"Head Injuries V"
"Head Injuries V"
HELMET HUT, article for August 2004
HEAD AND NECK INJURIES: SECOND IMPACT SYNDROME
For our readers who have kept pace with the HELMET NEWS section of the website, we know that concussion, or mild traumatic brain injury (MTBI) can be caused by a number of mechanisms.
We also know that it is not necessary to have a loss of consciousness, nor “obvious” mental alteration that shows immediately. It can take minutes or hours before the effect of a harsh blow makes itself known. The observable metal alteration may or may not accurately reflect the degree of physical or metabolic damage. Due to the variability of symptoms and diagnosis, it is often unclear when a football player should return to action. While diagnostic procedures improve and awareness of the seriousness of MTBI has increased, it is estimated that up to 70% of those players who are rendered unconscious during a specific game have been put back on the field the same day! This can be attributed to a general lack of understanding that an absence of serious, obvious symptoms does not often reflect the degree of cellular and/or metabolic disruption.
SECOND IMPACT SYNDROME refers to the consequences of a concussion that closely follows a previous MTBI. The athlete may or may not be symptomatic from the first injury relative to observable behaviors. However, at the cellular level, damage has occurred and recovery certainly has not yet been complete. The athlete is rushed back into play after a minor head injury and sustains a subsequent blow to the head. He is already more sensitive to injury due to the metabolic disruption that occurs with axonal injury as discussed in previous articles in this series. The second injury leads to an inability to regulate glucose and oxygen metabolism, congestion of blood in the vessels of the brain, and a dangerous or fatal increase in blood pressure within those vessels. Cerebral hypertension leading to cerebral edema or swelling of/within the brain can cause irreversible brain damage or death. Usually, teammates, coaches, and parents are shocked that a seemingly mild injury leads to such devastating results but it is the accumulative effect of closely spaced minor injuries that causes the inability of the brain to properly regulate the metabolism and use of chemicals and oxygen. While some Second Impact Syndrome deaths have been reported in ice hockey and boxing, most have occurred in football.
One problem related to Second Impact Syndrome is that the athlete may appear to behave in a normal manner. Typically, they suffer what appears to be a minor concussion. They return to classes and practice (or in professional football, meetings and practice) without incident and without any decline in observable response or ability. Their family reports that their activities have returned to normal and they show no outward sign of impaired behavior. Unfortunately, RESOLUTION OF THE METABOLIC DYSFUNCTION MAY TAKE UP TO SEVERAL WEEKS. Before resolution occurs, they suffer another (that is, a second) MTBI in practice or during a game. The blow does not have to be severe or major. The brain is still sensitive to subsequent damage due to the initial cellular disruption and metabolic alterations and the second blow does not have to be as severe as the original injury inducing impact. A “second blow” may not even be struck. Rapid acceleration and deceleration of the brain may stretch the axons enough to induce the damaging response. This can occur when a receiver goes to catch the ball and is struck in the back by the defensive back, or a running back turns up field and is struck in the chest by the linebacker’s helmet or pads, stopping or reversing his momentum. Shortly thereafter, the athlete will begin to suffer the observable symptoms associated with head injury or concussion but will rapidly decline as the enhanced metabolic disruption begins to play havoc in the brain. Quick, and often irreversible decline begins to occur and medical intervention is immediately required.
Neurologists who treat athletic event induced head injuries usually stress that recognition and proper diagnosis of the initial concussion must be made. Total resolution of symptoms must occur and appropriate rest from contact must be instituted. In the professional ranks, there is so much money allocated to player salaries that management expects the players to play. The pressure on coaches to field a winning team is enough to at times alter their decision-making ability regarding the suitability of using an injured player. The player does not wish to jeopardize his starting position and is anxious to get back onto the field. In all cases, time must be taken after any concussion to allow for brain and tissue metabolism to completely recover. The risk of fatal or long-term damage from Second Impact Syndrome demands this.