CHAPTER 143 – Clinical Assessment and Surgical Treatment of Conductive Hearing - PowerPoint Presentation

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CHAPTER 143 – Clinical Assessment and Surgical Treatment of Conductive Hearing LossChapter 144 - OtoscleroSis

Soroush Zaghi – October 30, 2013

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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 a

pproximately

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.

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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

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Micropascal and Pascal The variations in air pressure that our ears hear as sound are very, very small,

between

20 microPascals

(

m

Pa

), 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

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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

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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.

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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.

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Calculating decibels To compare the intensities of two sounds,

I

1

and

I

2

, 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

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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?

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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?

I

1

/

I

2 = 100; log 100 = 2.0 and 10 x 2.0 = 20 dB

.

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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. 10

12

; the log of

10

12

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.

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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

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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.

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Annotated Equal Loudness Curves

Source:

http://hyperphysics.phy-astr.gsu.edu/hbase/sound/eqloud.html#c1

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SPL vs. HL There are

two main decibel scales.

S

ound

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.

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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.

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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 frequency-specific 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.

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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? 


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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.

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Weber Test

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Rinne’s Test

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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?

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Degree of Hearing Loss

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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.

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Pure Tone Audiometry“The aim of pure tone audiometry is to establish hearing threshold sensitivity across the range of audible frequencies important for communication”

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Establishing a Pure Tone AudiogramEstablish which is the better ear and test firstStart 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

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Air Conduction vs Bone Conduction TestingAir conduction tests the entire auditory system. Bone conduction bypasses the conductive mechanism, so it tests only the inner ear.

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ASHA ProcedureHypothetical 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 +.

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Establishing a Pure Tone AudiogramAfter 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

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Speech AudiometryMaterialsTypesNonsense syllables

Monosyllabic words

Spondaic words

Sentence tests

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Speech AudiometryUses:Sensitivity for speech

Speech awareness threshold

Speech reception threshold

Pure tone cross check

Speech recognition

Differential diagnosis

Central auditory processing

Estimate of communicative function

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Speech AudiometryRelationship of redundancy of informational content and sensitivity to the effects of hearing loss on three types of speech recognition materials

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Speech AudiometryClinical MethodsSpeech thresholdsSpeech Reception threshold

Start audible

Present four spondees

Calculate percent-correct response

Follow down in 10, up in 5 rule

Stop at an intensity that provides 50%

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Determining Speech Threshold

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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?

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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?

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Speech Discrimination- One syllable words.

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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

.

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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 ?

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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.

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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.

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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.

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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.

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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.

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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?

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Unilateral conductive hearing loss

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Unilateral SNHL

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Audiogram Legend

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Audiogram Legend

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COCLIA- Auditory Function Tests#6 ) Be prepared to draw and describe the classification of tympanograms.

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Type A Tympanogram

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Type B TympanogramType 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

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Type C TympanogramType C - negative pressure in the middle ear system, represents Eustachian Tube Dysfunction. Immittance peak is measurable, but compliance peak is less than -150.

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What condition does each tympanogram represent?

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COCLIA- Auditory Function Tests#7 ) Educate us on the acoustic reflex. What does it mean if there is “no response”?

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Acoustic ReflexThe 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 low-frequency energy.

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Instrumentation for Acoustic Reflex Thresholds

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Acoustic Reflex- AbsentAbsence 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.

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COCLIA- Otosclerosis Objectives#1) Review the histopathology of this disease.

#2) Discuss

the etiology of

otosclerosis

.

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Otosclerosis- Pathophysiology Otosclerosis is an osseous dyscrasia, limited to the temporal bone.C

haracterized

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.

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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.

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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.

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Histopathology-   A solid stapedial footplate wherein the annular ligament has been totally replaced with otosclerosis.

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COCLIA- Otosclerosis #3) What is “Schwarze’s sign”?

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Schwarze’s SignThe 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.

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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's-early 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.

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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

.

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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.

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StapedectomyThe 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.

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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. 

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The curette is used to remove the posterior superior bony canal wall to obtain better visualization of the stapes.

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The curette is used to remove the posterior superior bony canal wall to obtain better visualization of the stapes.

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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.

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The diamond bur sometimes may be used to remove the posterior crus or weaken it.

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The microdrill and 0.7-mm diamond bur create a fenestra in the center of the stapes footplate.

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The piston is placed from the incus to the fenestra before removal of the superstructure.

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The piston is crimped around the incus before removal of the superstructure of the stapes.

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After removal of the stapes superstructure, blood is placed into the oval window as a seal.

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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 earSignificant 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

)

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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 H

z) vs. mechanical artifact.

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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.

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THANK YOU!