Hearing loss and Usher syndrome
The type of hearing loss experienced by people with Usher is called sensorineural hearing loss. To explain sensorineural hearing loss it is useful to understand a little about the workings of the ear.
Structure of the ear
The ear has three sections:
The outer ear: This part of the ear includes the auricle (also known as the pinna or the visible part of the external ear) and the ear canal. The ear canal leads to the ear drum, which is also known as the tympanic membrane.
The middle ear: This part of the ear is made up of three small bones (malleus, incus, stapes), known as the ossicles.
The inner ear: This part of the ear is made up of the cochlea, which contains the sensitive hair cells, and the vestibular system, which contains the semi-circular canals. The vestibular system is responsible for balance and orientation.
How we hear
- Sound waves, which exist as vibrations in the air, enter the ear canal after being collected via the auricle.
- The sound waves then reach the ear drum and cause it to vibrate.
- The vibrations are then passed through to the inner via the three small bones in the middle ear.
- The vibrations then reach the cochlea, which contains the hair cells.
- The vibrations are then changed into electrical signals via the hair cells.
- The electrical signals are carried along the auditory nerve (also known as cochlear nerve) to the brain, whereby the brain understands the signals as sounds.
Sensorineural hearing loss, the kind of hearing loss associated with Usher syndrome, is a form of hearing loss that is caused by damage to the hair cells and/or the auditory nerve described above
Sensorineural hearing loss impacts upon an individual’s ability to hear certain frequencies of sound as well as the quality of the sounds being heard.
In the case of Usher syndrome, it is damage to the hair cells that causes the sensorineural hearing loss. This damage is due to genetics rather than environmental factors.
The degree of sensorineural hearing loss varies from individual to individual (including siblings with the same form of Usher).
Currently, Usher type 1 presents itself, in most cases, with profound sensorineural loss at birth. In most cases of Usher type 2, the sensorineural loss is also present at birth but ranges from mild to severe. In contrast, Usher type 3 is associated, in most cases, progressive sensorineural loss later in life. Action on Hearing Loss have a useful guide describing the various possible levels of hearing loss.
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Created: February 2016
Review due: February 2018
First published: Wednesday 2 December 2015
Updated: Tuesday 6 December 2016