Renewed Fears Over Brain Injuries Cast Shadow Over NFL's Opening Weekend

A series of brutal hits on superstar Cam Newton renewed the discussion over CTE.

Also on Sunday, the players' union announced it was initiating a compliance investigation into the response to the hit on Newton.

It was not the only hit on Newton at Thursday's game that raised eyebrows.

Shortly after the hit by Marshall, familiar discussions percolated on social media about chronic traumatic encephalopathy (CTE), a disease believed to cause disorientation, headaches, memory loss, and erratic behavior in players.

The NFL released a statement on Friday saying the league's concussion protocol was properly executed, but the players' union suggested that it would exercise its right to investigate the matter, according to ESPN.

Former NFL head coach and current NFL Network analyst Steve Mariucci, who serves as part of the NFL's Player Safety Advisory Panel, also defended the league while speaking on TV, said the organization is trying to remove helmet-to-helmet contact from the game.

Officials from the Carolina Panthers told ESPN that Newton was questioned four times to ensure that he had no residual effects from the hits he took on Thursday and declared that he passed the concussion tests given to him.

Still, the issue is not likely to fade from view.

Quintiles Injury Surveillance and Analytics counted 271 concussions caused during games and practices in 2015, a number that jumped significantly from the 206 reported in 2014. The overwhelming majority of concussions caused in 2015 were as a result of helmet-to-helmet contact.

Duerson prior to killing himself sent a text message to his family asking them to have his brain studied by CTE researchers.