Concussions – Part 1

Concussion injuries have been a topic of focus in the media, sporting organisations, schools and the general public alike for the last few years. There was the movie ‘Concussion’ starring Will Smith which brought lots of attention to concussions and the potential long term health effects of singular or multiple concussions. There is a lot of information out there so in this blog series we’re going to spend time shedding some light on this complicated issue. We’ll identify what a concussion is, talk about the physiology of concussions and also touch on the management of acute concussions and long term management of Post-Concussion Symptoms or PCS.

What is a concussion?

A concussion occurs when enough force is applied to the brain, causing a shearing or rotational stress to the junction of the white and grey matter of your brain. The force required for this to occur is actually quite large (>70G forces) and so contrary to some reports, a concussion can’t come from a small impact such as bumping your head on a cabinet or something similar. When enough force has occurred, damage to the grey/white matter junction (see below) allows for the leakage of ions and neurotransmitters which results in a neurometabolic cascade – a fancy way of saying it causes something similar to an ‘electrical storm’.

There are a number of effects that either stem directly from this cascade, or the mechanical trauma itself, that play a role in concussion symptoms including but not limited to:

• An energy deficiency within the brain (more on this later!)
• Impaired blood flow to the brain
• Impaired cardiovascular regulation (heart rate, blood pressure etc)
• Disruption to the blood-brain barrier

These and other effects of the neurometabolic cascade can result in a wide range of symptoms, most notably:

• Loss of consciousness
• Seizures
• Vacant stare
• Delayed speech or movement response
• Confusion
• Disorientation
• Slurred speech
• Inco-ordination
• Emotional instability
• Memory deficits

It is important to note that although these are some of the main symptoms of concussion, you may only have one or two of these symptoms or you could have all of them and just because you didn’t lose consciousness (often the old-school idea of what a concussion looked like) doesn’t mean that you didn’t suffer a concussion. Furthermore, there is no evidence that those people who lose consciousness have worse concussions than those that don’t.

Who’s most likely to get concussions?
There are a number of studies comparing the relative risk of suffering a concussion when playing different sports. Overall there is a much greater risk of suffering a concussion when playing a competitive game compared with normal training. This makes sense when you consider that even when training your hardest, there is no way to fully replicate the intensity of game play. When we compare different sports, here’s how they stack up (for comparison purposes, we will use AE or Athletic Exposures, in which 1 AE equals one athlete participating in one game or practice):

• MMA – 147 concussions per 1000 AE’s
• AFL – 9.53 per 1000 AE’s
• Rugby – 3 per 1000 AE’s
• NFL – 2.5 per 1000 AE’s
• Ice hockey – 2.27/1000 (F), 1.63/1000 (M)
• Soccer 1.07 per 1000 AE’s

The caveat to this evidence is that not all concussions are reported. Recent research in this area showed that more than half of all concussions suffered are never reported to the relevant medical team. What the data also shows us, is that both females and children seem to be at greater risk of suffering a concussion – the exact reason has not been found as yet. It could be a result of these groups being more forthright in reporting their symptoms, or it could also be a result of differences in physical makeup.

Are multiple concussions worse for your long term health?

It depends. Research on this topic seems to suggest that it isn’t necessarily the number of concussions you have in total, but how close together you suffer them. As we touched on earlier, one of the major physiological effects of a concussion is an energy deficiency and metabolic dysregulation. It seems if you have a subsequent concussion within 5 days of the original concussion, the additive effect of the energy deficiency could result in cell death and permanent damage and possible disability. Furthermore, it can take up to 30 days for the rest of the effects of the neurometabolic cascade to reverse, so within this period you may be more vulnerable. What we also know is that even when your more evident symptoms have resolved and you might feel back to normal, there may still be subtle symptoms found on testing that show that your brain isn’t quite ready for a return to sport. This is where a thorough testing protocol is essential in order to return someone back to sport in a safe and evidence based manner.

We will talk more about acute concussion management in part 2 of this blog series!