Panel of experts says there is not enough evidence to give solid recommendations on many youth sports safety issues.
The telltale tau proteins present in the disease known as CTE display distinctive features.
New study suggests at least one in 10 NFL players could eventually develop the brain disease.
New safety rules pose challenges for players and officials.
The goals of a major push for football helmet safety should bring improvements, but the overall results remain unpredictable.
How new and improved sports protection equipment could help in concussion prevention.