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General information

• Types of Permanent Childhood Hearing Impairment
• Prevalence
• Diagnosis
• Early intervention and outcomes
• International perspective
• Australian perspective
• Hearing screening in Victoria
• The expanded program
• Aims

Types of Permanent Childhood Hearing Impairment

Permanent childhood hearing impairment may be congenital (one that a child is born with) or acquired (one that first develops when the child is older).   Sometimes, hearing loss can also be progressive, ie get worse over time.   It may involve both ears ("bilateral") or just one ear ("unilateral").

A permanent hearing impairment usually happens because there is an abnormality somewhere along the hearing pathway.  The abnormality may be in the outer ear, middle ear, or inner ear (usually the cochlea).  Very occasionally, the abnormality is in the nerve (neural) pathway inside the brain, somewhere between the ear and the auditory cortex.  Neural abnormalities are more common in babies who have been in the neonatal intensive care unit (NICU).

Hearing impairment is measured in decibels (dB).  Levels of hearing loss are typically described as mild, moderate, severe and profound.  As a guide, a child with a mild hearing loss can't hear sounds quieter than about 26-40 dB; a child with a moderate loss, 41-65 dB; a severe loss, 66-95 dB, and a profound loss pushes the hearing threshold above 95 dB.   Children with normal hearing can usually hear sounds quieter than 15 dB. (Note: there are several slightly different classifications available.)

Sound Level Guide

Level (dB) Sound Source
10  30  40  50  60  70  80  90  95   110	Breathing  Whispering Sound level of a quiet library Rainfall, refrigerator Normal conversation Freeway traffic Ringing telephone Tractor Electric drill Jackhammer, aeroplane taking off

Source: League for the Hard of Hearing: Facts on Noise

The newborn hearing screen aims to detect bilateral moderate, severe or profound congenital hearing impairment. 

Acquired or progressive hearing loss may only be detectable later in infancy or childhood.  The newborn hearing screen is not designed to reliably detect mild hearing loss (though some mild losses will be detected because of the screen).  The screen will also detect unilateral losses (ie hearing loss in one ear, with normal hearing in the other ear).

Prevalence

It is hard to be sure exactly how common permanent childhood hearing impairment is.  However, for every 1000 babies born, approximately one baby will have a moderate, severe or profound hearing loss in both ears. In other words, around 60-70 Victorian babies are born with bilateral moderate or worse congenital hearing loss every year.  In the NICU units prevalence of hearing loss at birth increases to around 2% (Van Straaten HL, et al. 2003. Acta Paediatrica 92:332-8).

Diagnosis

Children who receive a 'refer' result after a second hearing screen are referred for further testing.  This is called a Diagnostic Audiology Assessment, and is performed by a specialist in hearing (Audiologist).  The aim of the assessment is to get as complete picture of an infant's hearing as possible at that time.
The diagnostic test used is the Auditory Brainstem Evoked Response (ABR) test.  Sensors similar to the ones used in the screen will be placed on the baby's forehead with some sticky gel.  Soft clicking sounds will be played through headphones or earplugs to the baby. 

The baby's response to these sounds is recorded.  This gives information about the softest level of sound a baby can hear, and help to confirm whether further testing or interventions such as amplification (eg hearing aids) or special education may be recommended.

The baby may also have an Oto-Acoustic Emission test (OAE).  A small soft tipped ear-piece is placed in the outer part of the baby's ear and soft sounds played.

Early intervention and outcomes

International research suggests that early diagnosis and intervention such as amplification (hearing aids or cochlear implants) and special education helps most children with a hearing loss.  Usually, children who are diagnosed and receive intervention before the age of 6 months demonstrate better speech and language development and learning skills than those who are diagnosed at a later age.¹

Without a screening program, babies often aren't identified or diagnosed until at least one year of age, and often as late as 2 or 3 years, after language delays become clear. These babies are at higher risk of having poorer long-term outcomes in language and learning.

(1 Yoshinaga-Itano et al. 1998 Pediatrics 102:1161-1171)

International perspective

USA: NCHAM

In 1993 the National Institutes of Health (NIH) recommended that all newborn children should receive hearing screening before discharge from hospital.  NCHAM (hyperlink) (National centre for hearing assessment and management) was established in 1995 to assist hospitals in setting up and running universal hearing screening programs. Currently around 86% of newborn infants in the USA are being screened. (Sound Ideas Newsletter: Volume 5, No.3)

In the US, hearing screening protocols vary between states and programs.

UK: NHSP

The English government has also endorsed universal newborn hearing screening.  The National Hearing Screening Program (NHSP) was established in 2002, and by 2005 aims to be reaching all 600,000 babies born in England each year.  The English programs are managed locally.  In most areas, babies have a hearing screen before they go home from the hospital, but in some areas babies are screened at home when the Health Visitor first visits (the equivalent of our Maternal and Child Health nurses). 

All areas in England use the same hearing screening protocols, whether in the hospital or in the home.

Australian perspective

States and Territories

Infant hearing screening programs are currently being trialed or established in all states and territories except Tasmania.  These are at different stages of implementation.

The SWIS-H example

The New South Wales Statewide Infant Screening-Hearing (SWIS-H) program has been operating across New South Wales since December 2002. In the first year, 73,000 babies were screened, 145 babies received refer results in both ears and were referred to diagnostic audiology, and 64 of these were diagnosed with a significant hearing loss (permanent bilateral impairment). 

Prior to implementation of the SWIS-H program, the average age of detection of permanent hearing impairment in NSW was 18 months and the average age of hearing aid fitting was 22 months. SWIS-H now aims to ensure that intervention commences before 6 months of age.

Hearing screening in Victoria

In Victoria, the Victorian Infant Hearing Screening Program (VIHSP) has been operating since 1992.  In its current form, infants identified with the following 'risk factors' for hearing impairment are referred to diagnostic audiology as soon as the risk factor has been identified.

VIHSP Risk Factors

• Family history of congenital hearing impairment
• Rubella, cytomegalovirus, or toxoplasmosis during pregnancy or other perinatal infections
• Birth asphyxia as defined by an Apgar score of less than 4 at five minutes of age
• Birth weight below 1500g
• Exchange transfusion or serum bilirubin level greater than 350 ?mol/ l
• Congenital abnormalities of the head and neck
• Parental concern
• Admitted to NICU, but did not have a VicNIC hearing screen
• Admitted to SCN for 2 or more days, but did not have a VicNIC hearing screen
• Later risk factors, eg. Bacterial meningitis, developmental delay, head injury

This program has had moderate success in identifying children with hearing impairment, but accurate diagnosis can, and should, occur at a much younger age.

The modified Ewing Distraction Test, a hearing screen which was done for infants aged 7-9 months by Maternal & Child Health nurses, was discontinued in July 2005.

In Feb 2003, the VicNIC program commenced on weekdays in the four neonatal intensive care units in Victoria. It aims to offer a pre-discharge hearing screen to all babies admitted to the neonatal intensive care or special care nurseries of the Royal Women's Hospital, the Mercy Hospital for Women, the Royal Children's Hospital and Monash Medical Centre. In the first 18 months of the program's operation, 2200+ babies were screened.  40 babies with a moderate or greater hearing impairment have been identified through the program, with some only a few weeks old (corrected age) when diagnosed. These screens will continue as part of the expanded VIHSP.

Universal hearing screening programs are also currently run by some regional hospitals in Victoria.

The expanded program

Aims

The Victorian Infant Hearing Screening Program aims to help children born with significant hearing loss to realise their full potential for language, academic and social development by:

• offering a newborn hearing screen to all babies born in participating hospitals
• facilitating appropriate assessment and early management

Technology

Like the New South Wales, Queensland and ACT programs, VIHSP will be using Automated Auditory Brainstem Evoked Response (AABR) technology as the screening tool. The AABR involves sound being presented through a probe (ear-plug) or headphone, and measurement of the baby's electro-physiological response to this sound via scalp electrodes. AABR screening is painless and is done while a baby is in a quiet state, or asleep.

Babies will be screened either at their bedside or in a quiet room set aside for the purpose.

Following screening, a number of babies will be referred to diagnostic audiology for further testing and diagnosis.

Set-up Committee

A Steering Committee is overseeing the implementation and operation of the expanded Victorian Infant Hearing Screening Program.  This committee, chaired by Professor Frank Oberklaid (Director, Centre for Community Child Health), is supported by Working Groups focussing on specific areas such as hospital liaison, screening, diagnosis, data collection, and evaluation and quality assurance. An early intervention working group has been convened by the Department of Human Services. 

Members from a wide range of backgrounds and organisations, including parents, are participating in these working groups.

The core implementation and administrative group is based at the Centre for Community Child Health, at the Royal Children's Hospital.