New Light on Concussion?

By Jon Heck, MS, ATC
Coordinator of Athletic Training
7/24/00

This letter is a continued effort to keep our coaching staff informed. I hope to give you a better understanding regarding injuries and the decisions we make after an injury occurs. I continue with one of the most controversial topics, concussions in athletics, with an update on some recent developments.

It's Confusing
Concussions are one of the most frustrating injuries for athletes and coaches. One of the more confusing issues remains the very different effects a similar head injury has on different athletes. One athlete may be fine in a few days, and another a few weeks, months or even years. We still lack a concise understanding of the physiological effects of a concussion and why some athletes are more vulnerable to a secondary head injury. But based on recent studies with animals and humans more of the puzzle may have been revealed.

Just What Happens
After a concussion brain cells that are not irreversibly damaged exist in a vulnerable state for anywhere from minutes to days. This concept of post injury vulnerability is a major concern in the management of all athletes with concussion.

An increase in demand for glucose (fuel) and an unexplained reduction in blood flow to the brain (fuel delivery) characterize this period of brain cell vulnerability. This results in an inability to establish a normal chemical environment, particularly during periods of increased energy demand. Simply put, the ratio of fuel use and fuel delivery is out of balance in the brain. These altered environments can kill brain cells.

It appears the concussion results in a breakdown of the brain's harmony between energy demand, production, and delivery. The individuals with the greatest return of blood flow to the brain achieve the best outcomes. Those that encounter a prolonged reduction in blood flow have an increased potential for subsequent injuries, leading to extended problems and a worse outcome. The rate of cerebral blood flow after a concussion is probably a genetic factor and can not be altered.

This metabolic dysfunction is proven to occur in severe head injuries. The increased demand for glucose may last up to 2 weeks and decreased blood flow to the brain can last over one year. It is now being investigated whether this same process occurs in more mild concussions or brain injuries. It seems likely, with the variations we see in the milder grade 1 and grade 2 concussions (no loss of consciousness).

What Does It Mean
Right now this is just an academic theory that will have little impact on the treatment of concussions in sports medicine. Presently it is not feasible to test athletes after a concussion for this metabolic imbalance. And there is no way to manipulate or increase the cerebral blood flow even if we know it is depressed. But understanding the injury process is always the first step in better identification and treatment protocols.

Also keep in mind there is still no "test" that identifies a brain that has received a concussion injury. The x-ray, MRI, and CAT Scan can not identify concussed individuals (they are important to rule out other injuries such as bleeding within the brain). So if we send an athlete for an MRI after a concussion that comes out normal, this in no way rules out a concussion was experienced.

We are totally relient on the athlete's signs, symptoms and mental function to identify a concussion. At Stockton we also use a new tool called the Standardized Assessment of Concussion (SAC) to help identify athletes who have experienced a mild concussion. It seems reasonable that an athlete that is experiencing this metabolic imbalance in the brain will present with symptoms and complaints. But this is yet to be proven, as is how long it takes an athlete's brain to return to normal after their clinical symptoms (headache, dizziness, memory loss, etc) resolve.

There is still much more research to be done. In the mean time we will continue to follow our established concussion guidelines and protocols, which are the most current for concussion management.