A Danish team found that the odds of epilepsy more than doubled after mild brain injury or skull fracture and was seven times more likely in patients with serious brain injury.

The risk remained even 10 years on, more so in people older than 15, Jakob Christensen and colleagues at Aarhus University Hospital in Denmark and colleagues wrote in the journal Lancet.

"Traumatic brain injury is a significant risk indicator for epilepsy many years after the injury," they wrote.

"Drug treatment after brain injury with the aim of preventing post-traumatic epilepsy has been discouraging, but our data suggest a long time interval for potential, preventive treatment of high-risk patients."

The researchers analyzed data taken from a national registry on traumatic brain injury and epilepsy of 1.6 million young people born in Denmark between 1977 and 2002.