HEARING SCREENING IN NEWBORNS

Ali Ravanbod(Medical student)

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WHY IS EARLY IDENTIFICATION OF HEARING LOSS IMPORTANT?

Early identification and intervention can prevent severe psychosocial, educational, and linguistic repercussions. Infants who are not identified before 6 months of age have delays in speech and language development. Intervention at or before 6 months of age allows a child with impaired hearing to develop normal speech and language.

NEWBORNS HEARING LOSS

Hearing loss is one of the most common congenital anomalies, occurring in approximately 2-4 infants per 1000. Prior to implementation of universal newborn screening, testing was conducted only on infants who met the criteria of the high-risk register (HRR). It was found that the HRR was not enough, given that as many as 50% of infants born with hearing loss have no known risk factors.

Misconception Clinical Fact

Parents will know if their child has a hearing loss by the time their child is 2-3 months of age.

Prior to the universal screening, the average age at which children were found to have a hearing loss is 2-3 years. Children with mild-to-moderate hearing loss were often not identified until 4 years of age.

Parents can identify a hearing loss by clapping their hands behind the child's head.

Children can compensate for a hearing loss. They use visual clues, such as shadows or parental expressions and reactions, or they may feel the breeze caused by the motion of the hands.

The HRR is all that is needed to identify children with hearing loss.

The HRR misses approximately 50% of all children with hearing loss.

Hearing loss does not occur often enough to justify the use of universal screening programs.

Hearing loss affects approximately 2-4 per 1000 live births, and it has been estimated to be one of the most common congenital anomalies.

There is no rush to identify a hearing loss. The loss does not need to be identified until a child is aged 2-3 years.

Children identified when they are older than 6 months can have speech and language delays. Children identified when they are younger than 6 months do not have these delays and are equal to their hearing peers in terms of speech and language.

Children younger than 12 months cannot be fitted with hearing aids.

Children as young as 1 month of age can be fit with and benefit from hearing aids.

1-3-6 PLAN All infants will access hearing screening no later than 1 month of age

All infants not passing initial screening and subsequent rescreening should have confirmatory audiological and medical evaluations no later than 3 months of age

All infants with confirmed permanent hearing loss should receive early intervention as soon as possibleno later than 6 months of age

CONTINUED …

children identified as early as age 7-12 months had lower receptive and expressive language quotients than those of children identified by age 6 months. No significant difference was found between children identified at age 7-12 months and those identified at age 25-30 months.

HIGH RISK FACTORS:

•Family history of permanent childhood sensorineural hearing loss

•In utero infection such as cytomegalovirus, rubella toxoplasmosis, or herpes

•Craniofacial anomalies, including those with morphological abnormalities of ear

•Hyperbilirubinemia at a serum level requiring exchange transfusion

•Bacterial meningitis

•Syndromes associated with progressive hearing loss such as neurofibromatosis, osteopetrosis

•Head trauma

•Premature infants in the neonatal intensive care unit.

MODALITIES FOR PERFORMING HEARING SCREENING

Otoacoustic emissions (OAEs).

Auditory brainstem response (ABR) .

OAEOAEs are used to assess cochlear integrity and are physiologic measurements of the response of the outer hair cells to acoustic stimuli. Sounds are presented to the ear canal and a small microphone measures the response in the ear canalFast objective screening test to evaluate the function of the peripheral auditory system, primarily the cochlea, which is the area most often involved in sensorineural hearing loss. Quicker to perform than ABR.

There are two types of otoacoustic emissions tests which are used clinically. These are: 1. Transient (TEOAEs): These are evoked responses from stimulating the cochlea with a transient signal such as a click or tone burst acoustic signal. TEOAEs are a wide frequency response in the 500 to 4,000 Hz range. They typically do not occur when hearing loss is about 30 Dbhl or greater.

2. Distortion Product (DPOAEs): These are evoked response OAEs from stimulating the cochlea with two simultaneously presented pure tones of different frequency. This type of OAE may be recorded in individuals with a greater degree of hearing loss at higher frequencies. DPOAEs are typically measured in the frequency range of 750 to 6,000 Hz although many OAE devices are capable of measuring at higher frequencies.

AUDITORY BRAINSTEM RESPONSE

AABRAuditory brainstem response (ABR) is a neurologic test of auditory brainstem function in response to auditory (click) stimuli. AABR measurements are generally obtained by placing disposable surface electrodes high on the forehead, on the mastoid, and on the nape of the neck . The click stimulus (usually set at 35 dB hearing level [HL]) is delivered to the infant's ear via small disposable earphones designed to attenuate background noise.ABR is reliable after 34 wks postnatal age.ABR is the preferred screening method to evaluate hearing loss in NICU graduate.

AUDITORY BRAINSTEM RESPONSE

Sounds are presented and surface electrodes measure brainstem activity

Average test time 30-45 min/baby

Auditory Structure OAEs ABRs/AABRs

Outer ear Yes YesMiddle ear Yes YesInner ear Yes YesAuditory nerve No YesAuditory brainstem No Yes

ASSESSMENT OF THE AUDITORY SYSTEM BY OAES AND ABRS/AABRS

Although OAE screening continues to be cost effective in the well-baby nursery, OAE screening followed by AABR is a reliable protocol .

NICU >5 days in NICU ABR should be included to screen for neural loss

Rescreen BOTH ears, even if only one ear fails

Non pass – refer to Audiologist

Readmission – rescreen before discharge

Well baby nursery Screen with OAE or ABR

Repeat screen when necessary before discharge

When using 2 step protocol test order should be OAE then ABR

Rescreen BOTH ears, even if only one ear fails

PROTOCOL FOR NEWBORN HEARING SCREENING PROGRAM

PROTOCOL FOR NEWBORN HEARING SCREENING PROGRAM

THANK YOU FOR YOUR ATTENTION!