EBNEO COMMENTARY: RISK STRATIFICATION OF SENSORINEURAL HEARING IMPAIRMENT IN PRETERM INFANTS

[EBNEO]

Dr Chidi Anakebe, Dr Sohaib Bin Nawaz, and Dr Haji Sheeraz Khan from the UK review the article Hemmingsen D, Moster D, Engdahl BL, Klingenberg C. Sensorineural hearing impairment among preterm children: a Norwegian population-based study. Arch Dis Child Fetal Neonatal  Ed 2024;0: F1–F7. doi:10.1136/archdischild-2024-326870 for EbNeo.

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Acta Commentary:

Acta Paediatrica - 2024 - Anakebe - EBNEO Commentary Risk stratification of sensorineural hearing impairment in preterm.pdf

The incidence of moderate to severe bilateral hearing deficit (>50 dB) is estimated to occur in 1–3 per 1000 live births in healthy infants and 2–4 per 100 infants admitted to the NICU.¹SNHI can lead to developmental delays as well as psychological and mental health issues, which adds to the existing challenges of being born prematurely.²

Risk factors associated with SNHI include family history of hearing loss, craniofacial anomalies, complex congenital abnormalities, congenital infections (such as TORCH), low birth weight, prematurity, hyperbilirubinemia requiring exchange transfusion, use of ototoxic medications, bacterial meningitis, a low Apgar score (<7 at 5 min), mechanical ventilation for at least five days, and NICU care lasting >7 days.^2, 3

This extensive study included over 60 000 preterm infants over a 16-year period, focusing on the risk of SNHI in preterm infants born between 22 and 36 weeks. It allowed a follow-up period of five years to capture cases of late-onset hearing impairment. The findings align with previous studies, showing a higher prevalence of SNHI (1.4%) in preterm infants compared to the reference group (0.7%), with the highest risk observed (5.2%) in extreme preterm infants (gestational age 22–27 weeks). The increased incidence of SNHI in younger gestational age is related to the development of the auditory system, as the structural auditory system develops in the first 20 weeks of life, while the neurosensory system only becomes functional around 25 weeks.⁴ Insults to this developmental process can result in varying degrees of hearing impairment.

Routine hearing screenings for infants involve non-invasive methods such as otoacoustic emissions (OAE) and confirmatory Auditory Brainstem Response (cABR) testing.¹ Infants with hearing loss due to neural conduction disorders or auditory neuropathy may require ABR testing, as OAE alone may not detect their SNHI.³ This study made use of either diagnostic methods which may not have captured all infants with hearing impairment (HI) due to neurodysfunction. It also did not grade the severity of HI nor disclosed cases of isolated conductive HI and other forms of HI were broadly classed as ‘unspecified’.

Other limitations of this study include:

• No grade of the severity of intracranial hemorrhage or periventricular leukomalacia, despite considering them as risk factors for SNHI.
• No clear definition of non-invasive ventilation, making it unclear what types of respiratory support were included.
• Did not specify the treatment methods used for jaundice in infants.
• No data analysis of uni/bilateral hearing impairment.
• No information on infants who received hearing aids or cochlear implants.
• Data were collected from five mandatory health and social registries in Norway, though Norway has 17 national health registries,⁵ and no explanation was given on registry selection.
• The study did not mention other potential congenital infectious variables, such as congenital cytomegalovirus infection.⁶

Overall, while this study provides valuable insights into the prevalence and risk factors of SNHI in preterm infants, addressing these limitations could further enhance understanding in this area.