MORGANTOWN, W.Va. — Cincinnati Bengals receiver Chris Henry suffered from a chronic brain injury that may have influenced his mental state and behavior before he died last winter, West Virginia University researchers said Monday.

The doctors had done a microscopic tissue analysis of Henry’s brain that showed he suffered from chronic traumatic encephalopathy.

Neurosurgeon Julian Bailes and California medical examiner Bennet Omalu, co-directors of the Brain Injury Research Institute at WVU, announced their findings alongside Henry’s mother, Carolyn Henry Glaspy, who called it a “big shock” because she knew nothing about her 26-year-old son’s underlying condition or the disease.

Henry died in December, a day after he came out of the back of a pickup truck his fiancee was driving near their home in Charlotte, N.C. It’s unclear whether Henry jumped or fell. Toxicology tests found no alcohol in his system, and an autopsy concluded he died of numerous head injuries, including a fractured skull and brain hemorrhaging.

But Bailes, team doctor for the Mountaineers and a former Pittsburgh Steelers physician, said it’s easy to distinguish those acute traumatic injuries from the underlying condition he and Omalu found when staining tiny slices of Henry’s brain.

Bailes and fellow researchers believe chronic traumatic encephalopathy, or CTE, is caused by multiple head impacts, regardless of whether those blows result in a concussion diagnosis. A number of studies, including one commissioned by the NFL, have found that retired professional football players may have a higher rate than normal of Alzheimer’s disease and other memory problems.

What’s interesting, Bailes said, is that Henry was only 26, and neither NFL nor WVU records show he was diagnosed with a concussion during his playing career.

But it doesn’t take a collision with another player for brain trauma to occur.

“The brain floats freely in your skull,” Omalu said. “If you’re moving very quickly and suddenly stop, the brain bounces.”

And over time, with repetition, that causes big problems.

CTE carries specific neurobehavioral symptoms, Bailes said — typically, failure at personal and business relationships, use of drugs and alcohol, depression and suicide.

“Chris Henry did not have that entire spectrum and we don’t know if there’s a cause and effect here,” Bailes said. “It certainly raises the question and raises our curiosity. We’re just here to report our findings. That may be for others to decipher.”

Henry’s personal struggles were well documented.

Although he was a vital part of the Bengals’ offense as a rookie, he ended that season with an arrest for marijuana possession. After a playoff loss to Pittsburgh, he was arrested on a gun charge in Florida.

Henry was suspended for half a season in 2007 as the league cracked down on personal conduct.

When he was arrested a fifth time, a judge called Henry “a one-man crime wave” and the Bengals released him.

But Henry got a second chance and played 12 games in the 2008 season.

Teammates said they’d noticed a change his demeanor, and at the start of the 2009 season, he described himself as “blessed” and said he was turning his life around.

Glaspy gave Bailes permission to examine her son’s brain in detail.

“I was a little scared,” she said. “It was something new to me. I’m still trying to educate myself as to what it means. Some of it makes sense with some of the behavioral patterns in Chris — just like mood swings and the headaches.

“Hopefully I can share whatever they share with me with other parents and help the NFL deal with the matter of being hit in the head and concussions and to educate ourselves as mothers and fathers when we send our kids out there on the field.”

Omalu first came across CTE, a condition often seen in boxers, after studying the brain of Pittsburgh Steelers Hall of Fame lineman Mike Webster. Webster died in 2002 of a heart attack at age 50. He had suffered brain damage that left him unable to work following his career.

Bailes said he and Omalu have now analyzed the brains of 27 modern athletes, and the majority showed evidence of CTE. But it’s found in only a small number of players, he said.

“I think football is a great sport, and we want to make it safer,” Bailes said, “but we have to continue to move forward with changes made recently and take the head impacts out of the sport as much as possible.”