The brain can swell when it is injured just like any other part of the body. Swelling is the result of blood flowing to the injured area. Unfortunately, when excess blood flows to the brain area it can lead to a number of problems, some of which were discussed above. Because the brain is encapsulated within the skull that does not expand, the excess blood causes pressure to build up. This intracranial pressure pushes down on the brain and can damage its structure or restrict its necessary blood flow. Too much pressure against the brain can interfere with its critical functions, such as control of the heart rate and breathing. If the pressure is not relieved quickly, the damage will continue and the patient could suffer permanent brain damage or death. Doctors can perform surgery to drain the excess blood and install a valve, known as an intracranial monitor or ICP, to help release the excess pressure.