Nonsyndromic hearing loss is a partial or total loss of hearing that is not associated with other signs and symptoms. In contrast, syndromic hearing loss occurs with signs and symptoms affecting other parts of the body.

The causes of nonsyndromic hearing loss are complex. Researchers have identified more than 90 genes that, when altered, are associated with nonsyndromic hearing loss. Many of these genes are involved in the development and function of the inner ear. Mutations in these genes contribute to hearing loss by interfering with critical steps in processing sound. Different mutations in the same gene can be associated with different types of hearing loss, and some genes are associated with both syndromic and nonsyndromic forms. In many affected families, the factors contributing to hearing loss have not been identified.

Between 2 and 3 per 1,000 children in the United States are born with detectable hearing loss in one or both ears. The prevalence of hearing loss increases with age; the condition affects 1 in 8 people in the United States age 12 and older, or about 30 million people. By age 85, more than half of all people experience hearing loss.

As discussed above, nonsyndromic hearing loss has different patterns of inheritance. Between 75 and 80 percent of cases are inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. Usually, each parent of an individual with autosomal recessive hearing loss carries one copy of the mutated gene but does not have hearing loss.

Published Date: February 01, 2016Published By: National Institutes of Health