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Importance: Early detection and intervention of hearing loss may mitigate negative effects on children's development. Children who were admitted to the neonatal intensive care unit (NICU) as babies are particularly susceptible to hearing loss and risk factors are vital for surveillance. Design, setting and participants: This single-centre retrospective cohort study included data from 142 inborn infants who had been admitted to the NICU in a tertiary regional referral centre. Data were recorded for 71 infants with confirmed permanent congenital hearing loss hearing loss. To determine impact of NICU admission independently of prematurity, babies were individually matched with 71 inborn infants on gestational age, birthweight, and sex. Main outcomes and measures: Neonatal indicators were recorded for all children with permanent congenital hearing loss. Presence of UK and US risk factors for hearing loss were collected on the neonatal population with hearing loss and for the matched controls. Results: A fifth (21%) of babies with hearing loss had one or more UK risk factors whereas most (86%) had at least one US risk factor. False positives would be evident if US factors were used whereas the matched controls had no UK risk factors. Ten babies who at birth had no UK or US risk factors did not have any significant neonatal indicators identified in their records, one was ventilated for one day and two had a genetic anomaly. Conclusions and relevance: Current risk factors for hearing loss we identified for follow-up in this high-risk group are highly specific for congenital hearing loss. UK risk factors were highly specific for hearing loss but not sensitive and conversely, US risk factors are sensitive but not specific so false positives would be recorded. A national study of neonatal indicators could provide the utility to test which combinations of risk factors provide high sensitivity without losing specificity. [ABSTRACT FROM AUTHOR]

Need for admission to the neonatal intensive care unit (NICU) confers an increased risk of hearing loss in the newborn and of later neurodevelopmental impairment. In this retrospective longitudinal case-controlled study, we assess how the degree of prematurity, measured via gestational age, birth weight, and z-scores, in 138 infants admitted to the NICU are associated with permanent childhood hearing loss (PCHI) and 2-year developmental outcomes. Logistic regression analyses, Kruskal–Wallis analysis of variance, and Chi-squared tests were used. Independent of prematurity, PCHI and NICU admission were predictive of poor developmental outcomes. Twenty-one (47%) children with PCHI had a moderate-to-severe developmental delay, compared to three (7%) matched controls. Days in the NICU but not z-scores predicted PCHI. Z-score was not prognostic of moderate or severe developmental impairment in children with PCHI. The odds ratio of moderate-to-severe neurodevelopmental impairment with PCHI was high, at 12.48 [95% CI = 3.37–46.40]. Children with PCHI were significantly more likely to have cerebral palsy than their matched counterparts (30% vs. 2%). These findings challenge the conventional focus on gestational age and birth weight on neurodevelopmental outcomes for children with PCHI and NICU admission. A more nuanced approach to monitoring and intervention is needed. [ABSTRACT FROM AUTHOR]

Abstract Neural responses in the adult central auditory system to binaural stimuli can be altered by preceding acoustic events, including auditory motion. To determine whether the juvenile auditory system also exhibits this feature, we have examined interaural level difference (ILD) processing in the developing gerbil. A long binaural stimulus was followed without interruption by modulation of the level difference (virtual acoustic motion), which in turn was followed smoothly by a new steady state ILD. Auditory responses of single neurons in the inferior colliculus (IC) were assessed for sensitivity to the final steady state ILD. The response of EI neurons (excited by contralateral stimulation and inhibited ipsilaterally) was examined at postnatal (P) days 17–18, P24–25, and in adult animals. In adult animals, a sudden reduction of the inhibitory stimulus level resulted in a long-lasting (median = 4.3 s) enhanced discharge rate (conditioned enhancement). In P17–18 animals, conditioned enhancement only lasted for 1.2 s. When the inhibitory stimulus level was suddenly increased, adult neurons often displayed a conditioned suppression of discharge rate (median = 4.5 s), whereas P17–18 neurons remained suppressed for a much briefer period (median = 1.2 s). Moreover, the difference between conditioned responses and control discharge rates was three–four times greater in adult neurons compared to those recorded in P17–25 animals. Because conditioned responses are sensitive to the relative balance of contralateral excitation and ipsilateral inhibition, we examined the relationship between excitatory and inhibitory thresholds. In adult animals, excitatory thresholds were an average of 12 dB lower than inhibitory thresholds, while at P17–25 excitatory and inhibitory thresholds were roughly the same. These results indicate that computational properties of juvenile and adult IC neurons differ quantitatively, and this may reflect an imbalance between excitation and inhibition. The developmental differences described herein may limit the ability of young animals to locate a sound source with the latency and accuracy of an adult. [ABSTRACT FROM AUTHOR]

The Auditory Brainstem Response (ABR) technique was used to investigate potential dysfunctions in the auditory brainstem of the pigmented guinea pig (Cavia porcellus) associated with biological ageing. Animals aged from 58 days to 4 years 3 months were tested. ABRs were recorded at stimulation intensities from 85 dB HL to 10 dB HL. The auditory thresholds were found to undergo marked elevations in old animals, by an average of 32 dB. From the traces obtained, four positive deflection waves were reliably recorded. The latency of each of the four waves was evaluated at different stimulation intensities in guinea pigs of different ages. Although there was a trend for the latencies to increase in old age, these differences were not statistically significant. Similarly, there were no significant age-related changes in the inter-peak intervals. The latency/intensity functions of the four waves produced parallel curves. However, the curve from the old age group was shifted to the right, by an average of 35 dB, indicative of conductive hearing loss. There was no evidence of retro-cochlear hearing loss. Therefore, it appears that the threshold elevations in the old animals can be accounted for by conductive hearing loss, presumably in the middle ear. In 24% of the old animals tested, no ABR could be elicited. It would appear that these animals had suffered severe sensorineural hearing loss. [ABSTRACT FROM AUTHOR]