Sports Injury: Complex Concussion and Simple Concussion
The signs, symptoms and types of concussion
Article at a glance:
Concussion is a common problem in sport; participate in a contact sport and it’s estimated that on average you’ll get concussed once for every 4,000 hours of sport you play at best and once every 200 hours at worst! John Bye explains what concussion is and answers some of the questions frequently asked by athletes who have suffered from concussion.
What is concussion?
In 2004, the Second International Symposium on Concussion in Sport (the most recent meeting of international experts in the field) defined concussion as ‘a complex pathophysiological process affecting the brain, induced by traumatic biomechanical forces’(1). Put more simply, concussion is the way the brain responds to a ‘bump’. A ‘bump’ is really any significant force that passes through the brain – an uppercut in boxing, a clash of heads in football or a cyclist going over the handlebars onto the ground are a few obvious examples of direct blows to the head or face.
Less obvious are indirect blows where the force is transmitted up to the head from another part of the body; a good example is that of a stationary rugby player tackled from behind, his neck flicking back and some of the force of the tackle passing through his brain. He may end up concussed without ever taking a direct blow to the head.
Both direct and indirect bumps cause the brain (an organ with the consistency of jelly that is effectively suspended by a set of strings) to be shaken about inside the skull (a tight-fitting, hard box). There is an obvious potential for injury if you consider the brain in this way.
Concussion is the brain’s response to a significant bump and manifests itself as a range of symptoms and signs such as headache, confusion, amnesia, drowsiness, dizziness, balance problems, slurred speech and feeling sick (see box 1 for more).
There are two subtypes of concussion(1):
- Simple concussion – characterised by an uneventful progressive recovery within seven to 10 days with rest being the most important component of management. Most concussions fall into this category.
- Complex concussion – where recovery takes longer than seven to 10 days and/or is complicated by problems such as fits, recurrence of symptoms associated with exercise or prolonged unconsciousness.
By definition, the brain is not functioning normally in a concussed athlete. However, the experts are divided as to why the brain is not functioning properly – is structural damage to the brain the cause of concussion or is concussion a purely ‘functional’ problem? To understand these arguments, it’s necessary to have a basic understanding of the structure and function of the human brain (see box 2).
Advocates of the structural damage theory of concussion often talk about a cumulative effect of one concussion after another. If concussion were due to structural damage, we would certainly expect a cumulative effect given what we know about neurones being unable to repair themselves.
The British Medical Association (BMA) seems pretty convinced of a cumulative effect, having made the case for a boxing ban on this basis since the early 1980s. ‘Punch-drunk’ syndrome is a recognised phenomenon in older and retired professional boxers that has been attributed to repeated punches to the head. However, the BMA admit in their August 2006 position statement on the subject that relevant research studies have significant weaknesses and a recent article in the British Journal of Sports Medicine failed to show any cumulative effect for people with one or two previous concussions (although the authors admit that damage could have been missed by their assessment methods)(2). More research is needed in this area before any firm conclusions can be drawn.
More scientific evidence that structural damage does occur in even very minor impacts (below those required to cause concussion) comes from a study which looked at blood levels of SB-100 (a protein that exists in a certain type of neurone) and NSE (an enzyme found in neurones) in female football players before and after a match(3). When neurones are damaged, they spill SB-100 and NSE into the blood; this study showed that blood levels of both chemicals rose the more players headed the ball, suggesting that an impact as small as heading a football damages the structure of neurones.
Those who consider concussion to be a predominantly functional disturbance with little or no underlying structural damage cite a set of clinical symptoms and signs that are usually short-lived, recover spontaneously and fully, and that don’t fit with what would be expected from structural damage to a specific area of the brain. They also point to a set of symptoms, which in the short-term are more severe than would be expected from the minimal structural damage for which we actually have reasonable scientific evidence. This suggests that there must be a large functional component to concussion.
Head scans using magnetic resonance imaging (MRI) and computer topographic (CT) usually demonstrate normal structure in patients with concussion. Functional MRI (fMRI) scans have been shown to be abnormal in concussed sportspeople(4). However, it should be emphasised that MRI, CT and fMRI scans do not rule out structural damage; it may be that microscopic structural damage, too small for a CT or MRI scan to detect, is responsible for the functional impairment.
Assessing and managing concussion
Distinguishing concussion from a more serious, possibly life-threatening, brain injury as well as ruling out the presence of damage to the spine that could have happened at the same time as the head injury are the first priorities of management. These tasks are often far from straightforward and it is prudent to assume the worst – you should avoid moving the casualty and request emergency medical attention if you are at all uncertain. Concussed sportspeople should not be allowed to continue competing or training until they’ve been medically cleared.
Once serious brain and spinal injury have been excluded and the athlete has been removed from the field of play, a suitably qualified person such as a doctor or sports physiotherapist, should assess the severity of concussion. Problems such as fits, significant drowsiness or deterioration may warrant admission to hospital for observation.
Even if you have been medically cleared, you should not be left alone for the first 48 hours and should go to hospital immediately should any of the following occur:
- Worsening headache
- Vomiting more than once
- Problems recognising objects, people and places
- Numbness or weakness in your arms or legs
- Feeling unsteady on your feet
- Slurring your speech.
You will need a companion to look after you for 48 hours in case any of the following problems (which you won’t be able to notice yourself) occur:
- You have a fit
- You start behaving differently or irrationally
- You cannot be woken up.
Concussion can result in subtle but important changes in mental function. A number of assessment tools (collectively referred to as neuropsychological tests) have been designed to help athletes, coaches and medics to identify, grade and monitor recovery from concussion. These tests take a variety of forms, from simple pen and paper questionnaires to complex software programmes. Two of the simpler and more widely used tests are shown in boxes 3 and 4. It should be noted however that neuropsychological tests are only an aid to assessment and that they should not replace or preclude proper medical care.
Neuropsychological testing is an important part of a concussed athlete’s medical assessment. Athletes are generally eager to return to sport and have a tendency to under report and underestimate symptoms caused by concussion, possibly endangering their prompt recovery and health (see top right). Neuropsychological tests offer an objective method of assessing recovery from concussion and have been recommended as the ‘cornerstone’ of understanding the injury and managing the individual particularly in cases of complex concussion(1). An athlete’s neuropsychological tests should return to a baseline level (taken at the start of the season) and the athlete should be symptom free at rest and on exertion before returning to the field of play.
Recovery from concussion and return to sport
The golden rule of sport concussion is that the player should not be allowed to return to sport until they have completely recovered. Why not? To prevent the following problems:
- Another injury to the head or body being caused by the incompletely recovered athlete being clumsy or slow;
- Injury to another player for the same reason;
- Post-concussion syndrome;
- Second-impact syndrome.
‘Post-concussion syndrome’ is the term used to describe symptoms such as dizziness, fatigue and problems with concentration and memory, which can persist for weeks, months or even years after concussion. Post-concussion syndrome requires thorough investigation by a suitably qualified healthcare professional, although treatment is limited to rest and reassurance. Sport and exercise may prolong the condition and are therefore inadvisable.
‘Second-impact syndrome’ is a catastrophic condition where a person who hasn’t fully recovered from a concussion sustains another minor head injury, leading to massive and often fatal swelling of the brain. However, there’s doubt that this condition actually exists(6). If it does, it’s certainly rare – one study counted just 35 unconfirmed cases in 13 years of American football(7).
The length of recovery from concussion is very variable – from minutes to months – and there is little that can be done to speed recovery. It is recommended that concussed athletes refrain from sport for at least the rest of the day of the injury as an absolute minimum, even if they’re apparently fully recovered. The exception to this is the professional athlete who may have immediate access to appropriately qualified people with ample resources to properly assess them. Any athlete who has suffered a concussion should ideally make a gradual, graded return to exercise before returning to competitive sport under close observation to ensure that their recovery is indeed complete. Some sports such as boxing apply a minimum period of exclusion for those who are concussed but there is no good evidence for such rules – some people may need more time than the obligatory exclusion period for recovery, some less.
Concussion in children
There are currently no guidelines for the assessment and management of concussion in children. Children differ from adults in a number of important ways when it comes to concussion. Surprisingly, it is estimated that children require an impact force two to three times greater than that in adults to cause a concussion with the same symptoms(8). This may be because a child’s head is more resilient to force, having a different structure to that of an adult, or it could be that a child’s response to a bump is different to an adult’s. The different structure of a child’s brain and skull also makes them prone to the rare but potentially life-threatening complication of brain swelling. On the plus side, children with concussion appear to recover faster than adults.
So should you assess children in the same way as adults? Many do because of the absence of alternatives, but you should exercise caution. Neuropsychological testing in children is not as accurate as it is for adults because children are developing and their test results should be improving as they age, especially between the age of nine and 15 years. A child whose neuropsychological test result after a concussion is the same as it was before could actually have suffered significant damage if the baseline was done pre-season and the concussion sustained at the end of it. Children involved in contact sports might benefit therefore from regular baseline tests every six months rather than yearly.
Finally, children with concussion do not normally require any investigations such as skull x-ray, CT or MRI scan. As with adults, the ideal management is careful observation, rest and a graded return to exercise once symptoms have resolved.
Concussion in sport is common; the golden rule of its management is that athletes should not return to sport until they have made a full recovery. Distinguishing between concussion and more serious injuries can be difficult. In the case of suspected concussion, athletes and their coaches would be well advised to seek medical attention sooner rather than later. References
An ex-competitive cyclist, Dr John Bye is now a practising doctor and the director of specialist sports medicine company Alchemy Sports Consulting Ltd
- Br J Sports Med 2005; 39:196 – 204
- Br J Sports Med 2006; 40:72 – 75
- Br J Sports Med 2006; 40:313 – 316
- Neuroimage 2004; 22:68 – 82
- Clinical Sports Medicine (Brukner and Khan) 2006; Ch 13:204
- Neurology. 1998; 50:677 – 684
- emedicine.com 2006; Repetitive Head Injury Syndrome
- Br J Sports Med 2004; 38:516 – 519
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