membrane. Deriving the ear-canal reflectance requires decomposing the total acoustic pressure into its forward- and reverse-propagating components. This decomposition is conveniently achieved using formulas that involve the input and characteristic impedances of the ear canal. The characteristic impedance is defined as the ratio of sound pressure to volume flow of a propagating wave and, for uniform waveguides, the plane-wave characteristic impedance is a real-valued constant. However, in non-uniform waveguides, the characteristic impedances are complex-valued quantities, depend on the direction of propagation, and more accurately characterize a propagating wave in a non-uniform ear canal. In this paper, relevant properties of the plane-wave and spherical-wave characteristic impedances are reviewed. In addition, the utility of the plane-wave and spherical-wave reflectances in representing the reflection occurring due to the middle ear, calibrating stimulus levels, and characterizing the emitted pressure in simulated non-uniform ear canals is investigated and compared.

The effects of oral supplements with Sambucus nigra, Zinc, Tyndallized Lactobacillus acidophilus (HA122), Arabinogalactans, vitamin D, vitamin E and vitamin C in otitis media with effusion in children: a randomized controlled trial.

OBJECTIVE: To evaluate the ability of oral supplements with immune-stimulating molecules (Sambucus nigra, Zinc, Tyndallized Lactobacillus acidophilus (HA122), Arabinogalactans, vitamin D, vitamin E and vitamin C) to reduce the inflammation of the upper airway tract and improve the outcome of otitis media with effusion (OME) in children. PATIENTS AND METHODS: Randomized controlled trial. One-hundred ninety-eight children (CI 95%: 12-96 months) were divided into four groups. Group 1 (48 subjects) received 10 ml of oral supplements (OS) with immune-stimulating molecules for three months (20 days consecutively, then 10 days of suspension - the therapeutic scheme was repeated three times); Group 2 (54 children) underwent treatment with 10 ml of OS for 90 consecutive days; Group 3 (48 subjects) received 15 ml of OS for 45 consecutive days; a control group (48 children) underwent the standard treatment for rhinitis and OME. Outcome measures included otoscopy, tympanometry, fibroendoscopy, and the pure tone audiometry (PTA) at T0 (before treatment), T1 (45 days after treatment), and T2 (90 days after treatment). RESULTS: All children treated with OS showed a reduction of Upper Airway Infection (UAI) episodes and OME compared to the control group independent of the administration method and posology. The three groups treated with OS showed statistically significant differences between T0 and T2 for otoscopy, tympanometry, fibroendoscopy, and PTA. In Group 2, the otoscopy and the tympanometry scores improved at T1. Group 2 and 3 had better PTA results than Group 1. CONCLUSIONS: OS with immune-stimulating molecules should be considered as a supporting therapy in children affected by recurrent episodes of UAI associated with OME due to their capacity to improve the immune response and reduce the inflammatory phenomena. OS can improve the fibroendoscopic findings by restoring middle ear ventilation, in addition to their ability to reduce inflammation in the middle ear.

Methods for preventing middle ear barotrauma in computer-controlled pressurization of monoplace hyperbaric chambers.

Middle ear barotrauma (MEB), one of the side effects of hyperbaric oxygen (HBO2) therapy, sometimes cannot be directly diagnosed during the therapy itself. Instead, its incidence and degree are judged based on subjective statements made by patients when in conversation with medical staff regarding how they feel. To prevent MEB in practice, it is proposed that the tympanic membrane evaluation system and automatic control chamber developed in a previous study be applied as part of a prevention algorithm [16]. The proposed algorithm, which determines and equalizes the unbalanced pressure of a subject based on their tympanic admittance, was evaluated in conjunction with conventional HBO2 therapy in an experiment involving 100 subjects. Among the 50 subjects in the control group who received HBO2 therapy 16 subjects experienced MEB. In contrast, the experimental group of 50 subjects were treated with a hyperbaric chamber protocol incorporating the automatic control system and proposed algorithm. At the conclusion of the treatment, no subjects exhibited middle ear barotrauma. In the case of the control group, while the target pressure was achieved, middle ear barotrauma still occurred. However, in the case of the experimental group, the pressure inside the chamber was adjusted as per the algorithm, which allowed the target pressure for every subject to be achieved without experiencing MEB. When a particular subject was unable to perform any pressure equalization method such as swallowing or the Valsalva maneuver, the chamber was not pressurized based on the tympanic admittance and thus no MEB occurred.

Air-Conducted Vestibular Evoked Myogenic Potential Testing in Children, Adolescents, and Young Adults: Thresholds, Frequency Tuning, and Effects of Sound Exposure.

OBJECTIVES: Pediatric vestibular evaluations incorporate cervical and ocular vestibular evoked myogenic potential (c- and oVEMP, respectively) testing; however, in children, c- and oVEMP thresholds have been minimally investigated and frequency tuning is unknown. Children are also at risk for unsafe sound exposure secondary to VEMP. While it is unknown if VEMP threshold testing leads to cochlear changes, it is possible that this risk increases due to the increased number of trials needed to obtain a threshold. Obtaining VEMP thresholds at various frequencies in children provides further information for pediatric normative VEMP data. Assessing for cochlear changes after VEMP threshold testing would provide information on the safety of threshold VEMP testing in children. The objectives of this study were to (1) characterize c- and oVEMP thresholds in children, adolescents, and young adults with normal hearing using 500 and 750 Hz tone burst (TB) stimuli, (2) compare frequency tuning of 500 and 750 Hz TB, and (3) assess whether cochlear changes exist after VEMP threshold testing. It is hypothesized that children, adolescents, and young adults would not show age-related changes to the vestibular system. Therefore, reliable VEMP thresholds would be seen below maximum acoustical stimulation levels (e.g., <125 dB SPL) and frequency tuning will be similar for 500 and 750 Hz TB stimuli. DESIGN: Ten children (age 4-9), 10 adolescents (age 10-19), and 10 young adults (age 20-29) with normal hearing and tympanometry participated. All subjects received c- and oVEMP testing at maximum stimulation and threshold. To address frequency tuning, but not exceed recommended sound exposure allowance, subjects received a 500 Hz TB stimulus in one ear and a 750 Hz TB stimulus in the other ear. Subjects completed tympanometry pre-VEMP, and audiometric threshold testing, distortion product otoacoustic emission testing, and subjective questionnaire pre- and post-VEMP to study the effect of VEMP exposure on cochlear function for each stimulus frequency. RESULTS: (1) cVEMP thresholds were determined for both stimulus frequencies for children (500 Hz = 106 dB SPL; 750 Hz = 106 dB SPL), adolescents (500 Hz = 107.5 dB SPL; 750 Hz = 109.5 dB SPL), and young adults (500 Hz = 111.5 dB SPL; 750 Hz = 112 dB SPL). oVEMP thresholds were also obtained in response to both stimulus frequencies for children (500 Hz = 111.1 dB SPL; 750 Hz = 112.2 dB SPL), adolescents (500 Hz = 112.5 dB SPL; 750 Hz = 114.5 dB SPL), and young adults (500 Hz = 116 dB SPL; 750 Hz = 117 dB SPL). Similar thresholds were found between groups except for children who had significantly lower thresholds compared with adults for cVEMP (500 Hz: p = 0.002; 750 Hz: p = 0.004) and oVEMP (500 Hz: p = 0.01; 750 Hz: p = 0.02). In addition, equivalent ear-canal volume and VEMP thresholds were linearly correlated. (2) There was no significant effect of stimulus frequency on VEMP response rates, latencies, peak to peak amplitudes, or thresholds, suggesting similar frequency tuning for 500 and 750 Hz. (3) There were no significant effects of VEMP threshold testing on cochlear function for either stimulus frequency. CONCLUSIONS: Children, adolescents, and young adults show VEMP thresholds below high stimulation levels and had similar frequency tuning between 500 and 750 Hz. Use of 750 Hz could be regarded as the safer stimuli due to its shorter duration and thus reduced sound exposure. Children with smaller ear-canal volume had present responses at maximum stimulation and lower thresholds, suggesting that VEMP testing could be initiated at lower acoustic levels to minimize sound exposure and optimize testing.

Contrasting Effects of Pressure Compensation on TEOAE and DPOAE in Children With Negative Middle Ear Pressure.

In children with normal cochlear acuity, middle ear fluid often abolishes otoacoustic emissions (OAEs), and negative middle ear pressure (NMEP) reduces them. No convincing evidence of beneficial pressure compensation on distortion product OAE (DPOAE) has yet been presented. Two studies aimed to document effects of NMEP on transient OAE (TEOAE) and DPOAE. In Study 1, TEOAE and DPOAE pass/fail responses were analyzed before and after pressure compensation in 50 consecutive qualifying referrals having NMEP from -100 to -299 daPa. Study 2 concentrated on DPOAE, recording both amplitude (distortion product amplitude) and signal-to-noise ratio (SNR) before and after pressure compensation. Of the 20 participants, 5 had both ears qualifying. An effect of compensation on meeting a pass criterion was present in TEOAE for both left and right ear data in Study 1 but not demonstrable in DPOAE. In Study 2, the distortion product amplitude compensation effect was marginal overall, and depended on recording frequency band. SNR values improved moderately after pressure compensation in the two (overlapping) sets of single-ear data. In the five cases with both ears qualifying, a stronger compensation effect size, over 3 dB, was seen. The absolute dependence of SNR on frequency was also strongly replicated, but in no analysis, the frequency × compensation interaction was significant. Independent of particular frequency range, the data support a limited SNR improvement in 2 to 3 dB for compensation in DPOAE, with slightly larger effects in ears giving SNRs between 0 dB and +6 dB, where pass/fail cutoffs would generally be located.