NEW BORN HEARING SCREENING

HEARING LOSS

Incidence Over all: 1-3 per 1000 live births

In NICU: 2-4 per 100 NICU Graduates.

Etiology

1.Genetic A) mutation in connexin 26

B) As part of syndromes - alport syndrome - wardenberg syndrome - pendred syndrome - usher syndrome

2. Non genetic - secondary to injury to developing auditory system - infection , hypoxia, ischemia, oto toxic medication, hyperbilirubinemia, metabolic disease.

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THE HIGH RISK REGISTER

Family history of hereditary childhood sensorineural hearing loss. TORCH infections. Craniofacial anomalies. Low birth weight. Hyperbilirubinaemia at the level of exchange transfusion. Bacterial Meningitis. Ototoxic medications. Mechanical ventilation for more than 5 days. Syndromes known to include conductive or sensorineural hearing loss.

SCREENING TESTS

1. AABR (automated auditory brainstem response )

2. OAE (Oto acoustic emissions).

BERA Potentials recorded form ear and vertex in response to brief auditory stimulation to assess the conduction through auditory pathway up to the midbrain.

Waveform compononents. waves generators wave I -- viii nerve wave II -- cochlear nucleus wave III -- superior olivary n. wave IV -- lateral leminiscus wave V -- inferior coliculi Auditory brainstem response evaluation (sensitivity 90% Specificity 70-90%)

Normal BERA classic baep consists of 5-8 vertex positive peaks initial 5 are of clinical interest obligate BAEP waves are 1,3,5. 2,4,6,7, can absent in some normal subjects, but absence of any obligate wave is abnormal.

Abnormal BERA

Absolute latency interaural difference wave (IT5) – prolonged I-V interpeak interval interaural difference- prolonged Absolute latency of wave V- prolonged as compared to normative data.Absolute latencies and interpeak intervals latencies I- III, I-V, III-V- prolonged as compared to normative data Absent auditory brainstem response in involved ear.

Recording electrodes

E1

E2

V

NEONATAL NEUROLOGICAL DISEASE AND PROBABLE REGION OF INVOLVEMENT

HIE Cochlea, cochlear nucleus, inf. Colliculus.

Hyperbilirubinemia

Cochlear nucleus, inf. Colliculus, +/- 8th N. and cochlea

Meningitis 8th N.

Congenital viral infection

8th N. , cochlea.

ICH Cochlea.

OAE sounds which arise in the ear canal when (paradoxical) the TM received vibration transmitted backwards through the middle ear from the cochlea.

first measurement reported in 1978 by David Kemp from the institute for laryngologist and otology

The 4 types of otoacostic emission are as follows.

1. SOAEs (spontaneous otoacoustic emission) – sound emitted without an acoustic stimulation.

2. TOAEs (transient otoacoustic emission) - sound emitted in response to an acoustic stimuli of very short duration, usually clicks but can be tone bursts.

3. DPOAEs (distortion product otoacoustic emission)- sound emitted in response to 2 simultaneous tones of different frequencies.

4. SFOAEs sustain-frequency otoacoustic emission)- sound emitted in response to a continuous tone.

Cont……

For infant hearing screening both DPOAEs and TOAEs used.

RECORDING -- insert a soft probe tip in the ear canal to obtain a hermetic seal, similarly to immittamse audiometry.

FACTORS THAT CAN BE AFFECT OTOACOUSTIC EMISSIONS

poor probe tip placement or poor seal.

Cerumen occluding the canal or blocking a probe part

Vernix caseosa in neonates

Debris and foreign body in outer ear canal

Uncooperative patients

OAE vs BERA more easy to perform rapid 2-10 min. vs 1.5 hrs for ABR less expensive

sensitivity Specificity

BERA 97-100% 86-96%

OAE 84% 92%

NEWBORN HEARING SCREENINGEFFICACY OF EARLY IDENTIFICATION AND INTERVENTION.-The implementation of universal screening programmed has caused the definition of early identifation as early as 3 months with intervention by 6 months. - Diagnostic OAE and ABR testing is recommended for any infant who does not pass the second screening session. Both tests are necessary to differentially diagnose an infant’s hearing impairment.

Auditory structure OAEs BERA

Outer ear Yes yes

Middle ear Yes Yes

Inner ear Yes Yes

Auditory nerve No Yes

Auditory Brainstem No Yes

Flow chart for infant with hearing loss

(failed screening for BERA,OAE)

Repeat after 2 wks

normal Diminished hearing

Cont…

Mild, mod, deafness

H . Aid/ speech therapy

Rpt. Test 3 months, exclude progressive hearing loss.

Mod, sev, to profound deafness

h. Aid speech therapy

Aided audiometry and h. aid

Adequate help – cont. re-hab.

Inadequate help

Cochlear implants

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