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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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The LLR can be used to estimate hearing thresholds, similar to the ABR and MLR, but there are
aspects of the response to consider.
n
The response does not fully mature until individuals reach their late teenage years.
n
One advantage of the LLR has over the ABR is that the response amplitude is much greater
and therefore can be obtained in fewer sweeps.
n
The LLR reflects physiology at the level of the primary auditory cortex, providing the clinician
a broader picture of the central auditory nervous system versus the ABR, which only reflects
the central auditory system through the level of the brainstem.
n
The disadvantage of this response is the previously discussed maturation of the response (late
teens), as well as sleep state, which can diminish the response.
n
Finally, there are currently no norms published for the LLR.
Utilization of the LLR can be as follows:
n
Quantify the effects of HAs or cochlear implants through recording aided responses by
presenting stimuli through the soundfield.
n
The use of aided evoked responses is a way to potentially verify HA and implant
programming.
n
Aided LLR responses contribute to monitoring neuroplastic changes in the central nervous
system.
n
Finally, the LLR has been used to monitor neural change in response to auditory training/
rehabilitation.
P300
The P300 is unique in relation to other electrophysiologic auditory measures in that it requires the
patient or participant to be actively engaged with the task.
n
The auditory P300 is an electrophysiological test that reflects physiological function of the
primary auditory cortex (superior temporal gyrus), hippocampus, and the frontal cortex and is
observed around 300 ms after stimulus onset.
n
The response is elicited through an oddball paradigm in which the patient hears two stimuli:
a target/rare/oddball stimulus (approximately 20% of the time) and a nontarget/standard/
common stimulus (approximately 80% of the time).
n
The patient is often instructed to count the target stimuli.
n
The P300 can be elicited in other modalities, such as vision, but acoustically, it is traditionally
elicited with either tonal or speech stimuli at 60 to 80 dB peSPL.
n
As the P300 task complexity increases, the response latency will also increase with similar
effects seen on response amplitude (reductions). As the discrimination task becomes easier,
the latency should decrease while the amplitude should increase. Contrastingly, when the
discrimination tasks become more difficult, latency will increase (up to approximately 600 ms)
while amplitude decreases.
n
Latency is associated with processing speed while the amplitude is associated with the
attentional resource allocation used in the processing.
CHAPTER 5 Adult Assessment and Differential Diagnosis
A
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213
The utilization of the auditory P300 clinically in audiology is often debated as generation of the
response requires active participation in the discrimination task by the patient. The debate focuses on
the principle that if the patient is reliably able to do the task necessary to obtain a P300 response, then
what is the diagnostic value added to the case as the patient should be able to provide reliable behavioral
responses. Additionally, the P300 can be affected by state of arousal and fatigue, age, attention, task
complexity, handedness, depression, and dyslexia. While the auditory P300 is a clinically available
assessment, its use and diagnostic value is often questioned. For comparison, Figure 5–15 demonstrates
the ABR, MLR, and auditory P300 responses.
Mismatch Negativity
Mismatch negativity (MMN) is another electrophysiologic auditory measure that assesses higher-level
auditory function.
n
The MMN is an electrophysiological test that reflects physiological function of the primary
auditory cortex, frontal cortex, hippocampus, and the thalamus at approximately 100 to 300ms.
n
The response is elicited through an oddball paradigm in which a deviant stimuli is presented
alongside a standard stimulus (tone burst, speech vowels, or consonant-vowel combinations).
The MMN response is seen by subtracting responses seen from the standard stimuli to the
deviant stimuli.
n
Unlike P300, MMN is independent of attention.
n
Can be elicited with either tonal or speech stimuli at 60 to 80 dB peSPL
n
Recommended to tell the patient to ignore the stimuli during testing
n
Electrode placement is the same as P300.
n
Measurements are labeled as N1, P2, and MMN.
Similar to P300, MMN is not widely used clinically due to poor repeatability and applicability.
V
BR
+)
0
Amplitude)tlovorcim(
(–
012345678910
III
I
IV
II
Latency (msec)Latency (msec)Latency (msec)
FIGURE 5–15. ABR, MLR, and P300.
VI
VII
MLR
Pa
Nb
Na
(–)0(+)
0255075
P300
P3
P1Pb
(–)0(+)
0100 200300 400500 600
P2
N2
N1
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Testing for Specific Pathologies
Adult (Central) Auditory Processing Disorder
Beyond the standard comprehensive audiologic evaluation is central auditory processing disorders
([C]APD), which will be discussed in more detail in Chapter 6, as it is more common in the pediatric
population. Central auditory processing ([C]AP) is defined as the processing of auditory information
in the central auditory nervous system and the underlying activity that gives rise to electrophysiologic
potentials (ASHA, 2005a). (C)AP can be subdivided into specific skills, as shown in Table 5–15.
Individuals with (C)APD will often have normal hearing sensitivity on a standard audiologic
evaluation but will report many symptoms consistent with those individuals with hearing loss. For a
complete list of symptoms, see Chapter 6 and AAA (2010). Management of (C)APD is variable and
very much dependent on the specific deficit as described in Chapter 6 but may include:
n
Direct therapy
n
Indirect therapy
n
Environmental modifications
While it is beyond the scope of this chapter to have an in-depth discussion of (C)APD, the goal is
to provide a brief overview of the condition and consideration of evaluation for individuals for which
their difficulties cannot be explained using the standard audiologic evaluation. These concerns can arise
in adults and especially older adults.
AUDIOLOGY NUGGET
Many patients will present to an audiology clinic reporting difficulties with
hearing and believing they have hearing loss. However, their audiologic evaluation will generally be consistent with normal peripheral hearing sensitivity. The
standard audiologic evaluation (pure-tone air and bone conduction, SRT, WRS)
does not assess central auditory function and it is appropriate to consider a
(C)APD evaluation or make an appropriate referral to someone who can assess
auditory processing function. Screening tests and batteries have been suggested
(e.g., Dichotic Digits and Gaps in Noise; first page of the SCAN-3A).
Nonorganic Hearing Loss
While not very common, perhaps one of the most challenging situations in terms of audiological
assessment is with patients who have pseudohypoacusis, have nonorganic hearing loss (NOHL), or are
malingering. NOHL is the presence of a behavioral hearing deficit that is more significant or greater
than what can be attributed to pathology within the auditory system; it can also be referred to as
functional hearing loss or psychogenic hearing loss. The common thread with NOHL is that it exceeds
what can be explained by an organic/medical cause.
n
The prevalence of NOHL in the general population is 2% to 9%, with females twice as likely
than males to exhibit NOHL (Mathai et al., 2021).
CHAPTER 5 Adult Assessment and Differential Diagnosis
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Ability to tell the
difference between
sounds
LOCALIZATION AND
LATERALIZATION DISCRIMINATION
Representation of
auditory space due to
interaural timing and
intensity cues in order to
separate auditory signals
from competing noise
215
continues
TEMPORAL
PROCESSING
Perception of alteration
of sound within a given
Different auditory
PERFORMANCE WITH
COMPETING SIGNALS
(DICHOTIC LISTENING)
PERFORMANCE WITH
DEGRADED SIGNALS
(AUDITORY CLOSURE)
stimuli presented
distorted or missing parts
sound domain
simultaneously to both
ears
of the acoustic signal and
recognize the message
Temporal integration:
summation of neuronal
activity with duration of
sound energy (not often
Binaural integration:
report back both ears (no
order) (CW-FR, DD)
tested clinically)
Temporal masking:
masking of one sound
with an addition sound
presented immediately
Binaural separation:
report back one ear,
then the other or one
ear instead of the other
(CW-DE, CST)
prior to or following the
target sound (not often
tested clinically)
Temporal ordering:
processing two or more
auditory stimuli in order
of occurrence temporal
resolution: shortest
duration of time that is
discriminable between
two auditory signals
TABLE 5 –15. (Central) Auditory Processing Skills Information
Definition Ability to complete
Further
divisions
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Component of all
(C)AP tests
LOCALIZATION AND
LATERALIZATION DISCRIMINATION
Listening in Spatialized
Noise
TEMPORAL
PROCESSING
Ordering: Duration
Integration: Competing
PERFORMANCE WITH
COMPETING SIGNALS
(DICHOTIC LISTENING)
PERFORMANCE WITH
DEGRADED SIGNALS
(AUDITORY CLOSURE)
Words–Free Recall;
time-compressed speech,
Patterns: Frequency
Patterns, Duration
Patterns
Resolution: Gaps in
Noise; Random Gap
Detection
Dichotic Digits;
Dichotic Rhyme;
Dichotic Consonant-
Vowels; Dichotic
Sentence Identification
speech-in-noise tests,
synthetic sentence
identification with
ipsilateral competing
message
Separation: Competing
Words–Directed Ear
Competing Sentences:
Staggered Spondaic
Words; Synthetic
Sentence Identification
with Contralateral
Competing Message
TABLE 5 –15. continued
Tests Low-pass filtered speech,
CHAPTER 5 Adult Assessment and Differential Diagnosis
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n
Adults are often seeking compensation or financial gain, but also could be due to psychosocial
factors or situational avoidance.
n
Individuals scoring lower on measures of socioeconomic status have also been shown to more
likely be associated with NOHL (Mathai et al., 2021).
AUDIOLOGY NUGGET
Many individuals, both children and adults, who present with NOHL or intentionally malinger during an audiologic evaluation will often have an ulterior
motivation for the evaluation. Those motivations for adults may include some
type of financial compensation or incentive. For example, individuals who are
presenting for evaluation as part of a workers’ compensation claim, military
service, motor vehicle accident, disability payment, or any other (legal) claim in
which they stand to receive financial compensation may provide motivation for
that individual to elevate or exaggerate hearing loss (if hearing loss is present at all).
217
When completing a conventional audiological assessment, there are many signs or “red flags” of
NOHL and, subsequently, ways to approach further assessment:
n
Poor agreement between the SRT and the PTA: generally, a clinician should expect the
SRT and PTA to be within approximately 8 to 10 dB of each other with a few exceptions
(precipitous or reverse slope configurations). In cases of NOHL, the SRT will often be
obtained at a much lower (better) threshold compared to the PTA.
n
Additionally, air- and bone-conduction thresholds may not occur as expected based on
objective testing (tympanometry or MEMRs).
n
Patient behaviors: patients may exhibit excessive listening effort or appear to be trying
extremely hard to hear the stimulus.
n
Financial incentive: any assessment that is being completed for which the patient has a
financial interest (e.g., workers’ compensation claim, motor vehicle accidents, military service)
may also introduce a conflict of interest for the patient and should be approached with caution.
n
Aberrant unilateral test results: in cases of unilateral hearing loss, patients with NOHL may
never exhibit a shadow curve, meaning an unmasked stimulus is loud enough for cross-hearing
(exceeds interaural attenuation). No response is obtained from the patient with NOHL.
Figure 5–16 demonstrates a typical shadow curve when appropriate masking is not applied to
the NTE.
n
Testing considerations: patients may exhibit fewer false-positive responses as well as have a low
test-retest reliability.
n
Abnormal speech testing results: word recognition abilities may be much better than expected
at reduced SLs.
n
Objective test results disagreeing with behavioral results: normal MEMR thresholds at values
lower than would be expected with presenting behavioral thresholds or the presence of OAEs
in light of the severity of behavioral thresholds can indicate NOHL.
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FIGURE 5–16. Audiogram shadow curve.
n
General theme: poor reliability throughout testing and poor consistency/agreement within
and between behavioral and objective findings.
Testing for NOHL includes reinstruction, altering test parameters (e.g., ascending compared to
descending thresholds
— should be within 10 dB, but more exaggerated in NOHL), and the utilization
of the Stenger test, which can only be used in cases of unilateral hearing loss or significant asymmetry.
To complete the Stenger test, the asymmetry between ears needs to be at least 20 dB where it is
expected that the hearing loss is intentionally elevated and inaccurate. Please refer to the Specialty Tests
section for a description of Stenger test administration.
In addition to alterations and reinstructions that can be made as part of the behavioral audiologic
evaluation, there is a battery of objective tests that clinicians have at their disposal to provide additional
information regarding the physiology of the auditory system. The available objective tests include:
n
Acoustic immittance: MEMR thresholds that are approximate to the behavioral audiometric
thresholds (within 10–15 dB) are indicative of NOHL.
n
OAEs: present OAEs in the presence of more than a mild hearing loss (40 dB HL) are
indicative of NOHL.
n
Electrophysiological measures: thresholds measured via ABR or ASSR (as discussed in
Chapter6) are a close representation of true auditory thresholds when using correction
factors; if these objective thresholds are lower than the behavioral findings, it is safe to
suspect NOHL.
CHAPTER 5 Adult Assessment and Differential Diagnosis
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CASE EXAMPLE: NOHL
Patient is a 24-year-old male who was referred to the clinic by the Department of Workers’ Compensation. He reported a left unilateral hearing loss and tinnitus, which began after a workplace
accident 4 months ago. Patient is a carpenter and experienced noise exposure due to use of a nearby
nail gun at a work site. He stated that he is currently on administrative leave to assess the damages
that occurred. He stated that his hearing loss and tinnitus is debilitating and has severely impacted
his quality of life.
n
Audiometric findings using insert earphones demonstrated normal hearing in the right
ear and a profound hearing loss in the left ear. Unmasked bone-conduction thresholds are
worse than air-conduction thresholds in the right ear. There should be bone-conduction
responses near the right air-conduction thresholds. SRT and PTA were in agreement
for the right ear only with no response to SRT in the left ear. Word recognition scores
were good (88%) in the right ear and poor (0%) in the left ear. His initial audiometric
thresholds are presented in Figure 5–17.
n
Based on the case history and workers’ compensation claim in conjunction with
inconsistent behavioral audiologic results, it is reasonable to suspect a NOHL or
malingering.
n
In this particular case with a patient presenting with a unilateral hearing loss, the Stenger
test is appropriate and would provide the audiologist a relatively quick insight into the
validity of the thresholds.
n
Figure 5–18 and Table 5–16 demonstrate the appropriate presentation levels for the
Stenger test in this particular case.
219
FIGURE 5–17. Stenger case initial audiogram.
<
<
<
<
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FIGURE 5–18. Stenger case presentation-level audiogram.
TABLE 5–16. Stenger Case Presentation Levels
FREQUENCY (Hz)
500 1000 2000 4000
PRESENTATION
LEVEL (dB HL)
Better Ear
(Right Ear)
Poorer Ear
20 20 25 30
110 110 110 110
(Left Ear)
Tinnitus
Tinnitus is the perception of sound or noise that does not originate from an acoustical source (Baguley
et al., 2013).
n
The mechanisms behind tinnitus have yet to be fully understood, so it is important to note
that tinnitus is not viewed as a disease; it is considered a symptom of a variety of diseases and
pathologies.
n
Individuals who experience tinnitus will report the perception of a variety of sounds (e.g.,
ringing, hissing, humming, high-pitched tone).
Tinnitus can be described and classified in several ways:
1. Subjective or objective: subjective tinnitus is heard only by the patient, while objective tinnitus
is heard by the patient and others.
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2. Primary or secondary: primary tinnitus is either associated with an unknown cause or SNHL,
whereas secondary tinnitus has identifiable causes.
n
Noise-induced hearing loss (NIHL) and hearing loss have been highly correlated with
primary tinnitus. It is suggested that 90% of individuals with chronic tinnitus have hearing
loss (Hoffman & Reed, 2004; Wang et al., 2020).
n
Secondary tinnitus is typically caused by medical conditions (i.e., middle ear myoclonus).
This can also be described as somatosensory, where the perception of tinnitus is due to issues
in the somatosensory afference from the temporomandibular area or cervical spine (Michiels
et al., 2018).
AUDIOLOGY NUGGET
Somatosensory tinnitus can present as pulsatile, meaning that the tinnitus
matches an individual’s pulse. This patient should be immediately referred to otolaryngology. Further, secondary tinnitus can have auditory-related causes, such
as cerumen impaction, cochlear abnormalities, and auditory nerve pathologies,
to nonauditory causes, such as middle ear myoclonus, vascular abnormalities,
and temporal mandibular joint disorder.
To describe the tinnitus, it is important to understand what the patient is experiencing. Table 5–17
displays the different ways that tinnitus can be described.
There are numerous factors and causes that are associated with the development of tinnitus.
Associated factors can include:
n
Mental health: depression, attentional issues, anxiety, stress
n
Auditory concerns: presbycusis, noise exposure
TAB L E 5 –17. Description of Tinnitus on Different Parameters
Unilateral or Bilateral Right
Left
Bilateral
Temporal Characteristics Spontaneous
Temporary
Occasional
Intermittent
Constant
Duration Recent/acute (<6 months)
Persistent/chronic
Impact Nonbothersome
Bothersome
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