Head injuries when playing sport is a risk that can be minimized through careful planning, adherence to the rules, and wearing the correct equipment. Even then, there are some tragic cases. One, in recent years, was the suicide of American football star Junior Seau. Seau was an NFL linebacker who committed suicide in 2012 because he was suffering with brain trauma, sustained from his playing days. It was because of this case, and others, that the U.S. National Football League (NFL) paid out a compensation package valued at $765 million to help cover the medical expenses of more than 4,500 former players and to fund research on head injuries.
As well as adult players, concern about the risk from head injuries extends to youngsters who plays sport. In relation to this, Virginia Tech (Wake Forest University School of Biomedical Engineering and Sciences), has produced a concerning study into head impacts sustained by young football players aged seven and eight years old. The research found many of the impacts experienced by children playing football were of the order experienced by adults and were often too severe.
In light of such findings, and exemplifying the seriousness of the matter, the U.S. National Institutes of Health (NIH) recently awarded two $6 million grants to research groups in order to further understand the effects of traumatic injury on the human brain.
Separate from this funding, scientists from the Georgetown University Medical Center in Washington, D.C., have found the extent of brain injury relates to the number of successive head contacts within a set period of time. The researchers focus was with mild head injuries which can cause chronic behavioral, cognitive, and neurodegenerative conditions.
The research, led by Dr. Mark Burns, has found the brain can recover relatively quickly following a single head hit. However, there is considerable risk should multiple hits occur in quick succession. These rapid strikes do not give the brain sufficient time to recover.
Unlike earlier work, which is based on empirical data relating to football players (that is correlating incidences of head trauma with footage of games), the Georgetown University findings come from animal experiments. For this the scientists used mice, in studies designed to mimic what can happen during the playing of contact sports.
Here the anesthetized mice were exposed to a single — reportedly ‘mild’ — head hit. The level of the blow was scaled in such a way that it mimicked a blow to a sportsperson (how exactly is not fully defined.) The mild hit slowed down the return to consciousness, compared with control mice that were not hit, but there was no long-term observable brain damage.
There was, however, some loss of brain activity although the brains of the mice soon recovered. One day after the injury, a loss of dendritic spines was noted. These recovered three days later. A dendritic spine resembles a protrusion from a neuron’s dendrite. The function is to receives input to the neuron, as part of the body’s nervous system.
The mouse studies reveal, according to Science News, in what may help anxious parents watching from the touchline, that a single, mild head hit is not likely to cause any long-term harm, especially where concussion is avoided.
With successive hits, a different response was noted. Mice subject to 30 mild hits (which the authors contend could happen over several games of American football or soccer) did not lose any more dendritic spines but the recover did not happen. The mice were monitored for a period of up to six weeks following the injuries and no recovery was noted. The researchers then went back to the mice one year later, and again there was no sign of recovery. Poor recovery was evident in the behavior of the mice, in terms of their ability to balance and apparent stress.
One variable that did play apart was rest between the hits (as if a human player was rested from a game following a head injury); in these situations better recovery was noted.
Thus the authors conclude that the main danger with head injuries arises from re-injury and particularly the time period between injuries. This is more so where a simulation of concussion occurs. In a sense the study confirmed long-established medical advice, where those who sustain a head injury are advised to avoid another head injury.
Such results on animals are interesting and they may inform what happens with people, but there is no exact fit. Human players are often wearing helmets, which have been designed to help minimize injuries. Nonetheless, the finding of intervals between head hits opens up an important avenue for continued research. The average number (mean) of head hits per NFL player per season ranges from 431 to 1,850.
The findings are published in the American Journal of Pathology. The research paper is headed “Dendritic Spine Loss and Chronic White Matter Inflammation in a Mouse Model of Highly Repetitive Head Trauma.”
This article is part of Digital Journal’s evolving ‘essential science’ series. The five most recent articles have looked into:
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