Hearing loss may be present since birth or may occur later at any age. It is possible to help individuals with hearing loss, provided intervention is done early. The first step towards early intervention is early diagnosis of hearing loss.
NEWBORN HEARING SCREENING
Hearing loss in newborns is more common than generally believed. A child can develop speech and language only if he/ she can hear well. It is possible for a child with hearing loss to hear, and to acquire speech and language, provided intervention is done at the earliest.It is crucial that hearing screening, follow-up audiological evaluation and intervention be done as early as possible whenever hearing loss is suspected.
The Joint Committee on Infant Hearing (JCIH), which comprises of a team of health professionals, recommends a 1-3-6 protocol. This means that hearing screening should be completed by 1 month of age, hearing loss diagnosed by 3 months of age and intervention be no later than 6 months.
Newborn babies can be screened with the help of Otoacoustic Emissions (OAE) testing, or Automated ABR testing at birth before they are discharged from the hospital. The result may be a ‘Pass’ or ‘Refer’. If the screening result is a ‘Refer’ there may be a possibility that the baby has hearing loss. These babies need a re-testing at 3 weeks. Even if only one ear showed a ‘Refer’ at the initial test, both ears should be re-tested. If the re-testing also shows a ‘Refer’, the baby needs to undergo a battery of audiological tests such as a diagnostic BERA / ABR, Behavioral audiometry (BOA), etc. to confirm the findings.
Infants who pass the neonatal screening, but have a risk factor such as hyperbiluribinemia, sepsis, etc., should have at least 1 diagnostic audiology assessment by 24 to 30 months of age. Children with cytomegalovirus (CMV) infection, syndromes associated with progressive hearing loss, neurodegenerative disorders, trauma, or postnatal infections associated with sensorineural hearing loss, who have received extracorporeal membrane oxygenation (ECMO) or chemotherapy, or have a family history of hearing loss may require early and more frequent assessments.
Every infant with confirmed hearing loss should also be assessed by an otolaryngologist (ENT surgeon).
Studies have reported that children identified and treated prior to three months had more advanced language abilities at 12 to 16 months than infants identified after 3 months of age. (Vohr et al. Early Language Outcomes of Early-Identified Infants With Permanent Hearing Loss at 12 to 16 Months of Age. Pediatrics. 2008; Vol 122(3).)
Thus, every child’s hearing should ideally be tested at birth, soon after birth and as soon as hearing loss is suspected. A baby’s hearing can be tested even if he/she is a few days old. This can help in instituting early intervention so that the child can function at par with his /her hearing peers.
HEARING EVALUATION IN OLDER CHILDREN
Sensorineural hearing loss when seen in older children may actually be a congenital hearing loss (hearing loss since birth), which has remained undetected. In some cases the hearing may have been normal at birth but may have gradually worsened. In other cases it may be a delayed onset hearing loss, which has occured following infections, meningitis, certain medications or trauma.
Hearing loss in older children needs to be evaluated so that appropriate intervention can be instituted.
Some of the tests required for a complete audiological evaluation in such children are:
- Behavioural observation audiometry (BOA)
- Play audiometry
- Visual reinforcement audiometry (VRA)
- Pure Tone Audiometry
- BERA / ASSR
- Otoacoustic emissions (OAE)
HEARING EVALUATION IN ADULTS
Adults may develop sensorineural hearing loss following certain viral illnesses, meningitis, noise exposure, drug toxicity, or trauma. They may also have a progressively worsening hearing loss, which may occur due to genetic causes or may be age related hearing loss seen in the elderly. Hearing loss in adults also needs to be diagnosed and treated early as sound deprivation for a prolonged period can gradually lead to speech impairment. Pure tone audiometry (Unaided & Aided i.e. without and with hearing aids) and Speech Audiometry are some of the most commonly used tests for hearing assessment in adults.