Erik Berninger

Outcome of a universal newborn hearing-screening programme based on multiple transient-evoked otoacoustic emissions and clinical brainstem response audiometry

Abstract Conclusion: This universal newborn hearing-screening (UNHS) programme revealed high efficacy. The proportion of congenital sensorineural hearing loss was higher in left ears and in males than in right ears and females, which was in line with the systematic ear asymmetries and sex differences in transient-evoked otoacoustic emission (TEOAE) pass percentage. Objectives: To study the long-term outcome of a UNHS programme based on multiple TEOAEs and clinical click-evoked auditory brainstem response (ABR). Method: The study included all the newborns that were screened during a 6-year period (n = 31 092). TEOAE pass/fail was analysed in detail. In an assessment performed 10 years after the start of the 6-year UNHS, prevalence, degree and type of congenital hearing loss were studied. Results: The proportion of screened newborns was high, i.e. 98%. Multiple TEOAE recordings minimized the need for clinical ABR. Fifty-seven (0.18%) subjects showed bilateral hearing loss (exceeding ≈ 30 dB HL); median ABR threshold = 60 dB nHL (at 2.5 months of age). Bilateral and unilateral sensorineural hearing loss was found in 0.17% (n = 52; 56% males) and 0.06% (n = 18; 61% left ears, 56% males) of the screened newborns, respectively. Higher TEOAE pass percentages (p < 0.01) were demonstrated in right ears and in females than in left ears and males.

Characteristics of normal newborn transient-evoked otoacoustic emissions: Ear asymmetries and sex effects

Transient-evoked otoacoustic emissions (TEOAEs) were recorded from more than 30000 newborns over a six year period. Analysis was performed on all the TEOAEs that passed the bedside universal hearing screen (n=60431), in order to characterize the normal properties of neonatal TEOAEs and to study ear and sex effects. Short recording times (median=33 s) were observed in combination with high entire TEOAE level (median=18.8 dB SPL for an 81.8 dB SPL peak stimulus), and high reproducibility (median=86%). Signal-to-noise ratio (S/N) of the TEOAE was highly frequency-dependent, being poorer at low frequencies. Prolonged averaging increased median reproducibility to 97%, but the minor S/N-improvement at low frequencies did not justify the longer test time. Highly significant mean lateral asymmetries (right >left) and sex differences (female >male) existed in entire TEOAE level, S/N TEOAE, and in half-octave frequency bands (700–4000 Hz). Mean lateral and sex entire TEOAE level differences were 1.1 dB and 1.3 dB, respectively. Stimulus levels were not affected by ear or sex. Hence, physiological differences at the level of organ of Corti were demonstrated in newborns.

The Effect of Quinine on Psychoacoustic Tuning Curves, Stapedius Reflexes and Evoked Otoacoustic Emissions in Healthy Volunteers

Quinine causes reversible hearing loss, closely related to the quinine plasma concentration. The effects of quinine on psychoacoustic tuning curves, stapedius reflex thresholds and evoked otoacoustic emissions were studied in healthy volunteers. The tuning curves became shallower, whereas reflex thresholds were unaffected. The shift in the emission thresholds paralleled that of the pure-tone thresholds. There were also qualitative changes in the emissions: 1) the exponent of the stimulus-response function changed from 0.34 to 0.56; 2) decay time shortened; 3) the power spectrum shifted towards lower frequencies. The results are discussed in relation to various aspects of cochlear performance and are suggested to depend on an outer hair cell dysfunction.

The concentration-effect relationship of quinine-induced hearing impairment

Quinine‐induced reversible hearing impairment at the frequencies of 1000 and 2000 Hz was investigated in healthy volunteers to analyze the plasma concentration‐effect relationship of the drug. Six subjects were given two identical oral doses of quinine and a constant rate infusion of quinine over 6 hours (15 mg · kg−1) on three separate occasions. A simple pharmacodynamic model, E = k · Cγ (in which E is effect, k is a proportionality constant, C is drug concentration, and the exponent γ is a fitting parameter), was found to describe well the relationship between hearing impairment and quinine concentrations in a hypothetical effect compartment. No statistical differences were found in the estimated parameters when the three dosings were compared, indicating that quinine‐induced hearing impairment is independent of route of administration. The first‐order rate constant (keo), linking plasma concentrations to the concentrations in the effect compartment, was (mean ± SD) 0.71 ± 0.19 and 0.99 ± 0.37 hr−1 for 1000 and 2000 Hz, respectively. The corresponding values of k were 0.15 ± 0.10 and 0.12 ± 0.19 and the values of γ were 2.13 ± 0.57 and 3.44 ± 1.04 for 1000 and 2000 Hz, respectively. Effect was also analyzed by semiparametric pharmacodynamic modeling, which gave results comparable to those obtained with the link model. We conclude that a simple power function is a reliable pharmacodynamic model for describing quinine‐induced hearing impairment in healthy subjects.

Horizontal sound localization in children with bilateral cochlear implants: effects of auditory experience and age at implantation

Objective: To study sound localization performance in relation to auditory experience and age at implantation in children with bilateral cochlear implants. Study Design: Clinical study. Setting: University hospital. Patients: Sixty-two sequentially and 4 simultaneously bilaterally implanted children participated in this clinical sound localization study, at a median age of 5.6 years. They underwent sequential implantations at median ages of 1.9 and 4.2 years, respectively. Simultaneous implantations were performed at a median age of 2.0 years. Methods: Localization performance was measured with pink noise presented in random order from 5 loudspeakers in the frontal horizontal plane. Twenty-one subjects participated in repeated testing. Main Outcome Measure: Sound localization performance as quantified with an Error Index. Results: On group level, bilaterally implanted children pinpointed the sounding loudspeaker in the frontal horizontal plane. Sound localization performance improved significantly with increasing bilateral cochlear implant experience, as observed in the entire study group and intraindividually, albeit large interindividual variability existed. Regression analyses in the entire study group and in the sequentially implanted children did not reveal any relationship between sound localization performance and ages at first and second implantation, interimplant interval, or age. However, second implantation before 4 years of age contributed to faster sound localization improvement with increasing bilateral cochlear implant experience. Conclusion: Median perceived azimuths coincided with presented azimuths. We suggest that listening experience after bilateral cochlear implantation affects sound localization performance, possibly owing to the ongoing stimulus-driven maturation of the central auditory system. The amount of time listening with bilateral implants has methodologic implications on sound localization assessment in bilaterally implanted children.

Clinical study of Widex Senso on first-time hearing aid users

Using psychoacoustic tests and questionnaires, the aim of this study was to clinically test Widex Senso (WS) versus analogue hearing aids on 200 first-time wearers. Half of the participants were selected at random for fitting with the behind-the-ear model (WS C8) or the in-the-canal model (WS CX). On a group basis, WS was found to provide more benefit than a palette of 29 analogue, modern hearing aid models from 10 manufacturers. Only 3 of 100 subjects changed from WS to another hearing aid. On average, the abbreviated profile of hearing aid benefit (APHAB) (Cox & Alexander, 1995) demonstrated superior performance for WS, i.e. no conflict existed between high comfort and high speech recognition. Median aided frequency-modulated tone thresholds in the sound field were better than 25 dB HL at frequencies up to 4 kHz inclusive. A distinct mean aided improvement of speech threshold in competing speech of 2.5 dB was found in both groups.

Changes in 2f1 - f2 acoustic distortion products in humans during quinine-induced cochlear dysfunction.

Quinine is a suitable model substance for the study of otoacoustic emissions (OAEs) as it reversibly affects the outer hair cells, thus reducing sensitivity, frequency-selectivity and various forms of OAEs. The aim of this experiment was to study quinine-induced changes in the input/output (I/O) function of 2f1

Magnitude Changes in Transient Evoked Otoacoustic Emissions and High-level 2f1-f2 Distortion Products in Man During Quinine Administration

Quinine reversibly affects the outer hair cells (OHC). It is therefore an ideal drug for studying OHC-related phenomena, such as transient evoked otoacoustic emissions (TEOAEs) and distortion product otoacoustic emissions (DPOAEs). Pure-tone thresholds (PTTs), 1,000-4,000 Hz, TEOAEs, and DPOAEs were measured monaurally in 5 normal-hearing volunteers during quinine administration. DPOAE was evoked at 75 dB SPL (f2/f1 = 1.22) and analysed at 2f1-f2 with f2 at 6 frequencies (700-4,000 Hz), while TEOAE was obtained at 79 dB SPLp and analysed at the f2 frequencies (1/3 octave). The PTT-shift was flat, 10 dB, whereas the TEOAE-power and the global mean of the DPOAEs decreased 4.5 dB and 1.4 dB, respectively. No correlation was found between the intra-individual emission shifts. It is concluded that TEOAE is more sensitive than high-level DPOAE for identifying minor cochlear hearing losses. Support is given to the hypothesis that different sources are involved in generating DPOAEs at different evoking levels.

The effect of intravenously administered mexiletine on tinnitus-a pilot study

The effect of intravenously administered mexiletine on subjective tinnitus and hearing was studied in six patients, who initially responded positively to lidocaine. Distinct mexiletine-induced decreases in tinnitus loudness were demonstrated in three subjects, as reflected by maximum VAS (visual analogue scale) level reduction of 34%, 95%, and 100%, respectively. One subject reported change in tinnitus pitch, another one showed a slight (18% on VAS) tinnitus reduction, and one subject disclosed no effect. Side effects were seen only during one of seven infusions. Mexiletine induced shifts in pure-tone threshold, transient evoked otoacoustic emission, and acoustic reflex threshold, probably reflecting a reversible interference in the function of organ of Corti. The concentration effect relationship remained unclear and no general ‘therapeutic’ level could be identified. This study confirms the effect of mexiletine on the auditory function and its potential as a possible therapeutic agent or a model for further development in tinnitus pharmacotherapy.

Corneal-Reflection Eye-Tracking Technique for the Assessment of Horizontal Sound Localization Accuracy from 6 Months of Age.

Objectives: The evaluation of sound localization accuracy (SLA) requires precise behavioral responses from the listener. Such responses are not always possible to elicit in infants and young children, and procedures for the assessment of SLA are time consuming. The aim of this study was to develop a fast, valid, and objective method for the assessment of SLA from 6 months of age. To this end, pupil positions toward spatially distributed continuous auditory and visual stimuli were recorded. Design: Twelve children (29 to 157 weeks of age) who passed the universal newborn hearing screening and eight adults (18 to 40 years of age) who had pure-tone thresholds ⩽20 dB HL in both ears participated in this study. Horizontal SLA was measured in a sound field with 12 loudspeaker/display (LD)-pairs placed in an audiological test room at 10 degrees intervals in the frontal horizontal plane (±55 degrees azimuth). An ongoing auditory-visual stimulus was presented at 63 dB SPL(A) and shifted to randomized loudspeakers simultaneously with pauses of the visual stimulus. The visual stimulus was automatically reintroduced at the azimuth of the sounding loudspeaker after a sound-only period of 1.6 sec. A corneal-reflection eye-tracking technique allowed the acquisition of the subjects’ pupil positions relative to the LD-pairs. The perceived azimuth was defined as the median of the intersections between gaze and LD-pairs during the final 500 msec of the sound-only period. Overall SLA was quantified by an Error Index (EI), where EI = 0 corresponded to perfect match between perceived and presented azimuths, whereas EI = 1 corresponded to chance. Results: SLA was rapidly measured in children (mean = 168 sec, n = 12) and adults (mean = 162 sec, n = 8). Visual inspection of gaze data indicated that gaze shifts occurred in sound-only periods. The medians of the perceived sound-source azimuths either coincided with the presenting sound-source azimuth or were offset by a maximum of 20 degrees in children. In contrast, adults revealed a perfect match from −55 to 55 degrees, except at 15 degrees azimuth (median = 20 degrees), with 9/12 of the quartile ranges = 0 degrees. Children showed a mean (SD) EI of 0.42 (0.17), which was significantly higher than that in adults (p < 0.0001). However, children revealed a distinct age-related EI improvement of 16 percentage points per year (r = −0.68, p = 0.015, n = 12), suggesting an ongoing maturation of SLA in the studied age range (29 to 157 weeks). The eight adults showed high SLA and high reliability as demonstrated by the low mean (SD) EI (0.054 [0.021]) and the low variability in test–retest differences (95% confidence interval = −0.020 to 0.046). Conclusions: Corneal-reflection eye-tracking provides an objective and fast assessment of horizontal SLA from about 6 months of age and may enable gaze to be used as an objective measure for sound localization in this age group. Infant SLA is immature and improvements are related to increasing age. Adults show high overall SLA and low intra- and intersubject variability in SLA. The technique may be used as a clinical tool for the evaluation of very early intervention in a young, preverbal population and throughout the life span.