Information Sheets – Types of Hearing Loss
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Hearing losses may be located in the external, middle or inner ear or in a mixture of all three places. Damage to any part of the external, middle or inner ear can cause a hearing loss. The different types of hearing loss are:
Conductive Hearing Loss
If there is a problem in the external or middle ear, a conductive hearing loss exists. This means sound is not being conducted properly to the inner ear. Common causes of conductive hearing loss are:
· wax in the external ear;
· fluid in the middle ear;
· a hole or tear (perforation) in the eardrum;
· improper development of the outer or middle ear;
· damage to the small bones in the middle ear;
· an infection in the middle ear; or
· a blockage in the Eustachian tube meaning that air cannot move into the middle ear.
Conductive hearing losses do not cause the hearing to be lost completely but there is a loss of volume. Sounds may be quiet but there is no distortion. Sometimes this is from too much fluid in the middle ear which means the three small bones cannot vibrate properly. This is sometimes called “glue ear.” If a child has repeated ear infections, these may cause more permanent damage to the inner ear.
Sensorineural Hearing Loss (SNHL or nerve deafness)
If a problem occurs in the inner ear or auditory nerve, the hearing loss is sensorineural. Some people call this “nerve deafness.” With this type of deafness, there are problems with the cochlear or the nerve which carries sound to the brain
Sensorineural losses can range from mild to profound. Both the volume and clarity of sound are affected. Sound may be heard but it may be distorted.
What causes a sensorineural hearing loss?
Common causes of sensorineural hearing loss in young children are:
· certain pre-natal infections
· lack of oxygen during birth
· genetic factors
· use of some certain drugs
· premature birth
What are the genetic causes of hearing loss?
There are an increasing number of genetic causes of hearing loss being identified. For investigation into possible genetic causes of a hearing loss, contact:
The Paediatric Hearing Loss Investigation Clinic
Monash Medical Centre, Clayton
Ph: 03 9594 6666
Genetic Health Services
Murdoch Children’s Research Institute
10th Floor, Royal Children’s Hospital Flemington Rd, Parkville
Ph: 03 8 341 6201 Fax: 03 8341 6390
Genetic Services of WA
Princess Margaret Hospital for Children
Roberts Rd, Subiaco, WA. 6008
Ph: 08 9340 8828 Ph: 08 9340 1525 Fax: 08 9340 7058
The Royal Melbourne Hospital Genetic Services visits Hobart, Launceston and the North West.
Queensland Clinical Genetics Services
Royal Children’s Hospital
Back Road, Bramston Terrace Entrance Herston Qld
Ph: 07 3636 1686 Fax: 07 3253 1987
Mater Children’s Hospital
Ph: 07 3840 8195
New South Wales
Royal North Shore Centre for Genetic Education
St Leonards 2065
Ph: 02 9926 7324 Fax: 02 9906 7529
Department of Medical Genetics
Level 2 Sydney Children’s Hospital
High St Randwick 2031
Ph: 02 9382 1704