ENT (Otorhinolaryngology) · MU Sofia

11. Otosclerosis.

Covers otosclerosis, a bone disorder of the otic capsule that fixes the stapes footplate and can involve the cochlea, moving from definition to aetiopathogenesis and the three types: fenestral, cochlear and mixed. It then describes symptoms and signs such as Schwartze sign and the Carhart notch, the audiometry, tympanometry and HRCT findings, and treatment with sodium fluoride, hearing aids, stapedotomy and stapedectomy. Surgical indications, contraindications, complications and a differential diagnosis list close the note.

Inside: 7 sections · 2 labelled pictures · 15 flashcards · 5 min

Topic 11 of 52 in the MU Sofia syllabus for ENT (Otorhinolaryngology) (Medicine, Year 4). The free AceMed note covers it in 7 sections, about 666 words (5 min of reading), with 15 flashcards.

In this note

  1. Otosclerosis.
  2. Etiopathogenesis
  3. Classification
  4. Clinical Picture
  5. Paraclinical and Radiological Examinations
  6. Treatment Options
  7. Possible Complications

Otosclerosis.

1. Definition: Otosclerosis (otospongiosis) is a primary localized bone dyscrasia of the otic capsule characterized by:

  • Replacement of normal dense endochondral bone with vascular spongy bone (otospongiosis) → later sclerotic bone
  • Most commonly involves the fissula ante fenestram → stapes footplate fixation → conductive hearing loss
  • May also affect the cochlea → sensorineural component (cochlear otosclerosis)

Etiopathogenesis

  • Genetic Predisposition: It is a familial disorder in about 50% of cases, autosomal dominant inheritance pattern with variable expression. Several linked loci: OTSC1–OTSC10
  • Viral Infection: Measles virus may act as a trigger in genetically predisposed individuals.
  • Hormonal Factors: more common and often progresses faster in women, often worsening during pregnancy.
  • Race: More common in Caucasians than in other ethnic groups.
  • Autoimmune: Evidence of immune-mediated bone remodelling abnormalities
  • Bone remodeling disorder: Abnormal osteoclast and osteoblast activity

Pathogenesis

  1. 1. Spongiosis (Active Phase): Areas of abnormal bone resorption create a vascular, spongy, soft, demineralized bone.
  2. 2. Sclerosis (Inactive Phase): The spongy bone is replaced by dense, mature, but disorganized sclerotic bone.

When the focus of otosclerosis involves the stapes footplate, it restricts the normal piston-like movement required for sound transmission, leading to a Conductive Hearing Loss (CHL). If the focus spreads to the cochlea (cochlear otosclerosis), it can also cause Sensorineural Hearing Loss (SNHL) due to damage or biochemical changes within the inner ear.

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