We are going to be in a position to find out really quickly how this might be applied to the general population

Prof David Chadwick, University of Liverpool

Classical epilepsies affect an estimated 0.4% of the population and JME accounts for a quarter of those.

The researchers identified the gene by carrying out a study on a unique French-Canadian family.

Genetic screening

They screened 14 members of the family and found identical mutations of the GABRA gene in the eight people who have JME.

The six family members who do not have the condition did not carry the mutation.

They believe the mutations in this gene are significant factors in determining whether an individual is at risk of JME. The gene plays a key role in the transmission of signals in the brain.

David Chadwick, professor of neurology at Liverpool University, welcomed the findings but said they could not be applied to the general population as a whole.

"The problem is these families are quite unusual," he said.

But speaking to BBC News Online, Professor Chadwick added: "With the advent of the human genome map, we are going to be in a position to find out really quickly how this might be applied to the general population.

"Up until now we have understood very little about the mechanisms that lead people to have epilepsy.

"The better we understand it the more accurately we can target therapies. All of these findings will have clinical implications in the future."