Auditory neuropathy usually causes some type of hearing loss.
Auditory neuropathy, sometimes called auditory dysynchrony, is a hearing disorder in which the inner ear receives sound properly, but the sound is not properly recognized by the brain. Auditory neuropathy is usually characterized by some type of hearing loss, affects the ability to properly understand speech, and can affect the speech of those afflicted, according to My Baby's Hearing.
History
In the late 1970's doctors began to identify groups of patients with similarly abnormal auditory brain stem responses to sounds, but auditory neuropathy was not identified until the 1980's, when new technology measured action within the cochlea, or inner ear. In 1996, the disorder was defined as normal cochlear functioning with abnormal brain response, according to eMedicine.
Cause
The exact cause of auditory neuropathy is unknown, but researchers suspect it often involves damage to the hair cells in the inner ear, according to the National Institute of Deafness and Other Communication Disorders (NIDCD). Inner hair cells transmit sound information to the brain. Connections between hairs cells or the actual nerves are also damaged in some people with auditory neuropathy, but outer hair cells--those that amplify sounds entering the ear--function properly.
Risk Factors
Auditory neuropathy appears to have a genetic link and is sometimes inherited, but is more often associated with diseases or damage to the ear. Lack of oxygen at birth, severe jaundice, immune disorders, infectious diseases and other neurological disorders, such as Charcot-Marie-Tooth syndrome and Friedreich's Ataxia, are risk factors for developing auditory neuropathy, according to My Baby's Hearing.
Diagnosis
Some infants with auditory neuropathy are diagnosed during their first hearing screening, depending on the method of screening used. Other children with auditory neuropathy pass the initial hearing test, but begin to show signs of the condition as they age. If auditory neuropathy is suspected, a doctor will perform a series of hearing tests to measure otoacoustic emissions and auditory brain stem response. In people with auditory neuropathy, otoacoustic emissions are normal but auditory brain stem response is abnormal, the NIDCD says.
Prognosis
Some infants diagnosed with auditory neuropathy learn to speak properly as their hearing improves over time, while others do not show improvement. For some, symptoms worsen and outer hair cells stop functioning, according to the NIDCD. Adults diagnosed with auditory neuropathy usually do not show improvements in hearing. Hearing may remain stable, fluctuate or worsen.
Treatment
Hearing aids, cochlear implants and frequency modulation devices are all used in the treatment of auditory neuropathy, but results vary greatly from patient to patient, according to the NIDCD. Young children with auditory neuropathy may be taught sign language as their first form of communication, while older children--who have already begun to develop spoken language skills--and adults with auditory neuropathy may benefit from therapy focused on listening and language skills or learning to read lips.
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