A concussion is a traumatic brain injury (TBI) that may result in a bad headache, altered levels of alertness, or
It temporarily interferes with the way your brain works, and it can affect memory, judgment, reflexes, speech, balance, coordination, and sleep patterns.
Causes, incidence, and risk factors
A concussion may result when the head hits an object or a moving object strikes the head.
A concussion can result from a fall, sports activities, and car accidents. Significant movement of the brain (called jarring) in any direction can cause you to lose alertness (become unconscious). How long you remain unconscious may be a sign of the severity of the concussion.
However, concussions don't always involve a loss of consciousness. Most people who have a concussion never black out. You can have a concussion and not realize it.