Concussions and “Second Impact” Effects

Concussions affect millions of people each year and are especially prevalent in contact sports like football. Only motor vehicle accidents lead to more cases of traumatic brain injury in people ages 15 to 24. Some studies have shown that concussed athletes who have a second concussion before they recover fully may have permanent brain injuries. The reason for this has been elusive. So, Does This Explain The “Second Impact” Phenomenon?

A new study used arterial spin labeling, an advanced MRI technique that detects blood flow in the brain. It found that there was a reduction in cerebral blood flow at 24 hours post concussion, and this persisted at 8 days, even if the athletes seemed clinically improved. Reduced blood flow is likely a marker of neurons under continued physiological stress, and this measure supports efforts to reduce the risk of a second injury. It remains unclear at what point athletes should be returned to contact sports. Would blood flow be normal at 14 days? At 30 days? Obviously, more studies are needed, but erring on the side of caution seems prudent.

Presented at annual meeting of The Radiological Society of North America, lead author Y. Wang.

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