Which of the following tests is recommended for neonatal screening of hearing?
Correct Answer: Evoked OAE
Description: Ans. c. Evoked OAE (Ref: Nelson 20/e p3075-3079; Dhingra 5/e p116)Evoked otoacoustic emission (OAE) is recommended for neonatal screening of hearing.Neonatal/Infantile Hearing ScreeningAmerican Academy of Pediatrics endorses the goal of universal detection of hearing loss in infants before 3 months of age, with appropriate intervention no later than 6 months of age.The recommended hearing screening techniques are either otoacoustic emissions (OAE) testing or auditory brainstem evoked responses (ABRs).ABR test is an auditory evoked electrophysiologic response that correlate highly with hearing.OAE tests, used successfully in most universal newborn screening programs, are quick, easy to administer & inexpensive, and they provide a sensitive indication of the presence of hearing loss.Results of OAE are relatively easy to interpret.OAE tests elicit no response if hearing is worse than 30-40 dB, no matter what's the cause.Children who fail OAE tests undergo an ABR for a more definitive evaluation.Screening methods such as observing behavioural responses to uncalibrated noisemakers or using automated systems such as the Crib-o-gram or the auditory' response cradle are not recommended.Otoacoustic EmissionsDuring normal hearing. OAEs originate from the hair cells in the cochleaOAEs travel through the middle ear to the external auditory canal, where they can be detected using miniature microphones.Transient evoked OAEs (TEOAEs) may be used to check the integrity of the cochlea.In neonatal period, detection of OAEs can be accomplished during natural sleep.TEOAEs can be used as screening tests in infants and children for hearing at the 30 dB level of hearing loss.If a hearing loss is suspected based on the absence of OAEs, ears should be examined for evidence of pathology, and then ABR testing should be used for confirmation & identification of type, degree & laterality of hearing loss.Types of Otoacoustic Emissions (OAE)Spontaneous OAE (SOAEs)Sounds emitted without an acoustic stimulus (i.e, spontaneously).* SOAE are seen in 25-80% of neonates with normal hearing & absence of SOAEs is not necessarily abnormalTransient evoked OAE (TEOAEs)Sounds emitted in response to an acoustic stimuli of very short duration;usually clicks but can be tone-bursts* TOAEs commonly are used to screen infant hearing, to validate behavioural or electrophysiologic auditory thresholds & to assess cochlear functionDistortion product OAE (DPOAEs)Sounds emitted in response to 2 simultaneous tones of different frequencies* Particularly useful for early detection of cochlear damage as they are for ototoxicity & noise-induced damage.Sustained -frequency OAE (SFOASEs)Sounds emitted in response to a continuous tone* SPOAEs are responses recorded to a continuous tone.Advantages of using OAE as a screening test: Less time consuming & cost lower than ABRInfants who fail the OAE test are then screened using ABR.
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