The threat hangs over 50 million epilepsy sufferers worldwide, posing an ongoing challenge for researchers working on brain diseases. Although seizures can take many forms they mostly occur without notice. For years specialists have been looking for signs enabling them to anticipate seizures, if only by a few minutes.

In the US firms such as Seattle-based Neurovista are developing an implantable device that continuously analyses electroencephalogram (EEG) data to detect impending seizures. A study is under way in Australia and trials have also started in US universities, using epileptic dogs. The project has received $7.5m in National Institutes of Health funding.

France is involved in similar research. In 1998 a team led by Dr Michel Baulac, a neurologist at La Pitié-Salpêtrière hospital in Paris and researcher at the Brain and Spinal Cord Institute (ICM), published a key article in Nature Medicine showing that epileptic seizures do not occur entirely unannounced. "We established that in the preceding five or 10 minutes, changes in brain waves can be detected with a surface EEG," Baulac says. "But these findings could not be used clinically because the sensitivity/specificity ratio was too low, so there were too many false alarms."

The team is now exploring three approaches. The first uses micro-electrodes to map electrical activity in individual neurons. In a similar vein another part of the team is trying to reproduce seizures under laboratory conditions, working on brain tissue from patients who have undergone operations. Lastly, a partnership has been set up with the Institut Langevin to obtain real-time images of cerebral blood flow using a scanner.

The first line of research is already yielding results, thanks to micro-electrodes just 40 microns across implanted in the brain. "Several international teams use this technique, mainly for cognition protocols, studying memory in specific brain cells," says neurologist Dr Vincent Navarro. "We're among the few groups – and the only one in France – to use it for epilepsy."

The research protocol started less than a year ago with patients due to be operated on for epilepsy. In general preparations for surgery of this sort include EEG and video records spanning several weeks. The aim is to locate the exact point where seizures start and hence the target for surgery.

If surface EEG is not sufficient, electrodes are temporarily implanted in the brain. "We can insert a bundle of micro-electrodes inside the [larger] electrodes, which are about one millimetre across, enabling us to monitor single neurons," Navarro adds. Using this method, already applied to eight patients, the researchers have sometimes succeeded in observing electrical anomalies, but only a few seconds before the seizure, rather than a few minutes as had been hoped.

Dr Navarro is also taking part in Epilepsiae, a European project to assess the predictive value of a combination of 44 types of analysis to anticipate the onset of seizures. The colossal database, which contains weeks of recordings of the electrical activity of some 275 participants, has just been made available to the scientific community. "Initial analysis suggests that seizures could be anticipated in 10% to 15% of patients, but we have yet to determine their particular profile," says the neurologist.

Just a step away, at the ICM, a team led by Richard Miles and Gilles Huberfeld is trying to reproduce epileptic seizures in the laboratory. Huberfeld, a neurologist and researcher, uses fragments of the hippocampus from patients operated on for certain forms of temporal lobe epilepsy.

Lastly, Mickael Tanter at the Institut Langevin is working on a third approach: an ultrafast, ultrasonic scanning system for observing blood flow in the brain. The new system has been successfully tested, visualising variations in blood flow during epileptic seizures in rats.

Tanter is already planning applications in treatment, using the ultrasound waves on the brain, as is already the case with other organs, to stimulate, disable or destroy small sections remotely.

This article originally appeared in Le Monde