Low prevalence of hearing impairment among very low birthweight infants as detected by universal neonatal hearing screening.

OBJECTIVES: To (a) study the prevalence of hearing impairment in a cohort of very low birthweight (VLBW) infants and (b) evaluate the effectiveness of transient evoked otoacoustic emissions (TEOAE) as a first stage in-hospital hearing screening tool in this population. STUDY DESIGN: The study group was a cohort of 346 VLBW infants born in 1998-2000 at The Sheba Medical Center. The prevalence of hearing impairment in the study group was compared with that of all other newborn infants participating in a universal newborn hearing screening programme during the same period. To evaluate the effectiveness of TEOAE, a control group of 1205 healthy newborns who had no known risk factors for hearing impairment was selected. The results and follow up of hearing screening for these infants were examined retrospectively. RESULTS: Only one VLBW infant (0.3%) was diagnosed with bilateral sensory-neural hearing loss. In addition, nine infants (2.7%) were diagnosed with conductive hearing loss. Bronchopulmonary dysplasia and low Apgar score were the most significant factors for predicting the occurrence of conductive hearing loss. The percentage of VLBW infants who successfully passed the in-hospital TEOAE screening was 87.2, compared with 92.2% in the full term control group. No false negative cases were detected on follow up. CONCLUSIONS: The study shows a low incidence of sensory-neural hearing loss in a cohort of VLBW infants and a relatively high incidence of conductive hearing loss. TEOAE screening was found to be an effective first stage in-hospital hearing screening tool in this population.

Assessment of medial olivocochlear system function in pre-term and full-term newborns using a rapid test of transient otoacoustic emissions.

This study was conducted to investigate maturation of the medial olivocochlear efferent system (MOCS) in pre- and full-term neonates using Quickscreen (Otodynamics Ltd) and to confirm previous findings on transient otoacoustic emission (TEOAE) suppression in neonates. MOCS maturation was investigated in 46 neonates born at the Chaim Sheba Medical Center, Tel Hashomer, Israel, using Quickscreen. All neonates were normal with no family history of general or auditory disease and no risk factors for hearing impairment. MOCS function appears gradually in human pre-term neonates and is considered to reach maturity shortly after term birth. The clinical value of MOCS testing in specific populations of newborns at risk for hearing and/or brainstem function can be legitimately raised as activation of the MOCS clearly alters cochlear output. The present results can be interpreted to support the testing of infants at risk of developing abnormal MOCS function using a commercially available rapid TEOAE measurement system.

Auditory backward masking and the effect of training in normal hearing adults.

Recent renewed interest in auditory backward masking has stemmed from studies of children with language impairments who were found to have significant, elevated thresholds for this paradigm, compared to normal cohorts. There are, however, many unresolved theoretical and procedural issues. The present study was conducted to investigate some of these issues. Specific purposes were: 1) To establish the differences between backward masking and simultaneous masking in normal hearing subjects; 2) To investigate the effect of listening conditions, i.e., monaural versus binaural; 3) To measure the effect of training on the performance of a backward masking paradigm; and 4) To measure generalization of the trained condition to untrained conditions. Two experiments were conducted: In experiment I, we compared the performance of 10 normal-hearing adult subjects for backward masking and simultaneous masking paradigms in both monaural and binaural modes of presentation. Stimuli consisted of a 1000 Hz pure-tone and bandpass masker (600-1400 Hz). Tone thresholds for backward masking were significantly lower than those of the simultaneous masking. The binaural mode of presentation yielded lower thresholds than those of the monaural mode only for the backward masking condition. A significantly large inter- and intra-subject variability was observed in the backward masking paradigm. Experiment II was conducted to measure the effects of training and generalization. Two groups of subjects were included: a trained group and a control group of six and eight normal hearing adults, respectively. The trained group received 10 sessions of backward masking training with feedback. The control group was tested only twice, with a 2-week interval between testing. Only the trained group showed a significant improvement in backward masking thresholds, which amounted to an average of 10.7 dB. No significant improvement was observed in the non-trained group. A nonsignificant trend of generalization occurred for the trained task to the untrained ear. No generalization was evident in the untrained condition (simultaneous masking). The data have important clinical and theoretical implications regarding the ability to train for auditory tasks in general, and for backward masking in particular.

Speech perception results--the first 10 years of a cochlear implant program.

Long-term speech perception test results for prelingually deaf children were compared with those of postlingually deafened adults, both groups having undergone cochlear implant at our Center. Average open-set score results of adults were similar to those of the children. However, some qualitative differences were demonstrated on the perception of phonological contrasts between the groups.

The effect of partially restored hearing on speech production of postlingually deafened adults with multichannel cochlear implants.

The effect of auditory feedback on speech production was investigated in five postlingually deafened adults implanted with the 22-channel Nucleus device. Changes in speech production were measured before implant and 1, 6, and 24 months postimplant. Acoustic measurements included: F1 and F2 of vowels in word-in-isolation and word-in-sentence context, voice-onset-time (VOT), spectral range of sibilants, fundamental frequency (F0) of word-in-isolation and word-in-sentence context, and word and sentence duration. Perceptual ratings of speech quality were done by ten listeners. The significant changes after cochlear implantation included: a decrease of F0, word and sentence duration, and F1 values, and an increase of voiced plosives' voicing lead (from positive to negative VOT values) and fricatives' spectral range. Significant changes occurred until 2 years postimplant when most measured values fell within Hebrew norms. Listeners were found to be sensitive to the acoustic changes in the speech from preimplant to 1, 6, and 24 months postimplant. Results suggest that when hearing is restored in postlingually deafened adults, calibration of speech is not immediate and occurs over time depending on the age-at-onset of deafness, years of deafness, and perception skills. The results also concur with hypothesis that the observed changes of some speech parameters are an indirect consequence of intentional changes in other articulatory parameters.

Subclinical audiological findings in carriers of recessive genes for deafness.

The existence of subclinical signs in the hearing of carriers of recessive mutations for deafness has aroused much controversy in the literature. The present study comprised 30 carriers of recessive mutations for deafness, and a control group of 30 healthy volunteers, matched for gender and age. All participants underwent a series of hearing tests, including pure-tone audiometry, speech tests, Bekesy audiometry and notch noise tests. The main results were: hearing loss in high frequencies (3000 and 4000 Hz), an elevation of the acoustic reflex threshold, as well as an elevation of the identification of 2000 Hz pure tone in the presence of white noise and notch noise. A notch in the Bekesy audiogram was also identified in several carriers. An interaction was found between gender and the carrier trait in the hearing threshold at 4000 Hz, and in the ipsi- and contralateral acoustic reflex at 500 Hz and 1000 Hz. These subclinical signs may be complementary to DNA research in the investigation of genetic deafness of unknown origin.

Intracochlear schwannoma and cochlear implantation.

A case of intracochlear schwannoma in a 58-year-old candidate for cochlear implantation is described. The tumor was located in the basal turn of the cochlea and was discovered only during surgery. Computed tomography and magnetic resonance imaging obtained prior to surgery failed to detect the tumor. Intralabyrinthine schwannomas are rare tumors that grow either in the vestibule, as intravestibular schwannomas, or in the cochlea, as intracochlear schwannomas. Complete removal of this tumor was achieved through a posterior tympanotomy approach. Cochlear implantation, which resulted in good hearing, was successfully performed 3 years later.

Stress reaction to intense sound exposure under different arousal levels in guinea pigs.

The general impact of high intensity sound exposure on 25 guinea pigs was investigated at three different levels of arousal: 10 during general anaesthesia. 10 during partial arousal, and 5 during complete arousal. Parameters recorded before and during noise exposure were mean arterial blood pressure, pulse rate, and plasma norepinephrine levels. The anaesthetized group showed no increase in the three parameters during sound exposure. Under partial arousal, pulse rate and norepinephrine level increased significantly: pulse rate from 224.5 beats/min before exposure to 278.6 beats/min during exposure, and norepinephrine level from 558 pg/ml before sound exposure to 1276 pg/ml during exposure. At the time of the complete arousal state norepinephrine and pulse rates increased significantly during noise exposure, while blood pressure showed no additional increase as a result of sound exposure.

Contralateral Acoustic Effect of Transient Evoked Otoacoustic Emissions in Neonates.

Contralateral acoustic stimulation (CAS) has the effect of reducing the amplitude of transient evoked otoacoustic emissions (TEOAE) of the opposite cochlea. This phenomenon is considered to be mediated via the efferent pathway, from the superior olivary complex through the medial olivocochlear system to the contralateral cochlea. The assessment of this suppressive effect provides an objective and noninvasive technique for exploring the function of the efferent auditory system in humans. Two previous studies investigated the suppression effect of TEOAE in newborns and revealed a significant effect in 18 full-term neonates. In this study, the effect of contralateral acoustic stimulation on TEOAE was investigated in 13 full-term neonates (gestational age, 40-42 weeks). The TEOAE were recorded alternately with and without simultaneous, contralateral white noise. The CAS effect of TEOAE was present in all subjects; a mean of 2.21 dB +/- 1.7 (21% +/- 9.3%) was found. Our study demonstrated additional support for the functional maturity of the medial olivocochlear efferent system from birth.

Cochlear implantation in patients suffering from Cogan's syndrome.

Among patients who receive cochlear implants, those with Cogan's syndrome make a unique group. On one hand they are part of the post-lingual patients and good results can be anticipated. On the other hand, their basic illness is thought to have an autoimmune aetiology and for that reason more susceptible to complications, especially flap problems. In a series of 60 patients who were implanted at the Sheba Medical Center, three had Cogan's syndrome. No post-operative complications, including flap problems, were observed (followed-up for at least 18 months). Subjective and objective hearing results were very good.

Auditory brainstem response in obstructive sleep apnea patients.

Auditory brainstem responses (ABR) were recorded in 79 patients diagnosed as suffering from obstructive sleep apnea (OSA). The patients were divided into three subgroups (mild, moderate and severe) according to the severity of the syndrome. A statistically significant prolongation was found in the latency values of waves I, III and V in all three subgroups, compared to a control group of 29 healthy subjects. The transmission time between waves I and III and I and V was found to be prolonged in the moderate and severe OSA subgroups, compared to the control group. However, from a clinical point of view only 10% (eight patients) of the OSA group showed a clinically significant prolongation in their ABR latency values compared to the norms (mean +/- 2SD) of the specific ABR recording system used in this study. In addition, 36 of the OSA group underwent uvulopalato-pharyngoplasty (UPPP). There were no statistically significant differences in the ABR recording preoperatively versus post-operatively.

Auditory brainstem response to bone-conducted clicks in adults and infants with normal hearing and conductive hearing loss.

Knowledge concerning auditory brainstem response (ABR) by bone conduction (BC) is limited, and occasionally controversial. The present study was aimed at further elaboration of this issue. The research population consisted of 107 subjects. Four groups were investigated: group 1, normal-hearing adults aged 20-37 years; group 2, 10 children aged 5.6-8.4 years, with confirmed middle ear effusion (MEE); groups 3 and 4, 22 infants, matched by pairs, aged 5-18 months, 11 with normal otoscopy and 11 with suspected MEE. Comparison between ABR by AC and BC for all four groups is discussed. We observed that the AC-ABR threshold of group 2 was statistically significantly elevated compared to group 1. The same tendency was observed for group 4 compared to group 3. In AC ABR, the mean latency of wave V was significantly prolonged, compared to that of BC ABR in children with confirmed MEE, and infants with suspected MEE. We strongly suggest that by combining AC and BC ABR, more information concerning cochlear reserve status can be obtained in infants and young children who are difficult to test, or wherever a behavioral audiogram cannot be achieved.

Auditory temporal resolution and open speech recognition in cochlear implant recipients.

The recognition of speech events depends, among other factors, on the resolution function. The present study was conducted to evaluate the auditory temporal resolution function in cochlear implant (CI) subjects by a gap detection threshold (GDT) test. Fourteen postlingual deaf subjects who used the Nucleus 22 Channel CI system participated in the study. They were divided into two subgroups: (1) six patients who did not achieve a significant open speech recognition score; and (2) eight patients who obtained different levels of open speech recognition ability (OSRA). Gap detection thresholds were found for six noise burst durations: 85, 65, 52, 36, 25 and 10 msec. Absolute values of GDT in the CI group were longer compared with those obtained from normal-hearing subjects. The CI values varied in consistence with burst duration; namely, as burst duration decreased, GD increased. This trend was found in CI recipients with OSRA only. Examination of the relationship between GDT and OSRA indicated that the majority of CI recipients who had OSRA showed lower GDT.

Forty Years of Audiology in Israel.

A broad spectrum of audiology programs and services has been developed in Israel over the past 40 years. Tel Aviv University awards bachelor's and graduate degrees in audiology and speech-language pathology. There is a national licensing program for audiologists and speech-language pathologists who have earned at least a baccalaureate degree and have completed one year of service under the supervision of a senior professional. Wellequipped medical center clinics in the major geographic areas are easily accessible from all parts of the country. Privately operated audiology clinics and offices are run by licensed audiologists, and hearing aid dispensing establishments are staffed mostly by licensed audiologists. An organized national hearing screening program begins with infants and young children in well-baby clinics. Special education programs emphasize integration of children with severe and profound hearing loss in regular classrooms, and volunteer service centers provide supplementary habilitation and social and cultural experiences for such children. Hearing conservation programs for the retired population are carried on in community health maintenance centers for the older adult. Industrial and military hearing conservation programs have been established. Israeli scientists and clinicians engage in both basic and clinical research, and Israel's professional organizations organize periodic local, national, and international meetings, facilitating significant interaction and collaboration with colleagues and organizations abroad.

[Auditory achievements of cochlear implantation].

The cochlear implant, which stimulates the auditory nerve electrically, is a rehabilitative solution for the severely deaf who cannot benefit from a hearing aid. The implant enables them to rejoin the world of sound from which they were disconnected. We present the process of auditory diagnosis which determines the patient's suitability for cochlear implantation, the implant's tuning program and the rehabilitation process it entails. Each of the 22 implanted electrodes is checked through a computer program, and the specifications of the electrical stimulation are established to provide the most comfortable hearing level for the implanted device. These stimulation specifications determine the number of active electrodes and the ideal stimulation model. During the 8-week hearing-training program which follows implantation, the patients acquaint themselves with the new world of sound through which they will communicate with their environment. Of the 16 implanted patients 7 heard only via the implant, without the aid of lipreading, a result which is considered excellent. These patients are able to talk on the telephone with the aid of the implant. 1 patient refused to use the implant, while the others have had good to moderate results. Noteworthy is the fact that even those with only moderate results greatly benefit from the implant, and are not willing to function without it for even a single day.

Normative data for 40-Hz event-related potentials to 500-Hz tonal stimuli in young and elderly subjects.

Recordings of 40-Hz event-related potentials (ERPs) were obtained in 81 young subjects (18-40 years) and in 20 elderly subjects (60-77 years) with hearing normal for their age. The stimuli were 500-Hz logons. The first negative peak (N1) of the response was analyzed. With increasing intensity the amplitude of the responses increased and the latency decreased for all subjects. The 40-Hz ERP was obtained within 10 dB of the behavioral threshold for more than 80% of the population under study. The N1 was prolonged in latency and enhanced in amplitude in the older subjects. No differences were found between young and elderly subjects regarding binaural interaction, or in responses elicited by ipsi- and contralateral stimulation. From the clinical point of view, the 40-Hz ERP recordings of young and elderly subjects are similar.

[Cochlear implantation].

Since the Israeli cochlear implant program was started in June 1989, 74 candidates have been evaluated for implantation. The main causes for hearing loss were meningitis (16 patients), aminoglycoside toxicity (9), congenital (6), viral (e.g. mumps) (6), and middle ear infection. Candidates were rejected mainly due to psychosocial factors (40%) and audiological parameters (30%). 16 postlingual deaf were implanted. In 7 of them (43.7%) the results were excellent, in 4 (25.0%) good, in 3 (18.7%) fair; 1 case is currently in a training program and 1 is a failure. There were 2 major complications: facial nerve palsy which necessitated surgical decompression, and insertion of the electrodes into the hypotympanic air cells, corrected by reoperation.

Temporary threshold shift due to noise exposure in guinea pigs under emotional stress.

One of the factors which can affect the amount of temporary threshold shift (TTS) due to acoustic overstimulation is known to be the general metabolic state of the exposed subject. The present study was conducted to elucidate how preexisting intense emotional stress in awake guinea pigs could influence the TTS induced by exposure of 4 kHz at 120 dB SPL for 20 min. Considering the hypersympathetic activity in both 'stress' and 'noise' it was assumed that the two factors would act synergetically on the cochlear function. However, an unexpected result was obtained. The mean threshold for the stressed animals following noise exposure was significantly lower (better) than that of the controlled, sedated, guinea pigs.

Cooperation of hearing-impaired elderly subjects for participation in a hearing screening program.

Presbyacusis, the auditory disorder which accompanies the aging process, is well known. However, the practical assistance available to alleviate the breakdown in the communication ability of the older person is unsatisfactory, and provision for public awareness of a rehabilitation strategy has not yet been established in many countries. Four hundred and ninety-eight elderly subjects, aged 65-94 years, were hearing tested in different setups, a geriatric nursing home and in the community. It was found that the need for rehabilitation was high and the willingness to participate in a hearing screening program was low even though the rehabilitation treatment was provided without charge.

Sedation effect on temporary threshold shift induced by acoustic overstimulation.

The mechanism by which noise damages the inner ear has not as yet been fully elucidated. Experiments were done to study the influence of the sedation in temporary threshold shift (TS) induced by acoustic overstimulation, as barbiturates were found to improve the brain's tolerance to ischemia. Four groups of guinea pigs (GP) were used. The temporary TS was decreased with the reduction of the temperature in awake, as well as sedated, sound-exposed GP. However, the temporary TS in the sedated, but normothermic GP was as great as in the awake, normothermic group. The high temperature counteracts the protection effect of the sedation in nose-induced hearing loss.