Otosclerosis
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Ahlam DreamsOtosclerosis
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Ahlam DreamsOTOSCLEROSIS
DR AHLAM ALZUWAY
otosclerosis
General considerations:
slowly progressive unilateral or bilateral conductive hearing loss.
Most commonly presents by the third and fourth decades.
Frequent family history of otosclerosis.
Normal otoscopic examination or positive schwartze sign.
Audiogram with carhart notch and abnormal or absent stapedial reflexes.
otosclerosis
Otosclerosis is a disease process unique to the temporal bone ,it nearly
exclusively involves the otic capsule.
Characterised by abnormal removal of mature dense otic capsule bone by
osteoclasts,and replacement with the wove bone of greater thickness,
cellularity, and vascularity.
Its carries a distinct predilection for the region near the anterior border of
the oval window (fissula ante fenestram),but it may involve any part of the
bony labyrinth.
Women to men ratio 2:1 (hormonal influences during pregnancy might cause a
more rapid progression in women ,bringing them to clinical attention)
Most pts presenting between the ages of 20 & 45 yrs.
pathogenesis
The otic capsule & stapes form from a cartilaginous analge,which begins
endochondral ossification by the 19th wk of embryogenesis & complete by the
1st year of life.
The vestibular surface of footplate remain cartilaginous throughout the life.
However, with otosclerosis there is increased osteoblastic and osteoclastic
activity and vascular proliferation.
The otosclerotic focus is defined by an area of increased bony turnover and
metabolic activity and the term otospongiosis is most descriptive of the
histologic appearance at this stage of the disease.
As the disease stabilizes, the normal bone of the otic capsule is replaced
with a focus of metabolically quiescent dense mineralized bone.
pathogenesis
The most common location of the otosclerotic focus is the region of the
fissula ante fenestram.
Fixation of the stapes begins as the lesion spreads to involve the annular
ligament. Extension over the footplate is uncommon but may lead to total
obliteration of the footplate.
Less frequently, lesions may extend into the inner ear and involve the
endosteal layer of the otic capsule, resulting in hyalinization of the spiral
ligament and SNHL.
Rare cases of pure SNHL from isolated cochlear otosclerosis without ossicular
involvement have been reported.
pathogenesis
In most cases, the disease is inherited as a simple autosomal-dominant trait
(Polymorphisms in the COLlAl and RELN genes have been associated with
otosclerosis )
Recent findings suggest an association between the measles virus and
otosclerosis.
Symptoms and signs
History of slowly progressive hearing loss, usually bilaterally ,but may occur
unilaterally in 30% of pts
Patient may report improved hearing with background noise (paracusis of
willis)
Hearing deficits become apparent when reach 25 to 30 dB loss.
Tinnitus is a common and may indicate SNHL
Flactuations in hearing are uncharacteristic but may occurring during times of
hormonal instability. eg, pregnancy
Vertigo rare