Year : 2015 | Volume
: 21 | Issue : 2 | Page : 134--137
A study of brainstem evoked response audiometry in high-risk infants and children under 10 years of age
Ramanathan Thirunavukarasu, Ganesh Kumar Balasubramaniam, Ramesh Babu Kalyanasundaram, Gitanjali Narendran, Sajee Sridhar
Department of ENT, Thanjavur Medical College, Thanjavur, Tamil Nadu, India
Prof. Ramanathan Thirunavukarasu
Department of ENT, Thanjavur Medical College, Medical College Road, Thanjavur - 613 004, Tamil Nadu
Aims: To evaluate the hearing threshold and find the incidence of hearing loss in infants and children belonging to high-risk category and analyze the common risk factors. Subjects and Methods: Totally, 125 infants and children belonging to high-risk category were subjected to brainstem evoked response audiometry. Clicks were given at the rate of 11.1 clicks/s. Totally, 2000 responses were averaged. The intensity at which wave V just disappears was established as hearing the threshold. Degree of impairment and risk factors were analyzed. Results: Totally, 44 (35.2%) were found to have sensorineural hearing loss. Totally, 30 children with hearing loss (68%) belonged to age group 1-5 years. Consanguineous marriage was the most commonly associated risk factor. Majority (34) had profound hearing loss. Conclusion: Newborn screening is mandatory to identify hearing loss in the prelinguistic period to reduce the burden of handicap in the community. The need of the hour is health education and genetic counseling to decrease the hereditary hearing loss, as hearing impairment due to perinatal factors has reduced due to recent medical advancements.
|How to cite this article:|
Thirunavukarasu R, Balasubramaniam GK, Kalyanasundaram RB, Narendran G, Sridhar S. A study of brainstem evoked response audiometry in high-risk infants and children under 10 years of age.Indian J Otol 2015;21:134-137
|How to cite this URL:|
Thirunavukarasu R, Balasubramaniam GK, Kalyanasundaram RB, Narendran G, Sridhar S. A study of brainstem evoked response audiometry in high-risk infants and children under 10 years of age. Indian J Otol [serial online] 2015 [cited 2019 Sep 19 ];21:134-137
Available from: http://www.indianjotol.org/text.asp?2015/21/2/134/155306
A child's normal speech and language development depend on the ability to hear. The prevalence of hearing loss is 0.5-6/1000 neonates across the globe.  Various audiological procedures are used to assess hearing sensitivity in children such as behavior observation, free field audiometry, visual reinforcement audiometry, play audiometry, etc.  But these tests require cooperation of children and do not give consistent results. Brainstem evoked response audiometry (BERA) is a simple, noninvasive, objective test for early identification of hearing impairment in children and neonates. It can be used as a screening test and is useful in newborns, infants and other difficult to test subjects. In this study, threshold estimation was done using BERA in high-risk infants and children to detect hearing loss and also find the degree of impairment.
Subjects and Methods
This study was conducted among 125 infants and children in the outpatient department of our institution for a period of 1-year from September 2013 to August 2014. Neonates with high-risk factors, children with delayed speech and language development and those who did not respond to sound were included for the study.
Risk factors considered
Consanguineous marriage of parentsFamily history of deafnessBirth asphyxiaLow/increased birth weightDelayed cryPrematurityMental retardationNeonatal jaundiceMaternal infectionSyndromes associated with hearing loss.
Detailed history taking and general and ENT examination were done to rule out external ear and middle ear pathology. BERA was done in dust free, sound proof, air conditioned room. Feed was given 10-15 min before the procedure. Syrup pedichloryl 20 mg/kg was given to sedate the baby half an hour before the procedure. Intelligent hearing system BERA instrument was used. Vertex, forehead and both mastoid regions were cleaned with NuPrep gel, and surface electrodes were applied to Ten 20 electrode gel. Headphones were held in the ear canal. Monaural testing was done. Rare fraction click sounds were given at the rate of 11.1 clicks/s. Totally, 2000 recordings were averaged decreasing in steps of 5 dB starting from 99 dB. The morphology of the graph was noted until wave V is no longer identifiable. The minimum intensity at which wave V is identifiable is taken as the hearing threshold for that individual. Since threshold estimation was the only aim of the study, latencies and inter peak intervals were not considered. The child's hearing sensitivity was assessed based on the following: 
Normal hearing sensitivity ≤25 dBMild hearing impairment 30-45 dBModerate hearing impairment 50-65 dBSevere hearing impairment 70-85 dBProfound hearing impairment 90 dB and above.
Of the 125 infants and children screened, 44 (35.2%) were found to have hearing loss which indicates that risk factors hinder the maturity of the auditory pathway. Among those, 21 were males and 23 were females [Chart 1]. A total of 30 children with hearing loss (68%) are belonged to age group 1-5 years [Chart 2]. A total of 34 children were found to have profound hearing loss [Chart 3].
Among the risk factors evaluated, consanguineous marriage of parents, family history of hearing loss, low/increased birth weight, and neonatal jaundice had a significant correlation with hearing loss [Chart 4]. In this study, hearing threshold was within normal limits in babies with respiratory distress at birth, prematurity and history of maternal infection. This can be explained by efficient treatment facilities available for the above perinatal risk factors. The most common risk factor in children with hearing loss was consanguineous marriage (22 children). In this study, increased birth weight was more significantly associated with hearing loss than low birth weight postulating birth trauma during delivery can lead to hearing loss. The study included one baby with Wardenburg syndrome in whom BERA was normal. Totally, 14 children with hearing loss (31.81%) did not have any identifiable risk factor.
Hearing loss has a detrimental effect not only on the child's ability to speak and learn the language but also communication ability. Hence, early detection and intervention is the key to normal speech and language development. Interventions can vary from sign language to cochlear implantation.
Severe deafness in children is usually due to sensorineural hearing loss rather than conductive loss or auditory processing disorders. Sensorineural deafness can be due to causes such as: (1) Hereditary (genetic), (2) prenatal (rubella), (3) perinatal (kernicterus, birth asphyxia, etc.) and (4) childhood acquired deafness (following meningitis, trauma). 
Brainstem evoked response audiometry, and otoacoustic emission (OAE) are two commonly used objective tests for childhood deafness.  OAEs are widely used in neonatal screening programs as they are quicker to perform. Distortion product OAEs are preferred over transiently evoked OAEs. They provide information about outer hair cell function which is commonly affected in congenital hearing loss. It has a high incidence of false positive results as it is affected by external and middle ear function, which in neonates, is temporarily affected due to amniotic fluid residues. 
Brainstem evoked response audiometry though more time-consuming, is an accurate test for early detection of neural conduction irregularities in the auditory pathway. It is a short latency response. It detects electrical activity from the inner ear to the inferior colliculus. It can be reliably recorded even in premature infants of 30 weeks gestational age. It gives an estimate of degree and type of hearing impairment. It helps to find the cause of delayed speech. It is used to localize the site of lesion in patients with hearing loss and vertigo. BERA is superior to pure tone audiometry in malingering patients. Threshold estimation by BERA is used to identify hearing impairment in neonates thus facilitating early rehabilitation. The existence of peak V is considered as sound stimulus perceived by the ear. Pure tone threshold can be obtained by subtracting 5-10 dB from the point where wave V is just identifiable.
In this study, majority of children with hearing loss belong to age group 1-5 years. Of the 14 children without any risk factors, 10 children fall under age group 1-5 years. Much of the speech and language development occurs during this period. Hence, hearing loss is identified when the child presents with delayed speech. This indicates that neonatal screening can identify such children at an earlier stage which helps in early rehabilitation.
Diagnosing the nature of deafness and localizing the pathology alone is not sufficient. The etiological diagnosis is crucial to reduce the burden of handicap in the society. There has been a shift in the cause of pediatric hearing loss in the last 50 years. Earlier, perinatal infection was the most common cause. But recently inherited causes are on the rise. This is due to availability of advanced treatment facilities for perinatal factors such as birth asphyxia, infections, etc., In 20-50% children, the cause is idiopathic. Consanguineous marriage is commonly practiced in developing countries like India. The siblings of consanguineous marriage have significantly higher incidence of autosomal recessive diseases including hearing impairment (hereditary sensorineural hearing loss).  Hence, awareness should be created among the people to discourage consanguineous marriage. Low birth weight is an established risk factor for hearing loss.  But in our study, birth weight >3.5 kg was more significantly associated with hearing loss. This can be probably due to difficult labor causing head trauma leading to hearing loss. , Delayed cry, birth asphyxia, cerebral palsy, and neonatal seizures can cause brain hypoxia  affecting central auditory pathways leading to hearing loss. In babies with neonatal jaundice, bilirubin toxicity or transient brainstem encephalopathy can cause sensorineural deafness.  This is usually transient and improves with phototherapy. Persistent hearing loss in some cases is due to axonal degeneration and loss of myelin. There are several syndromes associated with hearing loss such as Waardenburg syndrome, Usher's syndrome, Pendred syndrome, etc., The most common syndrome causing hearing loss is Down syndrome which is usually associated with conductive loss. Waardenburg syndrome is a genetic disorder most often characterized by varying degrees of deafness, minor defects in structures arising from the neural crest, and pigmentation anomalies. It accounts for 2-5% of congenital hearing loss. It is commonly associated with sensorineural hearing loss.  But in our study, the child's hearing threshold was normal. Children can develop deafness following meningitis and encephalitis. Of the two babies with febrile encephalitis included in our study, one had hearing loss.
Hearing is not a visible disability. It commonly goes undetected until it affects the child's communication in the form of speech and language. This emphasizes the need for newborn screening. Though congenital hearing loss contributes to a majority of hearing loss in children, it can also occur in the later periods also due to meningitis, encephalitis, complications of prematurity, etc., Screening programs should not only include newborn screening but screening in later periods also based on the risk factors. BERA gives an accurate picture of hearing sensitivity. Hence, in all high-risk babies, BERA should be carried out as a routine procedure to detect hearing impairment. Regular follow-up should be done, and rehabilitative measures should be started as early as possible.
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