Concussion is defined by a bump, blow, or jolt to the head, face, neck, or elsewhere on the body that causes the head and brain to move rapidly back and forth, causing mechanical stretching of nerve axons (diffuse axonal injury) and disruptive biochemical changes. It is classified as a Minor Traumatic Brain Injury (mTBI), although the effects are certainly not minor. According to the Ontario Neurotrauma Foundation, 150,000 Ontarians are diagnosed with concussion each year, of which 40,000 are children and youth under 18. According to the Canadian Institute for Health Information, sports and recreational activities were the third leading cause of TBI admissions in Canadian hospitals in 2003-2004. Up to 3.6 million concussions occur annually, as estimated by the Centers for Disease Control and Prevention.
There are typically no structural brain abnormalities seen on neuroimaging studies such as CAT scan or standard MRI. According to The Centre for Disease Control (CDC), up to 15% of patients diagnosed with mTBI may have persistent disabling problems. When symptoms such as dizziness, headaches, fatigue, cognitive impairment, trouble sleeping, and vision problems persist beyond the typical recovery period of three months, the term post-concussion syndrome or disorder is applied. Symptoms may occur immediately or may not occur for days or weeks after the injury, and can be a different presentation with each individual.