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Usher Syndrome

Definition

Usher syndrome is a rare, inherited disorder that involves loss of hearing and sight. Hearing loss is due to the inability of the auditory nerves to send sensory input to the brain. This is called sensorineural hearing loss.
The vision loss, called retinitis pigmentosa (RP), usually happens after age 10. RP is a deterioration of the retina. The retina is a layer of light-sensitive tissue that lines the back of the eye. It changes visual images into nerve impulses in the brain that allow us to see. RP slowly gets worse over time.
Nerve and Retina of the Eye
Normal Anatomy of the Eye
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Three types of Usher syndrome have been identified: types I, II, and III. The age of onset and severity of symptoms separate the different types.

Causes

Usher syndrome is caused by a genetic mutation. A child must inherit one defective gene from each parent in order to develop Usher syndrome. A child with one defective gene is a carrier and will not have any symptoms. It is not clear what causes the mutation in the gene.

Risk Factors

The only known factor that increases the risk of Usher syndrome is having parents with the disorder and/or parents who carry the genes for the disorder. If both parents carry the abnormal gene, a child has a 25% chance of inheriting both of these abnormal genes and developing Usher syndrome.

Symptoms

The main symptoms of Usher syndrome are hearing and vision loss. Psychological or behavioral disorders may occur before vision loss. Some people also have balance problems due to inner ear problems.
RP limits a person’s ability to see in dim light or the dark. It also causes a person to lose side vision slowly over time. Eventually, any vision that is left is only in a small, tunnel-shaped area. Almost everyone with RP becomes legally blind. There is no way of knowing when or how quickly a person will lose vision.
Symptoms and characteristics of each type include the following:

Diagnosis

The doctor will ask about your symptoms and medical history. A physical exam will be done. Hearing loss is determined with standard hearing tests. Balance problems can be detected with a test called electronystagmography (ENG). In this test, the doctor flushes the ears with warm and then cool water. This causes nystagmus, which is rapid eye movements that can help the doctor detect a balance disorder.
An eye doctor will perform an eye exam, which will likely include the following:
If any problems are found on these tests, an electroretinography (ERG) is done. This test confirms a diagnosis of RP. It measures the electricity given off by the nerves in the retina. The test is done while wearing special contact lenses and looking at a flashing light.

Treatment

There is no cure for Usher syndrome. The best treatment is to identify the disorder as early as possible and begin educational programs and services right away. This helps reduce the communication and learning problems that can result from hearing and vision loss.
The specific programs and services depend on the severity of the hearing, vision, and balance problems, and the person's age and abilities. Options include:
Other potential treatments are being investigated. Talk to your doctor about the risks and benefits of participating in a clinical trial.

Prevention

There are no current guidelines to prevent Usher syndrome.

RESOURCES

National Eye Institute (NEI) http://www.nei.nih.gov

National Institute on Deafness and Other Communication Disorders (NIDCD) http://www.nidcd.nih.gov

CANADIAN RESOURCES

CNIB http://www.cnib.ca

Alberta Health http://www.health.alberta.ca

References

Dammeyer J. Children with Usher syndrome: Mental and behavioral disorders. Behav Brain Funct. 2012;8:16.

Lopes VS, Williams DS. Gene therapy for the retinal degeneration of Usher syndrome caused by MYO7A. Cold Spring Harb Perspect Med. 2015;5(6).

Usher syndrome. Boys Town National Research Hospital website. Available at: http://www.boystownhospital.org/research/molecularstudies/pages/ushersyndrome.aspx. Accessed February 12, 2016.

Usher syndrome? Foundation Fighting Blindness website. Available at: http://www.blindness.org/eye-conditions/usher-syndrome. Accessed February 12, 2016.

Usher syndrome. National Institute on Deafness and Other Communication Disorders website. Available at: www.nidcd.nih.gov/health/hearing/pages/usher.aspx. Updated April 30, 2014. Accessed February 12, 2016.

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