Overview of Concussion

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 1,2 million 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.

10 to 15% of high school rugby players will suffer a concussion in any season.

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:

SYMPTOMS

SIGNS

  • Headache
  • Dizziness
  • Nausea
  • Ringing in the ears
  • Sleep disturbances
  • Drowsiness
  • Fatigue
  • Sadness
  • Sensitivity to light
  • Sensitivity to noise
  • Blurred vision or partial loss of vision
  • Confusion & disorientation
  • Delayed reaction & response times
  • Slow or slurred speech
  • Vomiting
  • Diminished playing ability
  • Poor concentration
  • Poor performance in class
  • Irritability
  • Emotional changes, depression

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.

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.

In the last decade, a larger body of research has focussed on the potential long term consequences of recurrent and undiagnosed concussion. A condition known as chronic traumatic encephalopathy (CTE) has been described. The exact progress of the condition from concussion to potential CTE is unknown and not all cases of concussion will result in chronic deficits. CTE has most recently been the subject of the movie “Concussion” starring Will Smith.

CTEsummary

Summary & Conclusion

In summary, concussion needs to be taken very seriously and can be summarised as follows:

1. Severe Neurological Injury
Acutely, if not identified and managed appropriately, concussion may result in diffuse cerebral oedema (also referred to as Second Impact Syndrome) with resultant severe neurological compromise and even death.

2. Distinguishing Concussion from Other Forms of Brain Injury
The symptoms and signs of concussion may mimic other more serious forms of head injury including intra-cranial bleeds.

3. Post Concussion Syndrome
Failure to recognise and appro-priately manage concussion may result in symptoms persisting for weeks, months or years.

4. Cognitive deficits
Concussion often affects young people in a learning environment; failure to recognise and manage the condition may significantly impaired learning.

5. Impaired Performance and Increased Injury Risk
Previous concussions, especially those not managed appropri-ately, predispose to further con-cussions and also increase the risk of other injuries.

6. Chronic Neurological and Psychological Sequelae
An increased incidence of de-pression has been identified in athletes who have suffered recurrent concussion. Recurrent head trauma has also been associated with persistent cognitive deficits, especially in American Football players.

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