A brain imaging technique might allow doctors to detect a type of brain disease caused by repetitive head trauma in living patients.

This condition affects some professional athletes, including football players, but currently the only way to diagnose it for sure is during an autopsy.

While no treatments are available for chronic traumatic encephalopathy (CTE), earlier detection would allow doctors to monitor the progression of the disease. They could also measure the effectiveness of new treatments as they are developed.

CTE causes cognitive and behavioral symptoms, including memory loss and mood changes. One feature of the disease is the accumulation of clumps of a type of protein called tau in areas of the brain involved in mood and thinking.

These clumps are visible during a kind of brain scan called positron emission tomography (PET). This offers a potential way to diagnose the condition before death.

In a new study, published online today in Proceedings of the National Academy of Sciences, researchers at the David Geffen School of Medicine at the University of California, Los Angeles used PET scans to detect abnormal clumps of tau in the brain.

They scanned the brains of 14 retired professional football players. These athletes have an increased risk for developing CTE due to repeated concussions throughout their careers.

To make the clumps of protein visible on PET scans, researchers injected a chemical into the bloodstream — FDDNP — that is sensitive to tau protein. The brain scans showed more of the protein clumps in areas of the players’ brains that are involved in regulating pain and negative emotions — the dorsal midbrain and amygdala.

The brain scan results were compared to scans of people with normal cognitive ability and to scans of patients with Alzheimer’s disease. Alzheimer’s is sometimes misdiagnosed as CTE.

Learn the Facts: What Is Encephalopathy? »

Research Offers Hope for Early Detection

While the only definite way to know a person has CTE is to do an autopsy, this research offers a possible method for early detection.

“This work offers compelling evidence of the ability of [our brain imaging technique] to detect neuropathology in the living brain of American football players in a manner consistent with the pattern of deposition found at autopsy,” the authors wrote.

The PET scan “results in this work show direct early involvement of brain areas that participate in processing of emotions, mood, and behavior,” they added.

Mood changes can manifest as depression, aggressiveness, irritability, or suicidal behavior. Symptoms of CTE also include loss of short-term memory and certain cognitive abilities.

Initial symptoms may not show up for decades after an athlete suffers a blow to the head. Typically, signs appear between the ages of 40 and 50, but the timing may depend upon the number and severity of concussions.

Study Fuels Controversy Over Football Concussions in Teens »

No One Knows How Many Athletes Have CTE

The exact number of athletes affected by this condition is unknown.

According to the researchers, early studies estimate that up to 47 percent of retired professional boxers who had fought for more than 10 years showed symptoms of CTE, which was once known as “punch drunk syndrome.”

A more recent, but smaller study, published in Neurosurgery found that of 14 professional and three high school athletes who died unexpectedly, 13 showed signs of CTE during autopsy. These included football players, wrestlers, and a boxer.

Last year, the National Football League stated in federal court documents that it expects nearly a third of retired players to develop some kind of long-term cognitive problem. This estimate is based on actuarial data, not a research study.

CTE is a degenerative brain disease. The best approach for people who may have CTE is to avoid further head injuries.

People with CTE may also benefit from the kind of supportive care given to people with other types of dementia. This includes creating an environment with less clutter and noise, modifying tasks to allow for better focus, and exercising regularly.

Related News: Concussions Lead to Increased Dementia Risk in Older Adults »

Other diseases — including Alzheimer’s — also include deposits of tau protein in the brain. So the brain imaging used in this study may never be able to provide a simple yes or no test for CTE. Brain scans, however, could provide additional information along with medical history and physical exams to diagnose CTE.

“These promising results provide the basis for a larger trial to determine the scope of this imaging procedure for CTE,” the researchers wrote, “and for the use of this PET imaging technique to monitor disease progression in follow-up studies.”