Otosclerosis (Otospongiosis)

Description

• A primary bone dyscrasia involving the otic capsule
• This is the leading cause of conductive hearing loss in adults.
• There are two forms:
  • Histologic otosclerosis: asymptomatic form in which abnormal bone spares vital structures of the ear
  • Clinical otosclerosis: Abnormal spongy bone involves ossicular chain or other structures, leading to altered physiology.
• System(s) affected: sensory, hearing

Epidemiology

• Predominant age
  • Clinical onset usually in early 20s
  • Peak incidence 3rd to 5th decade
• Predominant gender: female > male (2:1)

• Histologic form: 4–8% among U.S. Caucasian population; 1% among African Americans
• Histologic form: U.S. Caucasian population: 5,000/100,000; African Americans: 1,000/100,000
• Clinical form: 0.3–0.4%

Etiology and Pathophysiology

• Unknown; possible association with measles virus infection, hormonal factors, cytokine-related inflammation, fluoride metabolism, and oxidative stress

• 50–60% of those affected give positive family history.
• Appears to be transmitted by autosomal dominant gene with variable expressivity

Risk Factors

Unknown, possibly measles virus infection

Commonly Associated Conditions

• Van der Hoeve syndrome (rare triad of osteogenesis imperfecta, blue sclera, and otospongiosis)
• Tinnitus, usually low frequency