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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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272
●
May show decreased amplitudes and frequency sensitivity at high intensity levels (Small
& Stapells, 2017)
Protocols for ABR Threshold Testing
n
Single or alternating polarity is acceptable, although alternating should be used for bone-
conduction testing.
n
Test air conduction for each ear (2000, 500, 4000, then 1000 Hz).
n
Can perform a click or chirp threshold first, then start frequency-specific testing 10 to 20 dB
above this threshold. Obtain responses down to 10 to 20 dB nHL for stimuli frequencies of
500, 1000, 2000, and 4000 Hz (Sininger et al., 2020).
n
To determine conductive component, especially when testing infants, can compare air- to
bone-conduction ABR thresholds to determine if air-bone gaps are present
Must consider masking when testing via bone conduction to obtain ear-specific results
n
Use high-intensity clicks to assess for ANSD or other neurological problems (see protocols for
ANSD below).
AUDIOLOGY NUGGET
ABR thresholds are measured in dB nHL, which has a reference to behavioral
thresholds that would correspond to the intensity that elicits an ABR response
(Krishnan, 2023). However, when used in determining degree of hearing loss
or in fitting amplification based on ABR results, correction factors are utilized
to allow for estimation of an equivalent HL value (i.e., dB eHL). For example,
the British Columbia Early Hearing Program uses a correction factor of −15
at 500Hz, −10 at 1000 Hz, and −5 at 2000 Hz (as cited in Small & Stapells,
2017). Using these correction factors, a child with an ABR threshold of 55 dB
nHL at 1000 Hz would be estimated to have a 45 dB HL behavioral threshold
at 1000 Hz (45 dB eHL). It is always recommended that each clinic develop
their own normative values for correction factors, but most manufacturers will
include presets to give an estimated audiogram depending on thresholds determined via ABR (or ASSR).
Protocols for ABR Screening
n
ASHA (1997) guidelines suggest the following stimulus conditions for screening ABR: click
at 35 dB nHL at rate 37/s, minimum 1,000 repetitions for operator-controlled ABR.
n
For automated ABR systems, a chirp stimulus at 35 dB nHL may be used at rates up to
92clicks/s (Krishnan, 2023).
n
Similar to screening OAEs, these results are reported as a “pass” or “refer” (or “fail”).
n
Thresholds are not established with screeners and follow-up diagnostic testing is required to
do so.
CHAPTER 6 Pediatric Assessment and Differential Diagnosis
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Protocols for Auditory Neuropathy Spectrum Disorder (ANSD). As ANSD has specific hallmark
273
ABR responses, a separate protocol is necessary for testing (Norrix & Velenovsky, 2014). Other results
that can indicate ANSD include present OAEs (may disappear with age), abnormal MEMRs, speech
recognition that is poorer than expected, and variable pure-tone thresholds.
n
Patients with ANSD have abnormal or absent ABR with present cochlear microphonic (CM).
CM arises from the outer hair cells and mimics the stimulus waveform/polarity (sinusoid
following the repetition rate of the stimulus).
Measured via a high-intensity (e.g., 90 dB nHL, 2,000 sweeps, rate of 21.1 clicks/s) click
with condensation and with rarefaction polarities (Krishnan, 2023).
Inversion of the responses with changes in stimulus polarity will be seen in normal responses
(Figure 6–4, panel A); alternating polarity cancels the CM (Figure 6–4, panel B).
Recommendations include a control run: closing off the insert earphone to prevent the
stimulus from going into the ear. This ensures the CM is no longer measured and that the
appearance of a waveform is not stimulus artifact.
Frequency Following Response (FFR)
The frequency following response (FFR) reflects sustained neural activity that is phase-locked to the
stimulus waveform, with the complex ABR (cABR) being a form of FFR. Although it has yet to be
widely adopted clinically, the FFR has had a resurgence in research in the past 20 years. A detailed explanation of the FFR and its applications can be found in Krishnan (2023). The following information is a
cursory review.
n
There are two forms of the FFR: envelope FFR (eFFR) and the FFR. Each is elicited in the
brainstem by harmonically related complex sounds, such as a consonant vowel (CV) stimulus
(e.g., ba or da).
A
B
FIGURE 6–4. ABR results seen with auditory neuropathy spectrum disorder.
Audiology Review: Preparing for the Praxis and Comprehensive Examinations
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274
eFFR reflects phase-locking to envelope periodicity (slow varying amplitude oscillations) of
the stimulus waveform.
●
The eFFR response typically occurs after wave V of the ABR (>5.5 ms).
●
To separate the eFFR from the FFR, an alternating polarity signal can be used wherein
rarefacting and condensing runs are summed.
●
The eFFR is also referred to as the auditory steady-state response (ASSR) to tonal stimuli.
The ASSR, as described in this chapter, is used in threshold estimation for individuals
unable to complete behavioral audiometry.
FFR reflects phase-locking to the temporal fine structure (rapid amplitude oscillations) of
complex sounds.
●
Response occurs simultaneously with the eFFR (i.e., onset after the cochlear microphonic
and wave V of the ABR). The traditional paradigm for recording the FFR includes the
use of 500 Hz tones, but tonal stimuli up to 2000 Hz or complex stimuli can be used.
●
Neural generators of the FFR have been the subject of many investigations, such
that there is thought to be unique generators for different frequencies of the FFR:
Low-frequency responses arise from the auditory cortex and surrounding areas while
high-frequency responses are from brainstem structures and CN VIII.
●
The FFR is analyzed relative to its spectral information, like the eFFR.
●
Like the eFFR, the FFR has limited clinical utility at present but has the potential
to allow for exploration of neural encoding in individuals with hearing loss, aging
individuals, and those undergoing auditory training.
The recording setup for these responses can be the same as the traditional ABR, but the
stimuli vary based on the auditory area of interest.
The recording window depends on stimuli duration: ~15-ms window for shorter tonal
stimuli; ~250-ms window for longer stimuli such as speech.
●
Frequency analysis: FFT, spectral correlation, spectrogram
●
Time analysis: response latency, stimulus-response correlation; autocorrelogram, phase
coherence (Krishnan, 2023)
Complex ABR (cABR)
A popular form of the FFR is the complex ABRs (cABR). These potentials are unique from the traditional ABR in that they use stimuli such as music, syllables, nonspeech vocalizations, and environmental
sounds (Skoe & Kraus, 2010). Stimuli are presented at suprathreshold levels with the goal of examining
the amount of neural synchrony to the onset, sustained component, and offset of the stimulus.
n
These responses arise from the brainstem to the cortex and have many research applications as
well as clinical applications in the realm of (C)APD, training measures, and other neurological
disorders (Skoe & Kraus, 2010). For more literature on the cABR, the reader is directed to
Skoe and Kraus (2010) and Krishnan (2023).
Middle and Late Latency Responses in Children
(See Chapter 5 for Testing Procedures)
Middle and cortical evoked responses applications when working with children vary and are still being
developed.
CHAPTER 6 Pediatric Assessment and Differential Diagnosis
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n
Middle latency response/auditory evoked (MLR/MLAEP) (Cacace & McFarland, 2015)
Threshold estimation: NOT used among children because they are highly variable and, in
some instances, not present when a child is asleep.
Central auditory processing disorders: abnormal MLRs have been seen in children with
learning disabilities.
Cochlear implants: MLRs evoked through electrical pulses (like a cochlear implant) are
similar to an acoustically evoked response.
Though potential is seen in these areas, there is the need for more research to verify
feasibility in clinical use.
n
Cortical potentials (CAEP) (Tremblay & Clinard, 2015)
P1-N1-P2 potential can be used as a measure of threshold for patients who are passively
cooperative.
●
Thresholds have been found to be within 10 dB of behavioral thresholds.
CAEPs can reliably be measured in the soundfield, which allows for testing using
amplification or cochlear implants; this is beginning to be used clinically as a verification
measure.
●
Differences of developmental patterns of P1-N1-P2 have been seen after cochlear
implantation.
275
The P1-N1-P2 has also been used to monitor performance following auditory training
exercises and in (C)APD.
Other potentials include the P300 and MMN and are more commonly used for research.
See Chapter 5 for additional information.
Etiology of Pediatric Hearing Loss
Etiology of hearing loss in the pediatric population can be related to many factors, including genetics,
ototoxicity, noise-induced hearing loss, infections, and other medical conditions (e.g., otitis media with
effusion or cholesteatoma). Hearing loss may also be syndromic (i.e., associated with other symptoms/
disorders) or nonsyndromic. In addition, hearing loss may be prenatal (e.g., due to maternal infections),
perinatal (e.g., oxygen deprivation during birth), or postnatal (e.g., bacterial meningitis). Etiologic
factors may be noted in the case history, or the audiologist may detect signs/symptoms that may necessitate referral to other professions (e.g., physicians, genetic testing). It is important to consider the risk
of progressive hearing loss in determining how to monitor hearing for children. Examples of syndromes
and of other infections/disorders seen in the pediatric population are noted below. Readers can refer to
Northern (2014) for a more comprehensive list of pediatric hearing disorders.
Syndromic Hearing Loss
Hearing loss can be associated with various syndromes. These syndromes may lead to conductive,
sensorineural, or mixed hearing losses. See Table 6–5 for common pediatric syndromes that are associated with hearing loss.
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TABLE 6–5. Examples of Pediatric Syndromes
SYNDROME/
DISORDER TYPE OF HL
Alport Syndrome Progressive SNHL X-linked (commonly);
Branchio-Oto-Renal
(BOR) Syndrome
Mixed, but can be
CHL or SNHL
GENETIC
INHERITANCE CHARACTERISTICS
Kidney failure; abnormalities
can be autosomal
dominant or recessive
of the eye (which may not
impact vision)
Autosomal dominant Preauricular pits, abnormal
pinna, stenosis, atresia,
fused ossicles, inner ear
malformations; kidneys may
be absent or underdeveloped
CHARGE
(Coloboma, Heart
defect, Atresia choane,
Delayed growth and
development, Genital
abnormality, Ear
abnormality)
Mild to profound HL
(depending on CNS
function); balance
problems
Sporadic gene
mutation
Hole in eye structure
(coloboma); blocked or
narrowed nasal passages;
abnormal CNS function;
auricular deformities (often
asymmetrical); middle or
inner ear malformations
possible; vestibular system
may be impacted; delayed
cognitive development
Cleft Palate CHL Autosomal dominant Malformed palate and/or
lip; risk of Eustachian tube
dysfunction and otitis media
Crouzon Syndrome CHL Autosomal dominant Craniosynostosis (fused skull
and facial bones); possible
stenosis, atresia, middle ear
deformities; high risk of otitis
media
Down Syndrome Primarily CHL; at
increased risk for
SNHL or mixed
HL as compared to
general population
Chromosomal
disorder, majority are
trisomy 21
Craniofacial characteristics
(e.g., broad nasal bridge,
almond-shaped eyes, large
tongue); heart problems,
ear infections; intellectual
functioning is impacted
Goldenhar Syndrome CHL, SNHL, or
mixed HL
Possibly hereditary,
sporadic cases
Unilateral problems with eye
and facial malformations;
unilateral microtia, atresia,
pits/tags, middle ear problems;
can impact heart, kidneys, and
CNS
Jervell and Lange
Nielson Syndrome
Profound bilateral
SNHL
Autosomal recessive Cardiac arrhythmia
(JLNS)
CHAPTER 6 Pediatric Assessment and Differential Diagnosis
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TABLE 6–5. continued
277
SYNDROME/
DISORDER TYPE OF HL
Landau-Kleffner
Syndrome
Auditory agnosia;
normal ABR but
abnormal behavioral
GENETIC
INHERITANCE CHARACTERISTICS
Autosomal dominant Sudden- or gradual-onset
aphasia and seizures; linguistic
regression
Neurofibromatosis II Progressive SNHL Autosomal dominant Bilateral vestibular
schwannoma; balance
problems, tinnitus, facial
weakness
Pierre Robin Sequence CHL Genetic, but usually
not hereditary
Stickler Syndrome Sloping HF SNHL;
Autosomal dominant Impacts connective tissue and
possible cleft palate
(mixed)
Micrognathia, retroglossia;
otitis media with effusion
collagen; inner ear structures;
vision may be impacted;
chronic otitis media
Treacher Collins
Syndrome
CHL Autosomal dominant Craniofacial impact;
malformed ears– microtia,
anotia, atresia; hypoplastic,
ankylosed, or absent ossicles;
may impact vision
Usher Syndrome SNHL; degree
depends on Type I, II,
or III
Autosomal recessive Retinitis pigmentosa; onset
of visual impairment is in the
first 10 years for Type I, with
later onset for Type II.
Vestibular problems are seen
in Type I.
Waardenburg
Syndrome
Wolfram Syndrome Bilateral, progressive,
Note. CHL: conductive hearing loss; SNHL: sensorineural hearing loss; HF: high frequency; CNS: central nervous system; HL:
hearing loss.
SNHL Autosomal dominant Pigmentation abnormalities;
can impact vision
Autosomal recessive Diabetes; can impact
sloping HF SNHL
intellectual function
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CASE EXAMPLE
Edie, a 9-month-old child with Down syndrome, is scheduled for an assessment.
The case history indicates that she was born full term with no pregnancy or birth
complications. She is being followed for problems related to her heart. Edie has
a significant history of ear infections. By parent report, the otolaryngologist
reported that Edie’s ear canals are too small for placement of pressure-equalization
(PE) tubes. Test results show no movement of the TM (Type B tympanograms)
for both 226 and 1000 Hz probe tones with ear canal volumes of 0.2, bilaterally.
DPOAEs are absent in both ears. Edie would not condition to the VRA task.
What is your interpretation of the test results, and what is the next step in
Edie’s plan of testing?
The ear canal volumes obtained during immittance testing are at the low
end of normal but could be consistent with small ear canals that can be seen in
children with Down syndrome. Moreover, the tympanograms would be consistent with abnormal movement of the eardrum, consistent with middle ear
infections. The absent DPOAEs could then be consistent with the abnormal
movement of the eardrum. Because of developmental requirements of VRA
testing, infants with Down syndrome can be delayed in their ability to successfully perform the task (Nightengale et al., 2020). Given these results, the
recommendation would be to schedule ABR testing to estimate the type and
degree of hearing loss. The ABR should include both air- and bone-conduction
testing. In addition to the baseline ABR testing, the hearing should be monitored,
given the risk for recurrent middle ear disorder and the risk for speech-language
delays in this population.
Infections and Disorders
Other infections and disorders may be associated with pediatric hearing loss. Examples can be found in
Table 6–6. It is important to note that certain infections (e.g., (s)TORCH infections) can be associated
with progressive hearing loss. The possibility of a progressive nature of hearing loss has implications for
consistently monitoring auditory status in these patients. The reader can refer to the 2019 Joint Committee on Infant Hearing revised risk indicators for recommendations regarding monitoring frequency
(Joint Committee on Infant Hearing, 2019).
CHAPTER 6 Pediatric Assessment and Differential Diagnosis
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TABLE 6–6. Examples of Pediatric Infections and Disorders
INFECTION/DISORDER
INFECTION/DISORDER ASSOCIATED HEARING LOSS
DESCRIPTION AND IMPACT
Childhood infections
279
Bacterial Meningitis Severe to profound
Bilateral/symmetrical
SNHL
Fluctuating or progressive
Mumps
(Mizushima &
Murakami, 1986)
Profound
Unilateral
SNHL
Bacterial infection that can enter and
damage the inner ear; can lead to
ossification of the cochlea; sequelae
also include problems with vision
and cognition
Viral infection that causes swollen
salivary glands and can damage the
inner ear
Sudden onset
In utero infections
Syphilis Severe to profound
Bilateral
SNHL
STD transmitted from mother to
fetus; in addition to hearing loss, can
impact central nervous system (CNS)
and vestibular system
Early onset/rapid progression
or late onset/sudden
Toxoplasmosis Sensorineural HL Parasitic infection from cat feces or
litter; in addition to hearing loss,
can impact vision and cognitive
function; can lead to hydrocephaly,
microcephaly, and cerebral palsy
Rubella Mild to profound
Bilateral
SNHL
Cookie bite configuration
common
CMV Severe to profound
Bilateral (symptomatic) or
unilateral (asymptomatic—
majority of babies)
SNHL
Can fluctuate or progress;
delayed onset
Herpes SNHL
Delayed onset, progressive
Risk depends on gestation of
transmission; in addition to hearing
loss, can impact heart function,
vision, and intellectual function
Type of herpes that increases risk if
transmitted during pregnancy or if
immunocompromised; in addition to
hearing loss, can impact vision
Prenatal or perinatal (more severe)
transmission; in addition to hearing
loss can lead to other neurologic
problems
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CASE EXAMPLE
Jamal is a 3-month-old infant being seen for an audiological assessment. In the
hospital, Jamal was in the well-baby nursery and did not have any symptoms
of infection. He passed the initial hearing screening via OAEs in the well-baby
nursery. However, testing in the hospital determined that Jamal had congenital
cytomegalovirus (cCMV). By parent report, he has been taking medication
for the cCMV, and his viral load has decreased significantly. Jamal is being
followed by early childhood intervention (ECI) due to his risk of developmental
delays. Recommendations following a passed hearing screening were for Jamal’s
hearing to be monitored regularly. On the current test date, tympanometry
using a 1000-Hz probe tone indicated normal TM mobility bilaterally. Based
on this case history information, the audiologist performed threshold auditory
brainstem response (ABR) testing using click and tone burst (500, 2000, and
4000Hz in both ears). Bone conduction ABR was also completed. The ABR
testing with masking revealed a moderate sensorineural hearing loss in the right
ear, with responses at normal intensity levels in the left ear. Why could a hearing
loss caused by cCMV be missed in a newborn hearing screening? What are the
recommendations for this child?
The hearing loss with cCMV can be progressive. As such, it is possible
that the right ear either had normal hearing or had a slight loss that would be
missed by screening OAEs. The hearing loss could have progressed to a moderate
hearing loss by the appointment when Jamal was 3 months old. Given the progressive nature of cCMV, it is important to counsel parents regarding options
for a unilateral hearing loss.
In this case, Jamal was fit with a hearing aid in his right ear. His hearing
continued to be monitored. At 12 months of age, Jamal’s hearing had progressed to a severe-to-profound loss in the right ear and a mild loss in his left
ear. At that time, he was referred to a cochlear implant team for his right ear.
Due to the continued possibility of progression of hearing loss, Jamal received
a cochlear implant at 14 months of age in the right ear. His hearing progressed
to a moderate hearing loss in the left ear, for which he received a hearing
aid. The recommendation also would include assessment and treatment by a
speech-language pathologist, in addition to continuation of monitoring by the
physicians on his team.
(Central) Auditory Processing Disorder ((C)APD)
(Central) auditory processing disorder presents in children with normal peripheral auditory sensitivity,
yet they experience difficulty with various (and more complex) auditory tasks. Its etiology is thought
to be abnormal function of the central auditory nervous system (CANS), whether due to an insult,
lesion of the system, or functional difficulties related to immaturity of the CANS. Characteristics of
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(C)APD are associated with difficulties not only in auditory skills but are seen in speech/language and
academic difficulties.
n
Common issues include difficulty in background noise, difficulty following oral directions,
poor listening skills, academic difficulties, poor auditory association skills, easily distracted or
inattentive to auditory signals, and hyperacusis. It is important to recognize that (C)APD is a
continually evolving field of research and there are different views on causes, symptoms, and
management. It is best managed by an interdisciplinary team that can examine the impact/
relation to not only auditory skills but to communication and education.
Definition and Purpose of (C)APD Testing
ASHA convened a group of professionals to develop a working definition of auditory processing difficulty in 2005. In 2010, AAA released their statement, which supported this definition.
n
“Difficulties in the processing of auditory information in the central nervous system (CNS) as
demonstrated by poor performance in one or more of the following skills” (ASHA, 2005)
Sound localization and lateralization
Auditory discrimination
Auditory pattern recognition
Temporal aspects of audition (including temporal integration, temporal discrimination,
temporal ordering, temporal masking)
Auditory performance in competing acoustic signals (including dichotic listening)
Auditory performance with degraded acoustic signals
n
Purpose of (C)APD testing is to diagnose (C)APDs and identify areas of difficulty; the second
purpose then is to devise management and treatment intervention programs for individuals
with (C)APD.
n
Categories of (C)APD include
Developmental (C)APD: present in children with normal audiometric hearing, with no
known etiology or defined lesion
Acquired (C)APD: occurs in patients with no previous of history of auditory processing
difficulties, who later present with auditory processing difficulties
n
Diagnostic criteria
Two tests at least 2 standard deviations below the mean for at least one ear (ASHA, 2005;
AAA, 2010); note that there is disagreement regarding this criterion in that some suggest
the use of as little as 1 standard deviation below the mean to make a diagnosis of (C)APD.
Poor performance on one test may be considered abnormal if results are 3 standard devia-
tions below the mean and/or consistent with severe functional difficulties (ASHA, 2005).
n
Educational implications
U.S. Court of Appeals for the Ninth Circuit ruled that (C)APD can be classified as
Other Health Impaired (OHI) for qualification for special education services through the
Individuals with Disabilities Act (IDEA) in E.M. v. Pajaro Valley Unified School (2019).
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