Of Hearing and Hearing Loss

Dr Rohan Gupta
What’s the activity which we do every moment while awake! We breathe, we see, and we HEAR! Today we are going to discuss everything related to Hearing and Hearing loss and its treatment! Indeed, Hearing is a very important function, isn’t it?? Just imagine life without Sound!! In fact, it’s hard to imagine a life without Sound! We all enjoy the JOY OF SOUND!
Today, on World Hearing Day, which is celebrated on 3rd March, every year , emphasis is laid on educating the masses about Hearing Health related matters.

world hearing day

Deafness means loss of hearing and it may be partial or total. Hearing impairment cannot be seen and hence its effects are not visible to others, so deaf suffers in silence. Unlike blindness, deafness often provokes ridicules rather than sympathy. The consequences for a child born with hearing loss are quite severe. It is well established that a child with hearing loss cannot develop speech and language abilities. This puts the child at a disadvantage in school, higher education, and limits future professional opportunities. The problem of the child deaf from the birth is quite different from that of an adult who has become completely deafened after school age or in adult life. The hard of hearing person whose deafness has developed slowly over the years is different again. But, for all of them, the handicap is the same – the handicap of the silent world, the difficulties of communicating with the hearing and speaking world.
It is important to note that without hearing a child cannot develop speech and language. Hence, the aim should be to recognize deaf child before the age of 1 year because till 3 years onwards neural plasticity of brain’s auditory cortex (the area in brain responsible for hearing and speech and language development) is maximum and gradually reduces if adequate auditory stimulation is not there. Unfortunately, hearing loss is often not detected until a child is 2, 3, or even 4 years old, especially in rural areas due to the poor awareness about deafness and its relationship with speech and language development.
The best strategy to ensure that children with hearing loss are identified and treated early is to ensure that every baby is screened for possible hearing loss at the birth in hospital. Early detection and consequent treatment leads to better speech development in children, enhanced scholastic achievements in school, and limitless professional opportunities. This strategy has been implemented in countries such as USA, Singapore, Australia, UK, and many more and has shown great results.
Unfortunately, India does not have such a program in place. There is clearly a need for a “universal newborn hearing screening” program in India.
I urge every parent to screen their newborn babies for hearing. I also humbly request the paediatrician community in India to give hearing screening the same level of importance as vaccination. Thus, focus should be on Early Detection of Newborn Hearing Loss and Intervention.
For mild to moderate deafness, there are assistive devices known as Hearing Aids which can provide significant benefit to improve the hearing and hence resulting in better Speech and language outcomes.
But here we are talking about the more severe form of deafness, i.e., Severe to Profound Hearing Sensorineural Hearing loss. It is for this form of deafness, that we have a technological miracle called Cochlear Implant.
A cochlear implant is probably one of the best inventions in the recent history of medical science for bilateral severe-profound deaf. It is the first device that can restore one of the five senses.
Cochlear Implant System is an implantable bio medical electronic device consisting of an internal component called Cochlear Implant and an external component called Speech/Sound Processor. The external component includes the microphone, battery, speech processor, external magnet, and transmitter antenna. The internal components include the internal magnet, antenna, receiver-stimulator, and electrode array. Sound is first detected by a microphone worn on the ear and subsequently converted into an electrical signal. This signal is then sent to an external sound processor, where, according to one of the several different processing strategies, is transformed into an electronic code. This digital signal is transmitted via radiofrequency through the skin by a transmitting coil that is held externally over the receiver-stimulator by a magnet. Ultimately, this signal is translated by the receiver-stimulator into rapid electrical impulses distributed to multiple electrodes on an array implanted within the cochlea (specifically, the Scala tympani). The electrodes, in turn, electrically stimulate spiral ganglion cells and auditory nerve axons, which then travel to the brain for further processing. By using these signals to systematically regulate the firing of intracochlear electrodes, it is possible to convey the timing, frequency, and intensity of sound.
The basic evaluation of CI candidates involves a medical, audiometric, and radiographic evaluation. A thorough otologic medical history should attempt to determine the aetiology of the hearing loss. Most pediatric CI candidates are prelingual deafened children, who are born with SNHL due to genetic mutations (e.g., connexin 26), perinatal environmental exposures, or unidentified (idiopathic) causes.
Candidacy for cochlear implantation relies heavily on the audiological evaluation. These assessments include otoacoustic emissions, auditory brainstem response testing, auditory steady-state responses, and behavioural testing. A hearing aid trial of at least 3 months was the earlier norm although now with candidacy being clearer and with linkage of better outcomes with early implantation, sometimes this is bypassed to save crucial time especially if child is above 1.5 years of age. Currently, the FDA requires children to be ?12 months of age; however, the age limit is lower in several European countries and some centers in the U.S. are implanting children as young as 6 months old.
Radiographic assessment is important to ensure that there are no contraindications to implantation, particularly complete labyrinthine aplasia, cochlear aplasia, cochlear nerve aplasia, and complete cochlear ossification.
In children, earlier implantation generally yields more favourable results. Post lingual deafened children or adolescents have excellent outcomes, achieving greater than 80% word understanding after implantation. In comparison, prelingual deafened children make slower progress toward oral communication and with more variable outcomes, but generally catch up to the post lingual deafened children by approximately 36 to 60 months postoperatively. Outcomes also depend on the surgery, the quality of habilitation, the device type, Unilateral or Bilateral intervention. Similarly, among prelingual deafened children, those implanted earlier (in the first year of life) perform better on word recognition testing compared with those implanted in the second or third year of life.
This entire program is collectively called as Cochlear Implant program as it involves various disciplines like Audiologists, Paediatrics, ENT Surgeons trained in Cochlear Implantation, Special educators, Speech therapists, Social workers, teachers and most importantly the parents.
At SMVD Narayana Superspecialty hospital, these Cochlear Implant Surgeries are happening quite consistently since past 6 years and more than 45 such surgeries have been performed successfully with zero rate of complications. These included many bilateral surgeries (implanting both the ears at the same time), with youngest being at 1 year of age and surgeries in difficult anomalies like Mondini’s (incomplete partition 2) etc. With availability of state-of-the-art facilities in the OT, it has become so easy for patients of J&K to get treated in their own state rather than struggling to go to Delhi/ Chandigarh. This has enabled faster, more economical yet high quality treatment. Moreover, Shri Mata Vaishno Devi Shrine board also supports families with BPL card with funding for this treatment!
(The author is consultant SMVD Narayana Super Specialty Hospital, Katra)