Otosclerosis

Question 1

What is otosclerosis?

Answer 1

Condition of the middle ear where one or more foci of irregularly laid spongy bone replace part of normally dense enchondral layer of bony otic capsule in the bony labyrinth.

Question 2

What is the presentation of otosclerosis?

Answer 2

Typically presents with gradual-onset, bilateral, painless hearing loss in adults aged 30–50 years

Conductive hearing loss, tinnitus, vertigo

There may be a family history of hearing loss.

The ear canal and tympanic membrane usually appear normal.

Question 3

What happens in conductive hearing loss?

Answer 3

Sounds reach the ear drum but are incompletely transferred via the ossicular chain in the middle ear, and thus partly fail to reach the inner ear (cochlea)

On audiometry, the hearing loss is characteristically low-frequency, with higher frequencies being affected later

Question 4

What causes otosclerosis?

Answer 4

Otosclerosis can be caused by both genetic and environmental factors, such as a viral infection (like measles)

Populations that have been vaccinated against measles had a significant reduction in otosclerosis

Question 5

What is key in the pathophysiology of otosclerosis?

Answer 5

The key lesions of otosclerosis are multifocal areas of sclerosis within the endochondral temporal bone

Fixation of the stapes footplate to the oval window of the cochlea. This greatly impairs movement of the stapes and therefore transmission of sound into the inner ear (“ossicular coupling”)

Additionally the cochlea’s round window can also become sclerotic, and in a similar way impair movement of sound pressure waves through the inner ear (“acoustic coupling”)

Question 6

How is otosclerosis diagnosed?

Answer 6

characteristic clinical findings:

1. Progressive conductive hearing loss
2. Normal tympanic membrane
3. No evidence of middle ear inflammation

Question 7

How would you manage otosclerosis?

Answer 7

Arrange an audiological assessment

Hearing aids