The goal of this post is to describe what a concussion is. Future posts will discuss specific concussion features.

The American Academy of Neurology defines a concussion as “a clinical syndrome of biomechanically induced alteration of brain function, typically affecting memory and orientation, which may involve loss of consciousness.”¹ This somewhat complex definition can be easier to understand when broken down into parts.
1. A clinical syndrome is a group of medical symptoms and signs. Common symptoms of concussion include headache, dizziness, lightheadedness, fatigue, difficulty concentrating, drowsiness, nausea, irritability, and sadness. Not all patients with concussion experience every symptom. A medical sign means something that can be seen (where a symptom means something that can be felt). Loss of consciousness is an example of a medical sign.
2. Biomechanically induced means that trauma or impact is required to have a concussion. The trauma is typically to the head, face, or neck. Trauma to other parts of the body can also cause a concussion when enough force is transmitted to the head.
3. Alteration in brain function means that a concussion results from an injury to the brain. Typically, a concussion injury does not show up on brain scans (CT or MRI), so we call it functional – the brain cells are affected, but the brain scan appears normal.
4. Memory and orientation are basic brain functions that are commonly affected following a concussion. Patients often are confused about what happened, and they can have difficulty answering simple questions.
5. Some of the older textbooks defined concussion as an injury that includes loss of consciousness. Based on our current definition, less than 20% of patients have loss of consciousness.

To summarize, a concussion is a group of symptoms (and signs) that is caused by traumatic injury and results in a change in how the brain functions.

Additionally, concussion is transient or temporary, meaning that full recovery is expected. Most individuals have improvements in symptoms within 7-10 days,² although some patients continue to report symptoms for months – even years – after the injury. It is possible that children with concussion have symptoms longer than adults with concussion, but it is not known why this happens. When symptoms continue beyond 30 days, the term post-concussion syndrome is used.

The next blog post will discuss post-concussion syndrome.


¹ Giza CC, Kutcher JS, Ashwal S, Barth J, Getchius TS, Gioia GA, Gronseth GS, Guskiewicz K, Mandel S, Manley G, McKeag DB, Thurman DJ, Zafonte R. Summary of evidence-based guideline update: evaluation and management of concussion in sports: report of the Guideline Development Subcommittee of the American Academy of Neurology. Neurology. 2013;80:2250-2257.

² McCrory P, Meeuwisse WH, Aubry M, et al. Consensus statement on concussion in sport: the 4th International Conference on Concussion in Sport held in Zurich, November 2012. Br J Sports Med. 2013;47:250-258.