For most of biomedical research history, the vast majority of scientific research and study relied on male mammalian subjects. In 1993, the U.S. National Institutes of Health (NIH) demanded women be enrolled in human studies, but it was only 2014 when the NIH said it would only fund early-stage studies that used equal number male and female lab animals.
Given that backdrop, it shouldn't come as a surprise that concussion research, like most other biomedical fields of study, is heavily skewed toward men. Add to it that concussions are often in the public eye as a result of the National Football League (which has no female athletes, although they are technically allowed), and you've got yourself a strong bias to study men's brains.
That's why more researchers and scientists are actively trying to find women's brains for concussion studies. After all, female athletes get concussions at higher rates than men in multiple sports, points out Usha Lee McFarling at Stat. And there's some evidence that men and women's brains react differently to concussions. For one, women might have a harder time than men recovering from a concussion, and where women are in hormone cycles might also lead to different responses.
We should add that because the research is limited, much more needs to be done to confirm and investigate if there are gender differences in concussion, and concussed brains. The only way to do that? Find more female brains to study, which places like Boston University's Brain Bank are actively attempting to do.