Mind monitor

A new brain implant could stop tremors in people suffering from Parkinson's disease and provide doctors with 24-hour remote monitoring of their condition.

The biomedical device was recently unveiled by IMEC, a Belgium-based nanotechnology research centre, at the annual Design, Automation and Test in Europe conference in Nice, France this April.

The implant is a prototype multi-electrode stimulation and recording probe for deep-brain stimulation. As well as Parkinson's, it could be used to treat other conditions such as depression when drug treatments have failed.

In use, the probes would be implanted in the area of the brain where problems such as unwanted physical movements originate.

Wolfgang Eberle, project manager at IMEC's bioelectronics research group, said that the probe's electrodes would target the network of neurons communicating incorrectly.

'The electrodes will apply a small electrical current to try and reset the [brain's] circuitry,' he said. 'It will then bring it back to a normal level again.'

Other electrodes would monitor the neurons around the probe and record whether the electrical stimulation is effective. The information could then be wirelessly transmitted to the patient or a 24-hour monitoring centre.

Eberle said constant monitoring of Parkinson's patients is not possible with current brain implants. The reason, he said, is current stimulation probes use larger electrodes - measuring millimetres in size - and they are only designed to provide untargeted electric stimulation to the brain.

The IMEC implant, however, uses electrodes sized between 10 and 50 micrometres. These more closely resemble brain neurons, which are five to 10 micrometres.

Eberle said it is only now possible to make the tiny electrodes with current semiconductor process technology, design software and advanced electronic signal processing. The smaller electrodes gave Eberle and his colleagues the flexibility to design a tiny, unobtrusive probe with stimulation and recording capabilities, he added.

Eberle also believes that the tiny electrodes have a more finely tuned electrical-field distribution and run less risk of misapplying electrical currents to healthy areas of the brain.

This sort of problem has occurred with Parkinson's patients who have brain implants, he said. There have been cases of patients falling into depression, he added, when electrical currents unintentionally enable a brain region responsible for mood.

The IMEC team designed its implant with multi-physics simulation software COMSOL 3.4 and 3.5. The software allowed the team to model the electromagnetic behaviour within the probe and the distribution of the electromagnetic field in its surroundings.

Eberle said it also allowed IMEC to simulate temperature increases caused by the application of electrical current. 'The brain is very sensitive to temperature increase so we wanted to get an idea if we're stimulating too much and learn what the safe range is for that.'

At the same time, the software allowed the team to model the electrochemical behaviour between the neurons and the electrodes.

IMEC has performed successful tests of its prototypes on laboratory rats and the team hopes to perform human trials in four to five years' time.

Eberle said it could take a while before these implants are commercialised, but certain elements of their technology could be made available over the next three years.

Siobhan Wagner