ASSESSMENT OF THE EFFECT OF HYPOXIA AND SEIZURES ON NEONATAL AUDITORY FUNCTION BY USING ABR

Abstract

SUMMARY H earing is the means by which the newborn comes into contact with the world of sound and with language structures. It is through oral language that humans are able to make contact with their fellowmen, and develop the ability to share their experiences, thoughts and ideas in the search for new knowledge. Hearing loss presents high incidence, affecting around 3 out of every 1,000 live births, and from 2 to 4 out of every 100 newborns leaving the neonatal intensive care unit (NICU). The initial signs of hearing loss are very subtle and systematic neonatal hearing screening is the most effective means of early detection. Early diagnosis and immediate intervention are decisive factors in the development and prognosis of these children. Because of the high risk of hearing impairment the National Institutes of Health recommend hearing screening of all infants at a NICU before discharge. The hearing loss risk indicators, as well as the use of objective methods for performing hearing screening and follow-up were established and reviewed by the Joint Committee on Infant Hearing (JCIH). For hearing screening in the newborns AABR, ABR and OAE test have been used. AABR and OAE can be used alone or, preferably, together. Prior studies have shown the successful use of auditory brainstem response (ABR) hearing screening in the neonatal intensive care setting. The present study was designed to determine the prevalence of hearing impairment by ABR in newborns admitted to the neonatal intensive care unit during the study period, to determine distribution of common risk factors in newborns with hearing affection and to assess the effect of hypoxia and/or convulsions on auditory function of neonates. This was done through evaluation of 60 neonates, admitted to neonatal intensive care unit (NICU) in Ain Shams University. They were classified as 40 newborn with suggested risk factors for hearing impairment and 20 healthy stable newborns as control group. Neonates included in this study had the following criteria: term babies with birth weight >2500 g; absence of family history of deafness; Serum bilirubin less than phototherapy limits; Apgar score ≤5 at 1 and/or ≤6 at 5 min; Perinatal hypoxia; Respiratory distress syndrome; Requiring artificial ventilation lasting for 5 days or longer; Bacterial meningitis; History of attacks of seizures. 22 (36%) out of 60 neonates had sensorineural hearing loss. Out of 20 neonates with seizures, 10 neonates had impaired ABR results. 22 neonates out of 26 mechanically ventilated neonates had impaired ABR results. Upon screening 24 neonates with low apgar score, It was found that 20 of them had failed the ABR test. There was statistically significant association between hypoxia (p<0.001), convulsions (p=0.02) and impaired ABR results. Conclusion It was found that there is statistical relation between perinatal hypoxia, convulsions and impaired ABR results. The prevalence of hearing loss in the study population, using ABR was 36%. Therefore, it is essential for all newborns who present isolated or associated risk factors to undergo hearing screening.