Usher Syndrome: Types, Causes and Treatment Options
Author: Thomas C. Weiss : Contact: Disabled World
Published: 2015-09-18 : (Rev. 2020-02-28)
Synopsis and Key Points:
General information and overview of Usher syndrome, a rare inherited disorder that causes gradual vision loss and deafness.
Other names for Usher syndrome include Hallgren syndrome, Usher-Hallgren syndrome, retinitis pigmentosa-dysacusis syndrome, and dystrophia retinae dysacusis syndrome.
Early diagnosis of Usher syndrome is extremely important because the earlier a child receives the help they need, the better prepared they are to manage their vision and hearing loss.
Usher syndrome is named for the British eye surgeon who first described it in the year 1914. Usher syndrome may also affect a person's balance. Usher syndrome is a relatively rare genetic disorder caused by a mutation in any one of 10 genes resulting in a combination of hearing loss and visual impairment, and is a leading cause of deaf-blindness. Other names for Usher syndrome include Hallgren syndrome, Usher-Hallgren syndrome, retinitis pigmentosa-dysacusis syndrome, and dystrophia retinae dysacusis syndrome. Usher syndrome is incurable at present.
Scientists have identified three types of Usher syndrome; 1, 2 and 3. Babies with Usher syndrome are born hard-of-hearing or deaf. Vision loss associated with the syndrome develops during childhood or adolescence.
The different types of Usher syndrome are divided by the degree of a person's vision and hearing loss, whether balance issues are present, and the age when the affected person's vision loss happens.
Within the three main types of Usher syndrome there are individual differences in how rapidly the condition progresses and symptoms. Between 3-6% of all children who are deaf and 3-6% of children who are hard-of-hearing have Usher syndrome. In developed countries such as America, approximately 4 babies in 100,000 born experience Usher syndrome.
Types of Usher Syndrome
Of the three types of Usher syndrome, Type 1 and Type 2 are the most common in America. These two types account for approximately 95% of all instances of Usher syndrome. What follows are descriptions of the different types of Usher syndrome.
- Usher Syndrome, Type 1:
Babies born with Type 1 Usher syndrome are almost entirely deaf at the time of their birth. They experience severe balance issues, sit without support at a later age than average and are late walkers. Children with Type 1 Usher syndrome experience night vision loss followed by vision issues prior to the age of ten. The loss of vision rapidly progresses to complete blindness. People with this type of Usher syndrome do not benefit from the use of hearing aids.
- Usher Syndrome Type 2:
Babies born with Type 2 Usher syndrome have average balance, experience moderate to severe hearing loss at the time of their birth and might benefit from using hearing aids. They develop night vision issues during adolescence, do not experience complete blindness and the disorder progresses more slowly.
- Usher Syndrome Type 3:
Babies born with Type 3 Usher syndrome have average hearing at the time they are born. They have almost average balance, although at times balance issues appear later on. Babies with Type 3 Usher syndrome experience gradual vision and hearing loss, although the rate of loss differs among children. Hearing loss becomes apparent by adolescence. Children with this type of Usher syndrome experience night blindness beginning in puberty, blind spots by their late teens or young adulthood, as well as complete blindness by middle age.
Causes of Usher syndrome
Scientists now know that Usher syndrome is an inherited disorder, meaning it is passed from parents to their children and is caused by changes or, 'mutations,' in genes. Genes are the chemically coded instructions in cells that tell cells what to do. A person's body contains 20,000-25,000 genes. Each person has two copies of each gene, one from each parent. Usher syndrome is an, 'autosomal recessive disorder,' meaning:
- Both females and males may be affected
- A baby may receive either the mutated gene, or the average one from each parent
- Both parents carry a mutated gene yet do not experience Usher syndrome themselves
A child who receives a mutated gene from each parent will experience Usher syndrome. The chance that a child of two parents who each have an Usher syndrome gene will experience Usher syndrome is around 1 in 4.
A person's retina is a tissue at the back of their eye that is needed for vision. The gene mutation in Usher syndrome affects the retina's light-sensing cells called, 'rods,' and, 'cones.' The condition is called, 'retinitis pigmentosa (RP).' With RP, the retina's light-sensing rods and cones slowly degrade, beginning at the outer edges. As RP worsens, the person loses their peripheral vision first, followed by loss of central vision.
Where Usher syndrome and causes of hearing loss is concerned, the cochlea is involved. The cochlea is a spiral structure in a person's inner ear that transmits sound. In Usher syndrome, the gene mutation affects the person's nerve cells in the cochlea so they do not transmit sound as they otherwise might.
Diagnosing Usher Syndrome
Usher syndrome is diagnosed based upon vision, hearing and balance testing. Testing for the Usher gene can confirm the diagnosis, yet is usually unnecessary. Genetic testing for different types of Usher syndrome is available at a number of laboratories in America. What follows are descriptions of different tests for Usher syndrome.
An, 'electronystagmogram (ENG),' measures the person's involuntary eye movement, something that may detect balance issues.
Nearly every infant born in America has a hearing test at the time of their birth. Babies who do not pass the newborn hearing test should have genetic testing performed to discover whether or not they have an Usher syndrome gene. Older children, adolescents or young adults with hearing loss should receive an audiology evaluation, an exam that measures how loud a sound must be before the person affected hears it.
Usher syndrome might go undiagnosed until the child or the child's parents notice a loss of night vision. The loss of night vision happens before the age of ten in Type 1, or during adolescence in Type 2. Vision testing includes a physical examination of the person's retina. The examination may detect changes in blood vessels, clumps of dead retinal cells, or a waxy appearance to the retina's surface. Visual field testing measures peripheral vision. An electroretinogram (ERG) is an examination that confirms the diagnosis of retinitis pigmentosa and also the retina's response to light. Due to the fact that the test requires insertion of a contact lens, general anesthesia is used in young children.
A pediatrician has the ability to answer a number of the questions parents of children with Usher syndrome have. The questions parents often have concern their child's physical growth and development. It is important to ask a pediatrician to refer you to vision and hearing specialists as soon as possible. The earlier a child begins working with these specialists, the more easily the child can learn to communicate with sign language, speak, and manage both vision and hearing loss.
Treating Usher Syndrome
While there is a good amount of research on Usher syndrome, a cure remains elusive. Treatment concentrates on helping the child to adapt to vision and hearing loss so they may enjoy life as much as possible. Options for treating Usher syndrome include the following:
- Hearing aids
- Auditory training
- Cochlear implants
- Braille instruction
- Low-vision services
- American Sign Language
- Assistive listening devices
- Orientation and mobility training
A long-term study from the Foundation for Fighting Blindness and the National Eye Institute showed that high doses of Vitamin A palmitate may slow down changes in an affected person's eye because of retinitis pigmentosa. If you are considering giving your child Vitamin A, consult your child's vision specialist beforehand.
While there is currently no cure for Usher syndrome, children with the disorder can live full and happy lives with the assistance of training and educational programs that meet their needs. Early diagnosis of Usher syndrome is extremely important because the earlier a child receives the help they need, the better prepared they are to manage their vision and hearing loss.
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