A quick head shake after a hard blow could signal a concussion, a new study based on the experiences of young athletes suggests.
It’s an easily recognizable movement that could significantly reduce the number of undiagnosed concussions if added to official evaluation guidelines, researchers from Mass General Brigham and the Concussion Legacy Foundation say.
“We describe it in detail as a moment where someone, after a blow to the head, shakes their head sideways at a rate between two and eight hertz. But that’s complicated medical terminology for something we’ve all seen,” said Dr. Dan Daneshvar, co-author of the study and co-chair of sports concussion at Mass General Brigham.
For example, cartoons often show a circle of birds flying away after the character shakes his head.
“There’s such a strong lay understanding that this is related to concussions,” he said, but it’s not included in guidelines or medical literature.
To better understand this movement — a spontaneous head shake after a kinematic event, or SHAAKE — and its relationship to concussions, the researchers surveyed hundreds of young adults who had played sports at the high school, college, or semiprofessional level.
They found that the vast majority of young athletes were familiar with the gesture and had experienced it more than once. In nearly three out of four cases, the people surveyed said they were experiencing a concussion at the time of the SHAAKE.
The concussions that study participants reported were often self-diagnosed, but the underlying reasons they typically reported for shaking their heads — such as disorientation or confusion, or changes in spatial perception — were consistent with symptoms known to be associated with concussions.
It’s “long past time we should have recognized this head shaking and its connection to concussions in a more formal way,” said Dr. Julie Stamm, a clinical assistant professor at the University of Wisconsin-Madison who was not involved in the new study.
“A couple of decades ago, we thought you had to lose consciousness to get a concussion,” she said. Now, science shows that concussions very rarely result in serious symptoms like these. Instead, subtler signs are known to be more common — and the severity of the symptoms doesn’t always correlate with the severity of the injury, she said.
“People were trying to shake off a ‘ringing’ or ‘seeing stars’ and kind of reset,” Stamm said. “We didn’t always consider some of those injuries to be concussions, and now we do.”.
Based on survey responses, researchers in the new study suggest that more formal recognition of SHAAKE as a sign of concussion could help identify up to a third of undiagnosed concussions.
“Based on our data, SHAAKE is a reliable signal that a concussion may have occurred, such as an athlete holding their head after contact, standing up slowly, or losing their balance,” said Daneshvar, who is also the chief of brain injury rehabilitation at Spaulding Rehabilitation and Harvard Medical School. “As with these other signs of concussion, athletes who exhibit SHAAKE should be removed from the game and evaluated for a possible concussion.”
The National Football League and the NFL Players Association agreed in October 2022 to update the league’s concussion protocol after intense scrutiny over decisions made after a hit that knocked Miami Dolphins quarterback Tua Tagovailoa to the field.
A sideline physician initially concluded that Tagovailoa’s fall was the result of a previous back injury, and he was cleared to return to the game, but was later hospitalized for a concussion. The imbalance he experienced was later attributed to ataxia, which describes a lack of coordination caused by a neurological problem. Under the NFL’s new concussion protocols, players are not allowed to play if they have ataxia.
But the researchers in the new study, published Wednesday in the peer-reviewed journal Diagnostics, suggest that the diagnosis and decisions for Tagovailoa might have been different if shaking his head had been part of the official concussion protocol.
“In this case, the SHAAKE he exhibited would be difficult to attribute to a previous back injury,” the researchers wrote. “Every physician who saw Tua, both on the field and in the days that followed, may have reconsidered and determined based on this additional evidence that a concussion diagnosis would be more consistent with both his imbalance and his SHAAKE.”
A board of independent and NFL-affiliated physicians and scientists developed the league’s official Game Day Concussion Diagnosis and Management Protocol in 2011, and it is “reviewed annually to ensure that players receive care that reflects the most current medical consensus on the identification, diagnosis and treatment of concussions,” according to a summary on the NFL’s website.
“The NFL’s medical committees regularly review new research, and we have been in contact with the authors of this study,” NFL Chief Medical Officer Dr. Allen Sills said in a statement about the new study. “As with any new research, we will discuss these findings with our experts and look at our own data to see if these findings can be replicated
“Our concussion protocol, a conservative process developed based on internationally accepted guidelines, is reviewed annually to ensure that players receive care that meets the most current medical consensus on the identification, diagnosis and treatment of concussions.”us news
For the new study’s researchers and other experts, including SHAAKE as a potential sign of concussion — in sports protocols and medical guidelines in general — could provide very significant benefits at very little cost.
“Our understanding of what concussions look like is evolving,” Daneshvar said. “From my perspective, this is one of those things where it costs nothing to pull an athlete out and evaluate them. But the potential negative consequences of not evaluating an athlete with a concussion could be catastrophic — for them, for their careers and for their lives.”
Concussions often go unreported, and recognizing more signs in the official protocol could help, Stamm said.
“It really gives clinicians the power to say, ‘No, this is real,’” she said. “It gives the clinician more reason to take them off the field, and if the athlete understands that the head shaking is happening because they have symptoms, maybe they’ll realize it’s a concussion, if they didn’t already.”