4/3/2010

I was channel surfing the other day when I came across a boxing match. I watched for a few moments out of amazement rather than interest. Boxing appears to be a sport with one purpose only – to inflict brain damage on one’s opponent. There may be a lot of body blows in a round, but what boxers are really trying to do is get a good shot at their opponent’s head for a knock down, or better yet, a knock out. How sick is that?

The past decade has seen a redefinition of what constitutes a concussion. Used to be it was a head injury characterized by a brief loss of consciousness. The requirement for loss of consciousness has been removed, leaving only the symptoms of temporary confusion and amnesia after a blow to the head.

When a force impacts the skull a shock wave of energy is transmitted to the brain. Like electricity, the shock wave travels the route of least resistance, which is out the base of the skull into the spinal canal. This route includes the brainstem, an area crucial to consciousness. If the force is great enough, the neurons supporting consciousness are temporarily disrupted, possibly resulting in a period of unconsciousness. But this period may be extremely short or never even occur. Nevertheless, brainstem circuits are temporarily disrupted, leaving symptoms of confusion, amnesia, headache, dizziness, ringing in the ears, nausea or vomiting, slurred speech, and fatigue. These symptoms may not appear until hours after the injury.

A common misperception is that concussions are trivial, leaving no residual. Actually repetitive concussions have a cumulative effect on brain function. A good example is the “punch drunk” retired boxer who may show slowed movement, Parkinson like tremors, and elements of dementia. For this reason professional neurosurgical organizations have spent a great deal of effort to encourage the use of protective helmets for sports that place the athlete at risk for head injury.