Study, inspired by quarterback Tua Tagovailoa’s brain injury, identifies a new concussion symptom

Concussions, and the long term health risks of repeated head injuries, continue to loom like a storm cloud over the NFL.

In an attempt to drive down the number of players who suffer traumatic brain injuries, the league has adopted new kickoff rules, and introduced helmets that manufacturers say are safer.

Yet nearly each week of the 2024 season has been marred, so far, by the unsettling sight of players suffering concussions, from Miami Dolphins quarterback Tua Tagovailoa to three members of the Philadelphia Eagles — right tackle Lane Johnson, wide receiver DeVonta Smith, and right guard Mekhi Becton.

Now, a new study, led by Harvard Medical School researchers and neuroscientist Chris Nowinski, has identified a symptom that might help training staff and coaches sooner identify a player who has suffered a concussion.

The study, published Wednesday in the medical journal Diagnostics, focuses on a specific motion: an athlete shaking his or her head rapidly from side to side, moments after they’ve suffered a head impact or collision, a movement that the researchers refer to as Spontaneous Headshake After a Kinematic Event (SHAAKE).

Researchers surveyed 347 current and former athletes, and found that 69% had exhibited a SHAAKE in the past, with 93% reporting that they had made the head-shaking motion in connection with a diagnosed concussion at least once.

The participants, who had an average age of 27, reported shaking their heads in response to a range of symptoms that are often associated with concussions: blurred vision, confusion, dizziness, and feeling like they needed to jump-start their brains.

“From our perspective, it’s sad that this has not been recognized as a concussion sign up until now,” said Daniel Daneshvar, the chief of brain injury rehabilitation at Harvard Medical School, and the study’s senior author.

Daneshvar, who also serves as the co-chair of sports concussion at Mass General Brigham, said researchers have reached out to medical organizations, professional sports leagues, and players’ unions to discuss having SHAAKE added to existing guidelines for concussion symptoms.

“Now that it’s been shown to likely be a reliable indicator of potential concussions,” he said, “it would be even more sad if someone’s brain injury were missed because a sideline clinician didn’t know that this could be an indicator of a concussion.”

The motion has long been found in popular entertainment. In action movies, comedies and professional wrestling matches, characters often shake their heads after absorbing a powerful blow; in cartoons, head shakes are sometimes accompanied by stars and fluttering birds.

But the primary inspiration for the SHAAKE study, Nowinski and Daneshvar said, was Tagovailoa.

During a Sept. 25, 2022, game against the Buffalo Bills, the quarterback was shoved by a Bills defender, then tumbled backward, and slammed his head against the field.

Tagovailoa stood, shook his head, and then nearly collapsed.

After telling medical officials that his fall had been caused by back and ankle injuries, Tagovailoa cleared the NFL’s concussion screening protocol, and was allowed to return to the game.

Four days later, during a Thursday Night Football game against the Cincinnati Bengals, Tagovailoa’s head again slammed against the field; this time, his hands jutted out in a fencing response, which is sometimes observed in victims of traumatic brain injuries, and he was removed from the game on a stretcher.

(Following Tagovailoa’s 2022 injuries, the league and the NFL players’ union agreed to new rules, which call for players who display signs of balance, motor or speech problems following a possible head injury to be removed from the game. The union also determined that an independent neurotrauma consultant who had evaluated Tagovailoa had made multiple mistakes, and then fired the consultant.)

“The head-shaking is something I’ve recognized as being associated with a concussion for a long time,” said Nowinski, a former professional wrestler, and the cofounder of Concussion Legacy Foundation, which advocates for athletes and military veterans who have suffered brain injuries.

“When it happened with Tua, and they didn’t pull him out of the game, I realized that it’s not actually on the list of possible concussion signs that anyone is looking for.”

Nowinski and the study’s other researchers reviewed extensive medical literature, and found no references to a link between head-shaking and concussions.

“It’s frustrating that we didn’t have this [diagnosis symptom] 10 years ago,” he said.

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Tagovailoa suffered another concussion earlier this year, during a Thursday Night Football game against the Bills; again, his hands jutted out in a fencing response.

The Dolphins placed him on injured reserve, and he missed four games.

On Monday, Dolphins head coach Mike McDaniel said that “medical experts have deemed it safe” for Tagovailoa to return.

“I appreciate your concern. I really do,” the quarterback told reporters. “I love this game. And I love it to the death of me. That’s it.”

He might play Sunday against the Arizona Cardinals.

“I hope that he has a positive, healthy experience for the rest of the season,” Nowinski said.

“The doctors have assessed him. Now, it becomes a question of how much risk are you willing to take?”