Nonsyndromic deafness is hearing loss that is not associated with other signs and symptoms. In contrast, syndromic deafness includes forms of hearing loss that are part of genetic syndromes. Syndromic deafness is related to characteristic sets of findings affecting other parts of the body. Genetic changes are related to the following types of nonsyndromic deafness. nonsyndromic deafness, autosomal dominant nonsyndromic deafness, autosomal recessive nonsyndromic deafness, mitochondrial nonsyndromic deafness, X-linked The different types of nonsyndromic deafness are named according to their inheritance patterns. Autosomal dominant forms are designated DFNA, autosomal recessive forms are DFNB, X-linked forms are DFN, and mitochondrial forms are DFNM. Each type is also numbered in the order in which it was described. For example, DFNA1 was the first described autosomal dominant type of nonsyndromic deafness. Most forms of nonsyndromic deafness are associated with permanent hearing loss caused by damage to the inner ear. The inner ear consists of a snail-shaped structure called the cochlea that helps process sound, nerves that send information from the cochlea to the brain, and structures involved with balance. Loss of hearing caused by changes in the inner ear is called sensorineural deafness. Some forms of nonsyndromic deafness involve changes in both the inner ear and the middle ear. This combination is called mixed hearing loss. The severity of hearing loss varies and can change over time. It can affect one ear (unilateral) or both ears (bilateral). Degrees of hearing loss range from mild (a person may have trouble understanding soft speech) to profound (a person is unable to hear even very loud noises). The loss may be stable, or it may progress as a person gets older. Particular types of nonsyndromic deafness show distinctive patterns of hearing loss. For example, the loss may be more pronounced at high, middle, or low tones. Nonsyndromic deafness can occur at any age. Hearing loss that is present before a child learns to speak is classified as prelingual or congenital. Hearing loss that occurs after the development of speech is classified as postlingual.