Head injuries are usually classified as “closed” — a blow to the head which does not break the skull, and “open” or penetrating — where an object breaks through the skull and enters the brain. The latter usually occurs with a car crash or gunshot to the head.
A head injury is termed a “traumatic brain injury” (TBI) when it affects the functioning of the brain. The most common is concussion, when the brain is shaken inside the skull. It may be referred to as a “mild” TBI, as they are not usually life-threatening. They can still be serious and should not be ignored, especially with repeated concussions.
Head injuries also include scalp wounds and skull fractures. Bleeding occurs externally and internally — in the brain tissue and in the layers surrounding the brain.
Symptoms of brain injury may appear suddenly or may be delayed for several hours or days. Get medical help if the injured person becomes very sleepy, behaves abnormally, develops a severe headache or stiff neck, has pupils (the dark central part of the eye) of unequal sizes, is unable to move an arm or leg, loses consciousness — even briefly, or vomits more than once.