The sobering science of repeat concussions

by Nancy Fliesler on May 29, 2012

The atrophied brain of chronic traumatic encephalopathy -- the result of cumulative concussions. (Courtesy Ann McKee)

At a May 18 conference on sports concussion and spinal injury, organized by Boston Children’s Hospital and Harvard Medical School, former hockey player Dan LaCouture and former New England Patriots player Ted Johnson told poignant stories of playing through multiple repeat concussions. I realize their cases are pretty extreme, but my overriding feeling as a parent was horror.

The effects of concussion were first medically described in 1928, in “punch drunk” boxers. Neuropathologist Ann McKee, MD, of Boston University and the Veteran’s Administration does brain autopsies for a living, and showed us the atrophied brains of ex-NFL players like John Grimsley and Dave Duerson. Both have abnormal deposits of a protein called tau. That’s the hallmark of a neurodegenerative brain disorder called chronic traumatic encephalopathy, or CTE.

Tau is the glue that holds the microtubules together — the cells’ backbones if you will. When neurons are wrenched apart by a concussion, tau forms into tangles – just as it does in soldiers exposed to bomb blasts, just as it does in people with Alzheimer’s.

These images, from three deceased NFL players, show tau deposits that progress with age (from top to bottom, ages 50, 66, 78). (Courtesy Ann McKee)

CTE is where you can end up after multiple concussions, especially if you’re not given time to recover from them. Hallmarks include short-term memory problems, loss of planning/organizational skills and judgment, dementia, irritability, aggressiveness, paranoia and depression/suicidality.

Here’s what we don’t know about CTE: who’s genetically susceptible to it, how to treat it and how to spot it early. There’s only prevention.

People think that helmets protect against concussion, but that’s not a given. Rapid rotational acceleration of the head is what causes much of the damage in concussion. Bill Meehan, MD, director of research for the Brain Injury Center at Boston Children’s, told us that slaughterhouses knew this 100 years ago. They would concuss animals prior to slaughter, as a “humane” measure, and found the most effective method was to immobilize the animals’ bodies, but allow their heads to move freely. So that when a weight was dropped on their heads, the animals’ heads spun from the force of the impact.

When you rotate the brain quickly, you’re applying a shear strain to its neurons – interfering with their ability to conduct electrical impulses, Meehan said. Adding insult to injury, concussion also reduces blood flow to the brain, making it harder to power this electrical flow.

Neurocognitive testing reveals cognitive deficits in concussed athletes even when they're asymptomatic (blue bars) compared with controls (red). (Courtesy Alex Taylor)

So if helmets won’t do any good, how can concussions be avoided, short of leaving sports entirely? Robert Cantu, MD, co-director of BU’s Center for Traumatic Encephalopathy along with McKee, and founder of the Sports Legacy Institute, summed it up like this: “Strengthen your neck, avoid taking as many hits as you can and hope that you’ve got the right genetic makeup.”

If your neck muscles are strong, the physics equation “force = mass x acceleration” is going to be a lot more favorable: Your head (the mass) will accelerate less from a hit. Alex McLeanTaylor, PsyD, director of neuropsychology at the Boston Children’s Brain Injury Center, notes that girls show more neurocognitive deficits after concussion than boys, perhaps because their necks are weaker.

Neurocognitive testing showing a typical trajectory of concussion recovery of about 3 weeks -- if the child is allowed to rest and there are no complicating factors. (Courtesy Bill Meehan)

If you’ve already had a concussion, the science shows that the best preventive measure is to rest your brain. That means no school, very little social interaction, minimal TV and definitely no texting.

It can be hard to fathom why kids would return to play without allowing time for cognitive rest, or why parents would let them. But the pressure on them is tremendous. They often don’t show obvious symptoms. Coaches want them back in the game. Teachers may accuse them of malingering, and schools are often reluctant to grant them accommodations during exams. (See this excellent guide for schools from the Centers for Disease Control and Prevention.) And let’s face it, cognitive rest is isolating and boring.

So it’s no wonder that there are websites that churn out fake doctor’s notes clearing kids to return to the field. Or that some young athletes deliberately do badly on pre-season baseline testing so they won’t look so impaired after a concussion.

Well, they’re putting their long-term brain function at risk. Meehan’s mouse studies show that repeated concussions, even mild ones, cause profound learning and memory problems. That the effects are cumulative. That they’re worse when concussions occur without time for recovery in between.

Ted Johnson perhaps said it best. He told us he got two to three concussions a week as a middle linebacker. “There was a shift from ‘it feels good to get these hits,’” he said, “to ‘this is hurting me as much as it’s hurting them.’”

A mind is a terrible thing to lose.

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