The brain is a high-level system that combines beauty and wisdom in the human body. Do not look at the head melon hard, hard as a wall, but, if there is a traumatic brain injury, brain tumors and other diseases, or even unknown to squeeze the face of the acne, the opportunity to contact with the outside world inside the head will be greatly increased. Thus, many small organisms from the outside can take advantage of the opportunity to sneak into the human body and make a fuss, and it will be uncomfortable, which is the intracranial infection. These small organisms can be called pathogenic microorganisms, which generally include bacteria, fungi, and viruses. The intracranial infections mentioned here are generally pathogenic microbial infections such as bacteria and fungi; if the intracranial infection is caused by a virus, it is called viral encephalitis. For the time being, viral encephalitis is excluded from the discussion. Common bacteria that cause intracranial infections include Acinetobacter baumannii, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, and so on. Bloodstream infections are mainly caused by open cranial injury, after craniotomy, and when bacteria from various other sites of infection reach the cranium with the blood. The early stage of intracranial infection occurs, usually 2 to 3 days after craniotomy or open craniosynostosis, with symptoms of fever, headache, and neck stiffness. Once the body fails to stop the attack of the bacterial and fungal little devils, the symptoms of infection will worsen and it will further develop into high fever, convulsions, epilepsy, and even coma. Of course, there is also the problem of intracranial pressure. The head is filled with cerebrospinal fluid, which then brings a certain pressure to the brain, with a normal pressure of 10 to 15 mmHg. If there is an intracranial infection, the intracranial pressure may increase, and the patient will feel dizzy and have a headache. If the intracranial pressure continues to increase, brain herniation may even occur until death. Moreover, intracranial infection is a complication after craniocerebral trauma and hyperbaric cerebral hemorrhage, which not only prolongs the hospital stay and increases the medical cost of the injured person, but also can affect the prognosis of the patient and can lead to the death of the patient in serious cases. Therefore, patients with abnormal postoperative body temperature (persistently higher than 38°) must be alerted to intracranial infection.