What is CTE?

Chronic Traumatic Encephalopathy (CTE) is a progressive neurodegenerative condition of the brain. It is the result of repeated sub-concussions to the head and body. CTE symptoms include problems with mood, thinking and behaviour. They typically do not appear until years after the sustained injuries and worsen over time, leading to dementia. CTE is classed as a tauopathy.

The correlation between dementia and repetitive head impacts has been observed for millennia. Before CTE was a known medical condition, “Punch Drunk” was a recognised complication of boxing in 1928. However, it wasn’t classed as CTE until 1940 when the term CTE was introduced. It described severe mood changes, memory loss, disturbance in thinking ability and eventually dementia, arising from repetitive blows to the head. 

Medical scientists did not really progress this understanding until 2002 when CTE was first identified in American football players. This followed the American NFL player, Mike Webster’s, death from the disease aged 50. Further cases of CTE have been diagnosed clinically in football, rugby union, rugby league and Australian Rules Football. Most recently, CTE has been diagnosed in 300 former rugby players. The medical and sporting worlds recognise the increasing number of contact sports players developing CTE.

What are the symptoms of CTE?

Typically, players of contact sports begin to develop symptoms in their 30s-50s. Early signs include mild forgetfulness, low mood, anger and slowing of thought process.

The individual then develops physical and cognitive symptoms, such as confusion, memory loss, tremors, slurred speech, and a gradual decline in thinking ability. Mood changes include aggression, depression and changes in personality. The condition eventually leads to dementia. These symptoms can become debilitating and life-changing for those affected and those around them.

Symptoms of cognitive decline and subtle changes in behaviour can be very non-specific, especially in the early days of CTE.

What causes CTE?

The progressive cognitive and behavioural symptoms in CTE are the result of a complex, chronic inflammatory process, which leads to the destruction of the normal connections between the brain cells and death of the brain cells.

With repetitive impacts to the head, the most significant injury occurs to the fine blood vessels that surround brain cells. This results in damage to the blood-brain barrier, a structure designed to protect the brain.

When this structure is damaged by repetitive trauma, an abnormal ‘immune mediated inflammatory response is triggered with the production of neurochemicals. The neurochemicals and inflammatory response should be protective.

However, when the brain is subjected to repetitive impacts and before the protective neurochemicals and inflammatory changes from the initial brain injury have had time to return to normal, the subsequent, repetitive head injuries can then result in an abnormally exaggerated, further production of neurochemicals and exaggerated inflammatory response. Instead of being protective, this is harmful to the brain. The response now damages the brain tissue and eventually leads to the irreversible death of brain cells.

Over time, this abnormal inflammatory pathway which is triggered, repeatedly, by frequent head injury in contact sports eventually leads to changes in a brain protein called tau.

The tau protein which is found within cognitive brain cells normally stabilises these brain cells to ensure they work efficiently and communicate effectively with all the other cognitive brain cells, so an individual can think and behave normally.

When the tau protein becomes damaged, it can no longer stabilise the brain cells and the brain cells lose their ability to function efficiently and effectively.

Furthermore, the tau protein starts to replicate itself inside the brain cells and eventually the tau completely fills the brain cells so they burst and die. Unfortunately, these brain cells cannot regenerate. The abnormal tau protein also develops the ability to “jump” from one brain cell to the next; once the abnormal tau protein enters a new brain cell, the process starts again, resulting in the death of that brain cell.

As the tau protein spreads around the brain affecting and killing more and more brain cells, needed for thinking and to control our emotions and behaviour, the symptoms of cognitive impairment and changes in behaviour become increasingly apparent. The resulting symptoms result in CTE.


A CTE brain is shrunken and smaller in volume than a normal brain given the death of brain cells. While the brain shrinks to some degree in healthy ageing, it does not lose brain cells in large numbers. Changes in brain tissue can be examined under the microscope after death, with the tau protein visible.

The image below shows a normal brain (top) compared to a CTE brain (bottom).

Normal brain scan vs CTE brain scan


CTE can be reduced by limiting head impacts, rotational forces and sub-concussions to the brain. That includes:

  • Educating and training contact sport players on the risk of sub-concussions;
  • Fewer contacts and hits during training and matches; and
  • Wearing Halos® to protect from brain injury.

Dr. Emer MacSweeney, BSc (Hons), MRCP, FRCR and Consultant Neuroradiologist, is an expert in CTE and understanding around the impact of sub-concussions in sport. Dr MacSweeney’s 2022 Ted Talk explains the importance of headgear that protects the brain, not just the skull, and reduces the damage caused by rotational forces to the brain. Halos® headbands for concussions and sub-concussions are proven to reduce rotational forces by 61%.

Reducing CTE requires innovation, improved education, player care and support, consideration to policy changes and game modifications and ongoing research.

Who is Most Impacted?

CTE is most commonly found in athletes, war veterans and individuals who have suffered repetitive brain traumas. Research into football brain injuries, as well as brain injury in rugby and hockey is helping us better understand the risk of CTE in contact sports.

What Treatment is Available?

There is currently no treatment to cure CTE.

At Re:Cognition Health, under an early access drug licence, a potential treatment to halt or slow the progression of CTE symptoms is underway.


Here you can find answers to commonly asked questions surrounding CTE.

CTE symptoms can include mood changes, memory loss, confusion, poor judgement and slurred speech. However, symptoms of cognitive decline and subtle changes in behaviour can be very non-specific, especially in the early days of CTE.

Yes, CTE is a fatal neurodegenerative disease.

Yes, but only very sophisticated MRI DTI imaging can demonstrate objective evidence of CTE. High-quality clinical and diagnostic assessments can offer a reasonably certain CTE diagnosis.

Brain injury consistent with CTE can now be diagnosed in life using novel sophisticated MRI DTI imaging sequences. The manta that CTE can only be diagnosed in death is no longer true.

No, CTE is not reversible or currently curable.

CTE has been diagnosed, clinically, in football (soccer), rugby union, rugby league and Australian Rules Football.

Rugby and American football players are, overall, subjected to more sub-concussive hits. This explains why CTE is ten times more common in players of theses sports, who tend to develop symptoms in their 30 or 40s, compared to football players who develop CTE symptoms in their 50s or later.

20% of people with CTE diagnosed after life, never had a single recorded concussion.

CTE is a progressive neurodegenerative disease. CTE will get worse over time and become life-changing for those affected, their family and friends.

CTE symptoms typically begin gradually and over the course of several years. CTE manifests in the brain years before symptoms begin to develop.

There is no known safe threshold tolerance for rotational forces to the brain, or if a certain number of sub-concussions leads to CTE.


Rotational forces from sub-concussions increases your risk of Chronic Traumatic Encephalopathy (CTE).

CTE is a progressive neurodegenerative disease caused by repetitive sub-concussive impacts to the brain. It is irreversible and incurable, causing life-changing physical and cognitive symptoms.