The brain is well protected inside the bony encasement of the skull, cushioned by a surrounding layer of spinal fluid. But sufficient force can cause damage to delicate brain tissue, and even minor injury can result in impairment of cognitive function and disturbance or mood and behavior. In a concussion, a mild brain injury, there may be no loss of consciousness, but the brain is injured and not working properly. The person may be confused or agitated, and may not remember what happens during this time.
Significant brain injury can occur even when the person does not actually hit their head against anything, as in the “whiplash” injury sustained in a car accident, when the forces can cause a twisting of brain tissue, resulting in “micro-tears,” swelling and inflammation that may not be visible on a brain scan. Even in cases of relatively mild head injury, or concussion, with brief or no loss of consciousness, a person may experience symptoms of brain injury for days, weeks or months. Dizziness, nausea and headache may be worst for the first few days. Headaches can persist, along with fatigue, irritability, and poor concentration.