There are four types of traumatic brain injuries (TBIs): Concussion: A concussion is a mild TBI that typically results from a blow or jolt to the head. Symptoms of a concussion can include headaches, dizziness, confusion, and memory loss. Contusion: A contusion is a bruise on the brain that can occur when the brain collides with the skull. Symptoms of a contusion can include vomiting, seizures, and a loss of consciousness. Penetration: A penetration injury occurs when an object penetrates the skull and enters the brain. Symptoms of a penetration injury can include bleeding, infection, and damage to brain tissue. Diffuse axonal injury: A diffuse axonal injury (DAI) is a severe TBI that occurs when the brain shifts rapidly inside the skull, causing tearing or stretching of nerve fibers. Symptoms of a DAI can include a loss of consciousness, coma, and severe cognitive and physical disabilities.