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Mild concussions may leave lasting brain changes months after symptoms subside

Concussion damage can linger past the time the patient has recovered, even if her or she no longer feels any symptoms, a new study shows.

Researchers looked at 50 people who had mild concussions and compared them to 50 people who had not suffered a traumatic brain injury. Four months after the incident, doctors still observed differences in the way fluid traveled through their brains -- even if they didn't have any concussion symptoms.

"The big take-home message is that even though people report feeling better, the brain might not be completely healed," study author Dr. Andrew Mayer, an associate professor of psychology at the University of New Mexico, said to the BBC.

Previous studies have also found concussions could lead to lasting brain changes. A study on children showed that concussions caused white matter changes that were not observed in kids who did not have concussions. White matter in the central nervous system is responsible for sending signals from one region of the brain to the other.

The need for longer recovery times in those who have experienced multiple concussions also suggests brain changes may be lasting. Children who had a concussion before their most recent episode needed twice as long to recover from symptoms in a recent study, compared to those who had just one traumatic brain injury.

The concern over concussions' lasting effect has grown especially because of the prevalence of chronic traumatic encephalopathy (CTE) in athletes who have reported numerous traumatic brain injuries.Athletes who suffer from the Alzheimer's like- neurodegenerative brain disease often experience memory loss, confusion, impaired judgment, impulse control problems, aggression, depression, and, eventually, progressive dementia. The condition typically can only be diagnosed after death, though recent studies have been able to find the condition in living patients.

The American Academy of Neurology (AAN) issued new guidelines in March for athletes that suffer a traumatic brain injury. Previously, doctors and coaches were told to grade the severity of the symptoms and then given a recommended time that the player should be held off the field. Now, the AAN recommends that if there is any doubt about the player's condition, they should be kept out of the game.

Kenneth Podell, co-director of the Houston Methodist Concussion Center who was not involved in the new study, said to HealthDay that the research shows that physical brain changes after a concussion are completely different from behavioral changes. He cautioned that while the study showed there were differences in the brain, it couldn't be linked to other diseases like depression or dementia.

"Everyone seen at four months should be followed in another four, six or eight months and then re-scanned," he said. "One of the biggest problems we have looking at concussions is we try to predict long-term effects from short-term findings. This injury is very difficult to commit the type of resources needed to do that kind of very expensive and time-consuming study."

The study was published online in Neurology on Nov. 20.

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