Is nausea normal after a mild head injury in a four year old?

http://www. familydoctor.org, a Website sponsored by the American Academy of Family Physicians, advises that "It's normal to have a headache and nausea, and feel dizzy right after a head injury. Other symptoms include ringing in the ears, neck pain, and feeling anxious, upset, irritable, depressed or tired." Note that "It's normal" means that "it's common and is not necessarily a grave sign." The most important issue is that when brain injury is known or suspected, the child should be seen by a physician. Injury to the brain can occur even when there are few or no visible signs of injury to the outside of the skull, as when a child is wearing a protective helmet and sustains shocks to the head. Why? Because the brain can bounce around inside the skull, causing injury as it rebounds from surface to surface. No one urges a parent to panic when there is the possibility of brain injury in a child, but everyone urges caution in paying attention to symptoms such as headaches, listlessness, balance problems, or throwing up.