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CHAPTER 143 – CLINICAL
ASSESSMENT AND SURGICAL
TREATMENT OF CONDUCTIVE
HEARING LOSS
CHAPTER 144 - OTOSCLEROSIS
Soroush Zaghi – October 30, 2013
COCLIA- Auditory Function Tests
• #1 ) Describe in detail the decibel scales used to measure
sounds and hearing (dB HL, dB SPL and dB SL).
• A decibel (dB) is one tenth of a bel, a unit named after
Alexander Graham Bell that was originally developed to
quantify the reduction in audio level over one mile of telephone
cable.
• The decibel scale is logarithmic, and doubling sound pressure
corresponds approximately to a 6 dB increase in level.
• A decibel is a unitless quantity, and decibels are expressed as
a ratio to a reference level sound; dB SL, db SPL, and dB SL
are decibel scales with different reference sounds.
Air pressure and sound
Air pressure at sea level is
about 101,325 Pascals (Pa) (about
one “atmosphere”) or 14.7
pounds per square inch (psi) or 1 kg
per square cm. This will register as
76 cm, or 760 mm, or 29.92 inches,
of mercury on a mercury barometer.
Sources:
http://www.usatoday.com/weather/wbaromtr.htm
http://www.valdosta.edu/~grissino/geog3150/lecture3.
htm
Micropascal and Pascal
The variations in air pressure that our ears hear as
sound are very, very small, between 20 microPascals
(mPa), or 0.00002 Pa (or newtons/m2, or 0.0002 microbar
or dyne/cm2), and 20 Pa.
Source: http://www.safetyline.wa.gov.au/institute/level2/course18/lecture53/l53_02.asp
Logarithms and the decibel scale
If you hear a sound of a certain loudness, and
then are asked to choose a sound that is twice as
loud as the first sound, the sound you choose will
in fact be about ten times the intensity of the first
sound. For this reason, a logarithmic scale, one
that goes up by powers of ten, is used to measure
the loudness of a sound. The exponent of a
number (here we use only 10) is its logarithm.
Example of a base 10 logarithm:
10 x 10 x 10 x 10 = 10,000 = 104
log10 10,000 = log 10,000 = 4
What is a decibel?
A decibel (dB) is a unit for
comparing the intensity of two
different sounds; it is not a unit of
absolute measurement. The usual
basis of comparison is a barely
audible sound, the sound of a very
quiet room, or 0.00002 Pa, at which 0
dB is set.
Bels and Decibels
The unit used to compare the
intensity of sounds was originally the
Bel (in commemoration of the work of
Alexander Graham Bell), which was the
logarithm of the intensity ratio 10:1.
This unit was considered too large to be
useful, so a unit one tenth the size of a
Bel, the ‘decibel’ (dB), was adopted.
Calculating decibels
To compare the intensities of two sounds, I1 and I2,
we place the larger value of the two in the
numerator of this formula:
10 x log I1/I2 decibels (dB)
Example: What is the difference in decibels between 3.5 and 0.02 watts?
10 log 3.5/0.02 = 10 log (175) = 10 (2.24) = 22.4 dB difference
Source: http://www.ac6v.com/db.htm
A power ratio of 1:100
If the intensity of one sound is 100
times greater than that of another,
then what is the difference in
decibels between the two sounds?
A power ratio of 1:100
If the intensity of one sound is 100
times greater than that of another,
then what is the difference between
the two sounds in decibels?
I1/I2 = 100; log 100 = 2.0 and 10 x 2.0
= 20 dB.
From softest to loudest
The intensity ratio between the faintest audible sound
and the loudest sound we can tolerate is one to one trillion,
i.e. 1012; the log of 1012 is 12, and 12 x 10 = 120 decibels,
the approximate range of intensity that human hearing can
perceive and tolerate. The eardrum would perforate
instantly upon exposure to a 160 dB sound.
Decibel levels of some common sounds
Sound Source
Sound Pressure Level (dB)
threshold of excellent youthful hearing
0
normal breathing, threshold of good hearing
10
soft whisper
30
mosquito buzzing
40
average townhouse, rainfall
50
ordinary conversation
60
busy street
70
power mower, car horn, ff orchestra
100
air hammer at 1m, threshold of pain
120
rock concert
130
jet engine at 30m
150
rocket engine at 30m
180
More decibel levels here: http://www.lhh.org/noise/decibel.htm
The Range of Human Hearing
Our sensitivity to sounds depends on both the amplitude
and frequency of a sound. Here is a graph of the range of
human hearing.
Annotated Equal Loudness Curves
Source: http://hyperphysics.phy-astr.gsu.edu/hbase/sound/eqloud.html#c1
SPL vs. HL
There are two main decibel scales.
Sound pressure level/ dB SPL- used by hearing aid
manufacturers to express the characteristics of hearing aids,
physics, engineering. Based on the standard reference sound
pressure in air or other gases is 20 µPa, which is usually
considered the threshold of human hearing (at 1 kHz).
The Hearing Level/dB HL scale is typically used on the
audiogram. Audiometric zero -- 0 dB HL -- is standardized as the
softest audible sound heard half the time by a group of young,
normal hearing listeners. The HL audiogram scale is normalized
in order to compare thresholds across frequencies more easily.
dB HL and dB SL
• The Decibel Hearing Level (dB HL) scale was developed
because the normal hearing person does not hear all tones
from 125-8000 Hz equally well. The reference value is different
for each frequency and corresponds to the average threshold
of audibility in a large sample of adults with normal hearing
tested at that same frequency.
• An audiogram uses the dB HL scale, and a completely normal
hearing person should have hearing levels at 0 db HL in all
frequencies.
• The Decibel Sensation Level (dB SL) is used to describe a
signal relative to an individuals auditory threshold at a
particular signal frequency. For example, if at 1000 Hz a
person’s threshold is 30 dB HL and a signal is at 50 dB HL,
then the sensation level of this signal is 20 dB SL.
What is the difference between dB SL
and dB HL?
The "SL" in dB SL stands for "Sensation Level". The "HL" in dB HL stands for
"Hearing Level".
SL is based on the hearing ability of an individual test subject, and dB HL
is based on the hearing ability of an entire population of test subjects.
The dB HL scale is the mean dB SL of a large population (theoretically the
world-population) of *normal hearing* people. They measured frequencyspecific thresholds for alot of people, and averaged them to give the dB HL
scale. Finally, dB nHL stands for "normalised hearing level". This is the same
concept as dB HL, except the number of test subjects contributing to the
average is smaller. It is standard practice for a Hearing Clinic to establish their
own dB nHL scale based on all the normal-hearing test subjects they have had
access to. This allows a clinic to ensure that the scale they use is correctly
calibrated to their test equipment.
COCLIA- Auditory Function Tests
• #1 ) Describe in detail the decibel scales used to measure
sounds and hearing (dB HL, dB SPL and dB SL).
• Which scale is measured relative to 20 micropascals (μPa) =
2×10−5 Pa which is approximately the quietest sound a human
can hear at 1000 Hz?
• Which scale is used in audiograms as a measure of hearing
loss and has a reference level that varies with frequency
according to a minimum audibility curve as defined by
audiology standards?
• Which scale is based on the hearing ability of an individual test
subject, and which scale is based on the hearing ability of an
entire population of test subjects?
COCLIA- Auditory Function Tests
• #2 ) You practice in Timbuktu (no audiologists to be found). Tell
us about tuning fork tests…how are they done and how should
they be interpreted?
• Evaluating hearing with a tuning fork, using combined information from the Weber and Rinne tests, can be
a useful screening tool to differentiate between conductive and sensorineural hearing loss. However, these
tests are associated with significant false- positive and –negative responses and therefore should be
utilized only as screening tools and not as a definitive evaluation of auditory function.
• Weber tuning fork test- This may be performed with a 256- or 512-Hz fork. The stem of a vibrating tuning
fork is placed on the head in the midline and the patient is asked whether the tone is heard in both ears, or
in one better than the other. With a unilateral conductive hearing loss, the tone is perceived as louder in the
affected ear. With a unilateral sensorineural hearing loss, the tone is perceived as louder in the unaffected
ear. As a general rule, a 5 dB difference in hearing between the two ears is required for lateralization.
• Rinne tuning for test- The Rinne tuning fork test is very sensitive in detecting mild conductive hearing
losses if a 256-Hz fork is used. A Rinne test compares the ability to hear by air conduction with the ability to
hear by bone conduction. The tines of a vibrating tuning fork are held near the opening of the EAC (AC),
and then the stem is placed on the mastoid process (BC). The patient is asked to indicate whether the tone
is louder by air or bone conduction. Normally and in the presence of sensorineural hearing loss, a tone is
heard louder by air conduction than by bone conduction. However, with a 30dB or greater conductive
hearing loss, the bone conduction stimulus is perceived as louder than the air conduction stimulus.
Weber Test
Rinne’s Test
COCLIA- Auditory Function Tests
• #2 ) You practice in Timbuktu (no audiologists to be
found). Tell us about tuning fork tests…how are
they done and how should they be interpreted?
• Weber tuning fork test at 512Hz lateralizes to the right. Rinne is negative on
the right and positive on the left. What kind of hearing loss?
• Weber tuning fork lateralizes to the right. Rinne is positive bilaterally. What
kind of hearing loss?
• Weber tuning fork test does not lateralize. Rinne is negative on the right and
positive on the left. The patient is found to have right-sided conductive
hearing loss. Is this an example of false positive or false negative?
• Weber tuning fork test does not lateralize. Rinne is negative on the right and
positive on the left. The patient is found to have normal hearing. Is this an
example of false positive or false negative?
Degree of Hearing Loss
COCLIA- Auditory Function Tests
• #3 ) What is the speech reception threshold (SRT) and how is it
measured?
Speech reception threshold is the lowest intensity at which a spondee
(equally weighted two-syllable word, such as “baseball”) is understood by a
subject approximately fifty per cent of the time.
In typical SRT testing, a subject is given a series of spondees through
headphones or speakers. In between the playback of each spondee, the tester
typically adjusts the sound intensity up or down until the subject's responses
are correct 50% of the time. The pure tone average and speech reception
threshold should be within 7 dB of each other.
Comparison of the speech reception threshold and the pure tone average
serves as a check on the validity of the pure tone thresholds. Discrepancies
between these measures may suggest a functional or non-organic hearing
loss.
Pure Tone Audiometry
“The aim of pure tone audiometry is to establish hearing
threshold sensitivity across the range of audible
frequencies important for communication”
Establishing a Pure Tone Audiogram
o
o
o
o
Establish which is the better ear and test first
Start air conduction testing at 1000 Hz
Begin at 30 dB HL. If there is no response, increase
intensity in 20 dB steps until you see a response
Follow the “down in 10, up in 5” rule
Air Conduction vs Bone Conduction
Testing
Air conduction tests
the entire auditory
system. Bone
conduction bypasses
the conductive
mechanism, so it
tests only the inner
ear.
ASHA Procedure
Hypothetical threshold search for a listener whose
threshold is 35 dB HL. A + indicates the listener heard
the presentation, and a - shows the listener didn’t
hear the tone. Notice that the hearing level of a trial is
raised by 5 dB following a - and is lowered by 10 dB
following a +.
Establishing a Pure Tone Audiogram
o
o
o
o
After several crossings of the same intensity,
pick threshold as an intensity where 50% of
the time the listener responds correctly
Move to 2000 Hz, 3000 Hz, 4000 Hz, and 8000
Hz (as a minimum)
Pick up the low frequency (500 and 250 Hz)
tones
Repeat for the other ear
Speech Audiometry
Materials
 Types
 Nonsense
syllables
 Monosyllabic words
 Spondaic words
 Sentence tests
Speech Audiometry
Uses:
 Sensitivity for speech
 Speech
awareness threshold
 Speech reception threshold
 Pure
tone cross check
 Speech recognition
 Differential diagnosis
 Central auditory processing
 Estimate of communicative function
Speech Audiometry
Relationship of redundancy of informational content and
sensitivity to the effects of hearing loss on three types
of speech recognition materials
Speech Audiometry
Clinical Methods
• Speech thresholds
 Speech Reception threshold
o
o
o
o
o
Start audible
Present four spondees
Calculate percent-correct response
Follow down in 10, up in 5 rule
Stop at an intensity that provides 50%
Determining Speech Threshold
COCLIA- Auditory Function Tests
• #3 ) What is the speech reception threshold (SRT) and how is
it measured?
• What do you call the average of hearing sensitivity at 500,
1000, and 2000 Hz?
• What do you call the lowest sound intensity speech at which
an individual can detect speech at least 50% of the time?
• What do you call the lowest sound intensity at which an
individual can repeat a spondee at least 50% of the time?
COCLIA- Auditory Function Tests
#4 ) How would you test speech discrimination?
•
Speech discrimination assesses an individual's ability to understand
a speech signal at normal or above-normal conversational levels.
• A phonetically balanced word list of fifty one-syllable words is
presented to the patient at a supra-threshold level.
Were those the same or different?
Speech DiscriminationOne syllable words.
Speech Discrimination
• A person with a hearing loss needs more volume in order
to hear the sounds that people with normal hearing can
hear.
• In contrast, speech discrimination is a measure of how
well you understand what you hear when speech is loud
enough to hear comfortably.
• Audiologists measure speech discrimination in percent. If
your discrimination scores are 100%, you understand
everything you hear. At the other end of the spectrum, 0%
discrimination means you can’t understand a single word
that is spoken, no matter how loud it is.
COCLIA- Auditory Function Tests
#4 ) How would you test speech discrimination?
• If a patient has hearing loss and speech discrimination is good
(80% or higher), will hearing aids be useful?
• If a patient has hearing loss and speech discrimination is poor
(below 40%), will hearing aids be useful?
• If a patient has poor discrimination ability in the presence of
relatively good hearing sensitivity, what else could be going on
?
COCLIA- Auditory Function Tests
#4 ) How would you test speech discrimination?
• If a patient has hearing loss and speech discrimination is good
(80% or higher), will hearing aids be useful?  YES.
• If a patient has hearing loss and speech discrimination is poor
(below 40%), will hearing aids be useful?  No. Will just make
things sound like louder gibberish.
• If a patient has poor discrimination ability in the presence of
relatively good hearing sensitivity, what else could be going on?
 Consider retrocochlear pathology, e.g. acoustic schwannoma.
COCLIA- Auditory Function Tests
• #5 ) Masking...what is it, why do we do it?
What is a masking dilemma?
Crossosver occurs when a sufficiently loud signal is presented
to the test ear crosses the skull and is perceived by the non-test
ear. The attained responses represent the performance of the
non-test ear rather than the test ear due to a large sensitivity
difference between the ears.
Masking is the presentation of a signal to the ear that is not
being tested to ensure that the responses obtained by the test
ear are reliable and have not been influenced by the sensitivity
of the non test ear.
• Interaural attenuattion is the reduction of sound when it crosses
from from one ear to another.
• The normal interaural attenuation of air conducted tones is 40-80 dB
depending on whether ear inserts (35-50 dB) or headphones (60-65
dB) are used. Inserts have less contact with the lateral temporal bone
than headphones, therefore less sound energy is delivered
contralaterally.
• The normal value for interaural attenuation for bone conduction is 0 -
10 dB. Interaural attenuation values tend to be smaller for lower
frequencies than higher ones.
• In the situation where the air conduction threshold of the test ear
exceeds the bone conduction threshold of the non-test ear by a value
greater than interaural attenuation, masking should be used.
When to mask Air Conduction?
• AC: when unmasked threshold in TE is greater than BC
threshold in NTE by the minimum IA value or more.
When to mask Bone Conduction?
• Mask any significant Air-Bone gap.
• Masking dilemma occurs when masking is necessary but not
possible.
• It usually occurs in cases of bilateral conductive or mixed
hearing losses with 50 dB or greater air-bone gaps.
• Its occurs when bone conduction thresholds are within normal
limits, but the air thresholds equal or exceed interaural
attenuation.
• Unmasked thresholds will likely reflect the responses of the
non-test ear, and masked thresholds may appear worse than
they actually are because of overmasking, where the masked
noise crosses over and affects the responses obtained for the
test ear.
COCLIA- Auditory Function Tests
• #5 ) Masking...what is it, why do we do
it? What is a masking dilemma?
Example: Normal hearing in the right ear. Air conduction
threshold in the left ear appears to be worse than 50 dB.
Do you need to mask the right ear to test air conduction in
the left ear?
At what threshold would you need to mask the right ear to
test bone conduction in the left ear?
Unilateral conductive hearing loss
Unilateral SNHL
Audiogram Legend
Audiogram Legend
COCLIA- Auditory Function Tests
• #6 ) Be prepared to draw and describe
the classification of tympanograms.
Type A Tympanogram
Type B Tympanogram
Type B is a flat trace with no
observed compliance or immittance
peak.
Average ear canal volumes for
children are 0.42-0.97 mL. Average
adult volumes are 0.63-1.46 mL.
• Type B (normal ear canal volume)
usually suggests effusion.
• Type B (small ear canal volume)
suggest cerumen impaction or that
the immittance probe is pushed
against the side of the ear canal.
• Type B (large ear canal volume)
suggests PET or perforation
Type C Tympanogram
• Type C - negative pressure in the middle ear system,
represents Eustachian Tube Dysfunction. Immittance
peak is measurable, but compliance peak is less than 150.
What condition does each tympanogram
represent?
COCLIA- Auditory Function Tests
#7 ) Educate us on the acoustic reflex.
What does it mean if there is “no
response”?
Acoustic Reflex
• The acoustic reflex is a
contraction of the stapedius
muscle of the middle ear in
response to loud sound.
• The pathways for this reflex
ascend from the peripheral
auditory system to the
brainstem and then descend
both ipsilaterally and
contralaterally, so presentation
of a loud sound in one ear
results in bilateral contraction of
the stapedius muscles.
• This contraction stiffens the
middle ear system, causing a
reduction in the transfer of lowfrequency energy.
Instrumentation for Acoustic Reflex
Thresholds
Acoustic Reflex- Absent
• Absence of acoustic reflexes In listeners with normal hearing,
the acoustic reflex threshold is elicited at levels approximating 85
dB HL (+/− 10 dB).
• The acoustic reflex is absent if the signal doesn’t reach the
cochlea with sufficient intensity, if there is damage affecting any of
the structures along the acoustic reflex pathway, or if there is a
stiff middle ear system in the probe ear.
• Examples: (1) CHL of 25 dB HL or greater in the stimulus ear
(2)CHL of 10 dB HL or greater in the probe ear (3) SNHL
exceeding 75 dB HL in the stimulus ear (4) a lesion of the facial
nerve in the probe ear (5)a lesion in the auditory brainstem
affecting the crossing pathway of the acoustic reflex arc (6)a
lesion of the vestibulocochlear nerve in the stimulus ear,
depending on the extent of the lesion.
COCLIA- Otosclerosis Objectives
#1) Review the histopathology of this disease.
#2) Discuss the etiology of otosclerosis.
Otosclerosis- Pathophysiology
• Otosclerosis is an osseous dyscrasia, limited to the temporal bone.
• Characterized by resorption and formation of new bone in the area of the ossicles
and otic capsule.
• The inciting event that initiates the onset this disease is unknown.
•
• The characteristic lesion of otosclerosis is a pleomorphic replacement of normal
bone with spongiotic or sclerotic bone.
• The extent and location of lesions vary. Some are relatively small and do not
involve the stapes. As the disease advances, the lesions spread across the
stapedial annular ligament, causing stapedial fixation.
• If the lesion progresses in the opposite direction to the cochlea, it results in
SNHL. It may spread in both directions, resulting in a mixed hearing loss.
• In 80-90% of patients, lesions are limited to the anterior oval window and affect its
pathology by calcification of the annular ligament or by involving the stapes,
resulting in the characteristic CHL.
Histopathology- Stapes footplate and anterior crus adjacent to an
anterior oval window otosclerotic process seen on the left. There is a small extension of
otosclerosis in the annular ligament extending to the stapedial footplate and causing
minimal fixation.
Histopathology- Three otosclerotic lesions involving the cochlear
capsule. The largest one in the anterior oval window area also is
fixing the stapedial footplate. This patient had sensorineural
hearing loss and conductive loss caused by stapedial fixation.
Histopathology-
A solid stapedial footplate wherein the annular
ligament has been totally replaced with otosclerosis.
COCLIA- Otosclerosis
• #3) What is “Schwarze’s sign”?
Schwarze’s Sign
• The earliest phase of otosclerosis
(spongiotic phase) is characterized by
resorption of bone around blood
vessels, with an increase in space
around the vascular channels, which is
replaced by cellular, fibrous connective
tissue.
• Vascular spaces become wider and if
the active focus reaches the periosteal
surface of the promontory, they may
cause a red-pink glow that can be seen
through the TM on otoscopy, known as
the Schwartze’s sign.
• This represents vascular shunts
between the otosclerotic foci and the
submucosal vessels of the promontory.
COCLIA- Otosclerosis
• #5) What is the clinical presentation of otosclerosis?
• Patients most often present with progressive hearing loss. Noticeable hearing loss
usually begins in late teens or early twenties, but it can also present later (30'searly 40's).
• Hearing loss may be accelerated by pregnancy.
• If the process involves the stapes, the hearing loss is conductive. The most
commonly affected area is the anterior crura.
• Otosclerosis may progress to involve entire stapes footplate or continue
anteriorly toward the cochlea, causing a sensorineural hearing loss. Patients may
also complain of tinnitus that progresses with the hearing loss. Occasionally, mild
to severe vertigo is also present.
• On physical, tuning fork exams are helpful but may be confusing in patients with
mixed hearing loss. The remainder of the physical exam is often normal. The
Schwartze sign is found in approximately 10% of cases and is characteristic of
otosclerosis; it occurs when increased vascularity of the promontary during the
active phase of otosclerosis is visualized as a pinkish hue behind the TM.
COCLIA- Otosclerosis
#6) You have given a clinic patient the diagnosis of otosclerosis. She is not
interested in surgery. What other options does she have?
Observation- In cases of mild CHL that does not bother patient, follow with yearly
audiogram.
Medication- Sodium fluoride therapy- In patients with evidence of progressive
sensorineural hearing loss, fluoride therapy has been shown to reduce the
progression of hearing loss. The mechanism of action is believed to be the
conversion of the active otospongiotic lesion to a more stable otosclerotic lesion.
Patients are typically treated with Florical, 8 mg three times per day, until hearing
loss stabilizes. Gastric distress is a side effect of fluoride medications; however,
most patients tolerate this effect without difficulty.
Amplification- Most patients have normal cochlear function with excellent speech
discrimination, and are therefore good hearing aid candidates.
COCLIA- Otosclerosis
#7) Discuss stapedectomy vs. stapedotomy.
• Stapedectomy: involves removal of all or part of the
stapes footplate.
• Stapedotomy: creation of a small hole in the footplate
where the prosthesis will articulate.
Stapedectomy
• The incudostapedial joint is first divided with a round or joint knife.
• Incus and malleus mobility are then checked.
• The stapedius tendon is divided with microscissors or a laser.
• A curved pick is then used to down fracture the suprastructure
towards the promontory and is then extracted. The footplate is then
removed with right angle hooks.
• Autologous tissue graft is placed over the oval window and an
appropriate sized piston or prosthesis is placed from the long process
of the incus to the graft.
Stapedotomy
- The advantage of stapedotomy include less risk of trauma
to the vestibule and less incidence of migration of the
prosthesis and fixation by scar tissue as is seen in
stapedectomy techniques.
- Microdrill vs. laser stapedotomy techniques to fenestrate
the footplate.
The curette is used to remove the posterior superior bony canal wall to obtain
better visualization of the stapes.
The curette is used to remove the posterior superior bony canal wall to obtain
better visualization of the stapes.
The distance from the incus to the footplate is measured from the lateral or medial surface
of the incus. The usual distance from the lateral surface to the footplate is 4.5 mm.
The diamond bur sometimes may be used to remove the posterior crus or
weaken it.
The microdrill and 0.7-mm diamond bur create a fenestra in the center
of the stapes footplate.
The piston is placed from the incus to the fenestra before removal of the
superstructure.
The piston is crimped around the incus before removal of the superstructure of
the stapes.
After removal of the stapes superstructure, blood is placed into the oval window
as a seal.
COCLIA- Otosclerosis
#8) What are the contraindications to surgery for otosclerosis?
Indications:
- Unilateral or bilateral otosclerosis in which the average air-bone gap of four frequencies (500, 1000,
2000, 4000 Hz) is 40 dB or more.
- Otosclerosis with severely declining bone conduction and an air-bone gap < 40 dB.
Relative contraindications:
- Air-bone gap less than 40 dB with normal bone conduction - Pediatric patient - Significant medical
comorbidities - Profound post-op vertigo from contralateral ear.
Temporarily absolute: - Otitis externa - Perforated TM (for large perforations that do not heal
spontaneously, tympanoplasty should be done prior to and separate from stapes surgery)
Absolute:
- Only hearing ear
- Significant complication in contralateral ear (arterial bleed, profound post-op sensorineural hearing
loss)
- Cochlear otosclerosis
- Coexistent Meniere's disease (significantly increases the possibility of residual hearing loss in the
operated ear)
- Documented dilation of the vestibule or the vestibular aqueduct on CT or MRI (also negatively
effects hearing outcome)
Carhart’s Notch
• #9) What is Carhart’s notch and why
does it disappear after successful
surgery?
• Carhart’s notch: An audiometric finding
characteristic of otosclerosis is a decrease
in bone conduction threshold with a peak at
2,000 Hz.
• Although the notch occurs at 2,000 Hz, a
reduction in bone conduction sensitivity is
seen from 500 to 4,000 Hz which is, on
average, 5 dB at 500 Hz, 10 dB at 1000 Hz,
15 dB at 2000 Hz, and 5 dB at 4,000 Hz.
• Carhart attributed this phenomenon to
“mechanical factors associated with
stapedial fixation.” Related to disruption of
the normal ossicular chain resonance (at
2000 Hz) vs. mechanical artifact.
COCLIA- Otosclerosis.
#10) What problems might you encounter intra-op and how would you deal with them?
Intraoperative complications of stapes surgery include:
• TM perforation: 1.9% incidence, repair if needed via underlay technique.
• Chorda injury: metallic taste, 30% of cases, usually due to stretch on nerve and resolves 3-4
months
• Bleeding: mucosal trauma (which can cause oval window fibrosis w/reclosure), persistent
stapedial artery (may bipolar artery or work around)
• Floating stapes footplate: can occur when stapes in mobilized, may be pushed into vestibule
if not careful. Control holes made to prevent further mobilization and use of hooks/needles to
get under footplate and remove safely.
• CSF gusher: CSF gush upon entering vestibule; Two sources: widened cochlear aqueduct or
defect in fundus of IAC.  Immediate HOB elevation, small hole stapedotomy and fascial
plug prior to prosthesis insertion to prevent further leak. Occasionally needed lumbar drain.
THANK YOU!