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 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 this news organization.
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.