Audiology Lecture 3

Otoacoustic emissions (OAEs) are sounds generated by the cochlea in response to auditory stimulation. They can be measured using specialized equipment and provide information about the health and function of the inner ear.

- –Transient Evoked (TEOAE): Transient evoked otoacoustic emissions (TEOAEs) are evoked by a brief click or tone burst stimulus.

–- Distortion Product (DPOAE): Distortion product otoacoustic emissions (DPOAEs) are generated when two tones of different frequencies are presented simultaneously to the ear.

The UNBHS (Universal Newborn Hearing Screening) program is a comprehensive screening program aimed at identifying hearing loss in newborns. OAE screening is a part of this program and is performed in most pediatric well visits to ensure early detection and intervention for hearing loss.

–Used as a screener at most pediatric well visits

–Used as a screener in many educational settings

In 2002, New Jersey passed a law mandating that all newborn babies receive a hearing screening before they leave the hospital. This ensures that every newborn has the opportunity for early detection of hearing loss and access to appropriate interventions.

EHDI stands for Early Hearing Detection and Intervention. It is a program that oversees newborn hearing screening efforts, follow-up services, and intervention programs for infants identified with hearing loss. In New Jersey, EHDI is responsible for managing the statewide newborn hearing screening program.

The "1-3-6" guidelines are a set of recommended timeframes for newborn hearing screening and intervention. It suggests that infants should have their initial hearing screening before one month of age, receive a full evaluation by three months if they receive a referral on the initial screening, and be enrolled in early intervention services by six months of age if diagnosed with hearing loss.

EDHI stands for Early Hearing Detection and Intervention.

multiple state agencies

–SLP

–Social Workers

–Pediatricians

–OT

–PT

OAE testing is a simple and non-invasive method used to obtain audiologic data, particularly in newborns. It helps determine if the outer hair cells of the inner ear are functioning properly, which is directly correlated to hearing ability.

Otoacoustic Emissions were first described by David Kemp in 1977.

An Otoacoustic Emission is a low-intensity sound that is recorded in the external ear canal. It is produced within the cochlea in response to a sound stimulus.

To measure an Otoacoustic Emission, a microphone is placed inside a probe tip, which is inserted into the external ear canal. The emission is recorded as a response to a sound stimulus presented to the ear.

If the middle ear is compromised or if there are issues with the sound transmission to the cochlea, the Otoacoustic Emission may be absent or reduced. Therefore, the absence of an Otoacoustic Emission can indicate problems in the middle ear or sound transmission pathway.

The presence of an Otoacoustic Emission tells us about the function of the cochlea and the outer hair cells. It does not provide information about the function of the auditory nerve (8th cranial nerve) or beyond.

TEOAE stands for Transient Evoked Otoacoustic Emissions.

The stimulus used in TEOAE is a very brief click or toneburst presented at a level of 80dB SPL (sound pressure level).

High frequency responses are elicited first in TEOAE because of the tonotopic organization of the cochlea. The hair cells responsible for high-frequency hearing are located on the outermost part of the cochlea, so their responses are detected first.

Mid- and low-frequency components of TEOAE occur a bit later, at around 10 milliseconds (ms) after the stimulus presentation.

Typically, 2000 sweeps are used in TEOAE to obtain a reliable measurement.

The TEOAE response is assessed based on its stability and reproducibility, with a desired criterion of at least 70% reproducibility. Additionally, the emissions should be at least 6dB above the noise floor for reliable detection.

DPOAE stands for Distortion Product Otoacoustic Emissions.

DPOAEs are generated by presenting two different tones to the ear. The resulting emission is a third tone, which is a distortion product of the first two tones.

The resulting emission in DPOAE is a distortion product that occurs at a frequency corresponding to the mathematical relationship between the two primary tones.

OAEs can help differentiate between different types of hearing loss. If a patient has moderate to profound hearing loss but has present OAEs, it suggests that the outer hair cells are intact. This finding can be helpful in diagnosing conditions such as retrocochlear loss or pseudohypacusis.

Retrocochlear loss refers to hearing loss caused by issues beyond the cochlea, typically involving the auditory nerve or central auditory pathways. When OAEs are present in a patient with moderate to profound hearing loss, it suggests that the cochlea is functioning normally, pointing to a potential retrocochlear cause.

Pseudohypacusis, also known as functional hearing loss or nonorganic hearing loss, refers to a condition where individuals intentionally feign or exaggerate hearing loss. OAEs can help identify pseudohypacusis by demonstrating intact outer hair cell function despite behavioral tests suggesting hearing loss.

–They can assist in differential diagnosis

–Aids in determining cochlear implant candidacy

No, OAEs do not directly indicate hearing thresholds. They are used as a pass/refer screening tool and are typically utilized alongside full audiometric batteries for a comprehensive assessment.

Yes, if there is an issue with the outer or middle ear, such as a blockage or dysfunction, it can alter the OAE response. Therefore, OAEs may be affected in the presence of such conditions.

No, OAEs may not be present in individuals with moderate or greater hearing losses. The presence of OAEs is more likely in individuals with milder hearing losses.

OAEs can provide objective screening specifically in the frequency range of approximately 1000-4000Hz. They are not as effective at evaluating other frequency regions.

OAEs enable us to monitor changes in cochlear function over time. By comparing OAE responses at different points, we can assess any alterations or improvements in cochlear health.

The three categories that OAEs can typically fall into are:

Normal: OAEs are present with strong emissions.

Present: OAEs are present but with low amplitudes.

Absent: No measurable OAE responses.

ABR stands for Auditory Brainstem Response, and it refers to the electrical activity of the auditory system in response to an acoustic stimulus.

Auditory evoked potentials are electrical responses generated by the auditory system in response to a sound stimulus.

ABR was first reported in the late 1960s.

ABR specifically looks at the first 10 milliseconds (ms) following the presentation of the stimulus.

2003

Auditory Brainstem Response

10ms post stimulus onset

Waves I-V

Yes, it is a very sensitive test.

High repeatability

Earphones

80-90dB SPL (Sound Pressure Level)

Click or tone burst

27.7/61.1 (per second)

Tone burst

Auditory nerve

Cochlear nucleus

Superior olivary complex

Lateral lemniscus

Inferior colliculus

One on each mastoid and two on the forehead.

The skin should be cleaned using an alcohol prep.

Abrasive cream can be applied to improve impedance.

The impedance should be less than 5 mV.

Natural sleep is encouraged for the patient during this test.

The patient should be seated in a comfortable chair or lying down.

Patients need to be as quiet and still as possible, avoiding eyeblinks, coughing, heavy breathing, and muscle movement.

Baby bottles and pacifiers should be avoided as they can introduce artifacts.

A sedated ABR is performed under anesthesia for patients who may not be able to cooperate or remain still during the test.

ABR testing is used to test neural integrity, determine the presence of retrocochlear pathology, and estimate thresholds for individuals who cannot participate in traditional audiometry.

Frequencies such as 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz can be used for tone burst presentation during ABR testing.

Wave V is the specific wave that is typically observed and analyzed in ABR testing.

Switching to a bone oscillator can help determine if the hearing loss is conductive (CHL) or sensorineural (SNHL).

ABR testing is also used in newborn hearing screening (NBHS) and intraoperative monitoring.

VNG stands for Video Nystagmography.

VNG testing is used for balance assessment and to determine if the inner ear is responsible for dizziness.

VNG was previously referred to as ENG, which stands for Electronystagmography.

The three portions of VNG testing are ocular motor testing, positional testing, and caloric testing.

The patient wears infrared video goggles during VNG testing.

Visualizing the patient's eye movements is crucial because it allows the examiner to accurately assess and analyze the characteristics and patterns of nystagmus, which is an involuntary rhythmic eye movement. By observing the eye movements, the examiner can gather important information about the function of the vestibular system and diagnose any underlying vestibular disorders or abnormalities causing dizziness or balance issues.

Nystagmus is an involuntary eye movement that can cause the eyes to move up and down, side to side, or torsionally (in a twisting motion).

Nystagmus can be caused by various factors, including vestibular stimulation, intoxication, spinning in circles, and riding in the back seat of a car.

When nystagmus is observed, it suggests that the inner ear is involved in the underlying cause of the patient's dizziness.

The case history is vital in assessing nystagmus as it provides valuable information about the patient's symptoms, medical history, and potential triggers or contributing factors. This information helps in determining the possible causes and appropriate management of nystagmus.

Some symptoms associated with nystagmus include double vision, blurry vision, and difficulty focusing. These visual disturbances can be experienced by individuals with nystagmus.

It is important to determine whether the dizziness is episodic (occurring in discrete episodes) or constant (persisting continuously). Additionally, knowing the duration of each episode is valuable, such as whether it lasts for seconds, minutes, hours, or even days.

Identifying the factors that alleviate or stop the dizziness can provide insights into potential triggers or alleviating measures. It can help determine if medication, closing the eyes, laying down, or other specific actions have an impact on the dizziness experienced by the patient.

It is important to inquire about specific movements that may trigger or worsen the dizziness. These can include getting up out of a chair, laying down, turning the head, or tilting the head back. Understanding the relationship between these movements and the onset or exacerbation of dizziness helps in the diagnostic process.

Assessing the frequency of dizziness helps in understanding how often the episodes occur. This information provides insights into the impact on the patient's daily life and helps in determining the urgency of the evaluation and management.

Changes in the severity of dizziness can indicate a progression or improvement of the underlying condition. This information helps in monitoring the course of the condition and evaluating the effectiveness of any treatments or interventions.

If the patient has taken medication to treat dizziness on the day of the evaluation, it may potentially affect the test results or mask the symptoms. It is important to obtain an accurate assessment of the patient's symptoms without the influence of medication.

Changes in vision or hearing during dizziness episodes can provide valuable clues about the potential underlying causes. Symptoms such as aural fullness, pain, ringing in the ears, or changes in visual perception help in differentiating between various vestibular and auditory conditions.

Assessing vision helps in understanding if there are any visual symptoms associated with dizziness, such as blurred vision, double vision, or difficulty focusing. These visual symptoms can provide important information about the relationship between the vestibular system and visual processing, aiding in the diagnosis and management of the condition.

–Gaze

–Saccades

–Smooth pursuit

–Optokinetics

Gaze refers to the ability to fixate and maintain a steady gaze on a stationary target. Assessing gaze helps determine if there are any abnormalities in the ability to maintain stable eye position, which can be indicative of vestibular or neurological disorder

Saccades are rapid eye movements that redirect the line of sight between different targets. Assessing saccades helps evaluate the accuracy, speed, and coordination of these eye movements, which can provide insights into the integrity of the ocular motor system and its interaction with the vestibular system.

Smooth pursuit refers to the ability to smoothly track a moving target with the eyes. Assessing smooth pursuit helps evaluate the coordination and accuracy of eye movements during tracking tasks, which can provide information about the integrity of the vestibular-ocular reflex and the smooth tracking system.

Optokinetics involve visual stimuli that move across the field of view to elicit eye movements. Assessing optokinetics helps evaluate the ability to visually track moving objects and the corresponding eye movements, providing information about the interaction between visual stimuli and the vestibular system.

–- Supine

–- Dix Hallpike

–- Head left

–- Head right

–- Body left

- Body right

The supine positional test involves lying the patient down flat on their back. It helps evaluate if changes in head position while lying down provoke nystagmus or dizziness

It involves a quick movement of the patient's head from an upright sitting position to a head-hanging position, typically with the head turned to one side.

Head left and head right refer to turning the head to the left or right, respectively, while body left and body right involve leaning the body to the left or right, respectively.

A test in which the patient lies down with their head at a 30-degree angle and receives four separate irrigations of air.

Two cool and two warm air irrigations.

The air is in their ear for 60 seconds each time.

To induce dizziness and observe nystagmus in order to assess the functioning of the vestibular system.