A jolt, injury, blow or penetration to the head can cause traumatic brain injury, or TBI, which can lead to permanent disability or death, according to the Centers for Disease Control and Prevention. TBI causes a disruption in normal brain function that can result in a range of brief or long-term functional abnormalities, including issues related to reasoning, sensation, emotion and language. It can also cause loss of consciousness, amnesia, epilepsy and increase future risk of Alzheimer’s and Parkinson's disease.
A head injury may be closed, as occurs when a blow to the head does not penetrate the skull, or open, which means that the blow penetrated the skull and brain, as MedlinePlus explains. Concussions, which describe when a blow shakes the brain, are the most common form of traumatic head injury. The brain can sustain bruising even if the injury is closed, causing swelling inside the skull or bleeding in the brain tissue or surrounding layers. Severe head trauma is likely to damage the spinal cord, and other types of injuries include scalp wounds and skull fractures.
Many symptoms occur immediately, but some symptoms can develop and appear over time, according to MedlinePlus. It is critical to get immediate medical attention if a head injury causes a person to behave abnormally, become very sleepy, lose consciousness, vomit or lose the ability to move limbs. Other indications of severe trauma from a blow to the head include headache, a stiff neck or a change in the size of pupils.