Scientists believe they have spotted the gene which causes sudden death during epilepsy fits.
Research at the Baylor College of Medicine showed that the potassium channel KvLQT in neurons in the nervous system could provide the answer to which patients are most at risk of sudden death.
Scientists have found this gene - previously only seen in heart muscle cells - in brain and nerve cells, which the authors believe provides evidence of the link between the heart and brain in epilepsy.
Dr Alica Goldman, an assistant professor working on the study, said: "Living with epilepsy is difficult enough, but unexpectedly dying from it, as happens in young adults with the disorder, is one of the greatest fears a family must face."
She is continuing her research by screening patients with epilepsy to test her theory.
A recent study led by Robert Nitsch of the Universitatsmedizin Berlin indicated that the protein PRG-1 could play an important role in epileptic seizures.