Hearing loss can range from a mild impairment to profound loss. Conductive hearing loss is largely preventable and can be managed by medicine/surgery. Sensor neural hearing loss may need fitting with hearing aids.
Early identification of hearing loss in newborn and young children is of critical as he develops language and speech by hearing to his surroundings.
In general neonates and infants could be tested by BERA, children in the age group of 2 – 3 yrs could be screened using free – field audiometry, children above 4 yrs could be conditioned and then a audiometry can be performed to test hearing impairment.
Babies should be screened for hearing at birth especially high risk ones.
Child with mild hearing loss is generally labeled as inattentive or slow learner. Hearing should be tested as child grows at any time on slightest suspicion of hearing deficit by Parents, care givers, teachers and family doctors.
Screening for hearing has been done for many years but still does not detect hearing impairment as early as desirable. Mother’s instinct for her child is usually correct even at early age and should not be neglected.
The type of tests used to identify hearing loss depend on the age of the child, and include:
* Behavioural observation audiometry (BOA) – for babies less than seven months of age.
It consists of making noises, such as shaking a rattle close to ear, and then observing the baby’s response.
* Distraction method – it is formalized method of behavioral observation audiometry for children 7-19 months.
Infant sits on mother’s lap and one tester standing in front uses toys to raise attention. Other tester behind the child presents signals like shaking a rattle, or drum beat. First tester observes the child’s response. Response may be head turn, eye turn, frowning, sucking etc. After each response the signal intensity used to elicit a response is measured.
* Visual reinforcement orientation (VRA) – useful for children 7-30 months of age. The baby is taught to move their head towards sound by pairing it with an interesting visual stimulus, located in the direction of the speaker. Their response to different sounds can then be measured. Test is done in sound proof room with speaker and headphone. The ears can be tested individually if the baby tolerates headphones.
* Performance audiometry test – older children are taught to respond to sounds by a performing a simple action or playing a game, such as dropping a marble when they hear the sound.
* Oto-acoustic emission – certain sounds generated by the inner ear can be recorded to check the function of the tiny hair cells in the cochlea.
* Auditory brainstem response testing – to check the electrical activity in the brain in response to a sound. Electrodes are placed on the head to measure the brain waves. It is most popular test for neonatal hearing assessment and for detection of hearing loss.
* Transtympanic Electrocochleography – to check the cochlea for signs of electrical activity in response to sound. It is better indicator of hearing threshold than any other auditory evoked response in children. An electrode is threaded through the eardrum to touch the cochlea and it requires general aneasthesia in children.
* Impedance audiometry or Tympanometry – a probe which snugly fits into the ear and air is pumped into the ear canal. Neonates and young infants may be examined so long as the probe tone is 660 Hz and not 220 Hz. Stapedius reflex are used to assess middle ear disfunction. Impedance audiometry is not an alternative to behavioral audiometry.t