Message in an implant

A micro-sensor that could be injected into the brain of those suffering from motor neurone disease and transmit data to a computer is being developed at Birmingham University.

In its most severe form, motor neurone disease can cause lesions in the upper brain stem, preventing signals from travelling between the brain and muscles. This leaves sufferers with normal mental functions, but unable to communicate with the outside world.

In a presentation at the Euro-NanoForum 2005 in Edinburgh, Jon Spratley of Birmingham’s School of Engineering claimed signals that would have previously controlled muscles could be harnessed to operate communications technology such as artificial speech programs, or even the movement of an electronic wheelchair.

Sufferers of epilepsy or Parkinson’s disease can have electrodes implanted in their brain to control their conditions, but this requires a major operation with risks of infection and complication.

Using micro-engineering techniques, Spratley is designing an unpowered passive sensor package that is small enough to be injected using a needle with a diameter of up to 1.5mm, removing the need for an operation.

Brain activity creates electromagnetic waves. These are currently routinely monitored by hospitals as part of treatment for sufferers of epilepsy, using electrodes connected to the surface of the scalp. However, the skull acts as an electromagnetic shield, meaning the images are blurred. The volume of signals and the distance of the scalp from the area where the signals originated makes it hard to single out precise signals from a specific location.

According to Spratley, by injecting micro-sensors into the motor cortex of the brain, localised and precise data could be gathered. The skull would be used to shield the device from external electromagnetic signals. The sensors would then communicate with a relay station implanted on the outside of the brain, under the skull, which would pass the signals to an external processing unit.

The device will be powered by drawing energy from the inductive field of the relay station, removing the need for a power source for the sensor itself.

‘The sensor has to be biocompatible and must resist the motion of the brain to ensure it stays where it is put,’ said Spratley. ‘When the user thinks about moving, an area of the brain will flare, creating activity that could control a mouse pointer on a computer.’

Spratley’s work is part of wider university research into the use of microsensors in medicine by the department of engineering’s microengineering and nanotechnology group.

Other systems under investigation include the use of implanted micro-sensors to monitor fracture healing and hip replacements, allowing remote monitoring of patients who have been discharged from hospital to recuperate at home and freeing up hospital beds. If complications occurred, the sensor could alert doctors by computer. Sensors could also be implanted in specific areas to monitor how much of a drug was reaching its target.