OAE and ABR testing - A comparative overview

Introduction

Hearing plays a vital role in every stage of life, serving as the gateway to learning, cognitive development, and meaningful communication. It influences how we connect with others and affects our ability to perform daily tasks and work. Given its wide-reaching impact on overall well-being, early detection of hearing loss is crucial for timely intervention and effective management.

Two of the most well-known tests for objectively evaluating hearing function—Otoacoustic Emissions (OAE) and Auditory Brainstem Response (ABR) - are commonly used across different age groups. While both tests are non-invasive and objective, they serve distinct purposes and provide distinct insights into hearing health.

Understanding what ABR and OAE testing is

To start, we will discuss what OAE and ABR tests are, what they measure and how they work. Both tests are objective tools for assessing hearing function, but they target different parts of the auditory system and are specific use cases to which each is most suited.

Auditory Brainstem Response (ABR) Testing

The brainstem is essential for processing and interpreting sound, serving as the link between the cochlear nerve and higher brain centers. This connection enables functions like pitch and loudness detection, sound localization, and reflexive responses.

There are two main types: screening ABR (AABR - Automated Auditory Brainstem Response) and diagnostic ABR. AABR serves as a screening tool, providing a simple pass or fail result at a single loudness level. A pass result suggests that the brain's response confirms sound detection. If the result is a fail, more detailed testing, such as a diagnostic ABR, may be recommended.

During ABR testing, small electrodes are placed on the patient’s forehead, earlobes, or mastoid bone, and earphones or inserts deliver sounds. For AABR, earphones are used, while diagnostic ABR typically involves insert earphones. The sounds played through the earphones trigger responses in the auditory nerve and brainstem, which are recorded via electrodes and displayed on a computer or smart device. This data provides insight into how the cochlea and hearing pathways in the brain are functioning.

Preparation for testing

The test does not require active participation from the patient, making it particularly useful for infants, young children, or individuals unable to respond, such as those with developmental challenges ^[1] [2].

ABR testing on infants or children is typically done while they sleep, with the duration limited to the length of their nap. Patients are kept awake and sleep-deprived beforehand to maximize sleep time. Sedation or anesthesia may be necessary if the infant cannot sleep long enough for accurate results. When this is considered, a thorough medical history, including any illnesses, medications, and drug allergies, is reviewed.

For adults, full sleep is not required, but they must remain quiet and relaxed to avoid movement or muscle artifacts. Prior to the ABR appointment, an audiologist or appropriate medical professional examines and clears the auditory canals to prevent interference with the auditory stimulus. If middle ear pathologies are identified, a referral to an Otolaryngologist or equivalent specialist may be necessary for further management before ABR testing to ensure accurate results^[1].

Once these criteria have been addressed, electrode placement can proceed for the ABR session.

Use cases for Auditory Brainstem Response (ABR) testing^[3]

Auditory brainstem response (ABR) testing is a versatile tool used to assess auditory function in various scenarios. Below are some common use cases:

• Newborn hearing screening: AABR is commonly used to detect congenital hearing loss in newborns, allowing for early intervention.

• Diagnosing complex auditory and neurological conditions: ABR can be used to diagnose vestibular schwannomas, brainstem lesions, de-myelination disease, and auditory neuropathy that can affect the auditory pathways and nervous system.

• Patients unable to participate in behavioral tests: ABR is ideal for patients, such as young children or individuals with developmental delays, who cannot respond to traditional hearing tests.

• Monitoring auditory development: ABR can track the maturation of auditory pathways in premature infants or children with developmental delays ^[3].

• Evaluating unexplained hearing loss: When hearing loss occurs without an obvious cause, ABR can help to start establishing whether the issue is cochlear or neural in origin.

• Intraoperative monitoring: Intraoperative monitoring is used for patients undergoing surgeries involving the vestibulocochlear nerve or nearby areas. Its purpose is to detect nerve injury early, allowing for immediate corrective measures during the procedure^[4].

Advantages of using ABR testing^[5]

ABR testing includes several advantages in the evaluation of hearing health, such as:

• Early detection: ABR testing can help to identify hearing issues in newborns, which allows for early intervention and treatment - critical for language and cognitive development.
• Objective assessment: ABR testing is not reliant on a patient’s response, which enables you to receive objective data about hearing function.
• Individualized treatment options: With ABR test results, hearing healthcare practitioners can create personalized treatment strategies, such as hearing aids, cochlear implants, or therapeutic interventions.
• Monitoring progress: ABR can be used to track the effectiveness of treatments and assess improvements in hearing function over time.

Otoacoustic Emissions (OAE) testing

Otoacoustic emissions are sounds generated by the outer hair cells of the cochlea in response to auditory stimuli. When sound enters the ear, hair cells in the cochlea vibrate, producing emissions that can be measured through the external ear canal. These emissions are recorded using a microphone placed in the ear canal, making OAE testing an effective tool for assessing cochlear health.

In OAE testing, sound is delivered to the ear through a probe, and the cochlear outer hair cell’s response is recorded. Since this test measures the function of the cochlea directly, it provides an objective assessment of auditory health.

Preparation for testing

To ensure accurate results, it is advisable to follow these steps before starting the OAE test^[5]:

• Perform an otoscopy to check for any obstructions in the ear canal, such as excessive wax or vernix (in the case of testing newborns), which can hinder the probe's function.
• Perform tympanometry to detect any abnormalities that may indicate middle ear pathology, which could interfere with the test results.
• Conduct daily OAE probe checks to ensure proper probe functioning before testing.
• Monitor environmental noise levels. Reducing background noise through environmental adjustments can greatly enhance test accuracy.

Use cases for OAE testing^[6]

• Early detection of hearing loss: OAE tests can detect hearing loss at an early stage, particularly in newborns, ensuring timely intervention for better language and cognitive development.
• Monitoring ototoxicity: The test helps monitor cochlear function in patients undergoing ototoxic medication regimens, allowing for early detection of auditory damage.
• Noise-Induced hearing loss monitoring: OAE testing is valuable for detecting early signs of noise-induced hearing loss. It can be used alongside other assessment tools in workplace environments, supporting hearing conservation programs to identify early indications of hearing loss^[7].

Advantages of OAE testing^[8]

• Objective testing: OAEs do not depend on a patient’s behavioral response or cognition.
• Painless: The test is painless and causes no discomfort to the patient.
• Reliable and quick: Technological advancements like our hearOAE solution, provide clinically-validated results and enable efficient screening and testing.
• Portable and convenient: Recent advancements in OAE equipment include hand-held, portable solutions with intuitive designs that are easy to use with the appropriate training, in a noise-controlled environment.
• Automated results: Screening OAE testing provides automatic pass/fail outcomes, reducing the chance for human error and allowing results to be electronically documented or printed.

hearX^®’s approach to OAE assessments

As hearing assessment technology continues to evolve, hearX has been at the forefront of creating innovative, portable, and user-friendly audiometry solutions. hearOAE is designed for efficient and accurate OAE testing in various settings, from clinical environments to workplace screening programs. hearOAE runs from our secure cloud-based data management portal, which enables you to manage patient data, test results and referrals in real-time, with ease.

Conclusion

Auditory Brainstem Response (ABR) testing is a valuable tool for assessing auditory pathways, making it ideal for detecting neural hearing disorders. On the other hand, Otoacoustic Emissions (OAE) testing provides insights into cochlear health, particularly the function of outer hair cells. Both tests’ objective measurements enable early detection of auditory issues in newborns, children and adults, to support timely intervention, support and care.

In infants and young children, conducting both AABR and OAE testing is highly effective for early hearing screening to detect potential hearing loss. For both children and adults, a comprehensive hearing assessment may include various tests, such as pure-tone audiometry, tympanometry, OAE, and acoustic reflex testing. ABRs are typically performed when indicated, making them a valuable addition to the assessment process. This integrated approach allows hearing health practitioners to assess not just cochlear function, but also the integrity of the auditory pathways and middle ear conditions.

Together, these tests provide a broader picture of auditory health, enabling the differentiation between types of hearing loss, whether conductive, sensorineural, or mixed. Ultimately, this ensures that patients receive effective, tailored care based on their unique hearing profiles.