A ruptured aneurysm is a medical emergency because it can cause bleeding in the brain. An aneurysm is an abnormal bulge or ballooning in the wall of a blood vessel. According to the Centers for Disease Control and Prevention, approximately 6 million people are living with unruptured brain aneurysms. Dr. Bernard Bendok, a Mayo Clinic neurosurgeon, says a ruptured aneurysm can be life-threatening.