Issue 33.4 FALL 2024
No Concussion ? A Blow to the Head Can Still Be Dangerous
In a football game , an athlete takes a bad hit to the head . He doesn ’ t feel dazed or confused : he seems to have escaped a concussion . However , despite the lack of concussive symptoms , the impact has disrupted the chemical balance in his brain , and this imbalance has consequences .
In a study published earlier this year in the Journal of Neurosurgery , Université de Montréal surgery professor Louis De Beaumont , a clinical neuropsychologist and researcher at the Hôpital du Sacré-Cœur de Montréal research center , looked into those consequences .
His conclusion ? Receiving powerful blows to the head leads to brain toxicity , even when there is no concussion .
20 athletes studied De Beaumont ’ s research team reached this conclusion by measuring the neural activity of about 20 male college athletes before and after a full-contact football game , using transcranial magnetic stimulation .
Compared with baseline measurements , football players who received a hit of 40 g ( equal to 40 times Earth ’ s gravity ) displayed “ cortical disinhibition .”
“ The data suggest that a blow that does
not produce concussive symptoms can still trigger an excitatory neurometabolic cascade similar to that of a concussion ,” De Beaumont said .
“ This cascade is caused by a disruption in the delicate balance between glutamate , the brain ’ s main excitatory neurotransmitter responsible for triggering nerve impulses , and GABA ( gamma-aminobutyric acid ), the primary inhibitory neurotransmitter responsible for deactivating neurons .”
He added that when this balance is upset , the brain enters an “ energy crisis ” that can lead to neurons dying .
Can last for weeks According to De Beaumont , this neurochemical imbalance typically lasts for days or weeks , and its severity is related to the severity of concussion symptoms .
However , repeated activation of the excitatory neurometabolic cascade , which is associated with frequent impacts in contact sports , can lead to lasting disturbances in the homeostasis between glutamate and GABA .
This can cause symptoms that affect memory , balance and mood . Moreover , these concussive symptoms tend to worsen with age , as the aging process reduces brain capacity .
De Beaumont believes that repeated imbalances between glutamate and GABA could increase the risk of developing neurological conditions such as amyotrophic lateral sclerosis ( ALS ), chronic traumatic encephalopathy ( CTE ) and mood disorders .
One or more blows Athletes who receive a head impact but have no concussion symptoms often stay on the field and continue playing . However , De Beaumont ’ s results suggest that receiving one or more further blows increases the excitotoxic response , making the athlete more susceptible to concussion during the game .
Knowing this , measuring brain activity and systematically monitoring the force of head impacts during every game and practice could be useful for injury prevention in contact sports , he said .
De Beaumont said , “ We could be on the sidelines , measuring the relationship between powerful head impacts and the brain ’ s excitatory response . The information gathered could eventually provide teams with an objective measure for pulling athletes from the field as a precaution , if it ’ s deemed the risk ’ s not worth it .” g
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