Yale Bulletin and Calendar

April 30, 2004|Volume 32, Number 28

Epilepsy: Even small seizures
can cause loss of consciousness

Even small epileptic seizures can trigger widespread abnormal signals in brain networks leading to loss of consciousness, according to new findings by a Yale researcher.

"We've known for a long time that the temporal lobe misfires during seizures," says Dr. Hal Blumenfeld, assistant professor of neurology and neurobiology at the School of Medicine and lead author of the study, "but we were amazed to discover that the temporal lobe also causes the rest of the brain to malfunction. That's why patients lose consciousness."

"Loss of consciousness during seizures often causes serious motor vehicle accidents, injuries and falls in patients with epilepsy," he adds. "The hope is that we can interrupt the process and prevent unconsciousness."

Blumenfeld focused his study on patients with seizures in the temporal lobe, the most common form of epilepsy. He and his colleagues used single photon emission computed tomography to view changes in brain activity during seizures. He also analyzed videotapes of patients during seizures to determine how their behavior was related to these changes.

The study found that in patients who lost consciousness during seizures, there were abnormal signals scattered across brain images like a fireworks display. In contrast, patients who had seizures but did not lose consciousness had localized increases confined to the temporal lobe.

"These results may help us target new treatments, such as brain stimulation, to prevent spread of abnormal activity outside the temporal lobe," Blumenfeld says. "Understanding the network abnormalities leading to loss of consciousness during seizures could also help solve an even more fundamental question -- what is the relationship between normal brain activity and conscious thought?"

The senior author was Dr. Susan Spencer of Yale. Co-authors included Dr. Edward Novotny Jr., I. George Zubal, Kelly McNally, Susan Vanderhill, A. LeBron Paige, Richard Chung, Kathryn David and Andrew Norden, also from Yale; Rik Stokking from the University Medical Center, Rotterdam; and Colin Studholme from the University of California at San Francisco.

-- By Jacqueline Weaver

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