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 Definition
Concussion, also known as mild traumatic brain injury (MTBI), is a pathophysiological process that affects the brain as a result of a direct or indirect blow to the head.
Common features include:
• Acute symptoms that represent functional disturbances, rather than structural changes to the brain.
• Symptoms that are rapid in onset, but usually resolve spontaneously.
• A range of clinical symptoms and signs (see below). That may or may not include loss of consciousness or
amnesia (loss of memory).
• Neuro imaging studies (brain scans) that are usually normal.
(Adapted from ACSM Physicians Consensus, 2005)
Incidence
In the USA, up to 300000 concussions occur in contact and collision sports per year. In South Africa, rugby has the highest incidence of concussion amongst collision team sports. 10 to 15% of high school rugby players will suffer a concussion in any season. Up to 50% of high school rugby players would have suffered a concussion in their high school playing careers.
Although high profile sports such as rugby receive the most attention in terms of head injury, it must be emphasised that concussion may occur in almost any sporting environment. Other contact sports such as soccer, boxing and ice hockey have a significant incidence of concussion.
High velocity ball sports such as cricket, baseball and field hockey result in head injuries were the athlete’s skull is struck by a fast moving, hard object. Athletes with significant traumatic brain injury in sports such as water polo, cycling (track, road, and off-road), horse racing and showjumping may be ignored because the association is not commonly made.
A high index of suspicion of potential head injury is required when assessing any athlete who has sustained a collision or has multiple injuries. Gymnasts who fall and dancers, whose head strikes their partners knee accidentally, have been shown to present with concussion. Finally, mild traumatic brain injury may, of course, occur in non-sporting scenarios such as childhood accidents, motor vehicle collisions and physical violence.
What is happening in the concussed brain?
Unlike more severe traumatic brain injuries, the disturbance of brain function in MTBI is related more to disturbances of brain metabolism rather than to obvious structural damage. A complex cascade of ionic, metabolic and physiologic events appears to be triggered by the impact. This appears to be initiated by the release of a neurotransmitter glutamate resulting in indiscriminate flow of potassium ions out of nerve cells and sodium and calcium in. This affects energy production on the cells’ powerhouses, the mitochondria, resulting in little energy (glucose) to fuel normal information processing. Hence clinical signs and symptoms of MTB such as poor attention, memory, speed of processing, and motor function are manifestations of this underlying neurometabolic cascade. Rest both from exercise and mental exertion (studying, computers etc.) is required for this imbalance to redress itself. (For a scientific explanation see Giza’s paper under Research/Pathophysiology.)
Clinical presentation.
Previous definitions of concussion relied on the presence of one or both of two specific symptoms to be present for the definition of concussion to be made namely, loss of consciousness or amnesia.
Loss of consciousness for any period of time and amnesia remain significant events. The amnesia may be retrograde (forgetting events that occurred before the impact) or anterograde (memory loss for events occurring after the impact).
However, it is now acknowledged that concussion presents in a number of guises, and any combination of a number of symptoms and signs should be looked for.
These include:
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SYMPTOMS |
SIGNS |
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Headache |
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Confusion & disorientation |
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Dizziness |
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Delayed reaction & response times |
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Nausea |
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Slow or slurred speech |
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Ringing in the ears |
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Vomiting |
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Sleep disturbances |
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Diminished playing ability |
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Drowsiness |
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Poor concentration |
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Fatigue |
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Poor performance in class |
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Sadness |
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Irritability |
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Sensitivity to light |
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Emotional changes, depression |
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Sensitivity to noise |
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Blurred vision or partial loss of vision |
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These symptoms may
persist from hours to weeks.
A player that is suspected to be suffering from ANY of these
symptoms
or signs must be examined by a doctor.
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Moreover, some of these symptoms may present immediately after the injury, while others may develop over hours to days following injury.
Significance of concussion.
By definition, the symptoms of concussion seem to resolve spontaneously over the course of time and there appears to be limited structural damage to the brain. Why then should traumatic brain injury which is 'mild ' be taken seriously?
Firstly, should the condition not be correctly diagnosed and appropriately managed (see Diagnosis & Management) symptoms are likely to persist for longer and hamper the recovery. As many of the symptoms listed represent changes to brain function, the developing brain of a young athlete may be significantly compromised not only in a sporting, but importantly also in a learning and social environment. A Post Concussion Syndrome comprising persistent headaches, sensitive eyes, poor concentration, fatigue and drowsiness, and disturbed sleep patterns may wreak havoc with the learner's performance in the classroom. Other symptoms such as mood changes and depression impact on the athlete's interaction with family and peers. Poor coordination, delayed reaction times, exercise-induced headaches and dizziness, and compromised vision will affect performance on the sports field, thereby greatly increasing the risk of recurrent head or other injury.
Secondly, although far less common, the risk of Second Impact Syndrome, a very serious and even fatal brain injury that may occur even with a relatively mild impact, appears to be particularly significant in young athletes. A rare disorder,
Second Impact Syndrome, occurs when an athlete suffers a concussion and then, within a short time later (usually within one week although it may be longer), receives a second blow to the head before the brain has recovered from the first concussion. It is possible for rapid brain deterioration and even death to occur. This happens because the brain is still affected from the first injury and the second injury results in rapid swelling and pressure within the skull. This intracranial pressure, if uncontrolled, can lead to death. There have been several episodes of suspected second impact syndrome in South Africa recently - See the following articles.
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