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Auditory neuropathy spectrum disorder (ANSD) is a rare condition that can affect a person's ability to hear. Although sounds enter the inner ear normally, signals from the inner ear to the brain are not transmitted properly. As a result, the condition may be associated with mild to severe hearing loss and poor speech-perception abilities (difficulty understanding speech clearly). ANSD can be associated with other neurological disorders such as Friedrich ataxia, Stevens-Johnson syndrome, Ehlers-Danlos syndrome, and Charcot-Marie-Tooth syndrome. The exact underlying cause of ANSD is not completely understood. In many cases, ANSD occurs in people with no family history of the condition. However, the condition does run in some families suggesting that genetic factors may play a role in some cases.