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If you’ve played a contact sport – or skied, or ridden horses, or fallen off an e-scooter – then you might have experienced a concussion and suffered symptoms like blurred vision, headaches, problems with balance, concentration and mood, ringing in the ears, vomiting, dizziness or fatigue.
It can take days, weeks or months to recover and for some people symptoms will continue over the long term. Around 20% develop post-concussion syndrome, a condition often misdiagnosed, particularly with children. A 2022 study from Tel-Aviv University showed that one in four children discharged from the emergency room after a mild head injury continue to suffer from persistent post-concussion syndrome and this can be mistaken for behavioural problems, ADHD, migraine or depression.
Rest is the most important thing for people after a concussion but it may not help much in the long term. Treatments tailored to the relief of symptoms include a type of physical therapy called vestibular rehabilitation and cognitive remediation to improve memory, attention, and information processing. There is some science behind using hyperbaric oxygen therapy to improve cognitive and behavioural function in children over age 8.
What happens after multiple injuries to the head is most concerning to researchers. Even relatively mild knocks may contribute to damage that leads to longer problems, explains Helen Murray, a senior research fellow at the University of Auckland’s Centre for Brain Research
“There are lots of different types of head impacts and just because they’re not severe enough to cause symptoms doesn’t mean there aren’t things happening in the tissue and the structure of the brain,” she says. “With the risk of neurodegeneration, it’s not necessarily how many concussions you’ve had, but how much exposure over your lifetime to lots and lots of these seemingly insignificant impacts.”
Professional sportspeople have been among the highest-profile head injury cases. A UK Rugby Health Project Study led by Durham University shows retired rugby players who suffered more than five concussions over their career have higher levels of proteins in their blood that makes them more prone to developing degenerative conditions like motor neurone disease – recently the cause of former All-Black Norm Hewitt’s death.
Another former All-Black Carl Hayman has spoken about his sporting career leaving him with dementia and, potentially, a degenerative brain condition known as CTE (chronic traumatic encephalopathy). He and fellow rugby player Regan King are among more than 200 claimants with neurological injuries who are suing world rugby bodies. Meanwhile, in Australia, a group of former AFL players are suing their teams and the league for damage sustained during their sporting careers that has left them with long-term brain impairments.
Scientists are still trying to identify exactly what these knocks are doing to the brain over time and why some people develop problems and not others.
“When you have a head impact, even if you’re wearing a helmet, your brain is moving inside your skull,” explains Murray. “That movement can cause it to bounce against the inside of the skull, squish, contort, twist, and that can damage the delicate brain cells that are in there. We think it can also damage blood vessels, causing inflammation that persists for a long time.”
As well as working as a research scientist, Murray is an ice hockey player – she has competed with the NZ Ice Fernz since 2013 – so she isn’t suggesting that people should necessarily abandon the sports they are passionate about.
“There’s a risk in everything we do in life,” she points out. “We get in a car and that’s a risk every day. But in sport we have to look at what we can do to reduce the risk as much as possible.”
There has been some progress to reduce the risk of neurological damage - like the smart mouthguard technology introduced by World Rugby as part of the sport’s head injury assessment and the three-week stand-down after a concussion.
“It’s a huge step forward,” says Murray. “But we also need to remember that it’s cumulative exposure over a lifetime and looking at what we can do to reduce that. Can we start playing contact sports later so that children aren’t having lots of head knocks unnecessarily when they’re young? Can we shorten the season length? Give more time for recovery and have fewer games just to reduce the exposure? I think we know enough now to be able to make some of these decisions.”
There is no way of saying how many head impacts is safe and exactly how long someone should rest after one. But scientists are making progress in understanding more about brain injury and how to identify the earliest signs of longer-term damage. In 2019, New Zealand’s first human Sports Brain Bank was launched. It is collecting tissue from donors who have played contact sports regardless of whether they’ve experienced a concussion or suffered later neurodegeneration.
“We need measurable biomarkers,” explains Murray. “Something that will identify people who might be heading down a neurodegenerative trajectory so they can make a decision about whether they play or not.”
