Andrée Durieux-Smith

Frequency-specific Audiometry Using Steady-state Responses

Objective: To evaluate the audiometric usefulness of steady‐state responses to multiple simultaneous tones, amplitude‐modulated at 75 to 110 Hz. Design: Steady‐state responses to multiple tones amplitude‐modulated at different rates between 75 and 110 Hz and presented simultaneously were recorded at different intensities in normal adults, well babies, normal adults with simulated hearing loss, and adolescents with known hearing losses. Response thresholds were compared with behavioral thresholds. Results: In normal adults the thresholds for steady‐state responses to tones of 0.5, 1, 2, and 4 kHz were 14 ± 11, 12 ± 11, 11 ± 8, and 13 ± 11 dB, respectively, above behavioral thresholds for air‐conducted stimuli, and 11 ± 5, 14 ± 8, 9 ± 8, and 10 ± 10 dB above behavioral thresholds for bone‐conducted stimuli. In well babies tested in a quiet environment, the thresholds were 45 ± 13, 29 ± 10, 26± 8, and 29 ± 10 dB SPL. In adolescents with known hearing losses, the steady‐state responses thresholds predict behavioral thresholds with correlation coefficients (r) of 0.72, 0.70, 0.76, and 0.91 at 0.5, 1, 2, and 4 kHz, respectively. Conclusion: Steady‐state responses to tones amplitude‐modulated at 75 to 110 Hz can be used for frequency‐specific objective audiometry. The multiple‐stimulus technique allows thresholds to be estimated for eight different stimuli at the same time.

Auditory steady‐state responses to tones amplitude‐modulated at 80–110 Hz

Steady-state responses can be recorded from the human scalp in response to tones that are sinusoidally modulated in amplitude at rates between 60 and 120 Hz. For 60 dB SPL 1000-Hz tones the maximum baseline-to-peak amplitude of about 0.06 microV occurs for modulation rates between 80 and 95 Hz. The phase of the response does not change with modulation depths greater than 25% and the amplitude saturates at modulation depths greater than 50%. The presence or absence of a response can be accurately determined by frequency-domain statistics and the response becomes clearly recognizable at intensities that are 16 +/- 8 dB above behavioral thresholds. With increasing intensity the response increases in amplitude at 1.9 nV/dB until an intensity of 70 dB SPL. As the intensity increases above 70 dB SPL the response increases in amplitude more rapidly at 7.8 nV/dB (at 1000 Hz) and contains significant energy at harmonics of the modulation frequency. This second stage of the intensity function is more prominent for stimuli with lower carrier frequencies (500 more than 1000 more than 2000 Hz) and is attenuated by high-pass masking. These steady-state responses should be helpful in evaluating human auditory physiology and in objective audiometry.

Thresholds for Short-Latency Auditory-Evoked Potentials to Tones in Notched Noise in Normal-Hearing and Hearing-Impaired Subjects

The thresholds for the short-latency auditory evoked potentials (SLAEPs) to short-duration tones presented in notched-noise masking were evaluated in 20 normal-hearing and 20 hearing-impaired subjects. The differences (dB) between these thresholds (dB nHL) and the pure-tone behavioral thresholds (dB HL) across all 40 subjects were 11.6, 6.1, 6.3 and 0.8 dB for 500, 1,000, 2,000 and 4,000 Hz, respectively. These differences were significantly smaller for the hearing-impaired subjects than for the normal-hearing subjects. Ninety-eight percent of the SLAEP threshold estimations were within 30 dB of the subjects pure-tone behavioral thresholds and 91% were within 20 dB.

Bilateral paediatric cochlear implants: A critical review

A recent trend has been the implantation of bilateral cochlear implants (CIs) for children with severe to profound hearing loss. A review of available research on bilateral CIs was conducted to determine the support for this trend. A replicable review was undertaken to evaluate published research studies that examined the effectiveness of bilateral paediatric cochlear implantation. Databases, reference lists, and journals were searched for relevant documents using a pre-determined search protocol. Twenty-nine articles met the reviews inclusion criteria and were retrieved and reviewed. This review adds to the previously published reviews on the topic by identifying additional paediatric studies. Sound localization and speech recognition in noise appear to be improved with bilateral compared to unilateral cochlear implants. Similarly, evoked potential measures suggest improved morphology when the second CI is implanted early. Well-designed and controlled studies that explore a variety of outcomes including cost-effectiveness, quality of life, speech, language, and psycho-educational measures should be further explored in order to provide additional support for parents and clinicians confronted with the bilateral cochlear implant decision.

A descriptive analysis of language and speech skills in 4- to 5-yr-old children with hearing loss.

Objective:Early intervention through hearing aids (HAs) and cochlear implants (CIs) aims to reduce the negative effects of childhood hearing loss and to promote optimal communication development over time. The primary goal of this study was to examine the communication outcomes of children with CIs and children with HAs at age 4 to 5 yrs and to consider their spoken language skills relative to a group of typically developing hearing peers. Design:In this multicenter observational study, communication results were obtained for a total of 88 children at age 4 to 5 yrs. Participants were recruited from three clinical programs in two cities in the province of Ontario, Canada. This study was undertaken shortly after the introduction of a new provincial population screening initiative and included both children who were screened and not screened for hearing loss. The study sample comprised 51 children with sensorineural hearing loss and 37 children with normal hearing. Of the 51 children with hearing loss, 26 used CIs and 25 used HAs. The degree of hearing loss ranged from mild to profound. All children were enrolled in rehabilitation programs focused on oral language development. Childrens language skills were assessed with an extensive battery of child- and parent-administered speech and language measures. Results:Assessment of language skills showed no significant differences between the children with severe to profound hearing loss using CIs and children with varying degrees of hearing loss using HAs. However, children with HAs showed better articulation skills. Overall, both groups of children obtained scores on communication measures that were lower than their hearing peers. The number of children with hearing loss who obtained spoken speech-language scores within 1 SD of normative populations ranged from 65 to 86% depending on the test measure. Children with average hearing loss of 70 dB HL or better generally obtained scores on all measures in line with those of age-matched norms while scores were quite variable for children with severe and profound hearing loss. Factors influencing performance in children with hearing loss included degree of hearing loss (pure-tone average) and parent education. Age at diagnosis of hearing loss was not a significant predictor of speech-language outcomes in this study. Conclusions:Results indicated that overall, children with all degrees of hearing loss who were fit with hearing technology and who received auditory-based rehabilitation services during the preschool years demonstrated the potential to develop spoken language communication skills. As a group, children with CIs and children with HAs did not differ significantly on language abilities although there were differences in articulation skills. Their performance at age 4 to 5 yrs was delayed compared with a group of hearing peers. The findings reinforce the need for research to identify factors that are likely to lead to age-appropriate communication skills for preschool-age children with hearing loss.

The impact of newborn hearing screening on communication development

Objective: Universal newborn hearing screening has become standard practice in many countries. The primary goal of this study was to assess the impact of early identification of permanent childhood hearing loss on oral communication development. Setting: Participants were recruited from three clinical programmes in two cities in the province of Ontario, Canada. The study sample was born during two consecutive periods of newborn hearing screening. The first period, prior to 2002, was targeted on high-risk infants only, and the second, from 2002, included both high- and standard-risk infants (universal newborn hearing screening – UNHS). All children were enrolled in rehabilitation programmes focused on oral language development. Methods: In this multicentre observational study, 65 children under the age of five years with onset of hearing loss before six months of age, 26 identified through systematic newborn screening (14 through targeted screening and 12 through UNHS) and 39 without screening, were assessed with an extensive battery of child- and parent-administered speech and language measures. The degree of hearing loss ranged from mild to profound with 22 children in the mild, moderate and moderately severe categories and 43 in the severe and profound categories. Data are reported for the three-year study period. Results: The screened group of children was identified at a median age of 6.6 (interquartile range, 3.0–8.2) months and children referred from sources other than newborn screening were diagnosed at a median age of 16.5 (interquartile range, 10.2–29.0) months. Assessment of oral communication development showed no significant difference between the screened and unscreened groups. The communication outcomes for children identified before 12 months of age did not differ from those of later identified children. Conclusions: Systematic screening of newborn hearing results in earlier identification and intervention for children with permanent hearing loss. Superior language outcome following newborn screening was not demonstrable in the setting of this study.

Parents’ perspectives on the impact of the early diagnosis of childhood hearing loss

Newborn hearing screening has been widely implemented to improve outcomes for children with permanent hearing loss. This study examined benefits beyond those typically measured clinically, by exploring parents’ perceptions of the effects of early/late identification of hearing loss. The parents of 17 children in Ontario, Canada, participated in the study. Seven children were identified through systematic screening and ten through traditional referral practices. All children were in oral rehabilitation programs. The study adopted a qualitative approach, examining parents views through individual interviews. Purposive sampling was used to select a diverse group of parents to allow a broad range of perspectives to emerge. Benefits of early identification included improved communication development and early access to hearing. Negative aspects of late identification included regret for the family and family stress around the childs language gap. Although, screening programs may offer a seamless transition to audiology services, the transition to intervention services appeared less fluid for some families. Overall, parents strongly support infant hearing screening and identify benefits that are not easily quantifiable through traditional clinical measures.

Prognostic validity of brainstem electric response audiometry in infants of a neonatal intensive care unit.

This study compared the results of brainstem electric response audiometry (BERA) in infants of a neonatal intensive care unit to those obtained on the same children with pure-tone audiometry at 3 years of age. Six hundred children were initially tested in infancy, and complete follow-up information was obtained on 333. In 297 (89%) the BERA results accurately predicted the hearing status at the age of 3 years. Twenty-nine (9%) of the discrepancies were related to conductive hearing losses: 17 patients with a conductive hearing loss in the first few months of life had normal hearing at 3 years, and 12 patients normal in infancy had a conductive loss at 3 years. Two patients evaluated as a sensorineural hearing loss by BERA had normal hearing. These may have been due to a conductive loss. Six patients assessed as normal by BERA had significant hearing losses at the age of 3 years. Five of these had normal hearing at one frequency between 1,000 and 4,000 Hz. The sixth may have developed a sensorineural hearing loss after birth.

Recording auditory brainstem responses from infants.

Auditory brainstem responses (ABRs) can be reliably recorded from infants in the first few months of life. Since they are normally recognizable down to intensities that are 30 dB above normal hearing thresholds, ABRs elicited by clicks are useful in screening for hearing-impairment in infancy. The ABRs can also provide further diagnostic information about the hearing losses that are detected by screening: the threshold for the response represents a reasonable estimate of the severity of the hearing loss; bone-conduction studies can assess the extent of a conductive loss; and frequency-specific techniques can evaluate hearing thresholds at different frequencies. At present, ABRs are mainly used for screening infants who have been treated in neonatal intensive care units. Because the majority of infants with hearing impairment are not seen in these units, it might be worthwhile to use ABRs in a more widespread screening program.

Mild bilateral and unilateral hearing loss in childhood: a 20-year view of hearing characteristics, and audiologic practices before and after newborn hearing screening.

Objectives: There is some evidence that the presence of even mild degrees of hearing loss and unilateral loss in early childhood can negatively affect typical development. Consequently, the identification of all children with permanent hearing loss including those with milder degrees of hearing loss is currently targeted through some newborn hearing screening initiatives. The objectives of this study were to document the proportion of children identified with mild bilateral or unilateral hearing loss (MBUHL) before and after the implementation of a universal newborn hearing screening program (UNHS). A second objective was to examine the clinical characteristics and audiologic management of this population of children. Design: This population-based study involved an analysis of data on children with hearing loss; these data had been collected prospectively over a 20-year period from 1990 to 2010 in a publicly funded pediatric teaching hospital in Canada, which provided diagnostic audiology services for all children in the region. The proportion of all children with hearing loss identified with MBUHL before and after implementation of UNHS and their clinical profiles were documented. Data related to amplification use were also retrospectively extracted from detailed medical chart reviews to investigate clinical recommendations regarding amplification and subsequent use of hearing devices. Factors affecting amplification decisions and amplification use were examined. Results: A total of 381 of 823 children (46.3%) aged 0 to 18 years who were identified with permanent nonacquired hearing loss presented with MBUHL. The proportions identified were similar in the pre- and post-UNHS periods (p = 0.207). Before UNHS children were identified at a median age of 5.0 years (interquartile range: 3.6 to 7.0) compared with a median of 0.8 years, (interquartile range: 0.3 to 2.3) post-UNHS. Progression of hearing loss was documented for 22% of all children, and for the group identified since UNHS, 32.4% experienced deterioration in hearing thresholds. Although 87.2 % of children received recommendations for amplification, more than 50% experienced considerable delay from identification to amplification. Age at identification and severity of hearing loss in the better ear were associated with amplification decisions for bilateral but not unilateral loss. Conclusions: MBUHL constitutes almost half of childhood hearing loss. UNHS has lowered age of confirmation of MBUHL by 4 to 5 years. Delay to amplification suggests uncertainty of the benefit of intervening early for these losses. Further research is required to determine the effects of early-identified MBUHL on children’s development and to document the benefits of early amplification.