Types of hearing loss

There are three types of hearing loss: conductive hearing loss, sensorineural hearing loss and mixed hearing loss.

Conductive hearing loss

Conductive hearing loss can be acquired or congenital and is caused by blockage or damage in the outer and/or middle ear. A conductive hearing loss leads to a loss of loudness and can often be helped by medical or surgical treatment.

Some of the causes of conductive hearing losses are:

• blockages of the ear canal by impacted wax or foreign objects
• outer ear infection (sometimes the result of swimming)
• 'glue ear' (middle ear infection), a common problem in young children
• perforated eardrum, maybe from a bad middle ear infection or an accident
• otosclerosis, a hereditary condition where the bone grows around the tiny stirrup bones in the middle ear
• partial or complete closure of the ear canal.

Sensorineural hearing loss

Sensorineural hearing loss can be acquired or congenital and is caused by damage to, or malfunction of, the cochlea (sensory part) or the hearing nerve (neural part).

Sensorineural hearing loss leads to a loss of loudness as well as a lack of clarity. The quantity and the quality of sound are affected and sometimes may limit the benefit of a hearing aid.

Causes of acquired sensorineural hearing loss include:

• the ageing process
• excessive noise exposure
• diseases such as meningitis and Meniere's disease
• viruses, such as mumps and measles
• drugs which can damage the hearing system
• head injuries.

In Australia, 20 children per 10,000 live births will be born with a congenital sensorineural hearing impairment. Causes include:

• inherited hearing loss
• premature birth, lack of oxygen at birth or other birth traumas
• damage to the unborn baby from a virus such as rubella
• jaundice.

Mixed hearing loss

Mixed hearing loss results when there is a problem in both the conductive pathway (in the outer or middle ear) and in the nerve pathway (the inner ear). An example of a mixed hearing loss is a conductive loss due to a middle-ear infection combined with a sensorineural loss due to damage associated with ageing.

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