Hearing Loss

 

• Differential diagnosis

  Sensorineural

  Unilateral:

  • Meniere's disease.
  • Acoustic neuroma. See brain tumours.

  Bilateral:

  • Presbycusis
  • Noise induced: high-frequency loss, with notch on the audiogram at 4 kHz.
  • Drug toxicity: aminoglycosides, furosemide, aspirin.
  • Congenital: CMV, rubella, Alport syndrome (plus glomerulonephritis), Pendred syndrome (plus goitre).

  Conductive

  Unilateral:

  • Impacted earwax.
  • Glue ear (uni or bilateral).
  • Infection: otitis media, otitis externa.
  • Cholesteatoma

  Bilateral:

  • Otosclerosis
  • Glue ear (uni or bilateral).

• Investigations

  • Pure tone audiometry to test hearing across range of frequencies, plotted on audiogram. Hearing >20 dB is normal.
  • Impedance audiometry (aka tympanometry) measures pressure in middle ear and tympanic membrane compliance.

• Presbycusis

  • Age-related, bilateral sensorineural hearing loss.
  • Mainly affects higher frequencies, with 'ski slope' appearance on pure tone audiometry.
  • Treated with hearing aids.

• Otosclerosis

  • Progressive, bilateral conductive hearing loss, mainly low frequency, and tinnitus.
  • Autosomal dominant inheritance.
  • Temporal bone initially becomes spongy and vascular, and later sclerosed.
  • Onset age 20-40 years, commoner in women and exacerbated by pregnancy.
  • Treat with hearing aids or surgical replacement of the stapes – via stapedectomy or stapedotomy – with a prosthesis.

• Meniere's disease

  Presentation

  • Vertigo, tinnitus, and unilateral sensorineural hearing loss. May feel fullness in ear.
  • Nystagmus may occur.
  • Recurrent episodes over several years, but usually resolves eventually.

  Management

  • Buccal or IM prochlorperazine during attacks.
  • Betahistine to prevent attacks.
  • Vestibular rehabilitation if chronic vertigo develops.
  • Contact DVLA and avoid driving until symptoms controlled.
  • MRI is needed to rule out acoustic neuroma, which also causes unilateral sensorineural hearing loss and vertigo.

• Cholesteatoma

  Pathophysiology and epidemiology

  • Non-malignant but expanding mass trapped in the temporal bone (middle ear or mastoid).
  • Histologically like an epidermoid cyst, with an epithelial lining shedding desquamated keratinized squamous cells into the mass.
  • Etiology unclear: may result from tympanic retraction which fills with keratin, and/or chronic middle ear infection.
  • Causes bony destruction and, less commonly, invasion into neighbouring structures.
  • Onset at any age, but most commonly 10-20.

  Signs and symptoms

  Ear:

  • Unilateral conductive hearing loss.
  • Offensive otorrhea.
  • Vertigo
  • Otoscopy may show crust in the pars flaccida ('attic crust').

  Invasion:

  • CN7 palsy.
  • Meningitis or brain abscess.

  Management

  Surgical removal.