oto hearing loss evaluation

Question 1

Name the four different subclasses of presbycusis.

Answer 1

● Sensory: Loss of sensory hair cells of the basal turn,
resulting in a precipitous high-frequency SNHL and
preserved speech discrimination
● Neural: Loss of VIII nerve fibers where speech discrim-
ination may be disproportionately affected
● Metabolic: Caused by atrophy of the stria vascularis affecting all frequencies (flat audiogram); speech discrimination is frequently preserved
● Mechanical: Caused by stiffening of the basilar mem-
brane, resulting in a gradual down sloping SNHL with
proportional loss of speech discrimination

Question 2

Define mild, moderate, moderately severe, severe, and profound hearing
loss.

Answer 2

● Mild = 26 to 40 dB
● Moderate = 41 to 55 dB
● Moderately severe = 56 to 70 dB
● Severe = 71 to 90 dB
● Profound > 90 dB

Question 3

At what air-bone gap range is Rinne testing
(512-Hz tuning fork) most reliable at detecting a
conductive hearing loss?

Answer 3

Between 17 and 30 dB; any value lower or higher is more

likely to produce a false negative result.

Question 4

What is the usual air-bone gap seen with a

maximal conductive hearing loss?

Answer 4

Roughly 60 dB

Question 5

What is the interaural decibel difference required

for a Weber examination to lateralize?

Answer 5

Sound should lateralize to the ear with the largest
conductive loss or the side with the “better nerve”; a
minimum of a 5 dB difference is needed.

Question 6

Describe the reliability of bedside hearing screening.

Answer 6

Finger rub, watch-tick, whispered speech, Rinne test, and
Weber test all carry a relatively good specificity (60 to
100%), but they have low sensitivity (< 50%).

Question 7

Define hearing level as it relates to measurement of

sound intensity.

Answer 7

Hearing level is a measurement (in decibels) relative to reference data from normal-hearing ears. Normal sensitivity is defined as decibels of hearing level, which varies in absolute intensity at different frequencies because of
different frequency sensitivities of the average healthy
human ear.

Question 8

Describe the anticipated test-retest variability seen with pure tone audiometry.

Answer 8

Test-retest variability should be 10 dB or less.

Question 9

Define asymmetric hearing loss.

Answer 9

Interaural differences of greater than 15 dB in two or more
pure-tone thresholds or a difference of greater than 15% on
speech discrimination testing

Question 10

What are the advantages of binaural hearing?

Answer 10

Horizontal plane sound localization and improved speech
understanding in noise from summation, squelch, and head
shadow effect

Question 11

Describe two mechanisms that permit sound
localization from an "off-center" source in the
horizontal plane (left- or right-sided).

Answer 11

● Interaural time difference: Sound will reach the closest ear
first (low-frequency dominated).
● Interaural intensity difference: The intensity of sound in the
ear farthest from the source will be attenuated by the
head shadow effect (high-frequency dominated).

Question 12

Why is masking used during audiometric testing?

Answer 12

If sounds presented to the test ear are sufficiently loud, they
can cross over to the non-test ear. Interaural attenuation is

the loss of intensity that occurs before arriving at the non-
test ear. If sounds are loud enough to be perceived after

interaural attenuation, masking is necessary to obtain an
accurate test. Interaural attenuation for air conduction and
bone conduction is roughly 40 dB and 0 dB, respectively.

Question 13

In audiometric testing, what is meant by the term

masking dilemma?

Answer 13

A masking dilemma occurs when the required masking level
is loud enough to cross over to the test ear. This most
commonly occurs in patients with significant bilateral
conductive hearing loss.

Question 14

Describe the phenomenon of recruitment.

Answer 14

Recruitment is characterized by minimal difficulty with quiet
sounds but having a disproportionately severe noise
sensitivity at higher sound levels.

Question 15

Describe the phenomenon of rollover.

Answer 15

Rollover is characterized by a paradoxical decrease in speech
recognition with increasing sound presentation levels and is
associated with retrocochlear lesions.

Question 16

What are appropriate ages to administer the different methods of behavioral audiometric test-
ing in children?

Answer 16

● 0 to 5 months: Behavioral observation audiometry
● 5 months to 2 years: Visual reinforcement audiometry
● 2 to 5 years: Conditioned play audiometry
● 5 + years: Conventional audiometry

Question 17

Describe how behavioral observation audiometry is

performed.

Answer 17

The tester evaluates for changes in patient behavior (e.g.,

quieting, eye widening, startle) after presentation of unconditioned sound.

Question 18

Describe how visual reinforcement audiometry is

performed.

Answer 18

The participant is conditioned to provide a specific response
when he or she is able to hear a sound. For example, a child
turns the head toward the sound source and a toy lights up
to reward the behavior.

Question 19

Describe how conditioned play audiometry is

performed.

Answer 19

The participant is conditioned to perform a play activity
(e.g., throw a ball, drop a block) when he or she is able to
hear a sound. After the child has demonstrated that he or she understands the “game,” sound is presented at varying levels to determine frequency specific hearing thresholds
and speech response threshold.

Question 20

What physiologic process generates the auditory

brainstem response?

Answer 20

Synchronized responses of specific neuron populations within the auditory pathway, with later waves correspond-
ing to neuron groups farther down the transmission
pathway:
● Wave 1: Distal (lateral) auditory nerve
● Wave 2: Proximal (medial) auditory nerve
● Wave 3: Cochlear nucleus
● Wave 4: Superior olivary complex
● Wave 5: Lateral lemniscus/inferior colliculus

Question 21

Why is ABR testing useful in evaluating for retrocochlear pathology?

Answer 21

Abnormally long delays between waves (interpeak latency
of Wave 1–5) suggest pathology, such as vestibular
schwannoma, that is affecting the conductivity of the
neurons that connect structures in the auditory pathway.

Question 22

What types of audiometry can be used for evaluation

of congenital hearing loss in a 2-month-old infant?

Answer 22

Behavioral observation audiometry, ABR, and otoacoustic

emissions

Question 23

What are otoacoustic emissions?

Answer 23

Otoacoustic emissions are sound generated by outer hair cells,
either spontaneously or evoked by an auditory stimulus, that
can be detected by a microphone. They are considered a
form of objective audiometry because they do not rely on
patient participation. Generally, this type of testing is capable
of detecting losses greater than 30 to 40 dB.

Question 24

What is the advantage of distortion product
otoacoustic emissions over transient evoked
otoacoustic emissions?

Answer 24

They are capable of providing frequency specific

information.

Question 25

What ABR pattern is expected in children with | auditory neuropathy?

Answer 25

Severely abnormal or absent ABR with a present cochlear | microphonic and otoacoustic emission response

Question 26

Describe the following tympanometry patterns (modified Jerger classification) : As, A, Ad, B, and C.

Answer 26

Tympanometry tests tympanic membrane (TM) compliance (admittance vs middle ear pressure). ● Type A: Normal ● Type As (shallow): Stiffened or hypomobile TM, ossicular fixation (e.g., otosclerosis, tympanosclerosis, malleus fixation), or “glue ear” ● Type Ad (deep): Flaccid or hypermobile TM, ossicular discontinuity, or flaccid TM ● Type B: Flat tracing with no compliance peak. Must combine with canal volume (normal child-adult 0.5 to 1.5 ml) ● Type B (large volume): TM perforation or patent tympanostomy tube ● Type B (normal volume): Middle ear fluid ● Type B (small volume): Cerumen occlusion or probe against side wall of EAC ● Type C: Left shift in peak (negative middle ear pressure) associated with eustachian tube dysfunction

Question 27

Describe how stapedial reflex testing is performed.

Answer 27

Tympanometry of the ipsilateral and contralateral tympanic membrane is measured when sound, typically between 80 to 110 dB hearing level, is applied to the ear at different frequencies (500, 1,000, 2,000, and 4,000 Hz). A stapedial reflex is measured as a decrease in compliance, resulting from stapedial muscle contraction.

Question 28

Describe conditions that may result in an absent or | abnormal stapedial reflex.

Answer 28

Conductive hearing loss (e.g., otosclerosis, middle ear disease), severe SNHL, eighth nerve pathology (e.g., vestibular schwannoma), ipsilateral seventh nerve pathol- ogy (e.g., Bell palsy)

Question 29

Describe the pattern of stapedial reflex testing | seen with right-sided retrocochlear pathology.

Answer 29

● The reflexes are always absent when stimulated in the ipsilateral ear. ● Left-sided stimulus: Left response present, right response present ● Right-sided stimulus: Left response absent/elevated, right response absent/elevated

Question 30

Describe the stapedial reflex pattern seen with a thick mucoid effusion in the right ear (type B tympanogram) causing a large conductive hearing loss.

Answer 30

● Middle ear effusion can result in dampening of the incoming auditory signal. Also, stapedial reflex detection can be impaired from decreased tympanic membrane compliance. ● Left-sided stimulus: Left response present, right response absent/elevated ● Right-sided stimulus: Left response absent/elevated, right response absent/elevated

Question 31

Describe the stapedial reflex pattern seen with bilateral thick middle ear mucoid effusions (type B tympanogram) causing significant conductive hearing loss.

Answer 31

● Left-sided stimulus: Left response absent, right response absent ● Right-sided stimulus: Left response absent, right res- ponse absent

Question 32

Describe the stapedial reflex pattern seen with | proximal right-sided facial nerve pathology.

Answer 32

● The reflexes on the ipsilateral side will be affected. ● Left-sided stimulus: Left response present, right response absent ● Right-sided stimulus: lLft response present, right res- ponse absent

Question 33

Describe the stapedial reflex pattern seen with a | large intra-axial brainstem lesion.

Answer 33

● In practice, the response depends largely on the location of the lesion. However, if the intra-axial lesion is large and affects the bilateral cochlear nuclei and/or the bilateral seventh nerve motor nuclei, then the following pattern may result. ● Left-sided stimulus: Left response absent, right response absent ● Right-sided stimulus: Left response absent, right res- ponse absent

Question 34

Describe the phenomenon of acoustic decay.

Answer 34

A stimulus is presented in the ear of concern and a contralateral probe is placed. A continuous pure-tone stimulus is presented 10 dB above the stapedial reflex threshold and held for 10 seconds. The test is positive if the magnitude of the reflex drops by more than 50% in 10 seconds.

Question 35

What is the difference between the speech awareness (detection) threshold and the speech reception threshold?

Answer 35

● Speech awareness threshold is the minimum volume level (in dB hearing level) at which the subject is able to detect the presence of speech stimuli 50% of the time (although the subject does not need to recognize the word). ● Speech reception threshold is the minimum volume level at which the subject is able to correctly identify a presented word (usually a spondee) 50% of the time.

Question 36

If a patient is found to have a PTA of 40-dB hearing level, what can be predicted regarding this patient’s speech detection threshold and speech reception threshold?

Answer 36

Both should correspond with the PTA (average of pure-tone thresholds at 500, 1,000, and 2,000 Hz) within approx- imately 5 to 10 dB.

Question 37

If there is significant discordance between the pure tone average and the speech detection threshold, what diagnosis should be strongly considered?

Answer 37

Exaggerated hearing loss or pseudohypacusis (factitious | hearing loss)

Question 38

Described the methods that can be used to | evaluate for factitious hearing loss.

Answer 38

● Objective audiometry: OAE and ABR ● Behavioral audiometry: Discrepancy between speech reception test (SRT) and PTA; significant difference in test-retest scores (> 15 dB) ● Acoustic reflex testing ● Lombard test, Stenger test

Question 39

Describe the Stenger test.

Answer 39

Based on the principle that if tones of the same frequency are presented simultaneously to both ears, only the loudest is perceived. Two simultaneous tones with matched frequency are introduced, but the alleged poor ear receives a tone at a greater intensity (usually > 20 dB). The truthful patient with normal hearing will report the sound in the ear with the loudest sound level; the truthful patient with asymmetric hearing loss will report the sound in the better hearing ear; and the untruthful subject will deny hearing any sound.

Question 40

Describe the Lombard test.

Answer 40

Noise is introduced into the ear with supposed hearing loss while the patient is asked to read. The noise level is gradually increased until the patient raises his or her voice or stops reading. If there is no change in the loudness of voice, this would support a true hearing loss.