The characteristics of high frequency (1000 Hz) acoustic admittance results obtained from normal neonates were described in this study. Participants were 170 healthy neonates (96 boys and 74 girls) aged between 1 and 6 days (mean = 3.26 days, SD = 0.92). Transient evoked otoacoustic emissions (TEOAEs), and 226 Hz and 1000 Hz probe tone tympanograms were obtained from the participants using a Madsen Capella OAE/middle ear analyser. The results showed that of the 170 neonates, 34 were not successfully tested in both ears, 14 failed the TEOAE screen in one or both ears, and 122 (70 boys, 52 girls) passed the TEOAE screen in both ears and also maintained an acceptable probe seal during tympanometry. The 1000 Hz tympanometric data for the 122 neonates (244 ears) showed a single-peaked tympanogram in 225 ears (92.2 %), a flat-sloping tympanogram in 14 ears (5.7 %), a double-peaked tympanogram in 3 ears (1.2 %) and other unusual shapes in 2 ears (0.8 %). There was a significant ear effect, with right ears showing significantly higher mean peak compensated static admittance and tympanometric width, but lower mean acoustic admittance at +200 daPa and gradient than left ears. No significant gender effects or its interaction with ear were found. The normative tympanometric data derived from this cohort may serve as a guide for detecting middle ear dysfunction in neonates.

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High-frequency (1000 Hz) tympanometry in normal neonates.

Patients in the neonatal intensive care unit were tested by hearing screening tests including auditory brain stem response (ABR), transient and distortion-product otoacoustic emissions (TEOAEs and DPOAEs), and acoustic stapedius reflex (ASR), and by middle ear function tests including multifrequency tympanometry and pneumatic otoscopy. Pass rates on hearing tests were 75% to 89%. TEOAEs produced the lowest pass rate, and DPOAEs the highest. TEOAE, DPOAE, or ASR testing followed by ABR testing of initial failures produced pass rates of about 90%. The most efficient combination was DPOAEs followed by ABR. Pass rates tended to decrease with age. Of patients who failed 226-Hz and 678-Hz tympanometry, 30% to 67% passed hearing tests, suggesting a high false-positive rate for these immittance tests. The 3 ears that failed the 1000-Hz tympanogram failed all hearing tests. Many ears were abnormal by pneumatic otoscopy but passed hearing tests, suggesting that the usual ear examination criteria may not apply to infants.(Otolaryngol Head Neck Surg 1999;120:799-808.)

Hearing Screening in the Newborn Intensive Care Nursery: Comparison of Methods:

Tympanometry using 226 Hz, 678 Hz, and 1000 Hz probe tones was undertaken on two groups of babies, age 2 to 21 weeks. A group of 104 babies with normal ABR thresholds or TEOAEs were compared with a second group of 107 babies who had evidence of temporary conductive hearing loss based on the findings of a test battery, which included air and bone conduction ABR. The tympanograms were classified by Method 1, a simple visual classification system, and Method 2, adapted from a system described by Marchant et al (). The majority of tympanograms recorded in both groups using the 226 Hz probe tone were ‘normal’ Type A, with no significant difference in middle ear pressure or static admittance. However, both classification methods demonstrated significant differences between the two groups using the higher frequency probe tones, with Method 2 being the preferred system of classification. Tympanometry using 226 Hz is invalid below 21 weeks and 1000 Hz is the frequency of choice.SumarioSe efectuaron timpanometrias ...

Choice of probe tone and classification of trace patterns in tympanometry undertaken in early infancy.

AIM To assess delay in confirming hearing impairment in infants identified by universal neonatal screening and to investigate the causes. PATIENTS Infants identified from 25 199 babies screened from January 1992 to December 1997. METHODS A two stage transient evoked oto-acoustic emission test (TEOAE), with a threshold auditory brainstem response (ABR) recording undertaken on those who failed. The screen identified infants with a permanent congenital hearing impairment (PCHI) averaging 40 dBnHL or worse in the best ear. Those with less impairment were also ascertained. The positive predictive value (PPV) of the ABR test and measures of delay between identification and eventual diagnosis were analysed. RESULTS A targeted PCHI was found in 1.18/1000 neonates. The PPV of the ABR for confirming a targeted PCHI was 100% when the ABR threshold was ⩾ 80 dBnHL. Nine of 11 infants with this threshold had severe or profound permanent deafness. The delay from ABR to audiological certainty was about 1 month—diagnosis was confirmed around 3 months. There was uncertainty when the ABR was 40–80 dBnHL. The PPV was 60% and 8% when the ABR thresholds were 70 dBnHL and 50 dBnHL, respectively. 85 of 111 infants with ABR thresholds in this range had a temporary conductive impairment. Their early diagnosis depended upon the type and degree of hearing impairment and diagnosis was delayed to about 8 months in these infants. CONCLUSIONS Hearing impairments identified by universal screening are delayed in all but those with severe or profound bilateral PCHI. This delay can be reduced by applying in early infancy a battery of audiological tests and requires further exploration. Key messages Useful implementation of universal neonatal hearing screens depends on the ability to confirm both the type and degree of deafness in early infancy Screening may be relatively straightforward but audiological diagnosis at this age is not Severe or profound deafness can be identified in early infancy with minimal delay but moderate deafness is confirmed on average at 8 months Targeting moderate deafness in early infancy demands that audiological tests are developed to confirm a permanent hearing impairment in those identified by the screen

https://adc.bmj.com/content/archdischild/81/5/380.full.pdf

Confirmation of deafness in infancy

Stimulated acoustic emissions were recorded in a consecutive series of 20 full-term and otherwise normal neonates with the equipment and method previously used in adults. One ear randomly chosen was tested in each baby, and otoscopy and tympanometry were normal in all ears. A 2 kHz click stimulus was presented with a repetition rate of 10/sec and the recordings were performed at three intensities, i.e. 70, 50 and -20 dBatt (dBatt approximately dB p.e. SPL). The 50 dB recording was repeated for check of reproducibility. A clear and reproducible response could be identified from all ears at 50 dBatt. However, as in the adults, the response pattern differed significantly from one ear to another, both regarding the number of 'echoes', their latencies, response amplitudes, and frequency content. The 'echo' group latencies and amplitudes were within the same range as in normal adults and the amplitude input-output curves exhibited a clear non-linearity. The relationship between latency and frequency was just as ambiguous as in the adults. Also, in the neonates, the cross correlation analysis proved to be an efficient method to indicate whether or not a true response was present. The results from this investigation are compared with those described in the literature from other audiological tests and it is concluded that the recording of the stimulated acoustic emissions could be applicable as a screening procedure in newborns.

Evoked acoustic emissions from the human ear. III. Findings in neonates.

Probe tones from 220 Hz to 2 000 Hz were used to measure the static and dynamic acoustic impedance of 44 neonates. Acoustic reflex thresholds to broad band noise were obtained from every neonate tested when employing the higher frequency probe tones. The reflex threshold levels measured are similar to those of adults. The static impedance values are discussed to give a possible explanation of why reflex thresholds cannot be detected using conventional 220 Hz impedance bridges.

The neonatal acoustic reflex.

Acoustic reflex impedance measurements are made on forty-seven normal and two otosclerotic ears using fixed probe frequencies from 220 to 2000 Hz. In general, the reflex increases the middle ear impedance up to 700 Hz probe frequency and decreases it thereafter. It is postulated that this characteristic is related to removal of the cochlear fluid resistance due to stapes decoupling. At one probe frequenc, in the range 500–900 Hz, the reflex of 50% of the normal ears has either a diphasic pattern or shows no change in the impedance vector length. The accompanying phase change is always monophasic. In the otosclerotic ear the diphasic reflex is present for every probe frequency. These factors should be taken into account when probe frequencies greater than 220 Hz are used for reflex measurement.

L. A. Weatherby

Papers

The neonatal acoustic reflex.

Multiple Probe Frequency Acoustic Reflex Measurements