[15] Otosclerosis

Question 1

What is otosclerosis?

Answer 1

A genetically mediated metabolic dysplasia affecting the bony tissue of the otic capsule and ossicles

Question 2

What is the otic capsule?

Answer 2

The skeletal elements enclosing the inner ear mechanism

Question 3

What is the pathology in otosclerosis?

Answer 3

Increased bone turnover leading to sclerosis and failure of the sound conduction mechanism

Question 4

Why is there failure of the sound conduction mechanism in otosclerosis?

Answer 4

Due to ankylosis (fusion) of the stapes footplate in the fenestra ovalis of the cochlea

Question 5

What does ankylosis of the stapes footplate in the oval window lead to?

Answer 5

Slowly progressive conductive hearing impairment

Question 6

What can happen to the conductive hearing impairment in some cases of otosclerosis?

Answer 6

Progresses to a mixed hearing loss

Question 7

Why can otosclerosis progress to a mixed hearing loss?

Answer 7

The bony tissue can extend into the cochlea itself

Question 8

What is the inheritance of otosclerosis?

Answer 8

Autosomal dominant with variable penetrance

Question 9

What does penetrance mean in terms of genetics?

Answer 9

Whether those who have the genotype display the phenotype

e.g. not all those with otosclerosis genotype will have the ‘condition’ (variable penetrance)

Question 10

What is thought to be critical in the phenotypic activation of otosclerosis?

Answer 10

Environmental factors

Question 11

What environmental factors are thought to play a role in the activation of otosclerosis?

Answer 11

• Oestrogens
• Fluoride
• Viral infections such as measles

Question 12

What are the risk factors for developing otosclerosis?

Answer 12

• White or asian
• Female
• Age 15 - 35
• Family history

Question 13

What are the main symptoms of otosclerosis?

Answer 13

• Progressive hearing loss

- Tinnitus

Question 14

In what percentage of cases of otosclerosis is hearing loss bilateral?

Answer 14

70%

Question 15

Are vestibular symptoms present in most cases of otosclerosis?

Answer 15

No

Question 16

What additional symptom may present in otosclerosis?

Answer 16

• Speaking in a low volume

Question 17

Why do patients with otosclerosis sometimes speak in a low volume?

Answer 17

Their voice appears loud to them

Question 18

What will be seen on a Rinne and Weber’s test in most cases of otosclerosis?

Answer 18

Conductive hearing loss

Question 19

What is the primary investigation of choice in otosclerosis?

Answer 19

Audiometry

Question 20

What does audiometry typically show in otosclerosis?

Answer 20

Conductive hearing loss particularly at low-tones

Question 21

What is a useful diagnostic investigation in otosclerosis?

Answer 21

CT scan

Question 22

Why is CT scanning useful in otosclerosis?

Answer 22

It can rule out other differentials and improve targeting for surgery

Question 23

What are the differentials for otosclerosis?

Answer 23

• Chronic suppurative otitis media
• Glue ear
• Damage to the ossicle from infection
• Congenital stapes fixation
• Post-infective tympanosclerosis
• Paget’s disease of bone
• Osteogenesis imperfecta

Question 24

How can the management of otosclerosis be divided?

Answer 24

• Medical

- Surgical

Question 25

How can otosclerosis be medically managed?

Answer 25

• Bilateral hearing aids

- Sodium fluoride to slow progression

Question 26

How can otosclerosis be surgically managed?

Answer 26

Stapedectomy (removal of footplate) or stapedotomy (hole made in the footplate)

Question 27

How can surgery help in otosclerosis?

Answer 27

Improves circulation of fluid within the cochlear canal

Question 28

What are the potential complications of otosclerosis?

Answer 28

• Hearing loss of 50-60dB

Question 29

Is deafness common in otosclerosis?

Answer 29

No