Dr. Sharon Cushing of the Hospital for Sick Children in Toronto explains auditory neuropathy and discusses the outlook for treatment for children diagnosed with hearing loss.
AUDITORY NEUROPATHY
Approximately 10% of children who are diagnosed with hearing loss at birth have auditory neuropathy usually due to genetic structure.
What is Auditory Neuropathy?
A type of sensorineural hearing loss in which the inner ear successfully detects sound, but is unable to send sound from the ear to the brain.
What Causes Auditory Neuropathy?
Researchers report several causes of auditory neuropathy. The most common genetic cause is insufficient production of a protein called otoferlin. The otoferlin protein allows communication between the inner ear sensory cells and the auditory nerve. When the otoferlin protein is deficient, the ear cannot communicate with the nerve and brain. This results in severe to profound hearing loss.
How Do We Know if Our Child’s Auditory Neuropathy is Related to Genetic Causes?
Auditory neuropathy is one of the most challenging forms of hearing loss to diagnose. Over the last two decades, scientists have made substantial progress in identifying genetic causes of hearing loss. Because of these advances, a simple genetic test can now diagnose otoferlin deficiency and other causes of hearing loss.
Researchers are still seeking effective treatments for children with auditory neuropathy.
Some but not all children may benefit from hearing aids, cochlear implants, and other technologies. Gene therapy, guided by an understanding of the complex biology of the inner ear, may hold the key for children whose hearing loss is determined to be caused by an otoferlin deficiency.
Learn how hearing works
Learn how hearing works
1Sound waves travel through the air and into the outer ear canal where they cause the eardrum (tympanum) to vibrate. This causes a series of small bones (ossicles) to vibrate, which vibrates a small membrane called the oval window. This causes fluid inside the cochlea to move back and forth.
2A portion of the cochlea known as the organ of Corti contains hair cells that convert this fluid movement into what our brain perceives as sound. There are two types of hair cells. Outer hair cells amplify quiet sounds, while inner hair cells primarily detect and transmit sound signals to the brain via the auditory nerve. There are roughly 3,200 inner hair cells and 12,000 outer hair cells in the human organ of Corti.
3Outer and inner hair cells are arranged linearly within the cochlea tonotopic array. Hair cells at the base of the cochlea detect the highest frequencies. Those located at the apex, or tip, detect the lowest frequencies.
4For normal hearing function, a variety of additional cell types and cellular structures must work together in concert. Broadly speaking, these include (but are not limited to):
- Stereocilia: structures that project from hair cells and respond to movement of fluid within the cochlea, enabling the sensation of sound.
- Synapses: specialized connections that are required for the efficient transfer of sound information from hair cells to spiral ganglion neurons.
- The stria vascularis: a group of cells that produce endolymph, a fluid in the cochlea that moves in response to sound waves.
- Spiral ganglion neurons: cells that transmit information from the cochlea to the brain, where sound is perceived.
Damage or dysfunction within any of these cell types can occur, and lead to symptoms of hearing loss, tinnitus, or hyperacusis.
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CLINICIAN PERSPECTIVE
WATCH: DR. SHARON CUSHING OF THE HOSPITAL FOR SICK CHILDREN
LEARN MORE ABOUT HEARING LOSS
To learn more about hearing loss, including auditory neuropathy, and efforts to develop and advance treatment, please visit:
Glossary of Terms
auditory neuropathy: a hearing disorder in which sound enters the inner ear normally, but is impaired when signals move from the inner ear to the brain
cochlear implant: an electronic device that is surgically implanted and works by directly stimulating functioning auditory nerve fibers in the inner ear; cochlear implants convert sound waves to electrical impulses and transmit them to the inner ear, providing people with severe to profound hearing loss the ability to hear sounds
congenital hearing loss: hearing loss that is present at birth
gene therapy: a technique that modifies a person’s genes to treat or cure disease
genetic hearing loss: hearing loss caused by a genetic deficiency or mutation of a gene
otoferlin (OTOF): a large protein expressed in cochlear inner hair cells that enables communication between the sensory cells of the inner ear and the auditory nerve by regulating synaptic transmission
sensorineural hearing loss: hearing loss that occurs from damage to the inner ear, the nerve that runs from the ear to the brain (auditory nerve), or the brain
Read our expanded access policy
Read our expanded access policy
Decibel Therapeutics is a clinical-stage biotechnology company dedicated to discovering and developing transformative treatments for hearing and balance disorders, one of the largest areas of unmet need in medicine. We are working relentlessly to bring cutting-edge, life-enhancing drugs to individuals with hearing and balance disorders.
To ensure that we meet our responsibility to deliver safe and effective treatments to patients, we collaborate with scientists, physicians, patients, and regulatory authorities to conduct rigorous clinical trials. We believe that it is through clinical trials and regulatory approvals that we can ultimately ensure safe and timely access to our treatments for as many people as possible. We encourage awareness of and participation in our clinical trials and believe that participating in clinical trials is the best way for individuals to access investigational products prior to regulatory approval.
Decibel Therapeutics understands that some individuals may wish to access investigational products that are not yet approved by the FDA or other regulatory authorities. The most appropriate way for patients to access our investigational products is by participating in our clinical trials, which are managed by a team of experts and are designed to determine whether the investigational products are safe and effective. These clinical trials are conducted so that the benefits and risks can be adequately understood. Any individual interested in participating in one of our trials is encouraged to discuss his/her specific needs with his/her physician. Information regarding our ongoing clinical trials can be accessed at www.clinicaltrials.gov.
Decibel Therapeutics understands there may be individuals interested in obtaining expanded access to our investigational products outside of a clinical trial. At the current stage of the development of our investigational products, there is insufficient clinical data to support expanded access use. Therefore, Decibel Therapeutics does not currently provide access to our investigational products through any expanded access programs.
In accordance with the 21st Century Cures Act, this policy may be revised at any time. Should you have additional questions, please reach out to your physician or contact clinical@decibeltx.com
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