When can a concussion occur?

Answer 1

A concussion happens when the brain, which is normally floating in fluid, strikes the inside of the skull. It can happen from direct trauma to the skull but it can also happen with whipping types of motions of the head on the neck. In fact, woman and small children are often more prone to concussions due to proportionately longer and weaker necks. It is also one of the reasons why football players wear neck braces (less whippping and so fewer concussions - not just to protect the neck).

Answer 2

A concussion occurs when the head hits or is hit by an object, or when the brain is jarred against the skull, with sufficient force to cause temporary loss of function in the higher centers of the brain.