5 things to know about CTE

The list of football players with a brain disease called chronic traumatic encephalopathy, or CTE, continues to grow. But what exactly is CTE? Here are five things you need to know:

1. CTE isn’t just about concussions

A concussion is a brain injury that occurs from a blow to the head. But it’s not just concussions that have researchers worried. Most scientists believe that CTE is a result of repeated, or sub-concussive, hits to the head. The concern is that each time the head takes a pounding, it shakes the brain inside the skull. All that sloshing around can lead to a buildup of an abnormal protein called tau, which can take over parts of the brain.

Family photos of former Minnesota Vikings football player Fred McNeill.

CTE in the NFL: The tragedy of Fred McNeill

2. Harder helmets aren’t the answer

People like to point to safer helmets as a solution, but helmets can’t do anything to protect your brain from sub-concussive hits. Imagine your brain like an egg; the shell is the helmet; the yolk is your brain. Just because you have a thicker shell, like an egg carton, doesn’t protect the yolk from moving back and forth whenever the egg is shaken or moved around.

3. Football players aren’t the only ones who need to worry about CTE

Despite all the talk about football players, they aren’t the only ones concerned about CTE. The disease has been diagnosed in soccer and baseball players, and possibly even in military veterans. In fact, the first mention of CTE was a disease in boxers called “dementia pugilistica” or “punch-drunk” syndrome in a 1928 issue of the Journal of American Medical Association. The article said, “For some time, fans and promoters have recognized a peculiar condition occurring among prize fighters which, in ring parlance, they speak of as ‘punch drunk.’ Fighters in whom the early symptoms are well recognized are said by the fans to be ‘cuckoo,’ ‘goofy,’ ‘cutting paper dolls,’ or ‘slug nutty.’ ”

Former pro football player Kevin Turner, shown here during a 1998 NFL game, had the most advanced stage of CTE when he died in March at the age of 46. Dr. Ann McKee of Boston University and the Concussion Legacy Foundation said that Turner's CTE brought on amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease.

CTE stands for chronic traumatic encephalopathy, a neurodegenerative disease associated with repeated head trauma. Scientists believe repeated head trauma can cause CTE, a progressive degenerative disease of the brain. Symptoms include depression, aggression and disorientation, but scientists can definitively diagnose it only after death.

BMX star Dave Mirra, who was found dead of a self-inflicted gunshot in February, was found to have CTE.

Charles "Bubba" Smith, a former football player and actor who died in 2011, was also diagnosed with CTE. Smith played for the Baltimore Colts, the Oakland Raiders and the Houston Oilers.

Former Minnesota Vikings linebacker Fred McNeill died in November 2015 due to complications from ALS. However, an autopsy confirmed that he suffered from CTE. What makes McNeill's case even more remarkable, though, is that he was potentially the first to be diagnosed while alive. Doctors used an experimental new technology to examine his brain.

Oakland Raiders quarterback Ken Stabler, a former NFL MVP who died in July 2015, suffered from CTE, researchers at Boston University said.

Kansas City Chiefs linebacker Jovan Belcher shot and killed his girlfriend before killing himself in December 2012. Pathology reports show he probably had CTE.

Hall of Fame offensive lineman Mike Webster was the first former NFL player to be diagnosed with CTE. After his retirement, Webster suffered from amnesia, dementia, depression, and bone and muscle pain.

The death of 36-year-old Pittsburgh Steelers offensive lineman Justin Strzelczyk put the link between football and CTE in the national spotlight. Strzelczyk was killed in a 2004 car crash crash after a 40-mile high-speed chase with police in New York.

Evidence of CTE was found in the brain of football player Lew Carpenter after his death in 2010 at the age of 78.

Pro Football Hall of Famer Louis Creekmur, who played for the Detroit Lions from 1950 to 1959, suffered decades of cognitive decline before his death.

Linebacker John Grimsley of the Houston Oilers died of an accidental gunshot wound to the chest in 2008. Analysis of his brain tissue confirmed damage to the neurofibrillary tangles that had begun to affect his behavior and memory.

Chris Henry played five seasons for the Cincinnati Bengals before dying at the age of 26. He died after falling from the bed of a moving pickup during a fight with his fiancée. His young age prompted concern over how quickly athletes start to suffer from CTE.