Concussion Basics

What is a Concussion: A concussion is a brain injury caused by an impact to the head, or by a blow elsewhere on the body that jolts the head and brain. It temporarily affects how the brain works. Symptoms can include headache, dizziness, confusion, sensitivity to light or noise, and changes in mood or sleep. Most people don’t lose consciousness, and standard brain scans usually look normal. Most people recover within a few weeks, but recovery varies, and anyone with a suspected concussion should be assessed by a doctor.

Reference: Patricios JS, Schneider KJ, Dvorak J, et al. Consensus statement on concussion in sport: the 6th International Conference on Concussion in Sport–Amsterdam, October 2022. Br J Sports Med. 2023;57(11):695–711. doi:10.1136/bjsports-2023-106898

What is CTE? Chronic traumatic encephalopathy (CTE) is a degenerative brain disease linked to a history of repetitive head impacts, including both concussions and hits that don’t cause symptoms. It involves a build-up of an abnormal protein called tau in a distinctive pattern in the brain. At present, CTE can only be confirmed by examining brain tissue after death. Many questions remain under active research and debate, including how much exposure is needed and why some people develop CTE while others don’t.

Reference: McKee AC, Stein TD, Huber BR, et al. Chronic traumatic encephalopathy (CTE): criteria for neuropathological diagnosis and relationship to repetitive head impacts. Acta Neuropathol. 2023;145(4):371–394. doi:10.1007/s00401-023-02540-w

What are Repetitive Head Impacts? Repetitive head impacts are the total number of hits to the head a person experiences over time, for example through years of contact sport. They include concussions and also “sub-concussive” impacts, which don’t cause obvious symptoms. Researchers are particularly interested in whether this cumulative exposure, rather than any single injury, affects long-term brain health.

Reference: Nowinski CJ, Bureau SC, Buckland ME, et al. Applying the Bradford Hill criteria for causation to repetitive head impacts and chronic traumatic encephalopathy. Front Neurol. 2022;13:938163. doi:10.3389/fneur.2022.938163