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