SHS 450 Exam 2

What does pure tone audiometry tell us?

• Pure tone audiometry tells us about the patient’s detection of important frequencies in speech (250-8000 Hz)

  • Characterizes the degree, configuration, and type of hearing loss

  • Stimuli are highly artificial

Why is including actual speech in hearing screenings important?

Including speech allows us to characterize a patient’s ability to hear real-world spoken language, because speech stimuli are more ecologically valid than pure tones

What is a VU (volume unit) meter?

In speech audiometry:

• a device that measures the intensity (loudness) of an audiologist’s voice to ensure that it’s being presented at the desired intensity level

  • If it peaks at 0, you are presenting at the desired intensity level

What are the 4 skills included in the hierarchy of hearing?

1. Detection: Determine the presence/absence of sound

2. Discrimination: Distinguish between two or more sounds

3. Recognition: Identify/label a sound

4. Understanding: Comprehend the meaning of sound

What is the speech detection threshold (SDT)?

The SDT is the lowest intensity level (dB HL) at which the patient can detect speech

• Also called Speech Awareness Threshold (SAT)

• Stimuli may be words or continuous speech

• You don’t have to understand the speech, you just have to recognize that it’s there

• Use if the patient cannot reliably repeat back words (e.g., young children)

What is the speech recognition threshold (SRT)?

The SRT is the lowest intensity level (dB HL) at which the patient can correctly repeat words

• Stimuli are spondees (two-syllable words with equal stress)

• Patient repeats back words

• A patient’s SRT is typically 5 to 10 dB higher (more intense) than their SDT

Why would an audiologist choose to run an SDT test instead of an SRT test?

SDT tests can be used for patients who can’t repeat words back, such as young children

What is a spondee?

Stimuli that are two-syllable words with equal stress used in SRT tests

A patient’s SRT threshold is typically ___ to ___ 10 dB higher/more intense than their SDT threshold.

5 to 10 dB

How would one obtain a speech recognition/detection threshold (SRT/SDT)?

• Threshold is the lowest intensity at which words can be detected/recognized in at least 2 out of 3 ascending runs

• Obtain using the bracketing procedure (down 10 dB, up 5 dB)

• Threshold is expressed in dB HL

• Threshold is obtained in each ear individually

How does pure tone average (PTA) relate to speech recognition?

• Some use PTA to characterize the degree of hearing loss

• PTA is also compared to threshold measures of speech to determine the reliability of pure-tone thresholds

How do the SRT and pure tone average (PTA) relate to one another?

• We use the SRT and PTA to judge the reliability of the patient’s pure-tone thresholds

• SRT and PTA are expected to be within ±10 dB of each other

  • Example: PTA of 30 dB HL is expected to have an SRT between 20 and 40 dB HL

• A >10 dB difference between SRT and PTA could suggest:

  • Patient did not understand your instructions

  • Reliability of pure-tone thresholds is poor

• If SRT & PTA do not agree, re-instruct and re-test

• If still not in agreement, note the poor reliability in your report

How do the SDT and pure tone average (PTA) relate to one another?

• SDT is expected to be within ±10 dB of the lowest pure-tone threshold between 250 to 4000 Hz

• Example:

  • Lowest pure-tone threshold in left ear = 20 dB HL

  • SDT in left ear expected to be between 10 to 30 dB HL

What are the purposes of word recognition testing?

• Estimate the difficulty of understanding speech

• Monitor the patient’s hearing ability over time

• Assess candidacy for amplification

• Provide insight into the potential site of the lesion

  • Conductive vs. cochlear vs. neural

What is the process of word recognition testing?

• The test assesses the patient’s ability to correctly identify monosyllabic spoken words presented above threshold

• Typical presentation level: 40 dB sensation level (dB SL)

  • Example: If SRT is 10 dB HL, present word recognition at 50 dB HL

• Audiologist scores the percent of words correctly repeated back

What are two examples of specific word-recognition testing paradigms?

1. W-22: Developed at Central Institute for the Deaf (CID)

2. NU-6: Developed at Northwestern University

How should one categorize word-recognition scores?

By percentage level, calculated depending on the number of items presented during the test

• 90-100%: Excellent—minimal to no difficulty

• 80-89%: Good—slightly difficult, similar to listening on a telephone

• 70-79%: Fair—moderate difficulty

• 60-69%: Poor—Marked difficulty following conversation

• <60%: Very poor—Patient may be unable to follow running speech

How can a word-recognition test help an audiologist determine the potential lesion site?

• Normal hearing: reaches 100% correct around 40 dB above the SRT

• Conductive loss: reaches 100% correct around 40 dB above SRT, but at higher intensity than normal hearing

• Sensory (cochlear) loss: does not reach 100% correct even at high intensity levels

• Neural (retrocochlear) loss: as intensity increases, performance reaches a point where it starts to decrease

What is a signal-to-noise ratio (SNR)? Which test is it used in?

• SNR: Decibel difference between the amplitude of the signal (speech) and competing noise

  • Positive values: Speech is higher in amplitude than the noise

  • Negative values: Speech is lower in amplitude than the noise

  • 0 dB: Speech and noise are equal in amplitude

• SNRs are used in QuickSIN (Speech in Noise) tests

  • Results are quantified in terms of “SNR loss”

What is the AzBio test?

• Sentences presented in quiet and at one signal-to-noise ratio

  • Male and female talkers speaking in more conversational style than other tests

• Patient repeats back as much of sentence as possible

• Audiologist scores number of keywords repeated back correctly

• Result is quantified in percent correct

• Used as part of evaluation for cochlear implant candidacy

What is the test battery approach?

• Each audiologic test provides a piece of information about the patient’s auditory function

• No one test provides all the information we need

• We therefore use a combination of tests (battery) to make a proper diagnosis

What are the 6 different physiological tests audiologists can perform?

1. Otoscopy

2. Tympanometry

3. Otoacoustic Emissions

4. Auditory Brainstem Response

5. Acoustic Reflexes

6. Audiometry

What does tympanometry test for?

• Tympanic membrane mobility

• Middle ear pressure

• Ear canal volume

What is impedance?

Impedance is the opposition to flow of energy

• Impedance of middle ear includes:

  • Resistance: frictional force due to ligaments holding ossicles together

  • Mass: weight of tympanic membrane and ossicles

  • Stiffness: pressure placed on the stapes by the cochlear fluid

What is compliance?

Compliance is the opposite of impedance.

• a measure of how easily the eardrum (tympanic membrane) and the middle ear system move and conduct sound vibrations in response to changes in air pressure

What is immittance?

An umbrella term combining the measurement of acoustic impedance (opposition to sound energy flow) and acoustic admittance (ease of sound energy flow) through the middle ear

What does acoustic reflex testing measure?

How the stapedius muscle contracts in response to loud sound

What are 4 examples of barriers to sound transmission in the middle ear?

1. Otitis media (fluid builds up behind the tympanic membrane)

2. Tumor in the middle ear space

3. Torn ligaments of the ossicles

4. Perforation of the tympanic membrane

What are some effects of Eustachian tube dysfunction?

• Build-up of pressure behind the tympanic membrane (because the Eustachian tube’s purpose is to equalize pressure on either side of the tympanic membrane)

• Reduced middle ear efficiency

• Feelings of aural fullness

What does a tympanometer measure?

Immittance (how easily sound energy moves through the middle ear as a function of changing air pressure in the external ear canal)

How does a tympanometer work?

• Probe tip is placed into the ear canal to form an air-tight seal

• Air pump changes the pressure inside the ear canal

• Loudspeaker presents a probe tone of 226 Hz into the ear canal

• Microphone measures how much of the 226-Hz probe tone is transmitted through the middle ear

True or false: Tympanometry involves the inner ear

False. Tympanometry only involves the outer and middle ear

What are the axes of a tympanogram?

• x-axis: Air pressure

  • Expressed in decapascals (daPa)

  • 0 daPa = ambient pressure

• y-axis: Compliance

  • Expressed in mL or mmho (1 mL = 1 mmho)

  • Larger values indicate more sound is transmitted through middle ear

What is a normal ear canal volume range in adults?

0.9 to 2.0 cc

What type is a Hypercompliant Tympanogram? What does it represent?

• Type A-D (D stands for deep)

• Compliance is abnormally high

• Peak pressure and volume are normal

• Causes include ossicular discontinuity and monomeric tympanic membrane

  • Ossicular Discontinuity: a separation or break in the chain of tiny bones (malleus, incus, and stapes) in the middle ear that stops sound vibrations from traveling properly to the inner ear

    • This causes the eardrum to become floppy and move with extreme ease, which causes the increase in compliance

  • Monomeric Tympanic Membrane: a thinned-out area of the eardrum that lacks its middle fibrous layer after a previous perforation heals

What type is a Shallow Tympanogram? What does it represent?

• Type A-S (S stands for shallow)

• Compliance is abnormally low

• Peak pressure and volume are normal

• Causes include otosclerosis and scarred tympanic membrane

  • Otosclerosis: abnormal bone growth in the middle ear that fixates the stapes bone and causes progressive hearing loss

What type is a Flat Tympanogram? What does it represent?

• Type B

• Causes include:

  • Otitis media

  • Cerumen impaction

  • Tympanic membrane perforation

  • Pressure equalization tube

• We use ear canal volume to differentiate between possible causes

  • Normal adult volume = 0.9 to 2.0 cc

If a patient has a Type B Tympanogram and an ear canal volume of 0.4 cc, what does this most likely indicate?

Cerumen impaction

If a patient has a Type B Tympanogram and an ear canal volume of 3.0 cc, what does this most likely indicate?

A tympanic membrane perforation or a pressure equalization tube

If a patient has a Type B Tympanogram and an ear canal volume of 1.0 cc, what does this most likely indicate?

Otitis media

What type is a Negative Middle Ear Pressure Tympanogram? What does it represent?

• Type C

• Compliance is highest when we make the pressure in the ear canal negative

• Peak pressure is abnormally negative

• Compliance and volume are normal

• Cause is due to Eustachian tube dysfunction

True or false: Tympanometry is not affected by pathology occurring beyond the middle ear

True

Which parts of the auditory system does acoustic reflex testing involve?

• Outer ear

• Middle ear

• Inner ear

• Auditory nerve

• Brainstem

• NOT INVOLVED: Cortex

What is an acoustic reflex?

• High-intensity sounds can trigger a reflex that decreases the compliance of the middle ear 

  • Compliance: the ease with which the eardrum and ossicles move

• The acoustic reflex may protect the ear from acoustic trauma

• Measurement of this reflex is also useful in audiologic diagnosis

What is the ascending acoustic reflex pathway?

1. Outer, middle, and inner ear

2. Auditory nerve (cranial nerve VIII)

3. Cochlear nucleus

4. Superior olivary complex and facial nerve (CN VII) nucleus

What is the descending acoustic reflex pathway?

1. Facial nerve (cranial nerve VII)

2. Stapedius muscle (muscle that contracts the stapes and reduces the compliance of the middle ear system. In other words, contraction of stapedius muscle stiffens ossicular chain, decreasing compliance)

What is the difference between the ipsilateral and the contralateral acoustic reflex pathways?

• Ipsilateral Pathway: 

  • Elicitor sound is presented to one ear via an earphone

  • The stapedius muscle on the same side is contracted

  • Compliance is measured using a probe

• Contralateral Pathway: 

  • Elicitor sound is presented to one ear via an earphone

  • The stapedius muscle on the opposite side is contracted

  • Compliance is measured using a probe

When are acoustic reflexes typically present?

• Normal hearing

• Mild and moderate sensorineural loss 

• (Rarely) lesions of the auditory cortex

When are acoustic reflexes typically absent?

• Conductive hearing loss (ipsilateral reflex)

• Severe and profound sensorineural hearing loss

• Lesions of the auditory nerve and brainstem

• Facial nerve disorders

What are the 2 exceptions you can have within acoustic reflex testing?

1. Contralateral reflexes can be present if elicitor presented to ear with conductive loss and probe is in unaffected ear (but threshold will be higher than normal)

2. Contralateral reflexes can be presented if elicitor is presented to unaffected ear and probe is in ear with severe/profound sensorineural hearing loss

How can you find the acoustic reflex threshold?

1. Start by measuring a tympanogram and obtaining peak pressure and compliance. Perform acoustic reflex testing at peak pressure, where the tympanic membrane is most efficient.

2. Find the acoustic reflex threshold

   • Lowest elicitor intensity that causes a decrease in compliance of ≥0.02 mL

   • Elicitor sounds may be pure tones (500-4000 Hz) or noise

3. Threshold measurement involves starting at a lower intensity (e.g., 70 dB HL) and increasing in 5-dB steps

   • Find lowest intensity that elicits a change of ≥0.02 mL

   • Ensure that the response is repeatable

   • Be prepared to stop if the elicitor becomes uncomfortably loud

What are the benefits of acoustic reflex testing?

• Acoustic reflexes are useful for determining site of lesion

  • e.g., middle ear, cochlea, auditory nerve, etc.

• Acoustic reflexes can also validate the results of other tests

  • For example: we expect absent acoustic reflexes in a patient with profound sensorineural hearing loss

What is the normal range of acoustic reflex thresholds?

70 dB to 100 dB HL

What describes the left contralateral acoustic reflex? 

Elicitor in left ear, probe in right ear

This patient has a severe sensorineural hearing loss in the left ear due to cochlear damage. Which of the following acoustic reflexes would be present in this patient?

Right ipsilateral and Right contralateral 

Which of the following acoustic reflexes would be present in this patient?

• Right ipsilateral 

• Right contralateral 

• Left ipsilateral 

• Left contralateral

This patient’s acoustic reflex threshold is ______ dB HL. 

85

• How to find it: causes a decrease of at least 0.02 in compliance (the lowest sound intensity that gives you that change). In this diagram, it’s at 0.3, where we find that characteristic dip 

What parts of the ear does Otoacoustic Emissions (OAE) testing involve?

• Outer ear

• Middle ear

• Inner ear

NOT INCLUDED:

• Auditory nerve

• Brainstem

• Cortex

What are Otoacoustic Emissions (OAEs)?

• Low-amplitude sounds created by the outer hair cells

• A byproduct of the amplification provided by outer hair cells

• Outer hair cells create a reverse traveling wave on the basilar membrane that returns to the middle ear and ear canal

• OAEs are measured in the ear canal using a sensitive microphone

How are OAEs measured?

• OAEs are measured with a loudspeaker and microphone probe placed in the ear canal

• The loudspeaker presents two tones to generate OAEs

• The microphone records the OAE returning back to the ear canal

True or false: you can be asleep during an OAE test

True, but both the patient and the room must be quiet because OAEs are low-amplitude sounds (10 dB SPL or less), so noise and vibration from the environment and patient interfere with the measurement

OAEs are absent in what type of hearing loss?

Conductive hearing loss, because it attenuates the incoming stimulus

• Lower stimulus amplitude = lower OAE amplitude

• Additionally, conductive hearing loss will attenuate the outgoing OAE reaching the microphone

Would a patient with sensorineural hearing loss have present DPOAEs?

It depends on whether that hearing loss is mild or not. We would need more information, but if the patient’s hearing loss is mild, then it is possible that DPOAEs will be present.

Which inner ear structures cause most sensorineural hearing loss?

Outer hair cells

If a patient has absent OAEs and an abnormal tympanogram, they most likely have _________________ hearing loss.

Conductive

If a patient has absent OAEs and a normal tympanogram, they most likely have _________________ hearing loss.

Sensorineural

DPOAE testing is a specific type of OAE testing. What does it involve?

• Presenting 2 pure tones (f1 and f2) at the same time to stimulate specific spots in the cochlea

  • f2 is 1.2 times higher in frequency than f1

• f1 is presented at 65 dB SPL

• f2 is presented at 55 dB SPL

• The inner ear naturally creates a "distortion" sound at 2f₁ - f₂ when hit with those two tones. The probe measures this exact frequency to check specific hair cell function.

What parts of the auditory system are involved in Auditory Brainstem Response testing (ABR)?

• Outer Ear

• Middle Ear

• Inner Ear

• Auditory Nerve

• Brainstem

NOT INCLUDED:

• Cortex

What is an Auditory Brainstem Response (ABR)?

• Electrical activity generated by the auditory system in response to sound

• Stimulus: short-duration stimuli played through earphones

• Measured with electrodes on the scalp and mastoid while patient is asleep or sedated

• Used for estimating pure-tone thresholds and for neurodiagnostic purposes

What is the pathway from the auditory nerve to the auditory cortex?

Auditory Nerve, Cochlear Nucleus, Superior Olivary Complex, Lateral Lemniscus, Inferior Colliculus, Thalamus (Medial Geniculate Body), Auditory cortex

• AN | CN | SOC | LL | IC | T | AC

  • A Nice | Child Never | Should Obtain Cyanide| Lest Laurie | Ingest Cyanide | Then | Arrive Coughing |

What are the 4 neural generators of auditory brainstem response (ABR)?

1. Auditory Nerve

2. Cochlear Nucleus

3. Superior Olivary Complex

4. Lateral Lemniscus

True or false: in ABR testing, each of the 5 waves reflects activity of progressively higher parts of the central auditory system

True

In ABR testing: Wave I represents which part of the brain?

Wave I: Peripheral (distal) portion of the auditory nerve

In ABR testing: Wave II represents which part of the brain?

Wave II: Central (proximal) portion of auditory nerve

In ABR testing: Wave III represents which part of the brain?

Wave III: Cochlear nucleus

In ABR testing: Wave IV represents which part of the brain?

Wave IV: Superior olivary complex

In ABR testing: Wave V represents which part of the brain?

Wave V: Lateral lemniscus

When measuring the auditory brainstem response (ABR), what are the typical steps taken?

1. Mostly focus on waves 1, 3, and 5

2. Present the stimulus and measure the ABR

   • Start around 80 dB HL

• Decrease stimulus intensity in steps of 10-20 dB

• Measure the latency of Wave V at each intensity

  • Latency is the time location of the peak of the wave

  • ABR wave latency increases as stimulus intensity decreases

How can you find the auditory brainstem response (ABR) threshold?

It’s the lowest stimulus intensity that results in a measurable wave V

• Obtained in each ear individually, either by air conduction or bone conduction

The auditory brainstem response (ABR) threshold is strongly correlated with what value?

• The pure-tone thresholds

• We can use ABR thresholds to estimate the degree of hearing loss

  • This is highly useful in patients who cannot be tested with pure-tone audiometry, such as infants

How can an auditory brainstem response (ABR) test give us information about brain tumors?

• Presence of tumor affects brainstem transmission time

• We compare the time difference between peaks (interpeak latency)

• Tumors cause abnormally long interpeak latencies

• Tumors are often unilateral, so we can compare the interpeak latencies in the patient’s affected ear to their unaffected ear

If a person has sensorineural hearing loss, what will their ABR results look like?

They will either have abnormal ABR thresholds, or they will have absent responses

If a person has conductive hearing loss, what will their ABR results look like?

ABR will be present, but threshold and latencies will be outside of normal range

As stimulus intensity decreases, the absolute latency of the auditory brainstem response (ABR):

Increases

In 2022, how many babies were born with permanent hearing loss?

6,000 (1.8 per every 1,000 births)

What percentage of hearing loss cases are due to genetics?

50-60%

What percentage of childhood hearing loss cases are due to maternal infection, environment, or birth complications?

30%

True or false: permanent hearing loss occurs more frequently than any other condition for which we can screen at birth

True

What is the average age at which permanent hearing loss is diagnosed?

35 months

What are the 1-3-6 guidelines for early hearing detection & intervention?

• 1: Hearing screening should take place no longer than 1 month of age

• 3: Children who refer on the screening should receive a diagnostic evaluation no later than 3 months of age 

• 6: Children diagnosed with hearing loss should receive intervention no later than 6 months of age

What are 5 examples of risk factors for either congenital, delayed onset, or progressive hearing loss?

• Caregiver concern regarding hearing, speech, language or developmental delay

• Family history of permanent childhood hearing loss

• In utero infections such as herpes, syphilis, and toxoplasmosis

• Craniofacial anomalies, including those that involve the pinna, ear canal, ear tags, ear pits, and temporal bone anomalies 

• Head trauma, especially basal skull/temporal bone fracture that requires hospitalization 

True or false: NICU babies are tested using DPOAEs.

False. Healthy newborns are tested with DPOAEs, but babies in the NICU must be tested with ABRs because they face a significantly higher risk of neural and sensory hearing loss