Intracranial infection is a common disease of the nervous system in children, because children have a lower level of immunity and imperfect function than adults, and are susceptible to infectious diseases, and viruses, bacteria and fungi can spread to the nervous system causing intracranial infections. The first is lumbar cerebrospinal fluid examination, which is a necessary test for the diagnosis of encephalitis and cannot be replaced by other tests; 2. This is because MRI is more sensitive to inflammatory changes, while CT is sensitive to lesions such as hemorrhage, calcification, and fractures, which can be used to understand the involvement of the brain parenchyma and its extent; 3. Many parents are resistant to lumbar cerebrospinal fluid testing because they believe that it is an invasive test that may cause some damage to the child or even leave neurological sequelae. The most common adverse reactions are pain at the puncture site and pain in the lower extremities, collectively known as post-lumbar puncture syndrome, which spontaneously resolves after 3-5 days, but does not occur in most children. Why is the importance of lumbar puncture for cerebrospinal fluid examination emphasized here? Early antibiotic application is needed because this type of encephalitis, which progresses rapidly, may present early with infectious shock, which is life-threatening. In the clinical aspect, it is often faced with the difficulty of diagnosing intracranial infection, while the exact nature is unknown, because when cerebrospinal fluid examination is performed after treatment, the results are mostly atypical changes, which makes it difficult to determine the nature of encephalitis, making it more difficult to diagnose and even to determine the specific course of treatment for your child, which is overall detrimental to disease treatment. Therefore, if your child is unfortunate enough to have encephalitis, it is better to bite the bullet and have a lumbar cerebrospinal fluid examination as soon as possible to clarify the diagnosis, which is more conducive to the choice of medication and the general determination of the specific course of treatment.