Any athlete with a suspected concussion should be IMMEDIATELY REMOVED FROM PLAY, urgently assessed medically, should not be left alone and should not drive a motor vehicle.
What is a Concussion?
A concussion is a disturbance in brain function caused by a direct or indirect force to the head. It results in a variety of nonspecific symptoms (like those listed below) and often does not involve loss of consciousness. Concussion should be suspected in the presence of any one or more of the following:
• Symptoms (such as headache), or
• Physical signs (such as unsteadiness), or
• Impaired brain function (e.g. confusion) or
• Abnormal behavior.
"The definition of concussion is a post-traumatic impairment of neural status. While the loss of consciousness and amnesia may have been viewed as the primary components of this injury and have formed the basis for most grading scales, some of the mild concussions, the so called 'bell-rung' or 'ding,' with no resulting loss of consciousness or post-traumatic amnesia, may go unrecognized by coaches, athletic trainers, fellow players or team physicians."
The brain sits inside a bony encasement called the skull. A collision, abrupt stop or whiplash motion can cause the brain to slam up against the inside of the skull like a pinball. Most of the time the brain tissue itself is not damaged (except in the worst cases), but a devastating cascade of chemical reactions is unleashed.
This slamming of the brain causes the brain cells (neurons) to fire off sending the brain into a panic almost like a brief seizure. This sinister wave of extreme electrical activity spreads across the brain telling the neurons to keep firing. This excess firing clogs the mitochondria (energy producing part of the neuron) and prevents it from doing its job. This is a big problem because the neurons are attempting to regain a normal state so that they can fire again and this scramble consumes a lot of energy. So just when more energy is needed, the mitochondria cannot produce it.
To compound the problem, the brain's blood vessels constrict, preventing the blood from carrying glucose ("fuel")and thereby causing an energy crisis. This can kill brain cells and result in permanent brain damage.
To make matters even worse, extra sodium enters the neurons causing them to swell and push against the skull. If the swelling is severe, the brain can crush itself against the skull causing more cell to die.
These chemical reactions peak rapidly, but it takes a long time to settle the brain back to normal. Once the brain can meet the high energy demand and does return to normal it goes into a state of metabolic depression, i.e. exhaustion. The more severe the concussion, the longer this chemical cascade can continue. "If a second concussion interrupts the brain's quest for equilibrium...a new cascade starts on top of the first one. The resulting damage is not just additive but multiplicative."
Shulman, Polly. "Blowing the Whistle on Concussions." ScientificAmerican Presents, 11(3):44-51, Fall, 2000.
See NFL Dodging the Concussion Issue