Bone-conducting implant could help deaf people hear normally

A new ear implant that uses the skull bone to transmit vibrations could help functionally deaf people hear normally, according to its creators.

Researchers from the Chalmers University of Technology in Gothenburg, Sweden, developed the 6cm-long Bone Conduction Implant (BCI) as a replacement for the middle ear, attached to the skull under the skin just behind the ear.

Unlike conventional bone-conducting hearing aids, the BCI doesn’t need to be anchored to the skull using a titanium screw through the skin, eliminating the risk of skin infection or the device falling off.

‘You hear 50 per cent of your own voice through bone conduction, so you perceive this sound as quite natural,’ said BCI creator Prof Bo Håkansson in a statement.

The device was first implanted in a patient at Sahlgrenska University Hospital, Gothenburg, last month and doctors say the operation went according to plan, although it will be another six weeks before the wound has fully healed and the implant can be switched on.

The device transmits signals from the external processor to an internal receiver and loudspeaker

The BCI comprises an implant featuring a coil at its upper end that operates using magnetic induction with an outer sound processor held in place by magnets and that the patient can easily attach to or remove from the head.

The processor transmits sound from the patient’s surroundings through the skin to the internal receiver. The audio signal is transmitted to a tiny quadratic loudspeaker anchored to the bone near the auditory canal, which recreates it as vibrations transmitted through the skull to the sensory organs of the cochlea.

This technique has been designed to treat mechanical hearing loss in individuals who have been affected by chronic inflammation of the outer or middle ear, or bone disease, or who have congenital malformations of the outer ear, auditory canal or middle ear.

Such patients suffer hearing loss that is not addressed by electronic hearing aids that compensate for neurological problems in the inner ear. However, the new device may also help people with impaired inner ear.

Måns Eeg-Olofsson of Sahlgrenska University Hospital and Bo Håkansson of Chalmers University of Technology, leaders of the research team behind the implant

‘Patients can probably have a neural impairment of down to 30–40dB, even in the cochlea,’ said Håkansson. ‘We are going to try to establish how much of an impairment can be tolerated through this clinical study.’

Earlier tests indicate that the volume may be around 5dB higher and the quality of sound at high frequencies will be better with BCI than with previous bone-anchored techniques.

The researchers hope to present the first clinical results of the operation in early 2013 and make the device available to other patients within the next couple of years, providing they can find sufficient investment.