Head injuries kill and disable more people under the age of 50 than any other type of neurological damage, and are the second leading cause of death in men under age 35. Although the thick, hard bones of your skull help protect your head, the brain is susceptible to many kinds of injury, even if the skull is not penetrated. In many cases, head injuries are caused by the sudden acceleration that follows a jolt, such as when you receive a forceful blow to the head or when a moving head strikes an immovable object. Severe head trauma can tear (tehr), shear, or rupture the nerves, blood vessels, and tissues in or around your brain, causing nerve pathways to be disrupted and bleeding or swelling to occur. Because your skull can't expand, increasing pressure can damage or destroy brain tissue, and sometimes severe brain damage can occur with what appears to be a minor head injury. Signs and symptoms of head injury that require immediate medical attention are loss of consciousness, confusion, drowsiness, personality change, inability to move a body part, severe headache, stiff neck, vomiting, blood on the scalp, convulsions, and loss of vision or blurred vision. Once you've sustained a head injury, your doctor may recommend a computed tomography (tawm-AW-gruh-fee), or CT (C-T), or magnetic resonance imaging, or MRI (M-R-I), scans to evaluate possible brain injury. Standard X-rays can identify skull fractures, but not brain injury.