Hearing Loss

• Main categories of hearing loss

  • Conductive hearing loss
  • Sensorineural hearing loss
• Conductive hearing loss


  Relates to a problem with sound travelling from the environment to the inner ear. The sensory system may be working correctly, but the sound is not reaching it
• Conductive hearing loss causes

  • Putting earplugs in your ears
• Sensorineural hearing loss


  Caused by a problem with the sensory system or vestibulocochlear nerve in the inner ear
• Basic Ear Anatomy

  There are three sections of the ear: Outer ear, Middle ear, Inner ear
• Basic structures of the ear

  • Pinna
  • External auditory canal
  • Tympanic membrane
  • Eustachian tube
  • Malleus, Incus, Stapes
  • Semicircular canals
  • Cochlea
  • Vestibulocochlear nerve
• The Eustachian tube

  Connects the middle ear with the throat to equalise pressure
• The malleus, incus, and stapes


  Are the small bones in the middle ear that connect the tympanic membrane to the structures of the inner ear
• The semicircular canals


  Are responsible for sensing head movement (the vestibular system)
• The cochlea


  Is responsible for converting the sound vibration into a nervous signal
• The vestibulocochlear nerve


  Transmits nerve signals from the semicircular canals and cochlea to the brain
• Hearing loss may be gradual and insidious. Patients may present because others have noticed they are not paying attention or missing
• Sound transmission


  Sound vibration is converted into a nervous signal
• Vestibulocochlear nerve transmission


  Nerve signals from the semicircular canals and cochlea are transmitted to the brain
• Patients with hearing loss

  Are more likely to develop dementia, and treating the hearing loss (e.g., a hearing aid) may reduce the risk
• Weber’s and Rinne’s Tests


  Used to differentiate between sensorineural and conductive hearing loss using a tuning fork
• Weber’s Test

  Strike the tuning fork to make it vibrate and hum. Place it in the centre of the patient’s forehead. In sensorineural hearing loss, the sound will be louder in the normal ear, while in conductive hearing loss, the sound will be louder in the affected ear
• Rinne’s Test


  Strike the tuning fork to make it vibrate and hum. Place the flat end on the mastoid process to test bone conduction. Ask the patient to tell you when they can no longer hear the humming noise. A normal result is when the patient can hear the sound again when bone conduction ceases and the tuning fork is moved next to the ear rather than on the mastoid process
• Rinne’s positive

  An abnormal result where bone conduction is better than air conduction
• The sound is not heard after removing the tuning fork from the mastoid process and holding it near the ear canal, suggesting a conductive cause for the hearing loss
• Conductive cause of hearing loss

  Sound is transmitted through the bones of the skull directly to the cochlea, meaning bone conduction is intact. However, the sound is less able to travel through the air, ear canal, tympanic membrane, and middle ear to the cochlea due to a conductive problem
• Causes of Sensorineural Hearing Loss

  • Sudden sensorineural hearing loss
  • Presbycusis (age-related)
  • Noise exposure
  • Ménière’s disease
  • Labyrinthitis
  • Acoustic neuroma
  • Neurological conditions (e.g., stroke, multiple sclerosis or brain tumours)
  • Infections (e.g., meningitis)
  • Medications (Loop diuretics, Aminoglycoside antibiotics, Chemotherapy drugs)
• Medications causing sensorineural hearing loss

  • Loop diuretics (e.g., furosemide)
  • Aminoglycoside antibiotics (e.g., gentamicin)
  • Chemotherapy drugs (e.g., cisplatin)
• Causes of Conductive Hearing Loss

  • Ear wax (or something else blocking the canal)
  • Infection (e.g., otitis media or otitis externa)
  • Fluid in the middle ear (effusion)
  • Eustachian tube dysfunction
  • Perforated tympanic membrane
  • Otosclerosis
  • Cholesteatoma
  • Exostoses
  • Tumours
• Last updated

  July 2021