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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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192
Tympanogram
Type Ad
Type C
Compliance (mL or mmhos)
FIGURE 5–3. Tympanometry classification types.
-400
Type B
-300
-100-200
Pressure (daPa)
Type A
Type As
0100
200
Audiologists must judge not only the tympanogram but also the four values provided: equivalent
ear canal volume (ECV), static-compensated acoustic admittance (Ytm), tympanometric peak pressure
(TPP), and tympanometric width (TW) or gradient. A variety of researchers have found different
CASE EXAMPLE: CERUMEN IMPACTION
Patient is a 38-year-old female who presented with left otalgia, plugged feeling,
and drainage. She stated that symptoms started approximately 1 week ago. She
denied hearing loss, ear infections, and any recent health concerns but did report
that she has had to have her ears cleaned out due to cerumen.
n
Otoscopy revealed clear right canal and normal tympanic membrane.
Left otoscopy revealed occluding cerumen.
n
Tympanometry revealed a flat Type B tympanogram with an ECV of
3
0.17 cm
n
The overall clinical impression is left cerumen impaction. Patient wished
.
to have cerumen removed at the clinic and was not diabetic or taking
blood thinners. Cerumen was successfully removed using irrigation and
patient reported immediate relief of symptoms.
CHAPTER 5 Adult Assessment and Differential Diagnosis
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normative ranges based on age (Hunter & Sanford, 2014). Table 5–5 displays the normative ranges
while Table 5–6 shows the classification types of tympanograms regarding their values.
The ECV measurement is vital when assessing Type B tympanograms since different pathologies
can impact ECV. A breakdown of the variations of Type B tympanograms can be seen in Table 5–7.
TABLE 5–5. 90% Measurement Ranges for Tympanometric Values for Males and Females
ADMITTANCE
ARTICLE ECV (cm3)
Wiley et al., 1996 0.9–2.0 0.2–1.5 — 35–135
Roup et al., 1998 0.9–1.80 0.30–1.19 −103.5–4.2 32.8–95.0
TABLE 5–6. Measurement, Classification, Description, Pathology, and Type of HL Expected
MEASUREMENT TYPE A TYPE As TYPE Ad TYPE B TYPE C
ECV WNL WNL WNL Depends WNL
(mmho) TPP (daPa) TW (daPa)
Admittance WNL Shallow (under
normative
Deep (over
normative range)
NP WNL
range)
TPP WNL WNL WNL NP Negative
pressure
present
Description Normal
middle ear
function
Pathology Normal Otosclerosis,
Type of HL SNHL SNHL, mixed,
Note. WNL: within normal limits; NP: not present; SNHL: sensorineural hearing loss; CHL: conductive hearing loss; OME: otitis
media with effusion; PE: pressure equalizing tube; TM: tympanic membrane.
TABLE 5–7. ECV variations in Type B Tympanograms
Stiff middle ear
system
ossicular
fixation, or
low-lying otitis
media
CHL
Hypercompliant
middle ear
Ossicular
disarticulation or
TM pathology
SNHL, mixed,
CHL
Flat/nonmobile TMNegative
middle ear
pressure
Fluid, OME,
PE, TM
perforation,
Eustachian
tube
dysfunction
occluding
cerumen
Mixed or CHL SNHL, mixed,
CHL
ECV PATHOLOGY
Normal ECV Fluid/otitis media
Small ECV Occluding cerumen
Large ECV TM perforation or PE tube
Audiology Review: Preparing for the Praxis and Comprehensive Examinations
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194
Wideband Tympanometry
An expansion in technology occurred that created wideband tympanometry (WBT) as well as multifrequency tympanometry (MFT). Both of these techniques will be discussed in Chapter 6. WBT provides
additional information not available in traditional tympanometry by utilizing a transient stimulus at a
variety of frequencies, which makes WBT useful in diagnosing middle ear pathologies.
n
The range of frequencies tested include 226 to 8000 Hz delivered via click stimuli.
n
Measurement data obtained from this includes admittance (Ya), conductance (Ga),
susceptance (Ba), and phase angle (
properties of the middle ear.
CASE EXAMPLE: OTOSCLEROSIS
Patient is a 43-year-old female reporting a left hearing loss, intermittent tinnitus, and difficulty
hearing when chewing. She stated that these issues have been present for the last 2 years and appear
to be getting worse. She denied aural fullness, otalgia, and dizziness. The patient reported that she
is in the beginning stages of perimenopause.
φa), which allow for a clearer picture of admittance
n
Otoscopy revealed clear and normal canal in the right ear and a reddish (Schwartz/e sign)
tympanic membrane in the left ear.
n
Tympanometry revealed a Type A tympanogram in the right ear and a Type As
tympanogram in the left ear. The tympanometry can be seen in Figure 5–4.
FIGURE 5–4. Otosclerosis case tympanogram.
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n
Audiometric findings demonstrate normal hearing in the right ear with a moderate rising
to normal CHL in the left ear. Additionally, a Carhart’s notch is present. SRT and PTA
are in agreement. WRS is excellent bilaterally. The audiometric findings can be seen in
Figure 5–5.
n
The overall clinical impression is consistent with left otosclerosis due to the presence of a
Schwartz/e sign, Carhart’s notch, and low-frequency CHL.
195
FIGURE 5–5. Otosclerosis case audiogram.
n
Instead of the typical tympanogram, normal WBT tympanograms are “M” shaped.
n
The most useful portion of WBT is the ability to calculate resonant frequency (RF). RF varies
from high to low based on different pathologies.
Pathologies with high RF: otosclerosis
Pathologies with low RF: ossicular discontinuity and external otitis media
Eustachian Tube Testing
Immittance testing also includes Eustachian tube function (ETF) tests.
n
The Eustachian tube (ET) is important in both mucus drainage and pressure equalization
between the air and middle ear space.
n
Typically, the ET is closed in order to protect the middle ear, but it does open when
swallowing, yawning, and chewing.
n
Sickness, such as ear infections, barotrauma, upper respiratory infections, and allergies, can
cause ET dysfunction (ETD) where the tube is unable to open.
n
There are two tests that can be completed to assess ETF. These tests require a traditional
tympanogram to be completed where the patient is sitting still, then having the patient
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either blow air while holding their nose (Valsalva maneuver) and then having them swallow
(Toynbee maneuver).
n
Once all three are completed, TPP is assessed to see if there are any changes.
n
If a shift in pressure is not seen in the different test conditions, than it is thought that there
is ETD. Table 5–8 highlights what is seen during testing, and Figure 5–6 reveals normal and
abnormal ETD findings and test conditions (normal breathing, forced breathing through both
nostrils, and forced breathing through one nostril).
If the ET remains abnormally open, it is termed a patulous ET (PET). PET can be assessed by
completing tympanometry during different breathing tasks. If admittance changes are noted during
the different breathing tasks, a PET is thought to be occurring.
TABLE 5–8.
ETF TEST
ETF Testing, Patient Condition, and Tympanogram Peak Shift
PATIENT CONDITION
(MOUTH CLOSED)
TPP FROM RESTING
TYMPANOGRAM
Valsalva Holding nose and blowing air Positive shift >15–20 daPa
Toynbee Swallowing Negative shift >15–20 daPa
0.60
0.50
0.40
0.30
0.20
Admittance (mmho)
0.10
0.00
0.02.0 4.06.0 8.0 10.012.0 14.016.018.020.0
Left Ear
Normal and Quiet Breathing
Forced Breathing
Through Both Nostrils
Forced Breathing Through
One Nostril
Right Ear
0.60
0.50
0.40
0.30
0.20
Admittance (mmho)
0.10
0.00
FIGURE 5–6. Normal and abnormal PET tracings.
Normal and Quiet Breathing
Forced Breathing
Through Both Nostrils
Forced Breathing Through
One Nostril
0.02.0 4.06.0 8.0 10.012.014.0 16.018.020.0
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Middle Ear Muscle Reflex (MEMR) or Acoustic Reflex (AR)
Another useful objective tool audiologists can utilize is the MEMR (sometimes referred to as the
acoustic reflex or AR). This can assist in the differential diagnosis of a retrocochlear versus cochlear site
of lesion. Further, MEMR is used as a part of the cross-check principle, as well as in cochlear implant
testing. While there are two middle ear muscles located in the human ear (tensor tympani and stapedius muscle), there is only one that is the main contributor to the MEMR or acoustic stapedial reflex.
n
The stapedius is the smallest skeletal muscle in humans and contracts when exposed to loud
sounds, creating a stiffer TM and ossicular chain, decreasing the amount of energy reaching
the stapes footplate and oval window.
n
This change can be measured via a tympanometer and reflex activator stimulus.
The activator frequencies include 500, 1000, 2000, and 4000 Hz. There is also the option
for broadband noise (BBN).
n
MEMRs can be obtained ipsilaterally and contralaterally. Due to this bilateral response, there
are four pathways in what is known as the reflex arc, which is shown in Figure 5–7.
n
During the measurement, a probe tone (226 Hz) is responsible for the admittance, while the
activator is responsible for creating the change in admittance. This means that the MEMR is a
measurement of the decrease in admittance when an activator frequency is presented. One can
see this change via the growth chart in Figure 5–8.
When testing, one can begin the intensity around 70 to 80 dB HL to start assessing for a response.
n
If no response is noted, then increase the intensity by 5 dB HL until a response growth is
noted.
n
A reflex threshold is obtained at the level between a no response run and an enlarged
deflection.
n
The absolute mmho value is not necessarily the most important determinant of the reflex
presence; instead, it is the evidence of a growth in the response. Some audiologists in practice
utilize a value of 0.02 to 0.03 mmho to show evidence of growth.
n
Normal MEMR thresholds can range between 70 and 100 dB SPL. See Table 5–9 for normal
MEMR thresholds.
n
Responses above 100 dB SPL are considered elevated, and absent responses occur when there
is no response even at equipment limits (110 or 115 dB SPL).
As shown in the table, ipsilateral responses occur at lower intensities than contralateral thresholds.
This is due to the different pathways that these must take.
n
Research has suggested that MEMR thresholds are approximately 70 to 90 dB HL above
behavioral thresholds obtained, hence why it can be used for as a cross-check.
n
While obtaining MEMRs is quite easy, the terminology surrounding the reporting of results
still causes confusion to this day.
n
It is important to remember that one must use ANSI S3.39 standards terminology (Feeney
& Schairer, 2014), which states that recording and naming is based on the stimulus ear,
not the probe ear. Table 5–10 highlights the ANSI standard for reporting MEMRs with
normative values.
OE
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OE: outer ear
ME: middle ear
SM: stapedius muscle
IE: inner ear/cochlea
CN VIII: cranial nerve VIII/ vestibulocochlear nerve
VCN: ventral cochlear nucleus
SM
CN VII: cranial nerve VII/facial nerve
CN VII
VCN
SOC
SOC
SOC: superior olivary complex
CN VII N: nucleus of cranial nerve VII
CN VII N
CN VII N
MEIE
Left Ear
VCN
CN VIII
CN VII
SM
Right Ear
OE ME IE
FIGURE 5–7. Reflex arc diagram. Solid lines represent ipsilateral pathways and dashed lines represent contralateral pathways.
198
CHAPTER 5 Adult Assessment and Differential Diagnosis
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Y 226 Hz Ipsi 2k L
199
80
.00
mL
FIGURE 5–8. AR growth chart.
HL
.16
TABLE 5–9. Mean Normal MEMR Thresholds
ACTIVATOR
.02
500 Hz 79.9 84.6
1000 Hz 82.0 85.9
2000 Hz 86.2 84.4
4000 Hz 87.5 89.3
BBN 64.6 66.3
85
HL
.05
IPSILATERAL
(dB HL)
90
HL
.07
CONTRALATERAL
(dB HL)
TABLE 5–10. ANSI Standards for Probe and Stimulus Placement for Ipsilateral vs. Contralateral
MEMR and Sample MEMR Threshold
MEMR PROBE STIMULUS 500 Hz 1000 Hz 2000 Hz 4000 Hz
Right Ipsilateral Right Ear Right Ear 85 85 85 85
Right Contralateral Left Ear Right Ear 95 95 90 95
Left Ipsilateral Left Ear Left Ear 85 85 85 85
Left Contralateral Right Ear Left Ear 100 95 100 95
Different pathologies reveal different responses for MEMRs. Table 5–11 demonstrates pathologies
and expected reflex patterns for MEMRs.
Decay
Another objective test that could be completed to assess for retrocochlear pathologies is decay testing.
Decay is assessing if the MEMR is sustained for a specific duration or if it decreases by half of its
magnitude.
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TAB LE 5–11. MEMR Reflex Patterns and Pathologies
PATHOLOGY IPSILATERAL CONTRALATERAL
None Right: Normal Left: Normal Right: Normal Left: Normal
Right Cochlear Right:
Left Vestibulocochlear Right:
Right Middle Ear (Mild) Right:
Left Middle Ear (Severe) Right:
Left Facial Nerve Right:
Right Brainstem Right:
n
In this test, a 226 Hz probe tone is used with either a 500 or 1000 Hz activator that is
Elevated/Absent
Left: Normal
Normal
Left: Elevated/Absent
Elevated/Absent
Left: Normal
Right: Elevated/Absent
Left: Normal
Right: Normal
Left: Elevated/Absent
Right: Normal/Elevated
Left: Elevated
Normal Left: Absent Right: Absent Left: Absent
Normal Left: Absent Right: Absent Left: Normal
Normal Left: Normal Right: Absent Left: Absent
presented for 10 seconds.
n
Completed contralaterally
n
The intensity of the activator is decided by the MEMR threshold obtained, usually 10 dB
above the threshold obtained at that frequency.
n
If admittance (the MEMR) is sustained for 10 seconds, that is labeled as a negative or normal
decay. If admittance is not sustained, that is a positive or abnormal decay.
Abnormal decay is consistent with retrocochlear disorders.
n
This is noted by assessing the reflex magnitude seen in Figure 5–9.
Both MEMR and decay testing can be impacted by abnormal tympanometric findings such as
Type B tympanograms (e.g., fluid or perforation). As such, it is important to complete tympanometry,
then MEMR, then decay.
Otoacoustic Emissions (OAEs)
OAEs were discovered by Dr. David Kemp, a British physicist, in the late 1970s (Dhar & Hall, 2018).
OAEs are an objective, acoustical measure generated in the cochlea as a by-product of the cochlear
amplifier and outer hair cell motility.
n
The two common forms of OAEs are distortion product (DPOAEs) and transient evoked
(TEOAEs).
n
There are three main anatomical portions of the ear that are involved in the generation of
OAE responses: the external ear, middle ear, and the cochlea.
The pinna has very little, if any, effect on OAE responses, and the external auditory canal
can modify OAE responses.
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50%
100%
50%
100%
Magnitude of the Reflex Response
50%
100%
01
23
4567
Seconds
FIGURE 5–9. Negative and positive decay.
Negative Reflex Decay:
Response does not decay
within 10 seconds
Negative Reflex Decay:
Response decays less
than 50% in 10 seconds
50% Decay
Positive Reflex Decay:
Response decays at least
50% within 10 seconds
8910
The OAE probe is placed in the ear canal and the stimulus is delivered toward the TM.
The variations in ear canal geometry can significantly influence the quality of OAE results.
This is also true of cerumen or debris present in the canal that can impede OAE stimuli or
recordings (Dhar & Hall, 2018).
n
The middle ear plays two critical roles in OAE generation and recording: propagation of
the signal toward the cochlea and the outward movement of the OAE into the ear canal for
recording.
The stimulus, as with all sounds, utilizes the area ratio between the TM and the oval
window and the lever advantage from the ossicular chain to create an advantage as the
stimulus moves inward.
As the emission moves outward, the middle ear will impede the emission, which contributes
to the low levels with which OAEs are typically recorded (Dhar & Hall, 2018).
OAEs are heavily influenced by middle ear status; therefore, if the patient has middle ear
pathology (otitis media, middle ear effusion), the OAE responses are likely to be reduced
or absent.
n
The OHCs in the cochlea serve as the third major anatomic site involved in OAE responses
and the generation source for OAEs.
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