Scientists have crafted a tool for predicting epileptic seizures with equations from chaos theory. The finding, reported next month in Physical Review Letters, could provide an early warning system and might eventually lead to methods for preventing seizures.
Approximately 3 million people in the United States suffer from epilepsy, and a third of them experience seizures that cannot be controlled with medication. Normal patterns of brain firing are seemingly chaotic, but during a seizure, neurons synchronize and fire convulsively in parallel. This synchrony spreads throughout the brain and jams neural pathways.
To investigate the mechanisms underlying seizures, Klaus Lehnertz, a physicist at the University of Bonn's Clinic of Epileptology, and his colleagues studied brain electrical activity (EEG) measurements taken from 16 epileptic patients with electrodes implanted in their brains. The scientists compared recordings from normal periods to those just before and during seizures; their yardstick was an algorithm developed from chaos theory to measure the degree of complexity in brain activity. The team teased out a signature of decreasing complexity that consistently heralded a seizure.
Because the pattern appeared 10 to 30 minutes before a seizure began, it could potentially serve as an early warning system for an impending seizure. "The big problem with people who have seizures is that you never know when it's going to happen," says neurophysicist William Ditto at Georgia Tech in Atlanta. "You could be holding a baby, so even a few minutes notice would be a big advance."
Researchers hope that someday computer chips implanted in the brain could monitor brain activity and prevent seizures before they start. "The brain becomes more regular when it's misbehaving, and if you could somehow induce it to become more chaotic or more irregular, that would help break the seizure," Ditto says. But Steven Schiff, a neurosurgeon at Children's Research Institute in Washington, D.C., cautions: "It's not clear yet what kind of accuracy this tool will have when it's used in practice."