Revolutionary microchip implanted in the ear could soon replace chunky conventional hearing aids
11:54 GMT, 30 April 2012
Cochlear implants have restored basic hearing to hundreds of thousands of people. However, the conventional device requires a microphone, speech processor and radio transmitter coil to be worn externally.
Many wearers feel self-conscious having their condition so publicly on display. It also prevents patients from activity like swimming.
A new kind of tiny microphone is shown here attached at the umbo where the eardrum meets the hearing bones
Traditional cochlear implants are very visible
Now a team led by the University of Utah have developed a tiny prototype that is implanted in the middle ear, which means it can't be seen.
The device is currently the size of an
eraser on a pencil and weighs just 25mg. However, research leader Professor Darrin Young said they must now reduce its size by a third and improve its ability
to detect quieter, low-pitched sounds before testing it on patients.
In a cochlear implant, the microphone,
signal processor and transmitter coil worn outside the head send signals
to the internal receiver-stimulator, which is implanted in bone under
the skin and sends the signals to the electrodes implanted in the
cochlea to stimulate auditory nerves. The ear canal, eardrum and hearing
bones are bypassed.
The proposed cochlear implant system: The speech processor and radio transmitter are implanted under the skin of the skull, and a new kind of microphone is surgically attached to the umbo
'It's a disadvantage having all these
things attached to the outside' Prof Young said.
He said it meant children couldn't go swimming and had problems wearing bicycle helmets.
He added: 'for adults, it's social
perception. Wearing this thing indicates you are somewhat handicapped
and that actually prevents quite a percentage of candidates from getting
the implant. They worry about the negative image.'
The new system implants
all the external components. Sound moves through the ear canal to the
eardrum, which vibrates as it does normally. But here a sensor
known as an accelerometer is attached to detect the vibration.
HOW DO MOST PEOPLE HEAR
Sound normally moves into the ear canal
and makes the eardrum vibrate.
At what is known as the umbo, the eardrum
connects to a chain of three tiny bones: the malleus, incus and stapes,
also known as the hammer, anvil and stirrup.
The bones vibrate. The
stapes or stirrup touches the cochlea, the inner ear's fluid-filled
Hair cells (not really hair) on the cochlea's inner membrane
move, triggering the release of a neurotransmitter chemical that carries
the sound signals to the brain.
Prof Young's (pictured) microphone would be implanted at the umbo.
sensor is also attached to a chip and together they serve as a
microphone that picks up the sound vibrations and converts them into
electrical signals sent to the electrodes in the cochlea.
The device would still require patients
to wear a charger behind the ear while sleeping at night to recharge an
However, Prof Young said he expected a battery to last several days between charging.
He added the microphone could also help patients who have degraded hearing bones
unable to adequately convey sounds from conventional hearing aids.
The proof-of-concept device has been successfully tested in the ear canals of four cadavers, and the researchers said tests on patients were about three years away.
The report was published online in the Institute of Electrical and Electronics Engineers journal Transactions on Biomedical Engineering.
The study was funded by the National Institutes of Health.