There are more causes of central nervous system infections, which are divided into the following categories according to the route of infection. First, direct infection, such as head injury, especially open cranial injury, easy to bacteria and other pathogens, etc. into the cranium to occur meningitis or brain abscess. Second, bloodstream infection, and through the infection of the blood, through the blood circulation pathogens easy to reach the brain and lead to intracranial infection. The most common clinical condition is lung infection leading to bacteremia and sepsis, which eventually leads to intracranial infection. Third, the main medical infection, sometimes puncture, surgery or invasive operation, bacteria through the open channel into the cranial and appear symptoms of infection of the central nervous system. Fourth, there are also pathogenic bacteria, such as tuberculosis, fungi, parasites, etc. are also factors leading to intracranial infections.