A hearing device that also releases a drug into the ear could help restore hearing in thousands of people. Standard hearing aids work by amplifying sounds and sending them into the inner ear, to the cochlea. This is a tiny, shell-like structure that relays sound waves to the auditory (hearing) nerve.
The cochlea contains sensory cells, called hair cells — typically, hearing loss is linked to damage to these cells, as a result of ageing, for instance, or injury from noise.
The new device is a form of cochlear implant. These are used to help people who are deaf or severely hard-of-hearing and in patients who aren’t helped by conventional hearing aids. A cochlear implant bypasses the damaged area completely and directly stimulates the auditory nerve that carries sound to the brain. First, an external microphone worn behind the ear picks up sounds from the outside.
These are then processed by the cochlear implant into electric impulses and transmitted via a number of electrodes inserted into one of the fluid-filled canals inside the cochlea responsible for transmitting sound vibrations to the auditory nerve. The impulses are then sent on to the brain, where they are interpreted as sounds.
Although cochlear implants can be highly effective, one of the problems is that the surgery to put them in can damage the area, including the cochlea, which may still have some residual function, and sometimes tissue grows around the electrodes, which stops the implant working. One theory is that the physical trauma caused by insertion and placement of the electrodes results in inflammation.
According to the researchers behind the latest implant, this occurs in a third of cases. The new cochlear implant works just like a traditional one, but also releases an anti-inflammatory drug into the ear to keep the implant working. Following successful animal studies, it is now being tested in the first human patients in a trial across six hospitals in Australia.
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