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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4612_Библиотеки_им_академика_М_И_Перельмана
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Audiology Review: Preparing for the Praxis and Comprehensive Examinations
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262
When testing in noise is being used for documentation (e.g., for an IEP), then tests with
age-appropriate normative data are needed. More flexibility is allowed in choice of test if the
purpose is to compare performance across different listening conditions (e.g., comparison of
different hearing aid settings or comparison of testing with and without a HAT system).
n
Appropriate WR list (e.g., PBK) can be used for testing in background noise. However,
normative data may not be available. For example, Chermak et al. (1984) found that reliability
of the NU-CHIPS was impacted when tested in background noise.
The background noise may be speech-shaped noise, multitalker babble, or environmental
noise (e.g., cafeteria noise). Multitalker babble may be a better representation of noise in the
classroom with multiple people talking (Deconde Johnson & Seaton, 2021).
Physiological Evaluation
Physiological tests allow the audiologist to objectively evaluate specific portions of the auditory system.
An important concept in pediatric audiology is the cross-check principle. This principle relates to the
importance of completing both behavioral testing and physiological testing to form a complete picture
of the child’s auditory abilities. The physiological tests do not require an active response from the child.
Immittance
See Chapter 5 for a review of immittance principles. Testing considerations for the pediatric population
are included below. Recall that sound transfer depends upon:
n
Impedance (Z): the resistance of energy flow and is made up of mass and compliance
reactance and resistance, which prevent movement of the system.
n
Mass reactance (Xm): the resistance of movement caused by the mass of a system
n
Compliance reactance (Xc): the resistance to movement caused by the stiffness of a system
n
Resistance (R): the opposition of movement caused by the friction within a system
n
Admittance (Y): how much movement a system will allow to pass through (made up of mass
and stiffness susceptance and conductance); it is the exact opposite of impedance and is what
current immittance bridges utilize for testing
n
Mass susceptance (Bm): how much movement that the mass of a system allows to pass through
n
Compliance susceptance (Bc): how much movement that the stiffness of a system allows to
pass through
n
Conductance (G): how much movement that the friction of a system allows to pass through
Tympanometry
The most common tympanometric measurement uses a low-frequency probe tone (220–226 Hz) in
children greater than approximately 6 to 9 months. High-frequency probe tones (e.g., 667 or 1000Hz)
can also be used. See the High-Frequency Stimuli section in this chapter for consideration of these
probe tones. There are child-specific norms for peak static acoustic compliance, tympanometric width,
tympanometric peak pressure, and ear canal volume. The normative values vary dependent upon the
desired sensitivity/specificity.
CHAPTER 6 Pediatric Assessment and Differential Diagnosis
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n
Current recommendations, such as the ASHA (1997) guidelines for middle ear screening,
recommend utilizing normative values for static acoustic compliance or tympanometric width
rather than type of tympanograms (Hunter & Blankenship, 2017; Roush & Corbin, 2017).
n
ASHA (1997) guidelines include recommendations for referral for a middle ear rescreening
for children older than 6 to 12 months to include static acoustic compliance of <0.3 mmho
or tympanometric width >200 daPa. For infants, the recommendation is static acoustic
compliance of <0.2 mmho or tympanometric width >235 daPa.
The use of tympanometric peak pressure is not recommended as part of the middle ear
screening protocol.
n
The American Academy of Otolaryngology-Head and Neck Surgery clinical practice
guidelines for PE tubes (Rosenfeld et al., 2022) includes information on Type B (flat
tympanograms) that are associated with middle ear effusion in 85% to 100% of cases. The
American Academy of Audiology endorses these guidelines.
n
Results may be interpreted using patterns, such as described by Jerger (1970) and Feldman
(1976). Tympanometric patterns are discussed in Chapter 5.
n
Normative data can vary. Example normative data for a 226 Hz probe tone for children are
included in Table 6–3. Compliance values below the normative range are consistent with
abnormal movement of the TM (such as effusion in the middle ear), while compliance values
above the normative range are consistent with increased movement of the TM (e.g., a flaccid
TM or disarticulation of the ossicular chain). Widths larger than the normative range are
consistent with abnormal movement of the TM.
263
High-Frequency Stimuli
The current recommendation is to utilize a 1000 Hz probe for children up to 9 months of age (Joint
Committee on Infant Hearing, 2019).
TABLE 6–3. Pediatric Immittance Norms
STATIC ACOUSTIC
COMPLIANCE (mmho),
5TH–95TH PERCENTILES
6–12 months 0.20–0.50 102–234
12–18 months 0.20–0.60 102–204
18–24 months 0.30–0.70 102–204
24–30 months 0.30–0.80 96–192
Source: Information from Roush et al., 1992, as cited in Hunter & Blankenship, 2017.
STATIC ACOUSTIC
COMPLIANCE (mmho)
3–10 years 0.25–1.05 80–159
TYMPANOMETRIC
WIDTH (daPa)
TYMPANOMETRIC
WIDTH (daPa)
Source: Information from Margolis and Hunter (2000), as cited in Martin and Clark
(2006).
Audiology Review: Preparing for the Praxis and Comprehensive Examinations
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n
Low-frequency probe tones are not effective in young infants (see upcoming Audiology Nugget).
n
High-frequency probe tone should have a peaked formation to be considered normal (e.g.,
Hoffman et al., 2013). See Figure 6–1, which shows a 226 Hz probe tone tympanogram (left
panel) compared to a 1000 Hz probe tone tympanogram (right panel).
AUDIOLOGY NUGGET
Due to incomplete maturation of the external auditory canal (EAC) and middle
ear, a standard 226 Hz probe tone may not provide accurate immittance results
for children less than 6 to 9 months of age.
Some factors that may influence immittance results in young children are:
n
Excessively compliant EAC
n
Horizontal orientation of the TM
n
Underossified ossicular chain
Sound transfer depends on mass and stiffness properties (see
Multifrequency Tympanometry section).
Wideband Acoustic Immittance
Wideband acoustic immittance (WAI) uses a wideband chirp signal that measures up to 10 kHz (range
that encompasses frequencies for speech perception), which measures reflectance, absorbance, and
impedance (admittance). It is a recent addition to the immittance battery and has utility in uncovering
more detailed information about middle ear disorders in newborns, infants, children, and those with
developmental disabilities, such as the presence of low absorbance from 1000 to 3000 Hz in individuals
with otitis media with effusion (Hunter & Blankenship, 2017).
FIGURE 6–1. Example tympanograms with low-frequency (226 Hz) and high-frequency (1000 Hz) probe
tone.
CHAPTER 6 Pediatric Assessment and Differential Diagnosis
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n
Power absorbance is a WAI measure that provides information regarding the amount of
acoustic power absorbed into the middle ear at the TM relative to the total power of a
stimulus (typically a broadband click or chirp stimulus) in the ear canal.
n
Values range from 0 to 1 or 0% to 100%, with 0 (0%) suggesting no sound energy absorbed
and 1 (100%) meaning all sound energy absorbed. Results are plotted as a function of
frequency and referred to as wideband absorbance (WBA).
n
Recent evidence suggests WBA to be more sensitive to certain middle ear pathologies than
traditional tympanometry (Shahnaz, Aithal, & Bargen, 2023).
n
Please review Shahnaz et al. (2023) for detailed information regarding WAI in children.
CASE EXAMPLE
A 2-week-old infant is referred due to not passing the newborn hearing screening
using otoacoustic emissions (OAEs). The infant is being seen for a rescreening appointment, and the child has absent OAEs in both ears. Tympanometric
testing is completed with a 226 Hz probe tone, indicating Type A tympanograms with normal static acoustic compliance, tympanometric width, and peak
pressure values. Would this indicate that the absent OAEs were consistent with
abnormal outer hair cell function?
Conductive problems or abnormal movement of the TM can lead to
absent OAEs. The audiologist should note that a low-frequency probe Hz is
not effective in determining mobility of the TMs in young infants. As such,
tympanometric testing should include a high-frequency (e.g., 1000 Hz) probe
tone. If the high-frequency tympanograms are abnormal, the absent OAEs could
relate to the abnormal movement of the TM rather than cochlear function. If
results indicate normal movement, then a battery of tests (e.g., air-conduction
and bone-conduction ABR) would be needed to determine the nature of the
hearing loss.
265
Multifrequency Tympanometry (MFT)
MFT utilizes the properties of the middle ear (i.e., susceptance and conductance) to identify middle
ear pathologies by varying the frequency of the probe tone and evaluating for the normal progression
of results. MFT is used in both children and adults to more accurately determine whether middle ear
abnormalities are due to mass (e.g., mucoid effusion) or stiffness (e.g., otosclerosis) related pathologies.
MFT utilizes the physical components of the middle ear system.
n
MFT is indicated when the following audiometric results are seen during testing:
Type A tympanogram with a wide width/gradient, an As or an Ad tympanogram
When 226 Hz (Y) admittance tympanogram has a consistent (there on repeated
tympanogram) notch (i.e., 3Y). This would indicate that the resonant frequency is
abnormally low (due to either mass-loading or abnormal flaccidity).
Type A tympanogram with a conductive hearing loss component
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Abnormally large acoustic reflexes at very low sensation levels
n
Typical patterns of results are expected related to the progress of results across frequencies and
the morphology of the results.
MFT will result in multiple peaks (B and G) appearing on the tympanogram (as opposed to
the single peak that is typically seen in a normal Y tympanogram).
●
B peaks represent susceptance of the mass and stiffness of the middle ear system.
●
G peaks represent conductance of the middle ear system.
At the resonant frequency, a 3B1G configuration should be noted. Resonant frequency
) is defined as the point at which the middle ear mass susceptance equals that of stiffness
(f
0
susceptance, which leaves conductance as the only force that will act against the transfer of
sound through the middle ear space. In other words, this is the frequency that will allow for
the most efficient transfer of sound through the middle ear.
At a specific frequency, the configuration is labeled based on the number of peaks and
valleys (or extrema) observed in the B/G tympanograms:
●
Normal results will appear in certain patterns depending on the frequency at which
testing occurs.
●
Vanhuyse model predicts that in a normally functioning middle ear system, B and G
peaks will appear in four distinct patterns relative to the frequency of the probe tone used.
●
The pattern progress is 1B1G, 3B1G, 3B3G, and 5B3G.
●
Figure 6–2 depicts progression through the Vanhuyse model.
For children, normal resonant frequencies occur between 800 Hz and 1800 Hz.
For adults, normal resonant frequencies may reach as high as 2000 Hz.
Configurations should progress in order from 1B1G to 5B3G as the probe tone moves from
a lower frequency to a higher frequency.
Morphology
1. There should never be more than 5B or 3G extrema, or
2. There should never be a greater number of G than B extrema, or
3. Outermost G extrema which do not fall within the width/gradient of the outermost B
extrema.
Three extrema configuration: the width/gradient between the outermost extrema
should be <75 daPa.
Five extrema configuration: the width/gradient between the outermost extrema
should be <100 daPa.
It is important to note that while B tympanograms may appear normal, G tympanograms
may still be abnormal because the conductance (friction) of the system is affected.
n
Clinical evaluation using MFT
To examine resonant frequency, a frequency sweep typically 500 Hz to 2000 Hz is
performed.
●
Testing at lower frequencies is useful for finding stiffness-related problems such as
otosclerosis.
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FIGURE 6 –2. Pattern progression of B/G tympanograms found in Vanhuyse model.
●
Testing at higher frequencies is useful for finding mass-related problems such as mucoid
effusion.
An abnormally low resonant frequency (<800 Hz) indicates that the middle ear space is
either mass-loaded or abnormally flaccid:
●
Type Ad tympanogram with a low resonant frequency = abnormally flaccid (e.g.,
disarticulation of the ossicles, monomeric TM)
●
Type A tympanogram with a low resonant frequency = mass-loading (e.g., mucoid
effusion adhering to the ossicles)
An abnormally high resonant frequency (>1800 Hz) indicates that the middle ear space is
abnormally stiff:
●
As tympanogram with a high resonant frequency = abnormally stiff (e.g., otosclerosis
[ossification and immobilization of the stapes])
Middle Ear Muscle or Acoustic Reflexes (MEMR; AR)
MEMRs are discussed in Chapter 5. The information below is specific to the pediatric population.
n
For infants younger than 6 to 9 months of age, use of high-frequency probe tone is recommended.
n
Clinicians should be cognizant of the SPL in the ear canal (due to reduced ear canal size) of
high-intensity MEMR-activating stimuli. For infants and children, the intensity should not be
higher than 95 dB SPL (McCreery & Walker, 2017).
Audiology Review: Preparing for the Praxis and Comprehensive Examinations
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Q & A
Figure 6–3 is an example of a measure of resonant frequency.
Question: If the resonant frequency is 1000 Hz, what information does that
provide regarding the middle ear system?
Answer:
The mass and stiffness of the system are typical because the resonant
frequency (i.e., where system shifts from mass dominated to stiffness dominated)
was within the range of 800 to 1800 Hz.
n
Sensitivity prediction with the acoustic reflex (SPAR) can be used to estimate hearing
sensitivity by comparison of pure-tone MEMR thresholds (500, 1000, and 2000 Hz) and
broadband threshold. This method is less effective with those with moderate hearing losses
(Jerger et al., 1978, as cited in Northern & Downs, 2002). The SPAR is utilized less often
with the use of more common physiologic tests (e.g., OAEs and ABR).
n
MEMR, used in conjunction with tympanometric measures, can be useful in determining
the presence of middle ear effusion. In addition, MEMR can be useful as part of a battery for
FIGURE 6–3. Case example of resonant frequency for multifrequency tympanometry.
CHAPTER 6 Pediatric Assessment and Differential Diagnosis
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diagnosis of auditory neuropathy spectrum disorder (ANSD), as absent or abnormal MEMR
is expected in this population (Berlin et al., 2005).
Otoacoustic Emissions (OAEs) in Pediatric Assessments
OAEs measure cochlear (outer hair cell) responses to sound and can be an integral part of the pediatric
screening and assessment of hearing. The child must be quiet/still, as noise levels can negatively impact
the ability to see the emission response. See Chapter 5 for additional and more general information on
OAEs. Absent OAEs can indicate the possibility of sensorineural hearing loss (i.e., a problem in the
outer hair cells of the cochlea). However, conductive components or abnormal movement of the TM/
function of the middle ear can also lead to absent OAEs. As such, immittance testing in conjunction
with testing of OAEs is an important cross-check in interpretation of absent OAEs. Children with mild
hearing losses or ANSD may have present OAEs. This confirms the need for cross-checking of OAEs
results with behavioral results or with ABR. In addition, OAEs are useful in monitoring of cochlear
function in cases with risk factors such as ototoxic drugs, as the negative impact on the cochlea may be
seen earlier with OAEs than with behavioral assessment of hearing (Dhar & Hall, 2018).
Distortion Product OAEs
n
Distortion product OAEs (DPOAE) — a distortion (a third tone, typically 2f1−f 2 ) created
by two presented tones; plotted on a DP-gram (Abdala et al., 2017)
n
Must have appropriate signal-to-noise ratio (SNR) to be present, often 3 to 6 dB
(Abdala etal., 2017), in addition to amplitude of the DPOAE of >0 dB SPL (Dhar &
Hall, 2018).
Diagnostic DPOAEs are classified as present, reduced, or absent, depending on the
SNR and overall amplitude of the response. Of note, for billing purposes, a diagnostic
(comprehensive) DPOAE consists of at least 12 frequencies tested.
Screening protocols often include “pass” criteria that must be met at a minimum number
of frequencies (e.g., present OAEs at three or four tested frequencies). Screeners use a more
limited number of frequencies and as such do not provide the fine-grained information
gathered from diagnostic DPOAEs.
n
Example pediatric parameters can be found in Table 6–4 (Abdala et al., 2017).
n
DPOAEs are measured over a large frequency range, with better responses than transient-
evoked OAEs (TEOAEs) at higher frequencies (> 2000 Hz). DPOAEs will be absent with
hearing losses from 25 dB HL up to 50 to 60 dB HL (Farinetti et al., 2018).
TABLE 6–4. Example of Pediatric Parameters for DPOAEs
L1= 60–65 dB SPL;
STIMULUS
Frequency Ratio F2:F1= 1.22
Frequency Range 1500–8000 Hz
L2 SEPARATED BY 10–15 dB
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Transient-Evoked/Click-Evoked OAEs
n
TEOAEs are reflection emissions produced by irregularities along the cochlea; evoked with a
broadband click presented between 80 and 84 dB SPL, which is averaged for approximately
20 ms
n
Present if response reproducibility is > 50% and a response is present above the noise floor
(SNR)
n
TEOAEs are absent if sensorineural hearing loss is more than 40 dB HL (Farinetti et al.,
2018).
Electrophysiological Evaluation
Auditory Steady-State Response (ASSR)
The ASSR is an auditory evoked potential that measures neural responses to modulated auditory
stimuli and can be used to predict hearing thresholds when behavioral thresholds cannot be obtained.
Interpretation is mathematically based on the relationship between bioelectric events and stimulus
repetition rate (Beck et al., 2007). ASSR analysis is objective and relies on determination of presence
of a response based on statistical analyses (Korczak et al., 2012). For a comprehensive review, please
refer to Korczak et al. (2012).
n
Responses can be detected at intensity levels close to behavioral (true) threshold.
n
Can include binaural presentation of stimuli
n
Advantages of ASSR as compared to ABR include:
Testing time can be significantly shorter than ABR, as ASSR can include presentation
of multiple stimuli simultaneously (up to eight frequencies; four in each ear) (Krishnan,
2023).
ASSR can differentiate between severe to profound hearing losses better than threshold
ABR (Eder et al., 2020).
n
Previously referred to as steady-state evoked potential (SSEP)
Other responses that follow modulations are called amplitude-modulation-following
response (AMFR), envelope-following response (EFR), steady-state response (SSR), and the
auditory steady-state response (ASSR).
n
The ASSR has a carrier frequency (CF; the frequencies being tested) and a modulation
frequency (MF).
Neural Generators of ASSR (Korczak et al., 2012)
n
ASSRs elicited by stimuli presented at modulation rates < 20 Hz have responses mainly
generated by activity in the primary auditory cortex.
n
ASSRs elicited by stimuli presented at modulation rates 20 to 60 Hz have responses mainly in
the primary auditory cortex, auditory midbrain, and thalamus.
n
ASSRs elicited by stimuli at rates > 60 Hz generated primarily by contributions from the
superior olivary complex, inferior colliculus, and cochlear nucleus (brainstem).
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These are unaffected by subject state (similar to the ABR), whereas those derived from
slower modulation rates (< 60 Hz) that result from activity at higher levels of the auditory
system are influenced by subject state.
Typically, higher stimulation rates are used in children when searching for threshold.
Protocols for ASSR
n
If used as a screening tool, recommendations are to use a “pass” intensity of 40 dB HL at
2000and 4000 Hz, 45 dB HL at 1000 Hz, and 50 dB HL at 500 Hz (Van Maanen &
Stapells, 2009, 2010, as cited in Korczak et al., 2012).
n
Recommended protocols include obtaining a chirp ABR threshold in both ears; use 10 to 20
dB above this threshold to start the frequency-specific thresholds for ASSR. Obtain responses
down to 10 to 20 dB nHL for stimuli frequencies of 500, 1000, 2000, and 4000 Hz (Sininger
et al., 2020).
Threshold Auditory Brainstem Response (ABR)
ABRs are auditory evoked potentials that can be used to assess the neurologic status of the auditory
system (i.e., neurodiagnostic) or used to estimate hearing sensitivity (threshold ABR). The primary use
for the pediatric population is to determine auditory sensitivity through threshold ABR testing. For a
description of abnormal auditory electrophysiological findings, see Appendix 6–A.
Stimuli for Threshold ABR
n
Clicks
Broadband signals that contain a wide range of frequencies and therefore not frequency specific
Leads to responses to a large portion of the cochlea and represents the part of the cochlea
with the best hearing within 500 to 8000 Hz (Krishnan, 2023)
n
Chirps
Brief tonal stimuli with frequencies adjusted in timing of presentation (i.e., low frequencies
presented first so that the more apical low-frequency regions of the basilar membrane are
activated at the same time as the high-frequency regions near the base)
Improve the neural synchrony (Krishnan, 2023), providing a larger wave V amplitude
compared to clicks due to how chirps simultaneously stimulate each frequency place along
the basilar membrane
Latency of chirp responses has been shown to be longer than responses to click stimuli
(Cobb & Stuart, 2016).
n
Frequency-specific stimuli
Tone bursts or pips (500, 1000, 2000, and 4000 Hz)
Narrowband chirps are filtered around center frequencies (500, 1000, 2000, and 4000 Hz)
to allow more frequency-specific results (Eder et al., 2020).
●
Produce larger wave V amplitude as compared to clicks and tone pips (Cobb & Stuart,
2016)
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