Concussion is a mild form of brain injury that most of us will suffer at some point. The brain is a vital organ and needs to be protected from harm but also repeated minor harm. Sports men and women have an increased risk and it is the responsibility of society, governing bodies and the individual to avoid injuries by changing behaviour but also to protect the brain.
The brain is naturally protected by a hard skull of variable thickness both between individuals but also in the same individual at different ages and at different sites, being thinnest at the temple (4mm). The meninges further protect the brain and in particular the cerebrospinal fluid, in the subarachnoid space, is an important protective layer but the movement of the brain away from the site of impact (coup) can cause a “contra coup” injury with impact against the inside of the skull at particular irregular points. Additional protection to the brain with helmets has a proven worth in reducing direct damage. The dissipation of energy through a fractured skull can injure the meninges (extra-dural bleeding), the brain (intracerebral bleeding with expansion outwards into the subarachnoid or subdural spaces or inwards to cause intra-ventricular bleeding). Indirect damage through the harmful effect of “g” forces (deceleration) can cause shearing damage to the white matter of the brain which can be devastating and it is probably a mild variety of this injury that leads to concussion.
The application of energy to the head has the potential for causing harm if the natural biological and manmade defences are overcome. Helmets prevent penetrating injuries, reduce impact deceleration and dissipate blunt trauma but direct trauma, shearing forces or cavitation from shock waves leads to brain injury, bleeding and swelling. Energy is determined by the mass and acceleration of the object that strikes the head plus the size of the impact zone. In a patient with concussion the delivered energy is greater than the protective forces with enough shock to stun the neuronal network but insufficient to cause “visible” structural damage.
The functional disturbance of brain function without structural change is one that is understood to be reversible. It is probable that as imaging methods improve structural changes will however be detected and allow greater understanding of these processes. It is intuitive that whilst the brain is injured that secondary injuries are best avoided so recognition, removal from play, recovery and phased return are advised. Referees and coaches are now educated to detect a concussed player and remove him or her from the field of play. A period of recovery is essential until all symptoms have settled and then a gentle return to physical activity and a graduated return to play should be enforced.
In the medical setting of a patient with severe head injury attention is focussed on avoiding secondary insults such as expanding haematomas, hydrocephalus, infection, seizures etc. In the context of the patient with concussion minimising injury and maximising recovery by avoidance of contact sports, no alcohol, plenty of sleep and healthy living are recommended.
The prevention of injury whilst playing sport is a responsibility of all concerned. The governing body needs to eliminate the potential for head trauma by avoiding contact in the very young (under12) but banding youth players according to weight and age. The use of helmets in cycling and rugby is advised but the wearing of the helmet may lead to more risk taking:
“Look at the NFL,” Dr Loosemore told Telegraph Sport, “where the risk of brain injury is extremely high despite the helmets that they wear. Rugby headguards would be just as ineffective; in fact, they would actively create problems.”
The “second impact syndrome” concern about a life threatening event for a patient sustaining a minor head injury is poorly understood and the supporting evidence poor. In the circumstances of any head injury the severity of the injury needs to be assessed by coaches, teachers, referees, physios, nurses and doctors. If the individual has been knocked out and continues to exhibit an altered conscious level then immediate hospital attendance is required for a brain scan. I suspect where people have died after a second “minor” injury close to the first that the first injury was not properly evaluated and a complication such as an haematoma occurred.
The long term effects of repeated concussion need to be taken seriously and a period of time off until all symptoms have settled and a graded return (21d) to training and then play is advised. The monitoring of each player and a record of the number of injuries sustained needs to be kept because as injuries mount-up the recuperation time may need to be lengthened. MR brain scans may be indicated in particular players who have prolonged symptoms or repeated injuries. Measurements of brain proteins released into the bloodstream from the injured brain may be available in the future as a blood test. The long term health of players and patients is paramount and anything that can be done to reduce or minimise the chance of memory problems or dementia is welcome.
The impact of concussion on an individuals life may have more than the short term impact with knock-on cumulative effects years down the line for the individual and society. Other life-style factors may be important but it is important that sportsmen and women are protected from head injury and concussion.