Simple blood test may predict concussion severity just as well as spinal tap

July 08, 2020

MINNEAPOLIS - A blood biomarker in people who have had concussions may be just as accurate at predicting the severity of the injury and how long it will last as biomarkers that are obtained through more expensive and invasive tests, according to a study published in the July 8, 2020, online issue of Neurology®, the medical journal of the American Academy of Neurology.

The study looked at a biomarker called neurofilament light chain, a nerve protein that can be detected in the blood and cerebrospinal fluid when nerve cells are injured or die.

"When your brain is injured, neurofilament light chain levels are higher in both your blood and your spinal fluid," said study author Pashtun Shahim, M.D., Ph.D., of the National Institutes of Health in Bethesda, Md. "Measuring this biomarker in your blood with a simple blood draw is faster and easier than measuring it your spinal fluid, which requires a more invasive spinal tap. Our findings are exciting because they show that the simple test may also be just as accurate for determining how severe the injury is and predicting how you might do long term."

The study involved two groups of people with head injuries.

The first group consisted of 104 professional Swedish hockey players. This group's average age was 27 and included 45 athletes who had a concussion within the past week, 31 athletes with who had multiple concussions, 28 athletes with no recent concussion or symptoms and 14 healthy people who weren't athletes. All of the participants had the biomarker levels in their blood tested. The 31 athletes with multiple concussions and the 14 healthy controls also had the biomarkers in their spinal fluid tested through spinal taps.

Researchers found that the amount of the biomarker in the athletes' blood was similar to the level in their spinal fluid. Researchers were also able to accurately predict based on the participants' biomarker levels whether they had no concussions, concussions less than a year before or concussions more than a year before.

The athletes with multiple concussions had an average of 18 picograms/milliliter (pg/mL) of the protein biomarker their blood, those with recent concussions had 12 pg/mL, the athletes with no recent concussions or symptoms had 10 pg/nL and the healthy non-athletes had 9 pg/mL. These levels correlated well with the levels researchers found in their spinal fluid.

Further, the biomarker levels in the hockey players' blood correlated strongly with more concussions and more severe concussions, even a year after the injury.

The second group, based at a Maryland clinic, had an average age of 43 and included 162 people with brain injuries and 68 healthy people. Researchers examined the role of the biomarker in distinguishing between mild, moderate and severe concussions.

In the clinic-based study, the group with head injuries had 12.8 pg/mL of the biomarker in their blood, while the healthy control group had 6.3 pg/mL. Again, those levels correlated closely with levels detected by more sophisticated tests like brain imaging. The level of biomarker in the blood accurately let researchers distinguish between mild, moderate and severe concussions. The difference in biomarker levels between people with concussions and the healthy controls was found up to five years after the concussion.

"In both of our studies, the same idea came through: Neurofilament light chain shows great promise as a biomarker in the blood," Shahim said. "This is notable because the test may help us identify people whose concussions might give them debilitating symptoms for years after the injury. And that may help doctors treat their patients more specifically for the type of concussion they have."

Shahim said one limitation of the study is the need for a longer follow-up study to determine the relationship between the blood biomarker and progressive neurodegeneration.
This study was supported by the National Institutes of Health, the Department of Defense and the Swedish Research Council.

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The American Academy of Neurology is the world's largest association of neurologists and neuroscience professionals, with over 36,000 members. The AAN is dedicated to promoting the highest quality patient-centered neurologic care. A neurologist is a doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system such as Alzheimer's disease, stroke, migraine, multiple sclerosis, concussion, Parkinson's disease and epilepsy.

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