Increased intracranial pressure is a common clinicopathological syndrome in neurosurgery, which is a common symptom of craniocerebral injury, brain tumor, cerebral hemorrhage, hydrocephalus and intracranial inflammation, etc. Due to the increase in volume of cranial cavity contents caused by the above diseases, the intracranial pressure continues to be above 2.0kPa (200mmH20), resulting in the corresponding syndrome called increased intracranial pressure. Increased intracranial pressure can lead to brain herniation crisis, which can cause death due to respiratory and circulatory failure, so it is important to diagnose and properly manage increased intracranial pressure in a timely manner. The cranial cavity holds three kinds of contents: brain tissue, cerebrospinal fluid and blood, and when the cranial suture is closed in children or adults, the volume of the cranial cavity is fixed, which is about 1400-1500 ml. The three kinds of contents in the cranial cavity maintain a certain pressure inside the cranium, which is called intracranial pressure (ICP). Since the intracranial cerebrospinal fluid lies between the cranial cavity wall and the brain tissue, the intracranial pressure is generally represented by the hydrostatic pressure of the cerebrospinal fluid, which is measured by lumbar puncture in the lateral position or by direct ventricular puncture to obtain this pressure value. Clinical intracranial pressure can also be continuously and dynamically observed by using intracranial pressure monitoring devices. Regulation and compensation of intracranial pressure: Intracranial pressure can fluctuate in a small range, which is closely related to blood pressure and respiration, with a slight increase in systolic intracranial pressure and a slight decrease in diastolic intracranial pressure; a slight increase in pressure during expiration and a slight decrease in pressure during inspiration. The regulation of intracranial pressure is mainly regulated by the increase or decrease of cerebrospinal fluid volume, in addition to partly relying on the intracranial venous blood being drained to the extracranial circulation. When the intracranial pressure is lower than 0.7 kPa (70 mmH20), the secretion of cerebrospinal fluid increases and the absorption decreases, resulting in an increase in the amount of intracranial cerebrospinal fluid to maintain a constant normal intracranial pressure. On the contrary, when the intracranial pressure is higher than 0.7kPa (70mmH2O), the secretion of cerebrospinal fluid decreases and the absorption increases, keeping the intracranial cerebrospinal fluid volume in the normal range to compensate for the increased intracranial pressure. In addition, when the intracranial pressure increases, some of the cerebrospinal fluid is squeezed into the subarachnoid space of the spinal cord, which also plays a role in regulating the intracranial pressure. The total volume of cerebrospinal fluid accounts for 10% of the total volume of the cranial cavity, while blood accounts for about 2%-11% of the total volume depending on the blood flow, and generally speaking, the critical volume allowed to increase intracranially is about 5%, beyond which the intracranial pressure begins to increase. When the volume of the cranial contents increases or the volume of the cranial cavity is reduced by more than 8-10% of the cranial volume, a severe increase in intracranial pressure is produced. The causes of increased cranial pressure can be divided into three main categories: 1. Increased volume of cranial cavity contents such as increased volume of brain tissue (cerebral edema), increased cerebrospinal fluid (hydrocephalus), obstructed intracranial venous reflux or excessive perfusion, and increased cerebral blood flow, resulting in increased intracranial blood volume. 2.Intracranial occupying lesions make the intracranial space relatively small such as intracranial hematoma, brain tumor, brain abscess, etc. 3, congenital malformation makes the volume of cranial cavity become smaller such as narrow skull, skull base depression, etc.