Hearing threshold prediction with Auditory Steady State Responses and estimation of correction functions to compensate for differences with behavioral data, in adult subjects. Part 1: Audera and CHARTR EP devices

Comparison of Auditory Steady-State Responses With Conventional Audiometry in Older Adults

Behavioral measures, such as pure-tone audiometry (PTA), are commonly used to determine hearing thresholds, however, PTA does not always provide reliable hearing information in difficult to test individuals. Therefore, objective measures of hearing sensitivity that require little-to-no active participation from an individual are needed to facilitate the detection and treatment of hearing loss in difficult to test people. Investigation of the reliability of the auditory steady-state response (ASSR) for measuring hearing thresholds in older adults is limited. This study aimed to investigate if ASSR can be a reliable, objective measure of frequency specific hearing thresholds in older adults. Hearing thresholds were tested at 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz in 50 participants aged between 60 and 85 years old, using automated PTA and ASSR. Hearing thresholds obtained from PTA and ASSR were found to be significantly correlated (p < .001) in a cohort consisting of participants with normal hearing or mild hearing loss. ASSR thresholds were significantly higher as compared to PTA thresholds, but for the majority of cases the difference remained within the clinically acceptable range (15 dB). This study provides some evidence to suggest that ASSR can be a valuable tool for estimating objective frequency-specific hearing thresholds in older adults and indicate that ASSR could be useful in creating hearing treatment plans for older adults who are unable to complete behavioral PTA. Further research on older adults is required to improve the methodological features of ASSR to increase consistency and reliability, as well as minimize some of the limitations associated with this technique.

Towards early intervention of hearing instruments using cortical auditory evoked potentials (CAEPs): A systematic review

As a result of newborn hearing screening, hearing aids are usually prescribed and fitted by 2-3 months of age. However, the assessment data used for prescribing hearing aids in infants and toddlers are limited in quality and quantity. There is great interest in finding appropriate physiological measures that can be help to facilitate and improve the management process of hearing impaired children. It seems that cortical auditory evoked potentials (CAEPs) can provide information before it is possible to obtain reliable information from behavioral assessment procedures. This article will review the studies conducted in this area during the past15 years to determine the advantages, disadvantages and future research areas of CAEPs as an objective method in the management of hearing impaired children.

Multichannel search strategy for improving the detection of auditory steady-state response

Auditory steady-state response (ASSR) is useful for hearing threshold estimation. The ASSR is usually detected with objective response detectors (ORD). The performance of these detectors depends on the signal-to-noise ratio (SNR) as well as the signal length. Since it is undesirable to increase the signal length, then, this work provides a multivariate technique for improving the SNR and consequently the detection power. We propose the insertion of a short calibration step before the detection protocol, in order to perform a search among the available electroencephalogram (EEG) derivations and select the derivation with the highest SNR. The ORD used in this work was the magnitude-squared coherence (MSC). The standard detection protocol is to use the same EEG derivation in all exams. Using 22-scalp positions, the new technique achieved a detection rate higher than that obtained in 99.13% of the standard detection protocol. When restrictions were applied to the search, a superior performance was achieved. Thus, the technique proposed was able to track the best EEG derivations before exams and seems to be able to deal with the variability between individuals and between sessions.

Validity of correction factors applied to auditory steady-state responses (ASSRs) in normal hearing adults in chartr EP system

OBJECTIVES

Even though many patients undergoing auditory steady-state response (ASSR) testing have some degree of hearing loss, some have normal hearing and ASSR often overestimates the behavioral thresholds in this group. In most commercial ASSR systems such as Chartr EP, a default correction factor is applied to compensate for this difference. Little is known, however, as how the correction factor compensates for the difference between ASSR and pure tone audiometry (PTA) thresholds as a function of carrier or modulation frequency (MF) in a commercial ASSR system. Our goal is to evaluate this relationship.

METHODS

Twenty-four normal hearing adults were examined for both PTA and ASSR (Chartr EP system, GN Otometrics). ASSR thresholds were obtained at three MFs (20, 40, and 80 Hz). The difference scores were obtained by subtracting PTA from ASSR thresholds at each frequency for each subject. The corrected ASSR thresholds, then, were compared with the PTA thresholds across MFs and carrier frequencies.

RESULTS

The default correction factors in the ASSR equipment differed significantly from the difference scores at all MFs and carrier frequencies (n = 24, p < 0.005). The correlation between corrected ASSR and PTA thresholds at most MFs and carrier frequencies were medium to poor.

CONCLUSIONS

At most MFs and carrier frequencies, the default correction factors defined by the manufacturer do not compensate for the difference between ASSR and PTA thresholds in normal hearing adults. The use of the default correction factors in Chartr EP system for the normal hearing adults needs special considerations.

The Relationship Between Hearing Thresholds and Hyperandrogenism in Polycystic Ovary Syndrome

Background

The purpose of our study was to investigate the association between polycystic ovary syndrome (PCOS) and hearing thresholds.

Material/Methods

Forty women diagnosed with PCOS (mean age, 24.33±6.38 years) and 40 healthy women controls (mean age, 26.38±6.75 years) were included in prospective study. Each case was tested with low (250, 500, 1000, and 2000 Hz), high (4000, 6000, and 8000 Hz) and extended high (EH) (9000–20000 Hz) frequency audiometry. The fasting plasma glucose, insulin, FSH, LH, total testosterone, and sex hormone-binding globulin were measured in all patients.

Results

The mean hearing thresholds at EH frequencies were statistically significantly higher in the PCOS group than in the control group (p=0.001 right ear and p=0.015 left ear). There were significant positive correlations among free testosterone index (FTI) values and hirsutism scores with EH frequency hearing thresholds.

Conclusions

At pure-tone audiometry (PTA) EH frequencies, we detected significantly higher hearing thresholds in PCOS patients than in controls. We also determined that elevated FTI and hirsutism score were positively correlated with elevated hearing thresholds in EH frequencies. These findings support that hyperandrogenism can play a role in the elevation of hearing thresholds in PCOS.

Towards neural correlates of auditory stimulus processing: a simultaneous auditory evoked potentials and functional magnetic resonance study using an odd-ball paradigm

Background

The neural underpinnings of auditory information processing have often been investigated using the odd-ball paradigm, in which infrequent sounds (deviants) are presented within a regular train of frequent stimuli (standards). Traditionally, this paradigm has been applied using either high temporal resolution (EEG) or high spatial resolution (fMRI, PET). However, used separately, these techniques cannot provide information on both the location and time course of particular neural processes. The goal of this study was to investigate the neural correlates of auditory processes with a fine spatio-temporal resolution. A simultaneous auditory evoked potentials (AEP) and functional magnetic resonance imaging (fMRI) technique (AEP-fMRI), together with an odd-ball paradigm, were used.

Material/Methods

Six healthy volunteers, aged 20–35 years, participated in an odd-ball simultaneous AEP-fMRI experiment. AEP in response to acoustic stimuli were used to model bioelectric intracerebral generators, and electrophysiological results were integrated with fMRI data.

Results

fMRI activation evoked by standard stimuli was found to occur mainly in the primary auditory cortex. Activity in these regions overlapped with intracerebral bioelectric sources (dipoles) of the N1 component. Dipoles of the N1/P2 complex in response to standard stimuli were also found in the auditory pathway between the thalamus and the auditory cortex. Deviant stimuli induced fMRI activity in the anterior cingulate gyrus, insula, and parietal lobes.

Conclusions

The present study showed that neural processes evoked by standard stimuli occur predominantly in subcortical and cortical structures of the auditory pathway. Deviants activate areas non-specific for auditory information processing.

Identifying congenital hearing impairment: preliminary results from a comparative study using objective and subjective audiometric protocols

To compare objective and subjective protocols assessing hearing loss in young children and evaluate frequency-specific hearing impairment through a comparison between auditory steady state responses (ASSR), auditory brainstem responses (ABR), transient otoacoustic emissions and conditioned orientation reflex responses (COR). Thirty-five hearing-impaired children (20 male and 15 female), aged between 14 months and 4 years, participated in the study. Hearing threshold levels and peripheral auditory function were assessed by measurements of ABR, ASSR, otoacoustic emissions and COR. The analysis of the COR and ASSR variables showed significant correlations in the majority of tested frequencies. The data highlight a characteristic of the COR procedure, which is an underestimation of the hearing threshold in comparison to the ASSR estimate. The data show that the COR threshold assessment follows the pattern of the other two established electrophysiological methods (ABR, ASSR). The correlation analyses did not permit evaluation of the precision of these estimates. Considering that the ASSR variables show a better relationship with ABR (higher correlation values) than COR, it might be advantageous to utilize the ASSR to gain frequency-specific information.