May 22, 2000

LOS ANGELES (AP) - Even mild head injuries result in major changes to the brain's metabolism and could make victims susceptible to more serious damage from a repeated blow, according to a study being released Monday.

The findings raise concerns about sending athletes back to the field or drivers to the road within minutes of any head injury, said Dr. Marvin Bergsneider, a study author and neurologist at the University of California, Los Angeles Medical Center.

"What is the risk of putting a quarterback back into a football game if he's been knocked unconscious just 20 minutes before?" he said. "This study implies it may be risky to do that because the brain isn't functioning normally metabolically."

Doctors typically assess brain injuries by asking victims simple questions and performing MRI and CT scans, which show the structure of the brain.

For this study, researchers performed positron emission tomography (PET) scans on 42 patients in the aftermath of a concussion. PET scans reveal how the brain is functioning by measuring its use of glucose, the fuel of brain cells.

The UCLA researchers found no difference in the PET scans of comatose patients with head injuries and those who were awake.

"Even though a person may appear normal, alert and able to talk, what occurs inside the person's brain is anything but normal," said researcher David Hovda, director of the UCLA Brain Injury Research Center.

The study is published in the May issue of Neurotrauma. Further research is needed to determine how long the lower use of glucose persists after an injury and to fully understand the effects. Patients in the UCLA study were found to be normal six months after the injury.

Previous animal studies have shown that the depressed level of glucose use can make a patient vulnerable to more severe damage after a repeated blow.

The study confirms something long suspected by doctors who treat people with head injuries, said Dr. Gregory O'Shanick, national medical director of the Brain Injury Association.

"We know just because people are walkie-talkies - because they can walk and talk - that that's not the full story," he said. "Many people blow that off as being innocuous. What this indicates is that clearly it's not."

Anyone who suffers a head trauma should think twice before resuming normal activities immediately after the injury, he said.

"Treat concussion as a sprain on the brain," O'Shanick said. "You don't run on a sprained ankle immediately. You go back into exercise slowly - it's the same thing with concussive injuries."