Story highlights Kevin Turner was a lead plaintiff in a concussion lawsuit against the NFL

Turner was diagnosed in 2010 with ALS, which was brought on by his CTE

(CNN) Former pro football player Kevin Turner died having the most advanced stage of chronic traumatic encephalopathy, known as CTE, a neurodegenerative disease associated with repeated head trauma.

Turner was a star running back at the University of Alabama from 1988 to 1991 before being picked in the third round of the draft by the New England Patriots. He played for the Patriots for three seasons followed by five seasons with the Philadelphia Eagles. He was diagnosed with amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, in 2010 and died in March of ALS.

It was believed that he had only ALS, but Thursday's announcement, made by Dr. Ann McKee of Boston University and the Concussion Legacy Foundation, changed that understanding.

In a statement, McKee said, "The severity of Mr. Turner's CTE was extraordinary and unprecedented for an athlete who died in his 40s.

"While he had typical cognitive symptoms and problems with impulse control associated with CTE, it also appears that CTE decimated the motor cortex of his brain at a young age, likely leading to his ALS symptoms," she added. McKee clarified that Turner's CTE brought on his ALS.