[Deafness in the neonatal period: basis for screening]

Various aspects of hearing loss in newborns: A narrative review

Hearing loss is considered the most common birth defect. The estimated prevalence of moderate and severe hearing loss in a normal newborn is 0.1%-0.3%, while the prevalence is 2%-4% in newborns admitted to the newborn intensive care unit. Neonatal hearing loss can be congenital (syndromic or non-syndromic) or acquired such as ototoxicity. In addition, the types of hearing loss can be conductive, sensorineural, or mixed. Hearing is vital for the acquisition of language and learning. Therefore, early detection and prompt treatment are of utmost importance in preventing the unwanted sequel of hearing loss. The hearing screening program is mandatory in many nations, especially for high-risk newborns. An automated auditory brainstem response test is used as a screening tool in newborns admitted to the newborn intensive care unit. Moreover, genetic testing and screening for cytomegalovirus in newborns are essential in identifying the cause of hearing loss, particularly, mild and delayed onset types of hearing loss. We aimed to update the knowledge on the various aspects of hearing loss in newborns with regard to the epidemiology, risk factors, causes, screening program, investigations, and different modalities of treatment.

Hearing loss and congenital CMV infection: a systematic review

BACKGROUND AND OBJECTIVE

Hearing loss caused by congenital cytomegalovirus (cCMV) infection was first observed in 1964. Today cCMV is the most common cause of nonhereditary sensorineural hearing loss in childhood. Our objective was to provide an overview of the prevalence of cCMV-related hearing loss, to better define the nature of cCMV-associated hearing loss, and to investigate the importance of cCMV infection in hearing-impaired children.

METHODS

Two reviewers independently used Medline and manual searches of references from eligible studies and review articles to select cohort studies on children with cCMV infection with audiological follow-up and extracted data on population characteristics and hearing outcomes.

RESULTS

Thirty-seven studies were included: 10 population-based natural history studies, 14 longitudinal cohort studies, and 13 retrospective studies. The prevalence of cCMV in developed countries is 0.58% (95% confidence interval, 0.41-0.79). Among these newborns 12.6% (95% confidence interval, 10.2-16.5) will experience hearing loss: 1 out of 3 symptomatic children and 1 out of 10 asymptomatic children. Among symptomatic children, the majority have bilateral loss; among asymptomatic children, unilateral loss predominates. In both groups the hearing loss is mainly severe to profound. Hearing loss can have a delayed onset, and it is unstable, with fluctuations and progression. Among hearing-impaired children, cCMV is the causative agent in 10% to 20%. Despite strict selection criteria, some heterogeneity was found between selected studies.

CONCLUSIONS

This systematic review underscores the importance of cCMV as a cause of sensorineural hearing loss in childhood.

A wider role for congenital cytomegalovirus infection in sensorineural hearing loss

BACKGROUND

Diagnostic problems in identifying congenital infection cases in infancy have thus far impaired the assessment of the role of congenital cytomegalovirus (CMV) infection in the etiology of sensorineural hearing loss (SNHL).

OBJECTIVE

To estimate the impact of congenital infection in children with SNHL by detection of CMV DNA in stored samples of neonatal dried blood (dried blood spots test).

METHODS

The Guthrie cards of 130 children with hearing loss >40 dB hearing loss were retrieved from the regional screening center. CMV DNA was extracted by thermal shock and amplified by PCR.

RESULTS

The percentage of SNHL cases attributable to congenital CMV infection was 10% (9 of 87) in infants whose SNHL had been diagnosed in their first 2 months of life and 34.2% (13 of 38) in children with deafness of unidentified cause that was diagnosed in early childhood. In the latter group 42.7% (12 of 28) of the children with a hearing loss of >70 dB were CMV-positive.

CONCLUSIONS

The results suggest that congenital CMV infection has a more relevant role in the etiology of SNHL than previously reported. The data obtained in both groups suggest that 20 to 30% of all deafness cases are caused by CMV. The percent of congenital CMV cases alone appears to account for all the cases previously attributed to all congenital infections. More than 40% of deafness cases with an unknown cause, needing rehabilitation, are caused by congenital CMV.

[Systematic screening of deafness at a maternity ward using evoked otoacoustic emissions: practical aspects and parental attitudes]

OBJECTIVE

Evaluation of the feasibility and parental attitudes towards a hearing screening programme using evoked otoacoustic emissions, implemented in a maternity ward in France.

METHODS

A hearing screening test using transiently evoked otoacoustic emissions (TEOAE) was proposed to each baby, and an anonymous questionnaire was given to parents to assess their attitudes towards the screening procedure.

RESULTS

Although the refusal of the test reached 16% (mainly during the first two weeks of the program), more than 92% of parents judged the test as being useful, and 65% wished it to be systematically done. However, nearly 35% of parents admitted to have a low level anxiety about being unnecessarily worried by the test results. One hundred and twenty-four babies were screened. Fifty three per cent of the tests have been performed in less than ten minutes, with an average of 12.2 minutes. This duration does not include delays due to programme and babies management. False positive rate (uni or bilateral fail) was 10.5% at the first stage. Repeating the test before discharge decreased the false positive rate to 6.5%.

CONCLUSION

Although limited in time, this study shows that a systematic hearing screening programme using TEOAE is possible and should be done in France. False positive rate was below 7%, and the test was considered as useful by more than 90% of parents, although knowledge about deafness in childhood and its consequences were clearly insufficient.

[Otoacoustic emissions screening as early identification of hearing loss in newborns]

The aim of this study was to examine the results of transient evoked otoacoustic emissions (TEOAE) as screening test for hearing impairment in newborn infants. We examined 9.951 of 11.405 infants born in our city from January 1st, 1995, to December 31st, 1998. A TEOAE test was performed prior to discharge and repeated one week later in cases who failed the first TEOAE. In case of suspected hearing loss auditory brainstem response (ABR) was performed 3 months later. Hearing loss was defined as ABR threshold > 20 dB. 157 infants (1.5%) were identified with hearing loss. Screening with TEOAE was sufficiently sensitive in identification of congenital hearing impairment and the efficacy increased with the experience.

Prevalence, aetiology, and care of severe and profound hearing loss

Severe and profound hearing loss (> 70 dB) were analysed in a retrospective study of 226 children, born between 1976 and 1985, and recruited from three French administrative departments. The prevalence was 0.54 per 1000 children under 9 years old, with no decrease over the study period. A hereditary origin was identified in 20.8% of cases and an infectious origin in 11.5%. Perinatal risk factors were present in 11.5%, while the aetiology was undetermined in more than half the cases. In 85.8% of the children there was no other severe impairment. Marked learning difficulties were observed: 36% of the children were two years behind their age group and 28% were more than two years behind. The age of initial care decreased over the study period but is still too advanced. Systematic neonatal screening would enable earlier care, which should limit the social and educational impact of hearing loss.