"We've known for a long time that the temporal lobe misfires during seizures," said Hal Blumenfeld, M.D., assistant professor of neurology and neurobiology at Yale 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 added. "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 (SPECT) to view changes in brain activity during seizures. He also analyzed videotapes of patients during seizures to determine how their behavior was related to imaging 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 said. "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 Susan Spencer, M.D., of Yale. Co-authors included Edward Novotny Jr., M.D., I George Zubal, Kelly McNally, Susan Vanderhill, A. LeBron Paige, Richard Chung, Kathryn David, and Andrew Norden, fromYale; Rik Stokking from the University Medical Center, Rotterdam, and Colin Studholme from the University of California at San Francisco.
Citation: Cerebral Cortex, Vol. 14: April 2004
Journal
Cerebral Cortex