Concept Intracranial pneumoperitoneum is the entry of gas from the outside into the skull and its accumulation in the epidural, subdural, subarachnoid space, brain parenchyma, ventricles, or brain pools. Epidemiologic studies have found that intracranial pneumatosis is not uncommon in clinical practice and has multiple causes, most commonly cranial injury and surgery (e.g., chronic subdural hematoma drilling and ventriculo-abdominal shunts), followed by intracranial tumors and infection. A large prospective study found a 0.77% prevalence of intracranial pneumothorax. Of these, craniocerebral injury accounted for 81%, chronic subdural hematoma after borehole drainage for 13%, and intracranial tumors for 1.5%. Clinical features Most patients with intracranial pneumonia are often asymptomatic, but 3.9%-9.7% of patients with craniocerebral injury may experience an exacerbation of their condition due to intracranial pneumonia. It is important to note that intracranial pneumothorax can progress to tension pneumothorax, causing increased intracranial pressure and brain tissue compression and other symptoms. Although tension pneumothorax is rare clinically, it is a neurosurgical emergency and usually requires emergency surgical treatment. Therefore, the following section highlights the characteristics of tension pneumothorax. Overview Tension pneumothorax can have an acute onset (within 72 hours of cranial injury or surgery) or a delayed onset (beyond 72 hours). The incidence of delayed tonic pneumothorax is very low, and only a few cases have been reported. A review of cases of delayed tonic pneumothorax in the last 20 years revealed that septal sinus fractures and frontal sinus endplate fractures are common causes. Common symptoms of tension pneumothorax include headache, vomiting, cerebrospinal fluid nasal leakage, vision loss, drowsiness and coma, which can lead to patient death. Diagnosis The diagnosis is based on the history of cranial injury, surgery, tumor and infection, combined with clinical manifestations and cranial CT examination. It should be noted that the diagnosis of delayed-onset tension pneumothorax can be clarified as early as possible mainly by closely observing the changes of the patient’s condition and reexamining the cranial CT if necessary. Therefore, in clinical work, on the one hand, it is necessary to use standardized scales (e.g., GCS) to regularly assess the changes of patients’ injuries and pay attention to the monitoring of clinical indicators; on the other hand, it is necessary to dynamically observe the CT manifestations, for example, it has been reported in the literature that the typical “Fujiyama” sign of tension pneumothorax can be seen on CT scan, which is thought to be due to subdural pneumothorax For example, some literature reported that the typical “Mt. In addition, the typical “Fujiyama” sign may not be present in tension pneumothorax and may be present in any part of the skull. The arrows show the typical “Fujiyama” sign and the circles show the occupying effect of tonic pneumothorax, compression of brain tissue, and disappearance of the basal pool. Treatment After the diagnosis of tension pneumothorax, early surgical treatment should be performed, mainly by 1) emergency drilling and decompression, and continuous decompression with drainage tubes, 2) tight suturing of the dura mater, skull base reconstruction, and complete closure of the leak. In addition, to prevent excessive drainage of cerebrospinal fluid and to prevent tension pneumothorax caused by medical origin.