types of hearing loss

The three primary types of hearing loss are conductive, sensorineural and mixed. There is a fourth type of hearing loss termed central, but this classification is often managed separately since the site of the hearing problem is not in the ear.

  • Conductive Hearing Loss
  • Sensorineural Hearing Loss
  • Mixed Hearing Loss
  • Central Hearing Impairment

Conductive Hearing Loss

Conductive hearing loss occurs when sound is not conducted efficiently through the ear canal to the eardrum and the tiny bones (ossicles) of the middle ear. It usually involves a reduction in sound level or the ability to hear faint sounds. This type of hearing loss can often be medically or surgically fixed.

Examples of conditions that may cause a conductive hearing loss include

  • Blockages of the ear canal by accumulation of earwax or foreign objects
  • Infection in the ear canal (external otitis)
  • Perforated eardrum
  • Middle ear pathology such as fluid in the middle ear from colds, allergies, Eustachian tube dysfunction, ear infection (otitis media), perforated eardrum and benign tumours
  • Absence or malformation of the outer ear, ear canal, or middle ear
  • A hereditary condition (otosclerosis) where the bone grows around the tiny stapes bones in the middle ear

Sensorineural Hearing Loss

This is the most common type of hearing loss with more than 95% of people with hearing loss being affected.

Sensorineural hearing loss occurs when there is damage to the inner ear (cochlea) or to the nerve pathways from the inner ear to the brain. Sensorineural hearing loss is a permanent loss that cannot be corrected medically or surgically. It involves a reduction in the ability to hear soft sounds and also affects speech understanding and ability to hear clearly.

Sensorineural hearing loss can be caused by

  • Aging process
  • Excessive noise exposure
  • Diseases such as meningitis and Meniere’s disease
  • Viruses, such as mumps and measles
  • Drugs that are toxic to the auditory system
  • Genetic syndromes
  • Head trauma
  • Tumours

Mixed Hearing Loss

When a conductive hearing loss occurs in combination with a sensorineural hearing loss, the hearing loss is referred to as a mixed hearing loss. In other words, there may be damage in the outer and/or middle ear and in the inner ear (cochlea) or auditory nerve.

Central Hearing Impairment

When the problem is in the brain or in the nerve pathway leading to the brain, hearing difficulties are called central hearing impairment. Unlike conductive, sensorineural and mixed hearing losses, a central hearing loss does not necessarily result in a loss of hearing sensitivity. The ears may send a clear message to the brain, but the brain has difficulty understanding it. The problem here is speech understanding.

Causes of central hearing loss include

  • Disease
  • Brain damage from a stroke
  • Car accident
  • Trauma

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