Permanent Childhood Hearing Loss in Infants with Hypoxic Ischaemic Encephalopathy: Incidence and Risk Factors

Objective: To study the incidence of permanent hearing loss in infants with hypoxic ischaemic encephalopathy (HIE) and the risk factors associated with hearing loss.

Study design: A single centre retrospective cohort study was completed in all term and near term infants with HIE over 9 years (2010-18). Newborn screening with one/two stage protocol was carried out initially (automated otoacoustic emissions only or with automated auditory brainstem testing if baby in NICU for more than 48 hours) of all babies with HIE. Babies with Stage 2 and 3 HIE were cooled. Those who failed this protocol had diagnostic auditory brainstem testing (ABR) which identified the hearing loss as sensorineural or auditory neuropathy spectrum disorder. Aetiological investigations were done to rule out other causes of sensorineural hearing loss including MRI IAMS, cytomegalovirus and Connexin 26 testing.

Results: Ninety-nine babies were eligible and 8 died. Ten out of 91 babies failed the newborn screen. Of the 10, 8 (8.8%) had permanent hearing loss. Six out of 8 babies had bilateral sensorineural hearing loss, 1 had unilateral sensorineural hearing loss and 1 had unilateral auditory neuropathy spectrum disorder. Permanent hearing loss was associated with low Apgar score at 1 and 5 min (CI 0.5, 3.9, p=0.01), persistent pulmonary hypertension (p=0.0002, CI-0.5,-0.2) and loop diuretics (CI-0.4,-0.1, p=0.0002). Permanent hearing loss was found in all grades of HIE.

Conclusion: This study adds to the previous studies indicating that there is high incidence of permanent hearing loss seen in term and near term babies with HIE (cooled as well as not cooled). Further studies with larger samples are needed to study the risk factors in this cohort and compare the incidence of hearing loss in cooled versus not cooled babies.

What’s new: This study confirms that permanent hearing loss of all degree and severity can occur in all grades of hypoxic ischaemic encephalopathy. It indicates that auditory neuropathy spectrum disorder can develop secondary to HIE. Association between low Apgar score at 1 and 5 min, PPHN, loop diuretics and development of permanent hearing loss is significant and needs to be explored further.

Keywords: Permanent hearing loss; Hypoxic ischemic encephalopathy

Abbreviations: PCHI-Permanent childhood hearing impairment; SNHL-Sensorineural hearing loss; HIE-Hypoxic Ischaemic Encephalopathy; NHSP-Newborn hearing screening programme; AOAE-Automated otoacoustic emissions; AABR (Automated auditory brainstem testing); BSA (British society of audiology); dbHL (decibel hearing loss); NICU- Neonatal Intensive Care Unit