Head injury=loss of brain tissue

A blow to the head that knocks a person unconscious can result in widespread loss of brain tissue, Canadian researchers have said, 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.

what the study found
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. "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 hospitalised. "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.

The reason behind the study
"What this study does, is it gives us a window into the underlying brain structure changes that might relate to that disability," he said.

Levine said the brain volume lost involved both frontal and posterior brain regions, and the damage was greatest to white matter, tissue that makes up the brain's communication network.

"What you have basically is a loss of brain connectivity. That is essential for the efficient processing in the brain," he said. "When you have a subtle loss of that, even if it is five to 10 percent, it will have a large effect on behaviour."

Levine said the study does not mean that people who have had mild head injuries will have a disability, but it might help to explain why some people never quite recover from their head injury. "You hear this all the time from people, that they're not the same. A lot of times doctors don't know why," Levine said.

According the US Centres for Disease Control and Prevention, at least, 1.4 million people in the United States suffer a traumatic brain injury each year.

At least 5.3 million Americans, or about two percent of the US population, need help to perform activities of daily living as a result of their brain injuries. – (ReutersHealth)

March 2008

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