Scientists once believed that all the damage to the brain in a head injury occurred within several swift seconds. Neurons died because they were wrenched apart as the brain was slammed around in the skull.
But, over the past decade it's become clear that much of what goes wrong in the brain after a traumatic injury occurs in slow motion.
And that new understanding may one day lead to therapies that minimize damage to the brain in much the same way that modern-day emergency treatments for stroke patients prevent lasting disability, experts say.
What Goes Wrong
Studies show that the initial injury to the brain kicks off a sequence of events that takes anywhere from hours to days to finish. Some experts even believe that deterioration of brain tissue continues years after an injury.
When the brain twists and stretches, rips can form in the axons, the long, slender, cable-like structures that project from the main body of the neuron. These tears allow chemicals to rush into the axon, causing it to swell. In response, the neuron itself releases proteins that chew the cell up from the inside out, eventually leading to self-destruction.
At the same time, in reaction to the initial wound, other brain cells release a flood of excitatory neurotransmitters. These chemical messengers are normally present in small amounts, but when they surge, it's “like throwing salt water over live electrical circuits,” says Douglas H. Smith, M.D., director of the Center for Brain Injury and Repair at the University of Pennsylvania. “It can also cause self-destruction of brain cells.”
Can It Be Fixed?
Specialists in traumatic brain injury predict that one day there will be a treatment to halt the devastating secondary injuries if it's given early.
There have been numerous attempts to find a drug that can stop the surging of excitatory neurotransmitters. So far none of the drugs tested in humans have worked, even though many have shown promise in animal studies. But researchers haven't given up the quest and there are several substances currently being tested in clinical trials.
Ultimately, Dr. Smith says, the solution may not be a single drug. “We won't have the Swiss Army Knife treatment-more likely it will be a cocktail.”