Article continues below advertisementSydney Sweeney has sparked concern among fans after revealing she suffered a concussion - with insiders fearing she could have inflicted lasting brain damage on herself while filming brutal fight scenes for her new boxing biopic, Christy.Article continues below advertisementSource: BLACK BEAR FILMS;MEGASydney Sweeney stars in the new boxing movie 'Christy.' Article continues below advertisementThe 28-year-old Euphoria star, who plays U.S.