1. SDL 18: Otosclerosis

2. Otosclerosis (vague def.) Abnormal bone growth around the stapes
(specific def.) Genetically-mediated metabolic bone disorder…involving the temporal bone
1st-fibrous ankylosis of the stapes footplate
2nd-bony outgrowth, fixing stapes to the cochlear oval window
Therefore, stapes cannot vibrate like normal…hence loss of hearing
Progressive conductive hearing loss (typical)
Can involve other portions of the cochlea and actually result in sensorineural hearing loss as well.
Also says annular ligament becomes ossified to the surrounding bone (otic capsule)

3. Otosclerosis Typically pts present w/ slowly progressive hearing loss.
Annular ligament is ossified to the otic capsule.
Main point is that the STAPES CANNOT VIBRATE like normal!
Therefore, we can’t hear as we normally would
Prego women experience rapid decrease in hearing.
Typically pts present w/ slowly progressive hearing loss.
Pts usually in 20s when this starts.
Can begin yo though.

4. Genetics and Epidemiology
1 parent has it: offspring 25%
Both parents have it: offspring 50%
Caucasians.
Not sex-linked, women are twice as likely to go see a doc about it though
Affects both ears in most cases
Most studies conclude auto dom with incomplete penetrance

5. IgG Viral etiology Measles! Supporting evidence: Nucleocapsids
Nucleocapsids similar to measles found in otosc. osteoblasts
Elevated IgG against measles found in perilymph
Less occurrence after measles vaccine
Now otosclerosis is classified as organ-specific to measles virus.
Nucleocapsids
Weasels virus!
(measles)
IgG

6. Pathophys
Some studies show this is just a process of bone remodeling that affects the otic capsule
Normally, bone remodeling does not occur in the otic capsule
Bone remodeling depends directly on cytokines:
OPG, RANK & RANKL
OPG competes with RANK for the RANKL receptor on osteoblasts…thus, competitive inhibition
Normally, we have type I fibrocytes producing very high levels of OPG in the otic capsule

7. Some Mouse Study..
Knocked out OPG in mice and guess what…they experienced symptoms similar to pts with otosclerosis.
Active remodeling in otic capsule
Histology: shows early signs of otosclerosis
A: Active otosclerotic lesion involving the complete stapes footplate. Hypercellularity, several osteoclasts and osteolytic lacunae can be observed
B: Larger magnification view of the previous section. The white arrow indicates a multinucleated osteoclast performing active osteolysis. Lamellar and woven patterns of cement lines is marked by black arrow
C: Polarized light microscopic view of the previous section. The woven structure of cement lines can be well identified (black arrow). An osteoprotegerin-specific RT-PCR gave negative result. Housekeeping control RT-PCR was positive.

8. More Pathophys
Osteosclerosis replaces normal bone with dense, sclerotic bone
Two histologic phases:
1. Osteospongiotic phase
2. Osteosclerotic phase
Osteospongiotic phase.
This osteospongiotic phase can lead to a Schwartze sign. See later.
Bone resorption around existing vessels

9. Otosclerotic Phase
Resorbed bone is replaced with dense bone with few blood vessels
Osteospongiotic lesion
Osteosclerotic lesion
O: Osteoslerotic bone
N: normal bone

10. More Pathophys
80-90% of pts have lesions of the anterior oval window & calcification of the annular ligament or involvement of the stapes (old news)
8% lesions will involve cochlea and other parts of the labyrinth  sensorineural hearing loss.
2% will have both ossicular chain involvement and labyrinth
So, a combination of the normal 80-90% and the rare 8% with labyrinth involvement

11. Clinical Presentation
Principal symptoms: gradual hearing loss and tinnitus
Pts first notice they can’t hear low-pitch sounds or whispers
Can also have issues with tinnitus, balance, dizziness
Dizziness/balance ?
Progressive
Low freq.
whispers
Tinnitus!

12. Physical Exam
Eardrum is not like otitis media, looks pretty normal except!...
10% of patients will have a Scwhartze sign
Reddish blue hue over
promontory and oval
Windows
Rich vascular supply and
Immature bone present too
This pt had conductive hearing loss.
Remember, the Schwartze sign is from the osteospongiotic phase, where bone resorption occurred around existing vessels

13. Diagnosis Conductive hearing loss:
Inability to hear low frequencies
Bc tones cannot reach the inner ear. (think of some kind of physical obstruction, rather than a neural problem)
ENT physicians deal with these dudes.
Pure Tone Audiometry is used to measure hearing sensitivity.
It produces an audiograph-which plots intensity as a function of frequency

14. Exciting Exciting Audiograms..
Just the chart setup.

15. Normal Hearing

16. Conductive Hearing Loss
Hear through bone normally, not thru air
At least 10dB variance
Probably going to hear high frequencies better than low
Once again, the issue is transmitting sound waves from the outer ear, tympanic membrane, or inner ear ossicles (ossicle chain)
Think physical obstruction issue.

17. Mixed Hearing Loss Bone conduction and air conduction are depressed
But, bone conduction is usually better than air
The difference bt the two thresholds is the air-bone gap

18. Sensorineural Loss
Both poor air and poor bone conduction thresholds. NO air-bone gap!
They are within 10dB of each other
Now, thinking of nerve issues, brain processing, etc. Not some simple physical obstruction.

19. Imaging and Prognosis
Could order a CT scan to view the stapes bound to the oval window of the cochlea
BUT, it can be very hard to detect such a small issue…so, a neg CT does not rule out otosclerosis
Prognosis
Usually deteriorates until yo. Then stabilizes.
Very good prognosis with stapedectomy by ENT physicians.
They remove immobilized stapes and replace with a prosthetic.
Almost all patients have increased hearing and can fix tinnitus as well.
stapedectomy