Head Trauma on the Field May Set Stage for Lasting Brain Injury Nov. 2, 2001 -- A new study offers important information for athletes and parents of children who play sports. Researchers have found that in the first 24 hours after a concussion, another head injury may mean serious damage down the road.

"Clearly, we do not always recognize concussions for what they are: brain injuries," says senior researcher Tracy K. McIntosh, PhD, in a news release. "The damage is not always noticeable either. That is, you do not have to fracture your skull to injure your brain," says McIntosh, a professor in the department of neurosurgery at the University of Pennsylvania School of Medicine in Philadelphia.

In the November issue of the Journal of Neurosurgery, the researchers report the results of their experiments with mice. They found that animals who experienced a single head injury showed temporary loss of muscle function due to nerve damage, that resolved itself within a week.

But mice that experienced one brain injury, followed by another within 24 hours, had much more pronounced nerve damage and severely impaired, lingering muscle function. Even so, the animals were completely recovered within two weeks. Or so the team thought.

As it turned out, the researchers began to notice changes in the double-injury mice, almost two months later -- long after the animals had appeared to return to normal.

"At about 56 days we began to see a measurable breakdown in [muscle function] and, subsequently, a breakdown in cells of the brain," says McIntosh. "This correlates with what we know about the nature of repetitive head injuries in humans."

It's unclear exactly what caused some of the brain nerves to die, but the researchers did find that mice with two brain injuries had an accumulation of a protein in their brain called "beta-amyloid precursor protein," -- the same substance suspected to be at work in Alzheimer's disease. They suggest that the build-up of this protein in the brain may have choked off and killed the nerve cells.

"Our findings represent the first real attempt to look at the science behind head injuries -- and we were startled to see how permanent the damage can be," McIntosh says.

"The desire to get back into the game is admirable, but ultimately not worth the risk," he adds.