This post originally appeared on CNN Health.
The NFL has been thrust back into the concussion debate after Miami Dolphins quarterback Tua Tagovailoa took two big hits just four days apart.
This time, the debate involves whether Tagovailoa was appropriately cleared to play, with some fans concerned he was at risk of a condition called second impact syndrome.
On Sunday, Tagovailoa left a game in the second quarter after a hit from the Buffalo Bills’ Matt Milano caused him to fall backward and hit his helmet on the turf. On his way back to the line of scrimmage, Tagovailoa stumbled and fell.
NFL Network reporter Ian Rapoport said Tagovailoa was checked for a concussion and cleared, and he came back onto the field in the third quarter.
In a postgame news conference Sunday, Tagovailoa explained it felt as if he had hyperextended his back.
“My back kind of locked up on me. But for the most part, I’m good. Passed whatever concussion protocol they had,” he said.
On Thursday, Tagovailoa was back in the lineup against the Cincinnati Bengals. During the second quarter, he was sacked by defensive lineman Josh Tupou and lay motionless for several minutes before being taken off the field in a stretcher and sent to a hospital for evaluation.
The Dolphins reported Tagovailoa was diagnosed with a concussion at the hospital but cleared to fly back home with the rest of his team. On Friday, head coach Mike McDaniel said Tagovailoa is following the NFL’s concussion protocol, with no clear timeline of when he’ll return to the field.
It takes time to recover from a concussion
A concussion is a brain injury which happens after a hit to the head causes the brain to move back and forth inside the skull. But even after the organ itself stops shaking, there can still be changes in the brain.
Neuroscientist Julie Stamm, a clinical assistant professor in the Department of Kinesiology at the University of Wisconsin-Madison, describes it as a cascade of chemical events. “It takes time. Each of these metabolites and chemicals in the brain has a different trajectory in how they recover,” she said.
She pointed out it can typically take 10 to 14 days after a concussion for the brain to get back to its baseline condition.
Stamm has not treated or evaluated Tagovailoa but noted, based on what she saw of Sunday’s game against the Bills, it is very possible he had a concussion.
“He initially grabbed his helmet and shook his head. That is a clear sign that you’re trying to shake the cobwebs,” she observed.
Watching him fall was particularly concerning. “It didn’t look like it was his back that caused him to fall down. It looked like he just lost balance, and then his teammates are trying to hold him up.”
The team stated it followed the concussion protocols, and Tagovailoa was cleared to return to the game.
Later, McDaniel told reporters, “Tua went out with a lower back. He really got bent back on a quarterback sneak earlier. … His legs got wobbly because his back was loose. As he described it, his lower back was like Gumby.”
But Stamm acknowledged even if someone doesn’t notice symptoms, they can still have a brain injury. “It’s possible that he may have felt better after, so he may not have felt like he had symptoms anymore.”
Before Thursday’s game, social media lit up about Tagovailoa starting despite his injury from Sunday. But after Thursday’s hit, many fans began to suggest Tagovailoa may have second impact syndrome.
What is second impact syndrome?
“What we currently believe second impact syndrome to be is a second blow to the head or second concussion prior to the resolution of a first one. And that can result in uncontrolled swelling of the brain,” explained Steven Broglio, director of the University of Michigan’s Concussion Center. He has also not been involved in Tagovailoa’s care.
Broglio said to think of your skull like a box, with your brain inside the box. In the case of second impact syndrome, the second hit compresses the box, and portions of the brain controlling vital functions like breathing and heart rate can stop working.
Stamm said the changes happen very rapidly and can lead to permanent brain injury or even death.
But both Broglio and Stamm stressed second impact syndrome in this sense is very rare, and happens typically among younger athletes.
“This is a part we don’t quite understand, but it tends to be only in younger athletes; so middle school or high school,” Broglio said.
Even if Tagovailoa had been concussed in Sunday’s game, what happened Thursday night wouldn’t be second impact syndrome in the traditional sense, Broglio emphasized. “If somebody had true brain swelling and potentially brain herniation through the bottom of the skull, he would not be getting out today.”
But even without brain swelling, a potential second concussion could make recovery worse, Stamm added.
“When someone has a second concussion before they’ve healed from the first one, we often see worse symptoms compared to the first one. Those symptoms can be more severe. The symptoms tend to last longer. The recovery is much slower,” she said.
The fencing response
Of greatest concern to Stamm is immediately after Thursday’s hit, Tagovailoa’s hands were stiff and splayed, a posture known as the fencing response.
“That was something that jumped out at me right away,” she recounted. “Whenever you have a posturing like that, it suggests an injury that is potentially involving the brain stem.”
McDaniel admitted after the game “it was a scary moment. … That was an emotional moment that is not part of the deal that anyone signs up for, even though you know it’s a possibility in football to have something that you have to be taken off on a stretcher.”
Tagovailoa issued a statement on Twitter on Friday, which read, “I’m feeling much better and focused on recovering so I can get back out on the field with my teammates.”
The NFL Players Association is conducting an investigation into whether the Miami Dolphins violated concussion protocols in determining Tagovailoa’s readiness to play.
This post originally appeared on CNN Health.