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How A Mere Prick Of The Finger Can Diagnose A Concussion


ON September 4, 2015, 17-year old Kenney Bui’s coach removed him from his Seattle high-school team’s football game with a mild concussion. Thirteen days later, a doctor cleared him to play. At a game a few weeks after that, on October 2, Bui took another hit, walked off the field showing signs of confusion, and while athletic trainers asked him questions from the school district’s standardized concussion screening protocol, he closed his eyes. He never opened them again.

Bui was one of six high schoolers to die on the football field in 2015 from a traumatic brain injury, but every year millions of people suffer milder concussions while playing sports. Recognizing these more subtle concussions is crucial for preventing deaths like Bui’s, referred to as second impact syndrome. But the tools available to do that are crude and often subjective. Doctors and trainers gauge how badly you’ve been banged up by instructing you to count backward from ten to one or follow a finger with your eyes. But with high-powered protein assays and microfluidic technologies, soon there will be a better way. And it will all start with the prick of a finger.

When your head takes a hit (from an airbag, or a fall, or a 300-pound defensive tackle), your brain is subjected to shear forces that can actually tear it apart from the inside—without any of the structural damage you can see on a CT scan or an MRI. Deep in the brain’s white matter, tissues of different densities pull and strain against each other as they accelerate and decelerate at different speeds. Axons, the long, stretched-out arms of neurons that allow them to talk to each other, get frayed and severed. This is why you might have trouble remembering things or thinking clearly if you get concussed—and why a doctor might ask you to tell them what year it is or who’s the president.

But there’s another thing that happens when these axons get damaged: They release a number of proteins into the cerebral spinal fluid. About one in a thousand of those proteins crosses the blood-brain barrier to enter the bloodstream. The more damage, the higher the blood protein concentration. Scientists have known this for a long time, but until very recently it’s been irrelevant to all but the most severe traumatic brain injuries. So few of the proteins end up in the blood that no one’s been able to detect them.

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