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Fact Sheets on Enlarged Vestibular Aqueducts, Pendred Syndrome Available Online

Two new NIDCD fact sheets—one on enlarged vestibular aqueducts (EVA) and another on Pendred syndrome—now are available online.

Vestibular aqueducts are bony canals that travel from the inner ear to deep inside the skull. Inside the vestibular aqueduct is a fluid-filled tube called the endolymphatic duct, which ends at a balloon-shaped endolymphatic sac. When the vestibular aqueduct is enlarged, the endolymphatic duct and sac grow large with excess fluid in comparison to their normal sizes. Although scientists do not think that EVA causes hearing loss, research suggests that most children with EVA will develop some degree of hearing loss.

The presence of EVA can also be a symptom of a genetic disorder called Pendred syndrome, a cause of progressive childhood hearing loss that also can affect the thyroid gland and a person's sense of balance. According to an NIDCD study, approximately one-third of individuals with EVA and hearing loss have Pendred syndrome.

To read these two fact sheets, go to and

Last Updated Date: 
June 7, 2010