Traumatic brain injury occurs when a sudden physical assault on the head causes damage to the brain. The damage can be focal, confined to one area of the brain, or diffuse, involving more than one area of the brain. Traumatic brain injury can result from a closed head injury or a penetrating head injury. A closed head injury occurs when the head suddenly and violently hits an object, but the object does not break through the skull. A penetrating head injury occurs when an object pierces the skull and enters the brain tissue. when touched.
Several types of traumatic injuries can affect the head and brain. A skull fracture occurs when the bone of the skull cracks or breaks. A depressed skull fracture occurs when pieces of the broken skull press into the tissue of the brain. This can cause bruising of the brain tissue, called a contusion. A contusion can also occur in response to shaking of the brain within the confines of the skull, an injury called "countrecoup."
Shaken baby syndrome is a severe form of head injury that occurs when a baby is shaken forcibly enough to cause extreme countrecoup injury. Damage to a major blood vessel within the head can cause a hematoma, or heavy bleeding into or around the brain. The severity of a Traumatic brain injury can range from a mild concussion to the extremes of coma or even death. A coma is a profound or deep state of unconsciousness.