Authors: Sudhir Rughani*, Bhadresh Vyas**, Vikas Sinha***, Maulik Shah****, Yamini Kapileshwarkar*****, Sonal Shah******
Resident Pediatrics, **Professor & Head Pediatrics, ***Dean & Professor & ENT, ****Associate Professor Pediatrics, *****Assistant Professor Pediatrics, ******Additional Professor Pediatrics
Institution: Department of Pediatrics, Otolaryngology and Head and Neck Surgery, M.P. Shah Medical College, Jamnagar-361 008, (Gujarat), India
Dr. Bhadresh Vyas
Prof. & Head Pediatrics
M.P. Shah Medical College
Jamnagar-361 008 (Gujarat), India
It is crucial to timely diagnose hearing impairment in infants as early intervention can lead to decreased morbidity and better prognosis. This study analyzes and compares the incidence of hearing loss in normal as well as high risk newborns. A nonrandomized, cross sectional study of 306 newborns less than two months of age was conducted in the settings of the NICU, high-risk clinic as well as well-baby clinic in the Department of Pediatrics, MP Shah Medical College, Jamnagar, India with the support of the ENT Department from March 1, 2010 to September 30, 2010 (6 months). All newborns (with or without risk for hearing loss) were considered eligible to be included in the study. Written consent of the parents was obtained. Patients were screened for hearing loss by Otoacoustic Emissions (OAE) testing in a soundproof room. The result of the test was noted in terms of PASS/REFER (FAIL). The overall incidence of hearing impairment in the study population of 306 newborns was found to be 8.2%. Out of the total study population of 306, the incidence of hearing impairment in 100 newborns having high-risk factor(s) was 22%. The incidence of hearing loss in newborns not having any of the high-risk factors (206) was 1.46%. The risk of hearing impairment increases as the number of high-risk factors increases. Even in the newborns without any risk factors, the incidence of hearing impairment was 1.46%, which is very hig. Thus we recommend hearing screening should be done in all newborns. A national newborn screening program which includes hearing screening should be implemented at all levels of health care facilities.
Hearing loss is the most important sense which we have. It is far more important than just warning us of dangers, it serves as the basis of communication and is the first step in learning language. Language is also important for acquiring social skills, developing proper emotional support and in advanced learning and academic achieving. Future employment and economic self-sufficiency are to a large extent dependent upon the early detection and habilitation of hearing loss. A child first hears, then speaks, reads then writes. If one does not hear, then the written language is very difficulty to learn. Helen Keller stated:
" I am just as deaf as I am blind. The problems of deafness are deeper and more complex, if not more important than blindness. Deafness is the much worse misfortune. For it means the loss of the most vital stimulus -- the sound of the voice that brings us language, sets thoughts astir, and keeps us in the intellectual company of man."
Usually parents are less concerned about hearing impairment as compared to vision and motor milestones. When these problems are found later in life in the post lingual phase, determining the time for intervention is extremely difficult. Hearing loss in infants should be recognized as soon as possible after birth. If gone undetected, the lack of stimulation will damage and prevent the proper development of the central auditory nervous system. Ideally, auditory intervention should begin before six months of age, surgery at a later age depending upon the diagnosis. The most critical period of language development is between 0 to 3 years.1
If the hearing loss is corrected at the right time, it can help to improve the outcome of those disabilities, improve quality of life, and decrease direct as well as indirect morbidities due to the disabilities. As advances in medical care, especially critical neonatal care, has led to increased survival of preterm infants and critically ill newborns, it is important to monitor the incidence of other morbidities such as hearing loss in NICUs (Neonatal Intensive Care Units). Otoacoustic Emission (OAE) and Auditory Brainstem Response Audiometry (ABR) are the diagnostic auditory assessments in infant hearing screening.
This report is aimed at studying and comparing the incidence of hearing loss in normal as well as high-risk newborns. Some risk factors for hearing loss were identified on the basis of this study.
A nonrandomized cross sectional study of 306 newborns, less than two months of age was conducted in the setting of the NICU, high-risk clinic as well as the well-baby clinic in the Department of Pediatrics, MP Shah Medical College, Jamnagar, India with the support of the ENT Department, from March 1, 2010 to September 30, 2010 (6 months). All newborns (with or without risks for hearing loss) were considered eligible to be included in the study. Written consent of the parents was taken for participating in the study. A detailed history and examination of the newborn was performed and the patient was screened for hearing loss by Otoacoustic Emissions (OAE) testing in a soundproof room. OAEs measure the peripheral auditory system, which includes the outer ear, middle ear, and cochlea. OAEs are produced in the cochlea. It is thought to be produced by the mechanical vibration of the outer hair cells in a sensory feedback loop. The middle and outer ear must be disease free and able to transmit the sound back to the recording microphone. In the current study, OAEs were used to screen for the the presence of normal versus abnormal hearing but more in-depth testing can be performed for the evaluation of individual frequency bands.
The result of the test was noted in terms of PASS/REFER (FAIL). The threshold level for hearing impairment was set to 15 dB. Patients having hearing impairment above 15 dB will be recorded as a failed OAE test. Those who were having hearing impairment below 15 dB were recorded as a passed OAE test. Four types of otoacoustic emissions are: Spontaneous otoacoustic emissions (SOAEs), transient otoacoustic emissions (TOAEs) or transient evoked otoacoustic emissions (TEOAEs), distortion product otoacoustic emissions (DPOAEs) and Sustained-frequency otoacoustic emissions (SFOAEs). For infant hearing screening, both DPOAEs and TOAEs are used.2
Babies with the following risk factors were identified as high-risk newborns:
• Birth Weight ≤ 1.5 kg
• Maturity ≤ 34 weeks
• Birth Asphyxia
• Kept on ventilator
• NICU Stay ≥ 2 days
• Ototoxic drugs given
The total number of infants included in the study were 306 (159 males and 147 females), out of which 100 babies had risk factors for hearing impairment (58 males and 42 females). Out of the 100 patients with a presence of one or more risk factors for hearing impairment, 22 (22%) showed hearing impairment. While out of 206 patients without any risk factors, 3(1.46%) showed hearing impairment. On applying the X2 test, X2 value is 35.182, the P value is less than 0.0001. The difference of hearing impairment found between the above groups (with and without risk factors) is highly statistically significant. The infants with high-risk factors for hearing impairment are at a significantly higher risk than those infants who have no risk factors for hearing impairment present.
In this study of 306 patients, 25 (8.2%), showed hearing impairment. There are scanty surveys showing incidence of hearing impairment in India but in one such study, Kumar, et al, in 1997 demonstrated an incidence of 6.3% of cases in an urban population.3
Table 1 demonstrates that most of the risk factors listed lead to increased risk of hearing impairment in newborns. Birth asphyxiated newborns are at higher risk for hearing impairment than their peers without birth asphyxia.
Only 7 patients had symptomatic hypoglycemia, out of whom, only 1 was found to have a hearing impairment. Neonates who have been exposed to ototoxic drugs are at the higher risk of hearing impairment than those who have not been exposed.4 Out of 3 patients with congenital anomalies, no patient was found to have hearing impairment by OAE. A larger sample size will be needed to make firm conclusions regarding the observed risk factors.
Table II shows that as the number of risk factors for hearing impairment increases, the risk of hearing impairment also
In the present study, we used OAE test as a screening test. To enhance the sensitivity and specificity, and for confirmation of the diagnosis, we need to have an Auditory Brainstem Response Audiometry which was not available in our center so we used OAE as a single test for hearing screening. It is advisable to do both tests for screening hearing in newborns. A National newborn screening program which includes hearing screening should be implemented at all levels of health care facilities. Community awareness regarding screening of hearing should be increased. More studies are required to find out other risk factors for hearing loss like symptomatic hypoglycemia. The newborns with high-risk factors for hearing loss should be identified and should be screened in time so that proper interventions can be made before it gives rise to permanent disability. Follow-up is required for those patients who are found to have hearing impairment for further evaluation and management in the appropriate center. Newborns found to have hearing loss should be referred to tertiary health care for disability limitation and rehabilitation. Hearing screening, disability limitation and rehabilitation should be included in appropriate health programs.
Newborns having the following risk factors are at higher risk of developing hearing impairment.
• Hyperbilirubinemia requiring exchange blood transfusion.
• Birth asphyxia.
• Administration of ototoxic drugs.
• Requirement of ventilator support during neonatal period.
• NICU stay for ≥ 2 days (Intensive newborn care).
• Birthweight ≤1.5 Kg.
1. Kapoor S, Kabra M. Newborn screening in India: current perspectives. Indian Pediatr. 2010 Mar;47(3):219-24. View Abstract
2. McPherson B, Li SF, Shi BX, Tang JL, Wong BY. McPherson B, Li SF, Shi BX, Tang JL, Wong BY. Neonatal hearing screening: evaluation of tone-burst and click-evoked otoacoustic emission test criteria. Ear Hear. 2006 Jun;27(3):256-62. View Abstract
3. Kumar S. Deafness and its prevention--Indian scenario. Indian J Pediatr. 1997 Nov-Dec;64(6):801-9. View Abstract
4. Rybak LP, Whitworth CA. Ototoxicity: therapeutic opportunities. Drug Discov Today. 2005 Oct 1;10(19):1313-21.