Concussion and head trauma are a real and serious risk for many Australians. While most people suffer from acute and relatively short-lived effects, such as dizziness and headaches, in some cases the symptoms persist for weeks, months or years. It can cause long-term and debilitating neurological damage.
Concussion in junior to elite level sport is prioritized as a public health concern in Australia. A Senate inquiry into concussions and repetitive head injuries in contact sports is expected to be filed in August. Notable in the hearings was the AFL’s acknowledgment of an association between TBI and chronic traumatic encephalopathy, a neurodegenerative disease seen in several deceased players.
The latest data shows that concussion can occur in nearly any sport, not just contact sports, with nearly 3,100 sports-related concussion hospitalizations in 202021.
But not everyone responds the same way to concussion. At present, there are few reliable indicators of who will experience specific or long-term effects. We know that the number and severity of symptoms and multiple concussions matter. And we’re developing an understanding of how a person’s genes play a role.
Head trauma
Concussion is a form of traumatic brain injury that can result in neurological dysfunction, including migraines, cognitive impairment, confusion, slowed reaction times, personality changes, drowsiness, and emotional changes. Some people also experience long-term problems with memory, thinking, and other symptoms, such as anxiety and mood disturbances.
After a brain injury there is a cascade of events that affect the health of neurons and affect the flow of chemical ions, such as calcium, into the brain. Mutations in genes that affect the transport of neuronal ions (atoms or molecules with a positive or negative electrical charge), called ion channel genes, can also affect how the brain works.
The strongest evidence for a connection between concussion response and ion channel gene function comes from patients with a family history of a rare type of migraine (hemiplegic migraine, which causes the sufferer to have a severe migraine associated with impaired motor and muscle weakness) and episodic ataxia (causing attacks of incoordination of movements).
Specific types of these severe neurogenetic disorders are caused by mutations in the calcium channel gene CACNA1A. Patients with these mutations can be very sensitive to head impacts. A few specific mutations can see a very minor head injury leading to concussion, seizures, brain edema (swelling), coma, and sometimes death.
Research also showed that 35% of patients with mutations in a second hemiplegic migraine ion channel gene, ATP1A2 which is linked to hemiplegic migraine, ataxia, epilepsy and other seizures and controls sodium and potassium levels in the brain reports symptoms of concussion following a minor head injury.
Focusing on all ion channel genes, our genomics lab (Griffiths Center for Genomics and Personalized Health) recently studied 117 people with concussion. We found mutations in 21 ion channel genes, 14 of which could impact concussion susceptibility or outcomes.
AAP/Darren England
Read more: Concussion: Nearly half of people still show signs of brain injury after six months
Other types of genes
In addition to the role of ion channel genes, there have been a number of other genes linked by research to concussion.
One of the most studied is the ApoE gene, which is involved in the transport of cholesterol in the body and has long been recognized as a risk factor for Alzheimer’s disease. Studies have indicated that a variant of this gene (ApoE4) is linked to poorer, longer-term concussion outcomes. Those who carry this variant are also more likely to have significant signs of brain degeneration after a concussion.
Another genetic variation in the ApoE gene that makes it less productive has been linked to a higher likelihood of concussion.
In addition to ApoE, genes that help control a variety of brain functions have been suggested as factors in concussion, including some involved in neuronal growth, dopamine receptors, and more recently in the development of the brain axon (nerve fiber ).
Read more: Hit your head while playing sports? Here’s what just happened to your brain
A predisposition to injury
Questions regarding the link between genetic predisposition to injury in sports are not new. Twenty years ago, the Australian Law Reform Commission referred to research that showed
[] a milder form of this condition [CTE or punch-drunk syndrome] could occur in players of rugby, soccer and other sports associated with repeated blows to the head.
In 2016, the Australian Institute of Sport (AIS) released a position paper on the ethics of genetic testing and research in sport. But the latest AIS Concussion and Brain Health Position Statement does not mention the use of genetic information regarding concussion-related susceptibility.
Currently, DNA diagnostic tests are available for the two ion channel genes already implicated in concussion, as this test is used for the diagnosis of familial hemiplegic migraine and episodic ataxia. But genetic testing is not currently being undertaken for concussion.
In Australia, it is difficult to find information on whether genetic testing is present in elite sport. Genetic testing is carried out in the UK, although it is not common. Athletes and support staff are open to the idea that genetic information is used to enhance sports performance and reduce the risk of injury.
Read more: Uncharted Brain: Decoding Dementia a three-part series for you to read and listen to
What’s next?
It is imperative that there is more careful consideration of the genetic factors involved in concussion development and response. Elucidation of the role of ion channel gene mutations and other gene variants, together with information from additional biomarkers and imaging, will be important in developing better concussion management and therapeutic approaches.
Before introducing genetic testing, regulatory and governance frameworks would also need careful consideration. The broader ethical and legal implications will need to be thoroughly examined, including healthcare privacy laws, privacy of genetic samples, anti-discrimination laws and employment laws, particularly in professional sports.
With growing awareness of concussion-related injury risks highlighted by the Senate inquiry, further research in Australia could also investigate attitudes towards the use of genetic testing and susceptibility to injury risk in sport.
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Image Source : theconversation.com