The severity of Chronic Traumatic Encephalopathy found in former Patriots running back Kevin Turner’s brain “was extraordinary and unprecedented” and likely led to the ALS symptoms that eventually caused his death at the age of 46, Boston University researchers announced today.

The BU CTE Center, in conjunction with the VA Boston Healthcare System and Concussion Legacy Foundation, revealed their diagnosis after examining Turner’s brain tissue, saying that Turner had the most advanced stage of CTE — stage IV out of IV. CTE is a neurodegenerative disease linked to repeated brain trauma that has been shown to cause ALS symptoms in some cases.

Turner died in March due to complications brought on by the ALS he battled since 2010. ALS, or amyotrophic lateral sclerosis, is a progressive neurodegenerative disease that affects nerve cells in the brain and the spinal cord. A lead plaintiff in a concussion suit brought by former players against the NFL, Turner donated his brain following his diagnosis due to his suspicion that football had contributed to his illness.

In its findings, the Center concurred with Turner.

“We believe the extreme severity of Kevin Turner’s disease is related to his 25-season career, and the fact he began playing tackle football at age 5, while his brain was still rapidly developing and more vulnerable,” said Dr. Robert Cantu, co-founder and medical director of the Concussion Legacy Foundation and clinical professor of neurosurgery at BU.

Added Chris Nowinski, former Harvard football player and co-founder of the Concussion Legacy Foundation, “We were surprised at the severity of the findings,” he said. “It’s just more evidence that starting football young can lead to CTE.”

At this stage, CTE can only be diagnosed by examining brain tissue post-mortem. Turner was diagnosed by Dr. Ann McKee, who serves as professor of Neurology and Pathology at BU School of Medicine, director of BU’s CTE Center, director of the Neuropathology Service for the New England VA Medical Centers and chief of neuropathology for the VA Boston Healthcare System.

“The severity of Mr. Turner’s CTE was extraordinary and unprecedented for an athlete who died in his 40s,” McKee said. “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.

“After now completing the analysis of the brains of 228 former football players, we have seen a clear trend that length of career is associated with CTE severity.”

McKee’s findings were announced at the 2016 BU CTE Continuing Medical Education Conference, attended by more than 100 physicians, researchers and policy makers. McKee was joined by Turner’s parents, Raymond and Myra Turner, as well as Tamara Alan, executive director of the Kevin Turner Foundation, formed in 2010 to further research into the connection between ALS and CTE. Also on hand were more than 70 family members of other brain donors who were attending the conference.

“While learning the results has been devastating for Kevin’s family and those of us close to him, unfortunately, we cannot say we are surprised,” said Alan. “It’s the whole reason Kevin started his foundation, as if he knew instinctively that he was living Ann McKee’s findings about the CTE/ALS connection. Despite the devastation to Kevin’s brain, he stayed true to the core as the caring man he always was, doing his best to warn others to avoid his fate. We will continue to honor Kevin’s wishes that we bring attention to this devastating disease.”

Turner’s brain is one of more than 380 brains donated since 2008 to the VA-BU-CLF Brain Bank, a collaboration between the US Department of Veterans Affairs, Boston University School of Medicine and the Concussion Legacy Foundation.