What Are the Main Methods Used for Infant Hearing Assessment in Malaysia?

As a new parent, the well-being of your child is the number one priority, and healthy hearing is fundamental to their ability to learn and communicate. You are not alone in seeking advice on a hearing test for infants in Malaysia. The positive aspect is that Malaysia has a strong system, the Universal Newborn Hearing Screening (UNHS), which is aimed at identifying possible problems at an early stage.

But what is this screening? You may be asking yourself about the non-invasive procedures of obtaining a proper hearing test for newborn babies without inflicting pain. This paper unravels the whole procedure, discussing the key techniques such as Otoacoustic Emissions (OAE) and Auditory Brainstem Response (ABR) that are employed by specialized clinics. Knowledge of these objective testing techniques will enable you to make sure that your child gets the intervention in time, and he/she has the best opportunity to develop speech and language successfully.

1. The Foundation: Universal Newborn Hearing Screening (UNHS)

The UNHS program in Malaysia is designed to screen every newborn, preferably prior to their discharge. The aim is straightforward yet strong:

• Detection by 1 Month: Screen all babies by one month of age.
• Diagnosis by 3 Months: Confirm any hearing loss before three months of age.
• Intervention by 6 Months: Begin intervention (such as fitting hearing aids or exploring cochlear implants) before six months of age.

This is the so-called 1-3-6 rule, which is crucial since early intervention significantly enhances the results of speech, language, and cognitive development. The screening process itself is fast, non-invasive, and most importantly, it is conducted when the baby is asleep or quiet, that is, it does not cause any distress.

2. The First-Stage Screen: Otoacoustic Emissions (OAE) Testing

The most common initial method used in hospitals for the UNHS program is the Otoacoustic Emissions (OAE) test.

What is OAE Testing?

OAE is a physiological test that works by measuring sound emissions produced by the cochlea itself. Specifically, it assesses the function of the outer hair cells—tiny sensory receptors within the inner ear that amplify sound.

1. Procedure: A small, soft foam-tipped probe or earphone is gently placed in the baby's ear canal.
2. Sound Emission: The probe emits quiet clicking or tonal sounds into the ear.
3. Response Measurement: If the outer hair cells are working normally, they respond to the sound by producing a faint, measurable echo that travels back out into the ear canal. The probe records this echo.

Key Characteristics of OAE in Malaysia

• Non-Invasive and Fast: The test takes only a few minutes per ear and is completely passive for the baby.
• Target: Primarily detects the response of the cochlea across crucial frequencies (typically 2-5 kHz).
• Result Interpretation: A baby "passes" the OAE screen if a clear echo response is recorded in at least three test frequencies per ear. A "Refer" result means the test needs to be repeated or the baby needs a follow-up assessment.

3. The Definitive Assessment: Auditory Brainstem Response (ABR) Testing

If a newborn fails the OAE screen, or if they are considered high-risk (e.g., premature birth, NICU stay, family history of hearing loss), they are typically referred for the Auditory Brainstem Response (ABR) test, often administered as an Automated ABR (AABR) during screening.

What is ABR/AABR Testing?

The ABR/AABR test, in contrast to OAE, evaluates the whole auditory pathway, including the inner ear (cochlea) all the way to the brainstem, to make sure that the auditory nerve is functioning correctly to transmit signals to the brain. This is essential in getting a complete and precise image of the hearing capacity of a baby.

1. Procedure: Small electrodes are placed gently on the baby’s head (usually on the forehead, mastoid, and neck). Soft earphones deliver clicks or specific frequency tones.
2. Recording Brain Response: The electrodes record the brain's electrical activity in response to the sounds. These recordings exhibit typical "peaks" which represent sound that has reached and been processed by the brainstem.
3. Reliability: ABR is regarded as the gold standard of reliably estimating hearing thresholds in infants who are not able to undergo standard behavioural tests.

ABR and Advanced Variants

In specialized audiology clinics across Malaysia, including 20dB Hearing, audiologists may utilise more advanced variants for detailed diagnostic assessments following an initial UNHS failure:

• Auditory Steady State Response (ASSR): This test is similar to ABR but uses continuous, frequency-specific tones and complex statistical analysis to estimate hearing thresholds for different pitches, offering a more comprehensive hearing assessment for newborn.
• Central Auditory Evoked Potential (CAEP): Used less frequently in infants, but invaluable for assessing central auditory processing abilities as the child grows.

4. Expanding the Assessment: Middle Ear Function and Follow-Up

For infants older than newborns, or as part of a comprehensive diagnostic battery, audiologists use additional objective measures to ensure accurate diagnosis.

Tympanometry

This test is necessary to assess the work of the middle ear- the ear drum and the small bones behind the ear drum.

• Function: It measures the mobility of the eardrum by gently changing air pressure in the ear canal.
• Importance: Middle ear issues, such as fluid from an infection (otitis media), are common in babies and can cause a temporary hearing loss that might interfere with OAE or ABR results. Tympanometry assists the audiologist to detect and consider these temporary problems prior to making a permanent diagnosis of hearing loss.

Middle Ear Muscle Reflex (MEMR)

This test evaluates the automatic reflex of the middle ear muscles to loud sounds, which is another confirmation of middle ear and inner ear functioning.
H3: The Critical Role of Follow-Up

A "Refer" result on an OAE or AABR screen does not mean the baby has permanent hearing loss. It simply means a more comprehensive assessment is required. These follow-up evaluations are critical and should be completed quickly.

Audiology centres such as 20dB Hearing offer the entire spectrum of diagnostic services, so that even in case a newborn cannot travel, the required services can be offered. For example, in special circumstances, some providers offer a home visit hearing test option to ensure continuity of care.

Conclusion: Ensuring Early Intervention Success

The systematic nature of infant hearing assessment in Malaysia, which is based on the UNHS 1-3-6 rule and supported by the objective and reliable techniques such as OAE and ABR, is essential in providing children with hearing loss with timely intervention.

Through these non-invasive methods, audiologists are able to make correct diagnoses at a tender age. This opens the door to instant assistance, whether in the form of hearing aids or special rehabilitation courses, to the fullest potential of the child to acquire natural communication skills.

In case you are worried about the hearing of your baby or need a detailed follow-up examination, you can call a professional audiology centre such as 20dB Hearing and be sure that you will be provided with the highest quality of local and international care.