There are two major types of TBI: open and closed.
Open vs. Closed
Depends on whether the skull is broken (broken skull = open TBI)
Open TBI (also called penetrating) results when the scalp/skull is broken, fractured, or penetrated. This may occur when a foreign object (e.g., a bullet) goes through the skull, enters the brain, and damages specific parts of the brain. This focal, or localized, brain damage occurs along the route the object has traveled. Symptoms following an open TBI vary depending on the part(s) of the brain that is(are) damaged.
Closed TBI results when an outside force impacts the head, but the skull is not broken, fractured, or penetrated. This may occur, for example, when the head strikes the windshield or dashboard in a car accident. Damage is typically widespread or diffuse. Symptoms following a closed TBI vary depending on the extent of the damage to the brain.