Tiny device with a big impact

Phil Bird implants 30 to 40 minuscule cochlear implant devices each year. He makes a tiny incision, lifts up the scalp and then drills through bone to reach the inner ear, taking care not to damage the facial nerve.

He then carefully places the internal implant – roughly the size of a 50c coin – into the inner ear. It is made up of more than 20 electrodes and a transmitting coil that curls like a fern frond.

‘‘The cochlea itself is very slightly larger than a pea. The actual electrode, the part that goes into the cochlea, is just over 20 millimetres long,’’ Bird says. ‘‘So everything’s rather small.’’

The cochlea – a small, spiral bony structure in the inner ear, named after the Greek word for snail – receives sound in vibrations that cause thousands of tiny hairs (stereocilia) to move. They translate those sounds into electrical signals that are sent to the brain to be interpreted.

But the hairs can become damaged, as a result of ageing, exposure to loud noise or because of a genetic condition, leading to hearing loss. The implant bypasses the tiny hair cells and directly stimulates the auditory nerve, which sends sound signals to the brain.

‘‘It takes a while for people to be able to turn that hearing into the ability to understand sound. Everyone’s different,’’ Bird says. ‘‘Some people will say it’s a little bit like hearing a metallic Donald Duck sort of sound.

‘‘There’s some really, really funny stories of people. I’ve heard on several occasions, people – especially women – being very embarrassed going to public toilets and hearing themselves pee.

‘‘They haven’t heard it for decades, and become very self-aware.’’