Otosclerosis

Risk factors

• Family history of otosclerosis
• White ancestry, particularly Northern European
• Female sex; pregnancy may unmask or worsen disease
• Possible role of measles virus in active lesions (controversial)

Pathophysiology

Foci of disorganized bony remodeling develop in the otic capsule, classically anterior to the oval window at the fissula ante fenestram. The earliest phase is otospongiotic — hypervascular, soft bone — followed by sclerotic mature bone. Encroachment on the stapes footplate progressively fixes it, producing conductive loss. Extension into the cochlear endosteum or release of cytokines into perilymph produces a sensorineural component, giving mixed loss.

Clinical presentation

Differential diagnosis

• Otitis media with effusion — Conductive loss with abnormal tympanogram (flat type B) and visible middle ear fluid on otoscopy; usually a child or follows a URI
• Tympanic membrane perforation — Visible perforation, often history of trauma or chronic otitis; conductive loss on audiogram
• Ossicular chain discontinuity — History of trauma or chronic ear disease; large air-bone gap with hypermobile tympanogram type Ad
• Cholesteatoma — Retraction pocket with keratin debris, foul otorrhea, possible conductive loss; CT temporal bone shows soft tissue and ossicular erosion
• Superior semicircular canal dehiscence — Tullio phenomenon, autophony, pulsatile tinnitus; conductive hyperacusis with intact reflexes; thin-cut CT confirms dehiscence
• Meniere disease — Episodic vertigo, fluctuating low-frequency sensorineural loss, aural fullness, tinnitus
• Paget disease of bone (temporal bone involvement) — Older patient, mixed loss, elevated alkaline phosphatase, classic skull radiographic findings

Diagnostic workup

Diagnostic algorithm

flowchart TD
  A[Young adult<br/>progressive hearing loss] --> B[Otoscopy<br/>+ tuning forks]
  B --> C{Normal TM?<br/>Weber lateralizes<br/>to worse ear?}
  C -->|Yes| D[Audiogram<br/>+ tympanometry<br/>+ acoustic reflexes]
  C -->|No| E[Pursue other cause<br/>OM/perf/cholesteatoma]
  D --> F{Air-bone gap<br/>+ Carhart notch<br/>+ absent reflexes?}
  F -->|Yes| G[Clinical otosclerosis]
  G --> H[Hearing aid trial<br/>OR<br/>stapedotomy]
  F -->|No| I[Consider alternative<br/>diagnosis / CT temporal bone]

Treatment

Complications

• Profound sensorineural hearing loss (cochlear otosclerosis or surgical complication)
• Persistent tinnitus that may not improve with surgery
• Dizziness or imbalance after stapes surgery
• Prosthesis displacement or extrusion requiring revision surgery

PANCE pearls

• Consider otosclerosis in any young adult, especially a woman, with progressive conductive loss and a normal tympanic membrane.
• Carhart notch at 2 kHz is a hallmark; it usually resolves after successful stapedotomy.
• Acoustic reflexes are an early and sensitive screen — they disappear before a large air-bone gap develops.
• Pregnancy can accelerate progression; counsel women planning pregnancy.
• If a patient with otosclerosis is intolerant of surgery or is a poor candidate, well-fitted hearing aids give comparable functional improvement.

References

• AAO-HNS — American Academy of Otolaryngology-Head and Neck Surgery Foundation: Clinical evaluation and management of otosclerosis
• Cochrane — Cochrane Review: Stapes surgery for otosclerosis
• Cummings Otolaryngology — Cummings Otolaryngology - Head and Neck Surgery, chapter on Otosclerosis