A new system of wireless microelectrodes for pinpointing epileptic regions in the brain could drastically improve the prospects for epilepsy patients who need surgical treatment. Currently under development in Switzerland, the new technique is less invasive, more precise and much more patient-friendly than the current method.
The majority of the 50 million people around the world who suffer from epilepsy can be treated by anticonvulsant drugs. Yet a handful of patients do not respond to the standard treatment. More and more of them are turning to surgery to give them back a normal life. The principle is to locate, with the help of electrodes, the region in the brain that is the source of the epilepsy and, in the most serious cases, remove it.
The current pre-surgical phase is complex and highly invasive. Patients undergo a cranial operation to have electrodes implanted on the surface of their cortex. Once the wound is closed, the patients must remain in bed in intensive care for several weeks with wires passing through their cranium. The electrodes are connected the entire time to a recording device, which is used to identify the source of the epilepsy during seizures.
Researchers in Switzerland are now developing a network of wireless microelectrodes that will monitor the patients’ brain activity with great precision, without requiring them to remain confined to their hospital bed.
Greater precision and less damage to the brain
The new wireless method still needs a cranial operation, but offers a number of advantages. In addition to avoiding cumbersome wires and sparing patients the ordeal of staying in intensive care during the pre-surgical phase, it extends the monitoring time, thanks to the reduced risk of infection. The source of the epilepsy can also be identified more precisely.
“We are developing electrodes that are less than 100 micrometres in diameter, versus 10 millimetres for electrodes used in traditional intracranial electroencephalograms,” says Gürkan Yilmaz from École Polytechnique Fédérale de Lausanne (EPFL). Yilmaz worked on this research as part of his PhD thesis, in collaboration with medical doctors and researchers from Bern University Hospital.
“As a result, measurements are much more precise, and the fewest possible neurons are removed during the operation. This allows us to minimise the damage that can result from this type of operation,” Yilmaz says.
With the new system, which consists of a network of electrodes, a microchip and an antenna, the electric signals are captured and processed under the skin in a miniaturised station. The internal device is powered from the outside by wireless power transfer, more specifically by electromagnetic induction. Thanks to this energy, the internal system can process a large amount of data, and then transfer the results to an external unit.
Epilepsy in figures
Epilepsy is the most common cerebral disorder in the world.
Around 50 million people are affected.
Most people can be treated with anticonvulsant drugs, but a small number of patients do not respond to that treatment and must undergo surgery.
In Switzerland, 80 to 100 epilepsy operations are done every year. Of these, 20-30 per cent require an invasive pre-surgical phase to locate the region that will potentially be removed.
The success rate of surgery is around 80 per cent.
(Figures provided by the World Health Organization and Dr Claudio Pollo, Bern University Hospital.)
“We could use a mobile phone to receive the data, but for reasons of data security, it is not the preferred method,” Yilmaz says. At this stage, tests have been successfully run on laboratory mice.
Innovative, less invasive therapies
Medical doctors are showing interest in the new technology. “We would be able to observe epileptogenesis [the gradual development of epilepsy in the brain] at the level of a few cells rather than tens of thousands of cells,” says Claudio Pollo, a neurosurgeon in charge of epilepsy surgery at Bern University Hospital.
“This would enable us to remove smaller epileptogenic zones, and to develop innovative therapies. For example, when a given region cannot be removed, we could deliver electrical stimulation to the lesions to prevent seizures.”
And this type of surgery produces excellent results. “The recovery rate is nearly 80 per cent, when talking about temporal lobe epilepsy. More and more children are operated on, and this drastically changes their future,” Pollo says.
In the laboratory, the researchers continue their work. Their goals include adjusting the size of the electrodes so that they can measure the activity of a single neuron.
Adapted from article by Laure-Anne Pessina, EPFL Mediacom