Knockout head injuries found to cause loss of brain tissue

By Julie Steenhuysen

CHICAGO (Reuters) - A blow to the head that knocks a person unconscious can result in widespread loss of brain tissue, Canadian researchers said on Monday, explaining why some people who suffer head injuries are never quite the same.

The more severe the injury, the more brain tissue is lost, they said.

"There is more damage and it is more widespread than we had expected," said Dr. Brian Levine of the Rotman Research Institute and the University of Toronto, whose study appears in the journal Neurology.

Levine studied brain scans taken from 69 traumatic brain injury patients whose head injuries ranged from mild to moderate or severe. The researchers used high-resolution magnetic resonance imaging or MRI to study changes in brain volume a year after the injury.

They ran a computer analysis of these images and found that even patients with mild brain injuries with no apparent scarring had less brain volume.

"When you have a blow to the head, it causes a neurochemical reaction in the brain cells that lead to cell death," Levine said in a telephone interview. "The more cells that die, the less tissue you have."

All the patients in the study had injuries severe enough that they needed to be hospitalized. "The amount of tissue loss seems to be related to the severity of the injury -- how long was the person was knocked out," Levine said.

He said the study helps to explain why some people with brain injuries often struggle with memory problems, mood changes, confusion and reduced information processing speed.