Osteosclerosis

Question 1

What is the pathophysiology of osteosclerosis?

Answer 1

Disease of otic capsule or bony labyrinth, where hard, compact labyrinth bone is replaced by patches of spongy bone

• Bony overgrowths affect footplate of stapes -> fixation -> CHL
• Involvement of spiral ligament -> SNHL

Question 2

What are the clinical features of osteosclerosis?

Answer 2

• *Chronic progressive HL
• Begins around 30yo
• Predominantly CHL (but can also be SNHL), usually bilateral
• May begin or worsen during pregnancy (thought to accelerate disease progression)
• +ve FHx

Quiet speech as patients are able to hear their own voice (? Due to loss of stapedial reflexes?)

Tinnitus

Positional vertigo

Question 3

What are the investigations done for otosclerosis?

Answer 3

• Otoscopy -> *normal TM
• **PTA-> characteristic “Carhart’s notch” around 2kHz (increase in BC threshold at 2 kHz)
• Tympanometry -> compliance may reduce after early stages
• Stapedial reflexes -> reduced/absent
• High-resolution CT -> hypodense area anterior to oval window, thickening of stapes footplate

Question 4

What is the treatment for otosclerosis?

Answer 4

Observation (if mild) +/- hearing aid (if symptomatic) *hearing aids help both SNHL or CHL

Stapedectomy (large hearing loss) 🡪 fixed stapes removed and replaced by piston which connects to incus to allow for transmission of vibrations; usually curative BUT risk of severe post-op SNHL (1-4% risk), or worsened tinnitus

Cochlear implant (expensive around SGD20k, and not 100% effective)