Concussion tells the story of how a Pittsburgh pathologist's research led to the discovery of chronic traumatic encephalopathy - CTE, the degenerative disease linked to repetitive brain trauma.

CTE can cause chronic headaches, dizziness and fatigue. Changes in behavior mimic dementia. The disorder also raises the risk for depression and abuse of alcohol and drugs. Several NFL players depicted in the movie committed suicide.

Movies often oversimplify complex medical issues. To fact-check this one - to measure the accuracy of how it shows the symptoms and science of CTE - we accompanied an expert to the cinema.

Robert Franks is medical director of the Rothman Concussion Institute and co-medical director of the Jefferson Comprehensive Concussion Center.

Excerpts from our discussion after the viewing:

How accurate was the movie's depiction of symptoms?

Because of time, the movie collapsed all of the symptoms of CTE, and details of specific cases for individual football players were left out. We saw a kind of time-lapse version of what players went through.

You have a global look at CTE, although in truth, not every symptom would happen for every person. In the movie they showed very quick, dramatic changes, but most cases progress more slowly.

Plus there were other factors in certain cases, such as substance and alcohol abuse, use of performance-enhancing materials that the movie didn't go into.

What about the science?

I think they tried very hard to depict how he [Bennet Omalu, played by Will Smith] went about finding CTE in professional football players. But when you show people a movie about science, you have to make it in a way people understand it. I'm not sure people watching the movie really will understand what stained slides are or what they were looking at.

One problem was that they didn't show a normal brain; without seeing a normal brain it's hard to make a judgment on what is abnormal. In the movie they focused on the darkness of plaques, but you need some basis of comparison.

In one special effect they try to show how the condition occurs in the brain during a hit on the field. But it's not necessarily how it happens in real life. CTE isn't caused by a dramatic change, but over time by a series of submaximal and concussive hits.

Do you think this movie will make people more aware of the topic?

With a movie named Concussion that opens just as the NFL playoffs are about to start, I think this will raise awareness, promote education - that's important - and increase safety. In fairness, it's not just football where we see this; it's a lot of other sports.

It's also important to say that a lot of changes have taken place since the time period that the film depicts, both in Pop Warner and U.S. soccer, up to professionals. Many states have limited the amount of hitting practices high schoolers can have and a lot of leagues for younger kids have gotten away from head-to-head drills to reduce submaximal impact. With or without the film, a lot of changes have taken place.

The NFL has made a lot of changes as well. Now, an independent neurologist on the sidelines makes a determination outside the medical staff on a player's condition. There is also an "eye in the sky" certified athletic trainer who, if they see something on the field, can call down and have that player pulled out for an examination.

Do we understand why some people get CTE and others don't?

At this point we really don't know except that people who have it have had several blows over their careers. The things to worry about are successive concussions, and if smaller blows lead to worse symptoms. We also track whether with each new hit, symptoms become worse.

What should be the most important takeaway from the film?

That we all need to know what to look for in concussions. Coaches, parents, and guardians should know the warning signs. Concussion should be evaluated and treated before it becomes a series of hits. It's much easier to treat than a person who gets hit in the first half, plays the second half, and takes multiple hits.

Overall, we really look at 30 or more symptoms, but in six different categories: neck pain - often people get whiplash-type injury; balance and coordination; cognitive signs; sleep; emotionality; and what's happening with the ocular system. People can feel dizzy, not answer questions appropriately, or have nausea.

There are many facets of concussion that are under study now and I think we're in the infancy of what we understand about this condition. We're getting better at it but we still have work to do.

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