Chronic traumatic encephalopathy (CTE) is a progressive brain condition that's thought to be caused by repeated blows to the head and repeated episodes of concussion.
It's particularly associated with contact sports, such as boxing or American football. Most of the available studies are based on ex-athletes.
CTE was previously known as "punch drunk" syndrome and dementia pugilistica. But these terms are no longer used because it's now known that the condition is not limited to ex-boxers.
There's still some debate about how common CTE is and how it should be diagnosed.
Currently, only supportive treatments are available and research is focused on finding a reliable technique to diagnose the condition.
The symptoms of CTE vary between individuals, but tend to be similar to those of other types of degenerative brain conditions, particularly Alzheimer's disease.
CTE usually begins gradually several years after receiving repetitive blows to the head or repeated concussions.
The symptoms affect the functioning of the brain and eventually lead to dementia.
Typical symptoms of CTE include:
As the condition progresses, further symptoms may include:
Any prolonged activity that involves repeated blows to the head or recurrent episodes of concussion is thought to increase the risk of getting CTE. But CTE and concussion are separate conditions.
Many people who are concussed do not go on to develop CTE, but evidence suggests a pattern of repeated minor head injuries increases the risk.
Although the exact causes are not fully understood, certain groups of people are believed to be most at risk.
It's a good idea to see your GP if you're worried about your memory.
If you're worried about someone else, you should encourage them to make an appointment and perhaps suggest that you go along with them.
Memory problems are not just caused by dementia. They can also be caused by:
Your GP can carry out some simple checks to try to find out what the cause may be, and they can refer you to a specialist memory clinic for more tests, if necessary.
There's currently no test to diagnose CTE. A diagnosis is based on a history of participating in contact sports, plus the symptoms and clinical features.
Your GP will talk to you about the problems you're experiencing and may ask you to carry out some simple mental or physical tasks, such as moving or walking around.
They may refer you to a specialist memory assessment service, staffed by experts in diagnosing, caring for and advising people with dementia and their families.
Memory clinic staff can listen to your concerns, assess your skills and, if necessary, arrange further tests to rule out other conditions.
In CTE, the changes to the brain do not always show up on routine brain scans or may be similar to other conditions.
This means the only way of confirming CTE is by carrying out a post-mortem after a person with the condition dies.
Research has found that the changes in the brain associated with CTE are different from those seen in Alzheimer's disease.
But both conditions are associated with shrinking of the brain (atrophy) and the presence of neurofibrillary tangles that contain a protein called tau.
Research is ongoing to determine whether other brain imaging techniques will be able to help diagnose CTE in the future.
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As with many other types of dementia, treatment for CTE is based around supportive treatments.
If you have been diagnosed with the condition, healthcare professionals, such as your GP or specialist, and social care services (normally your local council working with the NHS) will usually be involved in helping draw up and carry out a long-term care plan.
You may also see a speech and language therapist or occupational therapist.
The NHS dementia guide provides detailed information for people with dementia and their families, including:
The only way to prevent CTE is to avoid repetitive head injuries. Although many head injuries are difficult to predict or avoid, there are things you can do to reduce your risk.
For example, you should: