Sensorineural hearing loss is a serious neurodevelopmental    sequel   among high-risk neonates and is one of the most common congenital ailments. In the literature, its incidence varies from 2.5 to 17%. [1] Neonatal hyperbilirubinemia occurring in perinatal period makes neonate more prone to hearing impairment. In 70% term & 80% preterm neonates during first week of life, jaundice is commonly found. After delivery, newborn is exposed to increased oxygen concentration and increased bilirubin production. Bilirubin can cross blood-brain barrier & precipitate in different parts of nervous system like basal ganglia, brainstem, cerebellum & hippocampus. The prevalence of newborn & infant hearing loss is estimated to be 1.5 to 6 per 1000 live births. [2]

The risk factors according to the Joint Committee on Infant Hearing are family history, hyperbilirubinemia at serum levels requiring exchange transfusion, ototoxic medications, other findings associated with a syndrome known to include a sensorineural and/or conductive hearing loss. [2-4] Temporary & permanent changes in evoked potentials can occur by even transient increase in bilirubin level. Bilirubin toxicity has a serious impact on superior olivary nucleus, lateral lemniscus & inferior colliculus.  One of the most important cause due to which child is unable to speak is hearing impairment. If hearing loss gets detected at the earliest, then early satisfactory intervention is possible & there will be improved speech & language. This will maximize linguistic competence & literacy development of deaf  children  so  that  these  children  will not  fall  behind their hearing   peers  in terms of communication, reading, social  & emotional development.[5,6]

Brainstem evoked response audiometry is a neurophysiological test that assesses whether  central  auditory pathway  which  includes  structures  from  auditory  nerve  to  rostral  brainstem is functional or not. It is an objective tool which can detect neonatal deafness and assess auditory pathway’s  maturation.[7,8]

With the advent of BERA, detection & quantification of hearing impairment has been easier in pediatric patients who are unable to cooperate with routine testing.[9]

BERA output deviations from normal  would  suggest  a  central  auditory pathway dysfunction. These deviations can  be  used  to  diagnose sensorineural hearing loss due to disease, lesions at various points within this system & neurotoxicity & neurophysiological derangements in at risk cases.[10]

AIM & OBJECTIVE

Aim of the study was to determine hearing impairment in children affected by pathological jaundice & correlate it with gender.

This study was conducted in Department of Physiology, Electrophysiology research laboratory, SGT Medical College, Hospital & Research Institute, SGT University, Faculty of Medical and Health Sciences, District Gurugram, Haryana.  Children under 1 year of age referred from the pediatrics department after pre-evaluation by the ENT department of SGT Hospital to SGT Medical College’s Physiology department were selected for the study.

Inclusion Criteria

Age less than 1 year & History of pathological jaundice.

Methodology

Instrument used was two channel, PC based, NEUROSTIM-NS2, of Medicaid firm. Test procedure was done on patients whose hair were washed the night before the test, no chemicals, oils or lotion were applied on the scalp. A prior ENT check-up was done to rule out possibility of wax, ear infection or middle ear problems etc. Children’s parent/guardian were briefed about the procedure & written informed consent by the parents/guardians was obtained. Patients were properly fed before the test was done. Patients were sedated with syrup Pedichloryl 30-50mg/kg body weight or made fast asleep before the test was conducted. The scalp electrodes were placed according to the 10-20 International system of EEG electrode placement after preparing the skin. The ground electrode (fz) was placed at forehead, reference electrode (Cz) was placed at the vertex, at both mastoids active electrodes were placed (Ai & Ac).

Acoustically shielded ear phones were placed on the ear. Monaural auditory stimulus consisting of rare faction clicks with intensities in decreasing order were delivered to the patient’s ears. Contralateral ear was masked. Alternate polarity was used. Analysis time was 10 ms. About 2000 responses were averaged. The existence of peak V was considered as sound stimulus heard and perceived.

Statistical analysis

At the end of the study, the data was analysed statistically by using appropriate statistical methods.

Out of 20 patients, 11 were male & 9 were female, 13 were neonates & 7 were in post-natal age group, 18 had abnormal results (90%), maximum abnormal being male children & neonates. Latency of waves I & III were significantly prolonged. Latency of wave V was highly significantly prolonged. There was highly significant prolongation of inter-peak latency I-V. Latency of wave II of right ear of patients were significantly correlated with gender difference.

INFERENCE OF THE STUDY POPULATION

Table 1: Latency & Inference

Table 2: Prolongation of Inter-Peak Latency I-V

Table 3: Relation between Latency II & gender

BERA is auditory evoked responses arising from 8th cranial nerve, cochlear nucleus, superior olivary nucleus, lateral leminiscus & inferior colliculi. Evoked responses arise within first 10 ms of auditory stimulation. Hyperbilirubinemia in infantile period if severe affects brain causing bilirubin precipitation in nervous system, kernicterus & sensorineural hearing loss. Agarwal et al. also found significant correlation in prolongation of latency & inter-wave intervals with serum bilirubin more than 25 mg%.

Latency I was prolonged in our studies which was comparable to findings of Agarwal & Perlman but other authors observed that latency I is not prolonged due to non-involvement of cochlear nerve11-13.

Latencies of waves III & V were also prolonged in our study in consonance with other  studies11-13. Ramanathan et al.14 found that incidence of hearing loss in infants & children belonging to high risk category was 35.2 %  & 68% belonged to 1-5 years age group with 34 out of 125 children having profound hearing loss.

Isman et al found that increase in BERA latency in neonates with hyperbilirubinaemia is more significant for later waves (III & V) than for earlier waves, & I-V inter-peak latency increased significantly15-16. There is both central & peripheral auditory impairment in such children.

BERA is simple, objective, non-invasive, reliable investigative tool especially in difficult & uncooperative patients. It detects early phases of bilirubin toxicity on neural auditory pathway & hence subclinical auditory impairment. It is especially useful in newborns who cannot exhibit additional lethargy or hypotonia due to some pre-existing medical condition or treatment.

Pathological jaundice especially in neonatal age group is a risk factor for sensorineural hearing loss. Children screened by BERA at the earliest have chances of early rehabilitation. There should be proper follow up of such children for auditory evaluation by BERA. Further studies should be undertaken to correlate serum bilirubin levels with hearing impairment in a larger number of patients.

1. Borradori C, Fawer CL, Buclin T, Calame A. Risk factors of sensorineural hearing loss in preterm infants. Biol Neonate 1997;71:1-10.
2. American Academy of Pediatrics. Joint Committee on Infant Hearing 1994 position statement. Pediatrics 1995;95:152-6.
3. Joint Committee on Infant Hearing. American Academy of Audiology, American Academy of Pediatrics, American Speech-Language-Hearing Association. Directors of Speech and Hearing Programs in State Health and Welfare Agencies.Year 2000 position statement: principles and guidelines for early hearing detection and intervention programs. Pediatrics 2000;106:798-817.
4. Meyer C, Witte J, Hindmann A, et al. Neonatal screening for hearing disorders in infants at risk:incidence, risk factors, and follow-up. Pediatrics 1999;104:900-904.
5. Hyde ML. Newborn hearing screening programs: Overview. J Otolaryngol 2005;34(Suppl 2):S70810.
6. Nelson HD, Bougatsos C, Nygren P. Universal newborn hearing screening: Systematic review to update the 2001 US Preventive Services Task Force Recommendation. Pediatrics 2008;122:e266–76.
7. Samani F, Peschiulli G, Pastorini S, Fior R. An evaluation of hearing maturation by means of auditory brainstem response in very low birthweight and preterm newborns. Int J Ped Otorhinolaryngol 1990;19:121-7.
8. Ferber-Viart C, Morlet T, Maison S, Duclaux R, Putet G, Dubreuil C. Type of initial brainstem and risk factors in premature infants. Brain Dev 1996;18:287-93.
9. Hecox KE, Cone B, Blaw ME. BERA in the diagnosis of pediatric neurological diseases. Neurology. 1981;31:832-9.
10. Devyn Lambell, Joseph LA, Waco. The Auditory Brainstem Response: History and Future in Medicine, May-2013.
11. Agarwal VK, Shukla  R, Misra   PK, Kapoor  RK, Malik  Brainstem  auditory evoked response in newborn with hyperbilirubinemia. Ind J Peditr 1998: 35; 513-518.
12. Gupta AK, Anand NK, Raj H. BAER-a diagnostic tool in neonatology.IndPediatr 1990; 27:1039-1044.
13. Perlman M, Fainmesses P, Shohmer H, Tameris H, WazyPersmer B. Auditory nerve brainstem evoked response in hyperbilirubinemia. Pediatr 1983; 72: 703-708.
14. Ramanathan T, Balasubramaniam GK, Kalyanaundarsam RB, Narendhran G. A study of brainstem evoked response audiometry in high risk infants & children under 10 years of age. Indian J Otology 2015;21:134-7.
15. Al-Kandari JM, Alshuaib WB. Newborn hearing screening in Kuwait. Electromyogr Clin Neurophysiol. 2007;47(6):305-13.
16. Jafar I, Mangunatmadja I, Rohsiswatmo R, Suwento SR, Malik SG. Brainstem evoked response audiometry in healthy term neonates with hyperbilirubinemia. Paediatr Indones. 2010;50:144-8.