Otoacoustic emissions and auditory assessment in infants at risk for early brain damage

Hearing loss screening tool (COBRA score) for newborns in primary care setting

Purpose

To develop and evaluate a simple screening tool to assess hearing loss in newborns. A derived score was compared with the standard clinical practice tool.

Methods

This cohort study was designed to screen the hearing of newborns using transiently evoked otoacoustic emission and auditory brain stem response, and to determine the risk factors associated with hearing loss of newborns in 3 tertiary hospitals in Northern Thailand. Data were prospectively collected from November 1, 2010 to May 31, 2012. To develop the risk score, clinical-risk indicators were measured by Poisson risk regression. The regression coefficients were transformed into item scores dividing each regression-coefficient with the smallest coefficient in the model, rounding the number to its nearest integer, and adding up to a total score.

Results

Five clinical risk factors (Craniofacial anomaly, Ototoxicity, Birth weight, family history [Relative] of congenital sensorineural hearing loss, and Apgar score) were included in our COBRA score. The screening tool detected, by area under the receiver operating characteristic curve, more than 80% of existing hearing loss. The positive-likelihood ratio of hearing loss in patients with scores of 4, 6, and 8 were 25.21 (95% confidence interval [CI], 14.69–43.26), 58.52 (95% CI, 36.26–94.44), and 51.56 (95% CI, 33.74–78.82), respectively. This result was similar to the standard tool (The Joint Committee on Infant Hearing) of 26.72 (95% CI, 20.59–34.66).

Conclusion

A simple screening tool of five predictors provides good prediction indices for newborn hearing loss, which may motivate parents to bring children for further appropriate testing and investigations.

Risk factors for hearing loss in infants under universal hearing screening program in Northern Thailand

OBJECTIVE

To define the risk factors for hearing loss in infants (aged 3 months) under universal hearing screening program.

MATERIALS AND METHODS

A total of 3,120 infants (aged 3 months) who underwent hearing screening using a universal hearing screening program using automated otoacoustic emission test between November 1, 2010 and May 31, 2012 in Uttaradit Hospital, Buddhachinaraj Hospital, and Sawanpracharuk Hospital (tertiary hospitals) located in Northern Thailand were included in this prospective cohort study.

RESULTS

Of the 3,120 infants, 135 (4.3%) were confirmed to have hearing loss with the conventional otoacoustic emission test. Five of these 135 infants (3.7%) with hearing loss showed test results consistent with auditory brainstem responses. From the univariable analysis, there were eleven potential risk factors associated with hearing deterioration. On multivariable analysis, the risk factors independently associated with hearing loss at 3 months were birth weight 1,500-2,500 g (risk ratio [RR] 1.6, 95% confidence interval [CI] 1.1-2.6), APGAR score <6 at 5 minutes (RR 2.2, 95% CI 1.1-4.4), craniofacial anomalies (RR 2.5, 95% CI 1.6-4.2), sepsis (RR 1.8, 95% CI 1.0-3.2), and ototoxic exposure (RR 4.1, 95% CI 1.9-8.6).

CONCLUSION

This study concluded that low birth weight, APGAR score <6 at 5 minutes, craniofacial anomalies, sepsis, and ototoxic exposure are the risk factors for bilateral hearing loss in infants (aged 3 months) and proper tests should be performed to identify these risk factors. As an outcome, under the present circumstances, it is suggested that infirmary/physicians/general practitioners/health action centers/polyclinics should carry out universal hearing screening in all infants before 36 weeks. The public health policy of Thailand regarding a universal hearing screening program is important for the prevention of disability and to enhance people's quality of life.

[Cochlea development in infants with central nervous system impairment occurring as an effect of perinatal asphyxia]

Asphyxia in neonates with inadequate blood-inner ear barrier function causes damage to the inner ear included the degeneration of outer hair cells of the organ of Corti and oedematous changes in stria vascularis. The major consequences in the central nervous system (CNS) are found to be hypoxic-ischemic encephalopathy (HIE) in term newborns, peri- (PVH) or intraventricular hemorrhages (IVH) and periventricular leucomalacia (PVL) in preterm neonates.

THE AIM OF THE STUDY

was to carry out the objective assessment of the cochlea development using CEOAEs in infants with CNS impairment occurring as an effect of perinatal asphyxia, imaged during trans-fontanel ultrasonography.

MATERIAL AND METHODS

To the investigation 36 infants with HIE, IVH or PVL were included, the control group encompassed 32 born at term, health children. In all children three times otoscopic examination and CEOAEs recordings were performed: after birth, in 3rd and in 6th month of life using Otodynamics Otoacoustic Analyser ILO-88 in Quick Screen version. Perinatal anamnesis, general pediatric status, results of trans-fontanel ultrasonography and biochemical test results were taken into account in statistical analyses.

RESULTS

The mean amplitudes of CEOAEs in the first days of life were significantly reduced in InvG comparing to control babies. In half-octave frequency bandwidth analysis significant reduction of S/N Ratio at 1,5–4 kHz in InvG was observed. 3 and 6 months later the recorded responses significantly increased, they didn't reach values of CG but no statistical differences between groups were observed.

CONCLUSION

In conclusion, the outer hair cells activity in first days of life is reduced in newborns with CNS impairment and perinatal asphyxia in anamnesis comparing to health children. The maturation of the cochlea is intensive during first 3 months of life, later only subtle changes in CEOAEs are observed.