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Last Updated: Apr 28th, 2008 - 10:10:01 |
SIGHT AND SOUND
Am I the only one who is always amazed when a child is born with seemingly little or nothing out of the ordinary? With all the genetic and prenatal things that could go wrong, it is always amazing to me when everything goes right.
There are many syndromes with which children can be born. Many of these are genetic in nature, and some more debilitating than others. One of the more debilitating syndromes out there is Usher Syndrome. This is a genetic disorder that is characterized by both a partial or total hearing loss and gradual vision loss. The vision loss is a result of retinitis pigmentosa or RP. RP refers to the deposits of black pigment found in the retina of people with the disorder. At first the person becomes night blind as the eyes are no longer able to see in dim light. As the condition progresses, the retina deteriorates and the person ends up with only a tunnel of central vision.
If you recall back to your high school biology, humans have 46 pairs of chromosomes, with two that determine gender and the remaining 44 dictating other factors. . There are estimated 30,000 to 40,000 genes bundled along the chromosomes and we get one gene from each parent. The different types of Usher Syndrome are caused by mutations of different genes. Researchers believe that there are about 15 genes that can cause usher Syndrome, and approximately one in every 75 persons carries one of the usher genes.
Usher syndrome can also result in balance problems. Balance is the result of the interaction of three systems: the eyes, the proprioceptive system and the vestibular system. The role of the eyes is quite clear; we look around and this tells our brains where we are oriented in space. The proprioceptive system is the way in which receptors in muscles, joints and skin send information to the brain regarding movement and position in space. Finally, the vestibular system, which is in the ear, consists of the semi-circular canals. These are fluid filled canals that are set at different angles. As we move our head the fluid in the canals moves, telling the vestibular nerve all about the details of the speed of movement, direction of movement etc.
There are three primary types of Usher Syndrome, known as Types 1, 2, and 3. Each of the three is further divided into subtypes. The characteristics of each type are slightly different, but generally include hearing loss leading to deafness, loss of vision leading to blindness, balance problems and speech problems.
TYPES
Type 1: There are six subtypes of the Type 1 Usher Syndrome. Characteristics of this type include:
Profound deafness from birth
Speech difficulties
Balance problems
Eye problems beginning at about age 10
Vision loss developing within the first 10 years of life.
Type 2: There are three subtests of Type 2 Usher Syndrome.
Characteristics of this type include:
Moderate hearing loss in the lower sound frequency range
Severe hearing loss in the higher sound frequency range.
Balance is not affected
Vision loss and blind spots begin to develop in the teens and continue through the lifespan.
Type 3: There is only the one type of Type 3 Usher Syndrome.
Characteristics of this type include:
Normal hearing at birth
Near normal balance at birth
Significant hearing loss occurs by puberty
Vision los begins in the teen years and progresses through the lifespan
Balance deteriorates with age.
The majority of people with this type live in Finland.
While there is no cure for Ushers, supports such as hearing aides, adaptive technology and communication skills training can be useful.
Quotation of the Week
"Reality is merely an illusion, albeit a very persistent one."
Albert Einstein
Comments? Trish-Blair@redwoods.edu
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