Importance of assessing hearing in a new-born child

Hearing assessment in children is one of the dark areas in our discipline in spite of the fact that 2 out of every 100 children under 6 years of age have permanent bilateral deafness above 60 dB (i.e. moderate deafness). The incidence of severe bilateral congenital sensorineural deafness where a child is born with practically no hearing has been reported to be between 1 to 4 out of every 1000 live births in different studies carried out in different countries. It is believed to be about 3 in our country. Half of this is genetic in origin and the other half is due to acquired conditions like prenatal rubella, use of ototoxic drugs during pregnancy etc. To this large group of congenital deafness cases is added another very large group of childhood acquired deafness e.g., post-meningitis deafness / deafness after neonatal jaundice and the group of late-onset genetic deafness where the deafness is of genetic origin but is not congenital i.e., not present from birth and develops later in life like in Alport’s syndrome. Unfortunately, the deafness remains undiagnosed in a very large portion of these cases and when the deafness is finally diagnosed, it is already too late i.e., the child has reached an age where remedial measurers will not be adequately effective. The efficacy of remedial measures is reduced as the child gets older and after the child is about 3-4 years old the remedial measurers to teach the child proper speech and language are practically ineffective. A deaf / hearing-impaired child cannot learn language as language can only be learnt through hearing. As the deaf child does not learn language, the child cannot speak i.e. the child becomes mute. A child may be born deaf but is very rarely (practically never) born with a defect in language learning faculty. It is always the treating clinician’s callousness that delays the diagnosis of the deafness and makes a deaf child develop mutism (inability to speak). We have to change our social system so that these unfortunate children are recognised early so that their deafness can be corrected before the brain loses its power to learn language. The consequences of hearing impairment in a child are sinister and the implications of hearing loss in a child are not limited just to inability to hear or inability to speak. The handicap is much more than this.

A hearing impaired child develops psychological, social, educational and even cognitive problems. This happens even if the child is partially hearing impaired and not totally deaf. Even minor hearing deficits in a child do have sinister consequences. Hearing impairment in a child cannot be taken lightly and should be dealt with all seriousness. It is now known that the critical language learning period of a child is from birth to about three and half years of age. If the child has a hearing loss during this age, the language learning faculty of the brain becomes impaired. It is hence, imperative that the child has perfect hearing during this critical age for normal development of speech and language. If a child has a hearing impairment, the hearing impairment must be corrected before the child reaches six months of age. Late detection of the hearing loss and / or late remediation of the hearing loss will yield very poor results as regards development of speech and language in the child. Studies by many scientists especially that of M C Cowkey et al (2004) here confirmed that access to sound through devices such as cochlear implants / hearing aids at the youngest age possible gives children the best opportunity to acquire communication skills (speech and language) which is similar to their normally hearing peers.

Language and communication serve as the foundation for all forms of development (including sensorimotor development) of the child and hence delays in the acquisition of these skills affect the overall development of the child. The first year of the child is critically important for proper development of the auditory centers in the brain. The auditory centers in the brain are the specialized parts of the brain which process the auditory impulses once they reach the brain. The ears sense the sounds and pass the sensory data to the auditory processing centers in the brain. Here the sound is processed and only then can the subject make sense of the sound i.e. understand what a particular auditory cue means and also utilize the sound for other purposes like respond reflexly to a particular sound (e.g., we spontaneously turn away from a warning sound like a dog’s bark but a mother automatically turns towards her child’s cry). So these auditory processing centers in the brain are very important not only for our hearing but also for our survival. This is explained in more details in the section on central deafness/auditory processing disorders in the relevant section of this book. Every time a sound stimulates the auditory centers in a very young child, new connections develop in the brain. The growing network of connections in the developing child enables the child to make sense of the sounds, especially the complex sounds of language and generate connections between the auditory system and the other parts of the central nervous system. This network within the brain develops best in the very young child as the plasticity of the brain is at its maximum in the very early years of life. The clinician has to capitalize on this and if one misses out on this opportunity and the remedial intervention is delayed, the child will never develop normal speech / language. If the child has a hearing impairment, the auditory centers in the brain are not stimulated and the new neural connections in the brain are not made.

This cannot be done later on as the plasticity of the brain reduces drastically as the child grows older. It is hence essential that the child has access to sound be it through hearing aids or cochlear implants (or some surgery like myringotomy in case there is effusion in the middle ear) at the youngest possible age while the plasticity of the brain is still at its maximum level. There just cannot be any compromises on this. Yet then, there is unfortunately no denying of the fact that hearing loss in neonates / infants / young children remain undetected in the majority of cases (except in those places where the universal neonatal hearing screening program is effectively followed), though modern diagnostic methods are available by which reasonably accurate hearing tests are possible even in neonates and infants.

This unfortunate condition stems from the fact that children especially new-borns, infants and neonates and even the pre-school going children are difficult to confirmatively assess by our routine and the common clinical tests and investigations which apply to patients aged above 5 years. However, in spite of the difficulty in assessing or diagnosing this special group of clients (i.e., those aged 0 to 5 years), it behooves the society not only to identify the deafness, and undertake remedial measures as early as possible as very efficient diagnostic measures are now available for this. The first point in the diagnosis is that the parents must suspect that there is a probable hearing loss in the child and then take the child to the hospital for the hearing assessment. We must educate the public on when to suspect deafness and how to suspectit. This is all the more necessary as we do not have the Universal Neonatal Hearing Screening system in our country. The importance of this cannot be over-emphasised. It is our ethical, professional and social commitment to diagnose these unfortunate cases very early, since delaying the diagnosis may permanently deny the child the benefits of modern science and make the child a burden to the society. It costs the Government very dearly to rear such children and to take care of them when they grow up as they remain severely handicapped. It is much easier that we spend a little of our resources in spreading awareness and educating society on the importance of early identification of deafness and early remedial measures.

It has been my experience that whenever a parent (especially the mother) brings a child suspecting that the child is deaf, the parent is very rarely wrong. The parent’s convictions should never be dismissed without a very thorough audiological and clinical work-up. Irresponsible advises like “Wait and See” or “The child will improve its hearing as it grows up” are deplorable and must be avoided at all costs. Misleading statements like this from doctors have been the cause of irreparable damage in numerous children. So we need to teach doctors and health service providers also.

The remedy of congenital hearing loss lies in early identification of deafness and in the earliest possible institution of remedial measures in children where deafness is detected. The best process for early identification of deafness is neonatal hearing screening i.e. performing a hearing test as soon as the child is born. This process is in force in many places throughout the world and in most of the advanced countries neonatal hearing screening has been made compulsory by suitable legislature. Two types of neonatal hearing screening are practiced. The most effective one is the “Universal Neonatal Hearing Screening” program. In this method, all live births are screened for hearing impairment within 48 hours of birth. This has 100% specificity and no case of congenital hearing loss is missed. The other process is known as the “High Risk Neonatal Hearing Screening” program. In this process only babies born out of high risk pregnancies are screened for deafness. A specific list of “high risk” conditions has been enunciated and only babies born out of such types of pregnancies are made to undergo the hearing screening test. Babies not born out of high risk pregnancies do not have to undertake the hearing test. The specificity of this “high risk neonatal hearing screening” program is 50% only i.e. only half of all children having congenital hearing loss are identifiable if this program is followed, but the advantage of this process is that only a few babies have to go through the hearing screening test and so the costs incurred by the health provider are much lesser as compared to the “universal” program where each and every live birth is screened for hearing loss. The disadvantage of the “high risk hearing screening” program is that 50% of congenitally deaf babies remain unidentified as hearing loss is not restricted only to “high risk” pregnancies and 50% of congenitally deaf babies are born out of normal pregnancies and not high risk pregnancies.

In places where the universal neonatal hearing screening program is not in vogue or cannot be practiced due to infrastructural constraints, the neonatal hearing screening should essentially be done in each and every birth where there has been any one of the following conditions (high risk register) viz :

history of in utero infections such as rubella, cytomegalo virus, herpes, toxoplasmosis, syphilis
history of use of ototoxic drugs by the mother during pregnancy
history of excessive intake of alcohol by the mother during pregnancy
history of prolonged / hazardous labour
any illness that necessitated admission of the child in a neonatal intensive care unit (NICU) immediately after birth
any illness requiring hospitalization for 48 hrs or more in the first 4 weeks of birth
birth weight of the baby below 1500 grams
Apgar score below 4 at 1 minute or below 6 at 5 minutes after birth
any recognizable syndrome at birth where hearing loss is a known component of the syndrome like Down’s syndrome, Treacher-Colin’s syndrome etc.
family history of permanent marked sensorineural hearing loss
presence of any craniofacial anomalies including anomalies of the pinna and ear canal.
baby born out of consanguineous marriage

The above conditions constitute the high-risk register and a neonatal hearing screening is a must in all such cases. Over and above this, the International Joint Committee on Infant Hearing Screening has further recommended that in between the ages of 4 weeks to 2 years, a hearing screening test should always be done in the following conditions viz.

parental concern regarding the requisite development of speech, language and hearing.
delayed developmental milestones.
identification of any syndrome like Usher’s syndrome where a hearing loss is expected to be present.
any history of post-natal infections like bacterial meningits, encephalities
neo-natal indications like hyperbilirubinemia (neonatal jaundice with history of exchange transfusion), pulmonary hypertension.
presence of known neurodegenerative disorders like Hunter syndrome or sensorimotor neuropathies like Friedreich’s ataxia.
any history of head trauma
recurrent or persistent otitis media with effusion for more than 3 months.
ambiguous neonatal hearing screening test result.

The society should spare no effort to ensure that any hearing impairment in a child does not remain undetected. Unfortunately even many doctors are also unaware of this. Everybody needs to be made aware of this viz. the educated and uneducated public, doctors and social workers. Congenital or even deafness acquired in early childhood will lead to inadequate development of language/communicative skills, which in turn will lead to lack of access to education. This will result in social isolation for the child and makes the child an object of ridicule which is extremely detrimental to the cognitive/social/emotional/psychological development of the child. The consequences of lack of education and social isolation will be a potential inability to earn a decent living when the child grows up. The child will hence be a burden to the society and offering social security to such a handicapped child or even an adult will cost the government very dearly. It is much more judicious and cost-effective to undertake the universal (or if that is not feasible, at least a “high-risk”) neonatal hearing screening program such that the hearing impaired neonates / infants are detected early enough for the remedial measures to be fully effective. The government needs to spread this message to the population and this is possible only through mass media services of the government, through postering, videos, publication of booklets, holding seminars etc etc.