1994

NFL Commissioner Paul Tagliabue creates the Mild Traumatic Brain Injury Committee (MTBJC). Dr. Elliot Pellman is named chairman. Pellman says "concussions are part of the profession, an occupational risk." Tagliabue says "there is no increase in concussions, the number is relatively small. … The problem is a journalist issue."

2005

The MTBJC finds that returning to play after sustaining a concussion "does not involve significant risk of a second injury either in the same game or during the season."

January 2010

Dr. Ira Casson, co-chairman of the MTBJC, denies a link between repeat head impacts and long-term brain damage during a House Judiciary Committee hearing.

June 2012

A unified lawsuit combining more than 80 concussion-related lawsuits on behalf of more than 2,000 NFL players is filed in federal court in Philadelphia. The players accuse the NFL of negligence and failing to notify players of the link between concussions and brain injuries.

August 2012

The NFL files a motion to dismiss the concussion-related lawsuits filed by former players.

August 2013

The NFL and ex-players reach a deal in the class-action lawsuit that calls for the NFL to pay $765 million to fund medical exams, concussion-related compensation, medical research for retired NFL players and their families, and litigation expenses. The agreement needs to be approved by a judge.

Sources: CNN, PBS