When would doctors order ct scans when a child bumps his head?

For symptoms: Children sustain minor head "bonks" all the time. A cat scan is only necessary if the child has had prolonged vomiting afterward, exhibits neurological changes (seizure, weakness, persistent loss of consciousness), or if the cause of the trauma was severe (fall from height, high speed injury, etc). Also if the child has blood behind the eardrum or nasal drainage after the injury.