How head injuries can affect your brain for years

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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.