Hearing impairment is something that is not easily discernible in adults, much more in babies and little children. Studies have shown that even the slightest hearing impairment can translate to behavioural and learning difficulties in children. Those who suffer from more serious hearing problems can face a lifetime of speech and language deficits, poor academic performance and social and psychological problems. This is because even though the child can hear, he or she is missing some details of what is going on the environment, but cannot understand what is going on. It is thus important that children be screened early in life for hearing problems.
Hearing impairments may be congenital or acquired. Thus, screening for hearing loss should start early, in fact, right after the delivery of the baby. This means that a baby is screened before it leaves the hospital or the maternity clinic.
The two most commonly used hearing screening procedures for babies are (source: American Speech-Language Hearing Association (ASLHA):
- Otoacoustic emissions (OAEs) are inaudible sounds from the cochlea when audible sound stimulates the cochlea. The outer hair cells of the cochlea vibrate, and the vibration produces an inaudible sound that echoes back into the middle ear. This sound can be measured with a small probe inserted into the ear canal. Persons with normal hearing produce emissions. Those with hearing loss greater than 25-30 dB do not. OAEs can detect blockage in the outer ear canal, middle ear fluid, and damage to the outer hair cells in the cochlea.
- Auditory brainstem response (ABR) is an auditory evoked potential that originates from the auditory nerve. It is often used with babies. Electrodes are placed on the head, and brain wave activity in response to sound is recorded. ABR can detect damage to the cochlea, the auditory nerve and the auditory pathways in the stem of the brain.
The initial result of the screening is “pass” or “fail”. Those who pass are considered free from hearing impairment till the next screening. Those who fail require an intensive evaluation by an expert such as an audiologist or an ear specialist. They will be closely monitored for progression of the impairment plus other auditory-related effects.
In the clinical report of the American Academy of Pediatrics (AAP) entitle “Hearing Assessment in Infants and Children: Recommendations Beyond Neonatal Screening”:
“… researchers have developed an algorithm to assist pediatricians determine the course of treatment when a hearing screening indicates hearing loss in children from infants to 18 years of age. Confirmed abnormal hearing test results require ongoing evaluation and intervention by a team of specialists including an audiologist, otolaryngologist, speech-language pathologists and teachers. At least one-third of children with hearing loss will also have a coexisting condition, so they should continue to be monitored for developmental and behavioral disorders and referred for additional evaluation when necessary.”