The medulla is easily the most important part of the brain. It's functions are involuntary, or done without thought. We would not be able to live without the medulla because of the myriad of crucial tasks it performs including regulating blood pressure and breathing. As a part of the brain stem, it also helps transfer neural messages from the brain to the spinal cord.
During brain surgery, a surgeon has to be extremely cautious, or careful not to damage any part of the medulla. Although damage to other parts of the brain can be dealt with accordingly, damage to the medulla is the hardest to fix because of the many important functions that it carries out.