A New, Easily Identifiable, Sign of Concussion?

Researchers have identified a potential new sign of concussion in athletes, particularly football players, that can easily be spotted on the field, indicating the need for immediate removal from the game and evaluation for potential traumatic brain injury (TBI).

Spontaneous Headshake After a Kinematic Event (SHAAKE) refers to the rapid, back-and-forth head movement athletes exhibit following a blow to the head. This voluntary motion typically occurs within seconds to minutes after impact and is a familiar response in athletes.

In a recent survey, 7 out of 10 adult athletes recalled making this movement after a collision, and three out of four times they attributed this back-and-forth head movement to a concussion. The association was strongest among football players, who reported that over 90% of SHAAKE episodes were associated with a concussion.

The results were published online on October 23 in Diagnostics.

Call to Action

“Everyone” — including sports and medical organizations — “should be adding this to their list of potential concussion signs and their protocol immediately,” study investigator Chris Nowinski, PhD, CEO and co-founder of the Concussion Legacy Foundation, told Medscape Medical News.

Nowinski said it’s “fascinating” that this concussion sign hasn’t been formally studied or added to formal concussion screening metrics before now, given that it’s been depicted in movies, television, and cartoons for decades.

Coaches, medical professionals, and concussion spotters should be trained to recognize when a SHAAKE happens, he said.

“The interesting thing is, I don’t think coaches or parents need much training other than to officially tie this to suspicion of a concussion,” Nowinski added.

The Case of Miami Dolphins QB Tua Tagovailoa

Nowinski said he was tipped off to SHAAKE as a concussion sign after Miami Dolphins quarterback Tua Tagovailoa’s controversial undiagnosed concussion during a National Football League (NFL) game in 2022.

After Tagovailoa’s head hit the ground, he rapidly shook his head side to side, indicating displaying SHAAKE, before stumbling and collapsing. At the time, a sideline doctor attributed his collapse to a prior back injury.

If Tagovailoa had been diagnosed with a concussion, he likely would not have been playing in a game just 4 days later, where he lost consciousness after suffering a suspected second concussion and was removed from the field on a stretcher.

For the survey, Nowinski and colleagues showed 347 current and former athletes, including 109 football players, video examples of SHAAKE and them asked about their experiences with this potential indicator of concussion.

Nearly 69% of athletes reported exhibiting a SHAAKE during their career, and 93% of those reported a SHAAKE in association with concussion at least once. Athletes reported SHAAKE a median of five times in their lives.

Of the athletes who reported SHAAKE, 85% linked this head-shaking movement to concussion symptoms such as disorientation (71%) and dizziness (54%).

Across all sports, SHAAKE showed a sensitivity of 49.6% and a positive predictive value (PPV) of 72.4% for diagnosing concussions.

Among football players, sensitivity improved to 52.3%, with an estimated specificity of 99.9%, a PPV of 91.9%, and an estimated negative predictive value of 99.5%.

The main limitation of the survey was the potential for recall bias due to survey participants self-reporting prior concussions. The researchers called for future prospective studies to validate SHAAKE as a sign of concussion.

Instant Replay for Brain Injury?

Experts who spoke with Medscape Medical News echoed the need for validation.

SHAAKE represents a “promising advance” in objective TBI assessment, particularly for sideline evaluation, said Shaheen Lakhan, MD, PhD, neurologist, and researcher based in Miami, Florida, who wasn’t involved in the research.

Lakhan said the potential value of SHAAKE is “particularly notable given the well-documented tendency for athletes to minimize or conceal symptoms to maintain play eligibility, a limitation that has historically challenged our reliance on subjective reporting and observational assessments.”

“Moving forward, validation through prospective studies incorporating real-time video analysis, helmet sensor data, and clinician-confirmed TBI diagnoses will be essential. With appropriate validation, SHAAKE could emerge as a valuable component of our sideline assessment arsenal, complementing rather than replacing existing diagnostic approaches,” Lakhan said.

“SHAAKE could be the ‘instant replay’ for brain injuries that sports medicine has been waiting for — but like any new technology, we need to make sure it works for every player, not just some,” Lakhan added.

Also weighing in, Richard Figler, MD, director of the Concussion Center, Cleveland Clinic Sports Medicine Center, Cleveland, cautioned that the survey participants were recruited from a concussion registry and self-reported an average of 23 concussions — more than one third of which happened 5-10 years prior — which begs the question, “How much are they actually remembering?”

“Our goal is to make sure that the athletes are safe and that we’re not missing concussions, and we don’t have great tools to start off with. This study opens up the door for some prospective studies [of SHAAKE] moving forward. I think we need more data before this should be listed as a definitive marker,” said Figler, who also wasn’t involved in the study.

In any case, he said, when it comes to suspected concussion in sports, “when in doubt, you sit them out,” Figler said.

This research received no external funding. Nowinski has received travel reimbursement from the NFL Players Association (NFLPA), NFL, World Rugby, WWE, and All Elite Wrestling; served as an expert witness in cases related to concussion and chronic traumatic encephalopathy; and is compensated for speaking appearances and serving on the NFL Concussion Settlement Player Advocacy Committee. Daniel H. Daneshvar served as an expert witness in legal cases involving brain injury and concussion and received funding from the Football Players Health Study at Harvard University, which is funded by the NFLPA and evaluates patients for the MGH Brain and Body TRUST Center, sponsored in part by the NFLPA. Lakhan and Figler had no relevant disclosures.