ENT - Otosclerosis

Question 1

What is otosclerosis?

Answer 1

Remodelling of the small bones in the middle ear leading to conductive hearing loss

Primarily the base of the stapes is affected where is attached to the cochlea preventing it from transmitting sound effectively

Can be inherited in an autosomal dominant pattern

The development of otosclerosis is thought to result from a combination of environmental and genetic factors, although the exact mechanism is not understood

Question 2

Presentation of otosclerosis

Answer 2

Typically presents in patients under 40

Can be unilateral or bilateral

Hearing loss - tends to affect the lower pitched sounds more

Often there is a family history

Tinnitus

Due to conductive hearing loss with intact sensory hearing, the patient can experience their voice as being loud compared to the environment (due to bone conduction of their voice). This can lead to them talking quietly.

Question 3

Examination in suspected otosclerosis

Answer 3

Otoscopy - will be normal

Webers -

• normal if bilateral and both ears affected equally
• Otherwise louder in the more affected ear

Rinne’s -
- Conductive hearing loss pattern in the affected ears

Question 4

Investigations in suspected otosclerosis

Answer 4

Audiometry first -
- will show conductive hearing loss pattern, with more hearing loss at lower frequencies typically

Tympanometry - will show generally reduced admittance (absorption) of sound. The tympanic membrane is stiff and non-compliant and does not absorb sound, reflecting most of it back.

Can also do high-resolution CT scans to detect bony changes (not always needed)

Question 5

Management of suspected otosclerosis

Answer 5

Conservative - hearing aids

Surgical:

• Stapedectomy - removing the stapes and replacing it with a prosthesis
• Stapedotomy - removing part of the stapes bone and leaving the base of the stapes (the footplate) attached to the oval window. A small hole is made in the base of the stapes for the prosthesis to enter.