Auditory neuropathy
Encyclopedia
Auditory neuropathy is a variety of hearing loss in which the outer hair cells within the cochlea are present and functional, but sound information is not faithfully transmitted to the auditory nerve and brain
properly.
Also known as Auditory Neuropathy/Auditory Dys-synchrony (AN/AD) or Auditory Neuropathy Spectrum Disorder
(ANSD).
A neuropathy usually refers to a disease of the peripheral nerve or nerves, but the auditory nerve itself is not always affected in Auditory Neuropathy Spectrum Disorders.
(Amatuzzi et al.)
and otoacoustic emissions. Auditory brainstem response should be tested with both polarities (helps in identifying Cochlear Microphonics ).
Auditory neuropathy is diagnosed when a person has present Otoacoustic Emissions and/or Cochlear Microphonics in combination with absent or abnormal Auditory Brainstem Response. Patients with Auditory Neuropathy Spectrum Disorders have to date never been shown to have normal middle ear muscle reflexes at 95 dB or less despite having normal otoacoustic emissions. Berlin et al.
Auditory Neuropathy can occur spontaneously, or in combination with diseases like Charcot-Marie-Tooth disease
and Friedreich's ataxia
.
It appears that regardless of the audiometric pattern(hearing thresholds) or of their function on traditional speech testing in quiet the vast majority of sufferers have very poor hearing in background noise situations.
When diagnosing someone with auditory neuropathy, there is no characteristic level of functioning either. People can present relatively little dysfunction other than problems of hearing noise, or can present as completely deaf and gaining no useful information from auditory signals.
Hearing aids are sometimes prescribed, with mixed success.
Some people with auditory neuropathy obtain cochlear implants, also with mixed success.
In most parts of Australia hearing screening via AABR testing is mandated meaning that essentially all congenital (not those related to later onset degenerative disorders) Auditory neuropathy cases should be diagnosed at birth.
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
properly.
Also known as Auditory Neuropathy/Auditory Dys-synchrony (AN/AD) or Auditory Neuropathy Spectrum Disorder
Auditory Neuropathy Spectrum Disorder
Auditory Neuropathy Spectrum Disorder is a specific form of hearing loss defined by the presence of normal or near-normal Otoacoustic Emissions but the absence of normal Middle Ear Reflexes and severely abnormal or completely absent auditory brainstem response .Individuals presenting with this...
(ANSD).
A neuropathy usually refers to a disease of the peripheral nerve or nerves, but the auditory nerve itself is not always affected in Auditory Neuropathy Spectrum Disorders.
(Amatuzzi et al.)
Possible Sites of Lesion
Based on clinical testing of subjects with auditory neuropathy, the disruption in the stream of sound information has been localized to one or more of three probable locations: the inner hair cells of the cochlea, the synapse between the inner hair cells and the auditory nerve, or a lesion of the ascending auditory nerve itself .Diagnosing Auditory Neuropathy
Diagnosis is possible after a test battery, that must necessarily include the following: the auditory brainstem responseAuditory Brainstem Response
The auditory brainstem response is an auditory evoked potential extracted from ongoing electrical activity in the brain and recorded via electrodes placed on the scalp. The resulting recording is a series of vertex positive waves of which I through V are evaluated...
and otoacoustic emissions. Auditory brainstem response should be tested with both polarities (helps in identifying Cochlear Microphonics ).
Auditory neuropathy is diagnosed when a person has present Otoacoustic Emissions and/or Cochlear Microphonics in combination with absent or abnormal Auditory Brainstem Response. Patients with Auditory Neuropathy Spectrum Disorders have to date never been shown to have normal middle ear muscle reflexes at 95 dB or less despite having normal otoacoustic emissions. Berlin et al.
Auditory Neuropathy can occur spontaneously, or in combination with diseases like Charcot-Marie-Tooth disease
Charcot-Marie-Tooth disease
Charcot–Marie–Tooth disease- , known also as Morbus Charcot-Marie-Tooth, Charcot-Marie-Tooth neuropathy, hereditary motor and sensory neuropathy , hereditary sensorimotor neuropathy , or peroneal muscular atrophy, is an inherited disorder of nerves that takes different forms...
and Friedreich's ataxia
Friedreich's ataxia
Friedreich's ataxia is an inherited disease that causes progressive damage to the nervous system, resulting in symptoms ranging from gait disturbance to speech problems; it can also lead to heart disease and diabetes....
.
It appears that regardless of the audiometric pattern(hearing thresholds) or of their function on traditional speech testing in quiet the vast majority of sufferers have very poor hearing in background noise situations.
Residual Auditory Function
When testing the auditory system, there really is no characteristic presentation on the audiogram.When diagnosing someone with auditory neuropathy, there is no characteristic level of functioning either. People can present relatively little dysfunction other than problems of hearing noise, or can present as completely deaf and gaining no useful information from auditory signals.
Hearing aids are sometimes prescribed, with mixed success.
Some people with auditory neuropathy obtain cochlear implants, also with mixed success.
A Note To Parents
Universal Newborn Hearing Screenings (UNHS) is mandated in a majority of the United States. Auditory neuropathy is sometimes difficult to catch right away, even with these precautions in place. Parental suspicion of a hearing loss is a trustworthy screening tool for hearing loss too, so if one is suspected, that is sufficient reason to seek a hearing evaluation from an audiologist.http://www.cnn.com/2011/HEALTH/03/10/ep.neuropathy.kids.hearingIn most parts of Australia hearing screening via AABR testing is mandated meaning that essentially all congenital (not those related to later onset degenerative disorders) Auditory neuropathy cases should be diagnosed at birth.
See also
- Audiologist
- Auditory Brainstem ResponseAuditory Brainstem ResponseThe auditory brainstem response is an auditory evoked potential extracted from ongoing electrical activity in the brain and recorded via electrodes placed on the scalp. The resulting recording is a series of vertex positive waves of which I through V are evaluated...
- Auditory neuropathy spectrum disorderAuditory Neuropathy Spectrum DisorderAuditory Neuropathy Spectrum Disorder is a specific form of hearing loss defined by the presence of normal or near-normal Otoacoustic Emissions but the absence of normal Middle Ear Reflexes and severely abnormal or completely absent auditory brainstem response .Individuals presenting with this...
- Auditory processing disorderAuditory processing disorderAuditory Processing Disorder , also known as Central Auditory Processing Disorder is an umbrella term for a variety of disorders that affect the way the brain processes auditory information. It is not a peripheral hearing disorder as individuals with APD usually have normal peripheral hearing...
- Cochlear implantCochlear implantA cochlear implant is a surgically implanted electronic device that provides a sense of sound to a person who is profoundly deaf or severely hard of hearing...
- Hearing aids
- Otoacoustic emissions
- Sensorineural hearing impairment
External links
- Auditory neuropathy: What is it and what can we do about it? from the LSU Medical School
- Auditory Neuropathy Information site
- Auditory Neuropathy by Timothy C. Hain, MD
- Simulation A simulation of what auditory neuropathy "sounds like."