Hearing loss associated with Pendred syndrome is usually progressive, which means that a child will lose hearing over time. According to a study by the National Institute on Deafness and Other Communication Disorders (NIDCD), approximately one-fourth of the people with EVA and hearing loss have Pendred syndrome. How are enlarged vestibular aqueducts related to Pendred syndrome?ĮVA can be a sign of a genetic disorder called Pendred syndrome, a cause of childhood hearing loss. EVA can be an important clue pointing to what is actually causing the hearing loss.
However, scientists do not think that EVA causes the hearing loss, but that both are caused by the same underlying defect. Scientists also are finding that 5 to 15 percent of children with sensorineural hearing loss (hearing loss caused by damage to sensory cells inside the cochlea) have EVA. Research suggests that most children with enlarged vestibular aqueducts (EVA) will develop some amount of hearing loss. How are enlarged vestibular aqueducts related to childhood hearing loss? Ions are needed to help start the nerve signals that send sound and balance information to the brain. Scientists believe that the endolymphatic duct and sac help to ensure that the fluid in the inner ear contains the correct amounts of certain chemicals called ions. The functions of the endolymphatic duct and sac are not completely understood. If a vestibular aqueduct is enlarged, the endolymphatic duct and sac usually grow large too. This is called an enlarged vestibular aqueduct, or EVA the condition is also known as a dilated vestibular aqueduct or a large vestibular aqueduct. Recent studies indicate that a vestibular aqueduct is abnormally enlarged if it is larger than one millimeter, roughly the size of the head of a pin. Running through each vestibular aqueduct is a fluid-filled tube called the endolymphatic duct, which connects the inner ear to a balloon-shaped structure called the endolymphatic sac. These organs, together with the nerves that send their signals to the brain, work to create normal hearing and balance. These organs are the cochlea, which detects sound waves and turns them into nerve signals, and the vestibular labyrinth, which detects movement and gravity. The temporal bone also contains two sensory organs that are part of the inner ear. The aqueducts begin inside the temporal bone, the part of the skull just above the ear. Vestibular aqueducts are narrow, bony canals that travel from the inner ear to deep inside the skull (see figure). Congressional Testimony and the NIDCD Budget.Research Training in NIDCD Laboratories (Intramural).
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