A nod or a shake of the head, with "ehenawa" (can hear) or "ehenne ne" (can't hear). A boy of seven is undergoing a hearing test. Next in line is a baby of about six months, who takes the test seated in her mother's lap but with different machines. There is a sound and if the baby looks in that direction, she is rewarded with the sight of a dancing bunny in a lit box.
All these tests are now being conducted absolutely free at the premier Lady Ridgeway Hospital for Children in Colombo, whereas till a couple of years ago they were available only in the private sector for a fee.
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| A child undergoing a hearing test at the LRH. |
"Childhood deafness needs to be diagnosed and treated as early as possible," says Consultant ENT Surgeon Dr. A.D.K.S.N. Yasawardene of the LRH, emphasizing that it has a major impact on the child's power of speech.
Treatment is required soon, he stresses, because after about five years of age whatever is done to correct deafness, it might not give the child speech, which is a pity in the light of revolutionary treatment methods for deafness now available in the country.
In those days though childhood deafness could not be diagnosed early, MediScene learns, with modern technology, it can now be detected even in newborns and Sri Lanka has the know-how and the technique.
Explaining that in other countries every newborn is screened for ear problems under the universal neonatal screening programme (UNSP), Dr. Yasawardene says it is very difficult for parents to know at the early stages that the child is deaf. Realization dawns only when the baby is about 6-7 months or even as late as 1 ½ years old.
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| Dr. Yasawardene |
That is why UNSP was initiated with the help of some special tests.
Once the initial screening is done, more advanced testing in the paediatric audiology laboratory follows to ascertain the degree and type of deafness.
Around 24,000 children with ENT problems visit the Ear-Nose-Throat Clinic which operates from Monday to Saturday at the LRH, every year.
The causes of early onset of deafness fall into two categories:
Genetic - One's genes contribute to around 50% of deafness in children in developed countries. Consan-guineous marriages (marriages between relatives) cause more genetic deafness than those between non-relatives. Other cases are due to gene mutations.
Non-genetic - Problems in the mother's pregnancy, pregnancy-related illnesses such as diabetes and hypertension and use of certain drugs during pregnancy such as anti-epileptic medication, oto-toxic drugs, certain antibiotics like aminogycosides and diuretics could cause deafness in the baby. If an expectant mother is exposed to radioactive material the baby could have hearing problems. ("That's why mothers are advised to wear protective guards even when using computers," says Dr. Yasawardene.)
Difficulties during birth such as asphyxiation and infection during delivery could also cause hearing problems. Other factors could be severe jaundice in the newborn, severe head injury or encephalitis or meningitis infections. In most instances if the baby is in the neonatal ICU for more than 48 hours it is considered a risk factor for developing deafness, says Dr. Yasawardene.
Ear problems could occur in any part of the ear - the external, middle or internal ear. The absence or narrowness of the canal in the external ear or an infection or the absence of the small bones in the middle ear could be the cause. "The most serious problem would be if it is to do with the cochlea in the inner ear, because language development would be affected due to the so-called sensorinueral deafness," says Dr. Yasawardene.
A yardstick for the prevalence of deafness among children in Sri Lanka could be the 250 hearing aids provided by LRH every year. Some are funded by the government while kind sponsors also donate hearing aids, MediScene learns.
The tests available to evaluate a child's overall hearing function at the LRH are:
Pure tone audiometry – Hearing is measured at frequencies varying from low pitches (250 Hz) to high pitches (8000 Hz).
Tympanometry – This is a measure of the stiffness of the eardrum and evaluates middle ear function. It is helpful in detecting fluid in the middle ear, negative middle ear pressure, disruption of the ossicles, tympanic membrane perforation, and otosclerosis.
A soft probe is placed in the ear canal and a small amount of pressure applied. The instrument then measures movement of the tympanic membrane (eardrum) in response to the pressure changes. The result of the test is recorded in a visual output, called a tympanogram.
Otoacoustic Emissions – This assesses hearing in newborns and also determines whether the cochlea is functioning. A probe with a tiny speaker and a tiny microphone is inserted into the ear canal, with quiet tones being sent from a speaker, which travel through the middle ear and stimulate the hair cells in the cochlea. The hair cells respond by generating their own minute sounds, which are detected by the microphone. Small babies may require sedation for this test.
It can measure the hearing threshold (level) in any age group. If there is a hearing loss, the hair cells in the cochlea do not generate these minute sounds.
Brain Stem Evoked Response (BSER) – This is a simple, non-invasive test which measures the conduction of nerve impulses along the auditory nerve to the brainstem.
If there is a tumour pressing on this nerve, it will usually slow the nerve conduction velocity. If the BSER is abnormal, an MRI (Magnetic Resonance Imaging) test may be required.
After the tests, the interventions must begin.
The follow-up in any intervention is vital, says Dr. Yasawardene, adding that it is the parents' responsibility to bring the children for clinic visits when required.
Back to hearing
The interventions include the use of a hearing aid, surgery to correct any malformation or the latest revolutionary cochlear implants.
A hearing aid is a machine which amplifies desired sounds to desired levels. "It is not just an amplifier," says Dr. Yasawardene. It is generally worn behind the ear. Earlier it was analog but now with the transition to digital there have been marvellous results. The machine comes from the manufacturer but the ear mould should be made in the country itself because it has to be custom-built."The introduction of the hearing aid, will be followed by listening therapy and also speech therapy. The child must wear it about eight hours a day," he says.
Thereafter, the child should be fitted into a suitable educational system, be it a mainstream class or a special class and for that the educational authorities must work together with the health authorities. "The Special Education Unit must liaise with the Health Ministry to place such students," urges Dr. Yasawar-dene. In some countries, MediScene understands, there is a special FM microphone which the teacher wears, with another small gadget being fixed to the child's hearing aid during the lesson so that the child can concentrate on what the teacher is saying. Hearing aids could cost from Rs. 10,000 to 150,000 but if one buys in bulk there could be a reduction in the prices, says Dr. Yasawardene.
A cochlear implant is a surgically implanted electronic device that provides a sense of sound to a child who is profoundly deaf or severely hard of hearing. The cochlear implant is often referred to as a "bionic ear". Unlike hearing aids, the cochlear implant, costing between Rs. 1.5-2.5 million, does not amplify sound, but works by directly stimulating any functioning auditory nerves inside the cochlea with the electric field stimulated through an electric impulses. External components of the cochlear implant include a microphone, speech processor and a RF transmitter. Similarly a RF receiver is implanted beneath the skull's skin, says Dr. Yasawardene. For the first time in Sri Lanka's state health sector, the LRH is hoping to carry out a cochlear implant in September. |
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