ENT-Head & Neck Department, MITERA General & Children’s Hospital, Athens, Greece.

12th International Congress of the European Society of Pediatric Otorhinolaryngology

31 May 2014 – 03 Jun 2014
Dublin – Ireland

Introduction:

An otoacoustic emission (OAE) is a sound which is generated from within the inner ear. Having been predicted by Thomas Gold in 1948, its existence was first demonstrated experimentally by David Kemp in 1978and otoacoustic emissions have since been shown to arise through a number of different cellular and mechanical causes within the inner ear.Studies have shown that OAEs disappear after the inner ear has been damaged, so OAEs are often used in the laboratory and the clinic as a measure of inner ear health.

Method:

There are two types of otoacoustic emissions: spontaneous otoacoustic emissions (SOAEs), which can occur without external stimulation, and evoked otoacoustic emissions (EOAEs), which require an evoking stimulus. OAEs are considered to be related to the amplification function of the cochlea. In the absence of external stimulation, the activity of the cochlear amplifier increases, leading to the production of sound. Several lines of evidence suggest that, in mammals, outer hair cells are the elements that enhance cochlear sensitivity and frequency selectivity and hence act as the energy sources for amplification. One theory is that they act to increase the discriminability of signal variations in continuous noise by lowering the masking effect of its cochlear amplification.

We use transient-evoked OAEs. TEOAEs are evoked using a click (broad frequency range) or tone burst (brief duration pure tone) stimulus. The evoked response from a click covers the frequency range up to around 4 kHz, while a tone burst will elicit a response from the region that has the same frequency as the pure tone.

43.810 neonates were tested from January 1998 until December 2012. 17.406 of them were in NICU and the rest 26.404 in the clinic.

Results:

NICU neonates : Positiv OAEs : 16.283           93,55%

                        Negative OAEs: 1.123             6,45%

Clinic neonates : Positive OAEs  : 24.973           94,58%

                         Negative  OAEs : 1.431             5,42%

Total neonates that need to be re-examine after a month : 2.554

They came back for re-examine 1.969 neonates (only 77,10%).

Positive OAEs : 1.792         91%

Negative OAEs : 178          9%

These 178 neonates need further audiological and neuro-otological examine!

Conclusion:

Otoacoustic emissions are clinically important because they are the basis of a simple, non-invasive, test for hearing defects in newborn babies and in children who are too young to cooperate in conventional hearing tests. Many western countries now have national programmes for the universal hearing screening of newborn babies. Periodic early childhood hearing screenings program are also utilizing OAE technology. The primary screening tool is a test for the presence of a click-evoked OAE. Otoacoustic emissions also assist in differential diagnosis of cochlear and higher level hearing losses (e.g., auditory neuropathy).