Having targetted the infants under 6 months of age for Hearing assessment , we need to discuss the specific AUDIOMETRY TESTS that help us explore Deafness ( Hearing Loss) for timely and corrective interventions.
1. OAE = OTOACOUSTIC EMISSION Test
- It measures Outer Hair Cell response in Cochlea.
- This screening test measures the sound waves produced in the inner ear. A tiny probe is placed in the ear canal. The probe delivers a low volume sound stimulus into the ear. The Cochlea responds by producing an OTOACOUSTIC EMISSION often described as an Echo , that travels back through the middle ear to the ear canal and is analysed by the screening unit
- Otoacoustic Emissions are sounds given off by one small part of the Cochlea, when it is stimulated by soft clicking sounds. When the sound stimulates the cochlea, the outer hair cells vibrate . These vibrations produced a nearly inaudible sound that echoes back into the middle ear.
- This newborn screening test, OAE, detects only the shortfall in Cochlear Functioning.
- Result of OAE TEST is either PASS or REFER
- If the result is REFER, repeat after 15 days.
- If two tests show REFER, do ABR TEST ( BERA) for correct diagnosis.
OAE TEST is easy to perform, takes just few minutes and is user-friendly. Best done at the first visit in the neonatal period.
2 . # ABR TEST = AUDITORY BRAINSTEM RESPONSE ( also termed as BERA ) … It is a diagnostic tool for more definitive diagnosis of Hearing Loss.
ABR measures the Electro-Physiologic activity in Auditory Nerve and BRAINSTEM pathways.
Electrodes placed on the child’s head detects the response to the sounds, presented through earphones.
- Up-to six months age, it is performed during natural sleep.
- Beyond six months, it is performed under sedation.
- TWIN BENEFITS of ABR TEST
- Detects the general level of hearing, up-to the Brainstem.
- It also gives frequency specific Hearing Data
- Diagnostic ABR can also be performed with bone conduction to separate Conductive Deafness from Sensorineural Deafness
- ABR is the gold standard for determination of Hearing Thresholds in infants younger than six months of age.
For older children Hearing assessment can be done by VRE = Visual Reinforced Audiometry, by an experienced Audiologist.
Other Audiometry Tests are ASSR , Tympanometry , Play Audiometry and Conventional Pure Tone Audiometry.
Children with unilateral or mild Hearing Loss should be evaluated further, as they are at the same risk of compromised Communication Skills and lagging Social / Emotional / Educational development.
This Blog has been reviewed by two experts, namely :
- Dr . Abraham Paul – Kerala
- Dr . Parul Valia – Vadodara.
I am obliged by their kind support and guidance.
Dr . Dhananjay Shah
Ped. Practice of 40 years
@ Rajkot. Gujarat.