Paediatric auditory brainstem response and pure-tone audiometry: threshold comparisons. A study of 142 difficult-to-test children

Is behavioral audiometry achievable in infants younger than 6 months of age?

BACKGROUND AND GOAL

When carried out in addition to objective tests, behavioral audiometry performed in children with the so-called "Delaroche protocol" [IJORL 68 (2004) 1233-1243] enables to determine hearing thresholds by air and bone conduction over the whole auditory frequency range. In the present report, seventy-three hearing-impaired infants with different levels of motor and cognitive development were tested behaviorally before 6 months of age. Reliability of these early determined behavioral thresholds was then after analyzed using: (a) cross-sectional study, and (b) longitudinal study.

METHODS

Cross-sectional study compared click-evoked ABR thresholds in the better ear with binaural high-frequency hearing thresholds. In longitudinal study, early measured binaural hearing thresholds from 500 through 4000 Hz were reassessed at 18 months.

RESULTS

In 13% of babies behavioral testing was not fully completed by 6 months of age. Nevertheless, both cross-sectional and longitudinal studies yielded intraclass correlation coefficients above 0.80, suggesting that behavioral testing is applicable to this very young population.

CONCLUSIONS

Assessment of hearing after newborn screening should not be restricted to objective tests before 5 ½ months. It should also include bone- and air-conduction behavioral tests adjusted to developmental stage and performed in presence of parents.

Clinical experience of auditory brainstem response testing on pediatric patients in the operating room

Objectives. To review our experience of conducting auditory brainstem response (ABR) test on children in the operating room and discuss the benefits versus limitations of this practice. Methods. Retrospective review study conducted in a pediatric tertiary care facility. A total of 267 patients identified with usable data, including ABR results, medical and surgical notes, and follow-up evaluation. Results. Hearing status successfully determined in all patients based on the ABR results form the operating room. The degrees and the types of hearing loss also documented in most of the cases. In addition, multiple factors that may affect the outcomes of ABR in the operating room identified. Conclusions. Hearing loss in children with complicated medical issues can be accurately evaluated via ABR testing in the operating room. Efforts should be made to eliminate adverse factors to ABR recording, and caution should be taken when interpreting ABR results from the operating room.

Behavioral audiometry: validity of audiometric measurements obtained using the "Delaroche protocol" in babies aged 4--18 months suffering from bilateral sensorineural hearing loss

OBJECTIVE

Evaluation of the validity of the audiometric measurements obtained in babies aged from 4 to 18 months suffering from bilateral sensorineural hearing loss (SNHL) using an original behavioral audiometry (BA) protocol called the "Delaroche protocol" [IJPORL 68 (2004) 1233-1243].

METHODS

(1) We compared the auditory brainstem (ABR) threshold in the better ear with the mean of the BA thresholds obtained, bilaterally, at 2000 and 4000 Hz, both measurements being performed in the diagnostic phase. (2) We compared the BA thresholds obtained prior to the age of 18 months, bilaterally, at the frequencies of 500,1000, 2000 and 4000 Hz, with the thresholds of the better ear obtained at the same frequencies at the age of 3--4 years by BA.

RESULTS

(1) Cross- sectional study (78 children). When there was no ABR at 100 db, there was no BA response at 100 dB in 84.2% of cases, resulting in a kappa coefficient of 0.72. When there were ABR, the difference between the ABR and the BA thresholds was equal to or less than 10 dB in 67% of cases and equal to or less than 20 dB in 95% of cases. (2) Longitudinal study (50 children). The difference between the behavioral thresholds obtained within 4 and 18 months (median age=12 months) and those obtained at 3 or 4 years old in the same children (median age=39 months) was equal to or less than 10 dB in 94% of cases at the frequencies of 1000, 2000 and 4000 Hz and in 78% of cases at 500 Hz.

CONCLUSION

The two analysis evidence the validity of the behavioral measurements obtained at an early age using the protocol described.

The prognostic value of electrocochleography in severely hearing-impaired infants

This paper presents a longitudinal evaluation of electrocochleographic assessment in severely hearing-impaired infants. Electrophysiological data were obtained by transtympanic electrocochleography to tone-burst stimuli at octave frequencies of 500 to 8000 Hz at the age of 0-6 years in a group of 126 subjects. The results are compared with auditory thresholds determined at school age in the same children by means of pure-tone audiometry. Cochlear microphonics could be recorded in virtually all ears, although the majority of subjects had hearing losses of 90 dB and more. Compound action potentials (CAPs) showed waveforms varying from normal to a wide range of abnormalities. Audiometric thresholds correlated generally well with the compound action potential (CAP) thresholds obtained in infancy. The error in the predicted audiometric thresholds is between 15 and 20 dB, as compared with 11 dB reported for more moderate hearing losses. It is shown that, in spite of the high stimulus levels used, substantial frequency-specific threshold information is retained. Occasional large discrepancies in thresholds were often associated with markedly abnormal response waveforms. Among the many cases in which no ABR could be elicited, 68 per cent produced detectable electrocochleographic responses in the 1000-4000 Hz range. It is concluded that electrocochleography is a valuable method for the assessment of residual hearing in infants suspected of having a severe hearing impairment.

Hearing, vocalization and the external ear of a marsupial, the northern Quoll, Dasyurus hallucatus

As part of a continuing study of the development of the marsupial auditory system, auditory brainstem responses (ABR) were recorded and an ABR audiogram was constructed for five female Northern Quolls (Dasyurus hallucatus), which are nocturnal carnivores. The best frequency for hearing lies between 8 and 10 kHz, and at 50 dB SPL there is a range from about 0.5 to 40 kHz. Vocalizations of adult quolls and pouch-young were recorded with a digital audio tape recorder, and the power spectra of representative calls were compared with the ABR audiogram. The common adult vocalizations have most energy at the lower end of the hearing range, whereas frequencies that are dominant in the isolation calls of the pouch-young lie close to the best frequency of hearing. Samples of nocturnal sounds of the habitat of the quoll were also recorded and analyzed. Power spectra have peak energy at frequencies between 2 and 5 kHz, with a smaller contribution above 10 kHz. The spectrum contains relatively little power at the best frequency of hearing. Measurements of the sound pressure level at the external ear canal as a function of stimulus frequency and location in space suggest that the directional amplifying properties of the pinna will operate most effectively on sound frequencies at the upper end of the quoll's hearing range, a region that may be important in prey detection. Comparisons are made with other mammalian nocturnal carnivores and with other marsupials. We speculate that, for nocturnal carnivores, one role of the low-frequency part of the hearing range concerns the recognition of adult conspecifics, the mid-frequency range is important for the detection of pouch-young, and the upper range may be particularly concerned with prey/predator detection.

Low-frequency specificity of the auditory brainstem response threshold elicited by clicks masked with 1590-Hz high-pass noise in subjects with sloping cochlear hearing losses

In this study, the frequency specificity of the ABR threshold to stimulation with a click masked with 1590-Hz high-pass noise was determined in subjects with sloping cochlear hearing losses both high- and low-frequency in character. The results show that the ABR threshold elicited by this stimulus is low-frequency specific. The standard error in estimating the 1,000-Hz pure-tone threshold from the high-pass-noise-masked click-evoked ABR threshold is 10.2 dB which equals that for estimating the 3,000-Hz pure-tone threshold from the routinely used unmasked click ABR threshold. The ABR threshold elicited by a click masked with 1590-Hz high-pass noise can therefore be regarded as an accurate tool to predict the pure-tone hearing loss at 1,000 Hz. However, this method is less suitable for routine clinical testing because of the masking noise needed: the occasional high loudness level adversely affects the response quality and reduces the dynamic range of pure-tone hearing losses to be assessed. A third disadvantage is that determining the masking level electrophysiologically for each ear is time consuming. The search for a method with no or less masking noise should therefore continue.

Hearing identification in difficult-to-test children. A study of 142 infants and children

Prior to auditory brainstem response (ABR) threshold determinations in 142 anaesthetized 'difficult-to-test' children, 125 had one or more behavioural auditory tests performed. We used the ABR thresholds as a basis and retrospectively analysed the case records in relation to some parental and behavioural auditory aspects. The accuracy of the parental opinion regarding hearing has been evaluated, and showed a relatively high rate of false-negatives (29%). In contrast, the presence of a hearing loss was correctly identified in 53%. The reliability of one or more standard behavioural auditory tests was poor in children with normal hearing, but in hearing impaired, there was agreement between ABR and behavioural results in more than 70% of cases. Median age at the ABR examination was 32 months. These and other results are discussed in view of the need to minimize diagnostic delay.

Low-level 0.5 and 1 kHz auditory brainstem responses. A search for the low-frequency point in the two-point ABR audiogram

We have compared the auditory brainstem responses (ABRs) to 0.5 and 1 kHz tone burst stimuli with high-pass noise masking in 10 normal-hearing adults. The overall quality of the low-level responses was poor, but a two-point ABR audiogram is feasible by using the summation technique described. The 1 kHz stimulus gave slightly better responses than 0.5 kHz, and a correction factor of 30-40 dB seems necessary. Our data indicate that these low-level, low-frequency responses are frequency-specific.