Otosclerosis

Background

  • A disorder limited to the temporal bone, causing breakdown and poor reformation of the ossicles (mainly stapes footplate) causing profound conductive and sensorineural hearing loss.
  • There is usually a family history (50%- autosomal dominant- variable penetrance) and is often associated with osteogenesis imperfecta (a triad of hearing loss, spontaneous bone fractures and blue sclera).
  • Common cause of hearing loss in young adults; slightly more common in females

Presentation

  • Hearing loss- progressive and conductive; often bilateral
    • Hearing is often better in loud environments (e.g. crowded rooms) (paracusis)
      • Loss of deep-pitch is lost first
  • 75% will also have tinnitus (progresses with hearing loss) and some will have mild transient vertigo
    • Dizziness is uncommon but occasionally vestibular involvement can cause severe nystagmus and vertigo (rotational)
  • More common to present in pregnancy, with menstruation (exacerbates) or at menopause
  • Otoscopy is usually normal but around 10% show a reddish-blue discolouration over the promontory (Schwarte’s sign)

Investigations

  • Audiometry – (usually conductive but occasionally mixed hearing loss)
  • Tympanometry- stiffness curve (low tympanic compliance)
  • Fine-slice CT- ‘halo’ sign in the temporal bone (abnormal deposition)

Management

  • Hearing aids
  • Occasionally sodium fluoride or bisphosphonates can be used but surgery (stapedectomy/stapedotomy) is the mainstay of ‘definitive’ treatment

Prognosis/Complications

  • Severe hearing loss (rarely complete deafness)
  • Stapedectomy
    • Risk of total hearing loss, facial nerve injury, eardrum perforation (correctable), taste disruption (transient in most cases); worsening tinnitus
    • In general, however, results are good

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