When there is an occupying lesion in a subchamber of the cranial cavity, the pressure in that subchamber is higher than the pressure in the adjacent subchamber, and brain tissue is displaced from the high-pressure area to the low-pressure area, thus causing a series of clinical syndromes called cerebral herniation. The supratentorial brain tissue (hippocampal gyrus and hook gyrus of the temporal lobe) is squeezed through the cerebellar curtain notch to the inferior curtain, which is called cerebellar curtain notch herniation or temporal lobe herniation. The inferior cerebellar tonsils and medulla oblongata are squeezed into the spinal canal through the foramen magnum, which is called herniation of the foramen magnum or herniation of the cerebellar tonsils. The cingulate gyrus of one cerebral hemisphere is squeezed into the contralateral compartment through the subfalx foramen, which is called subfalx herniation or cingulate herniation. Herniation can be caused by any large intracranial occupying lesion that causes uneven pressure distribution in the cranial cavity. If the lesion is supratentorial, it can cause a herniation of the cerebellar curtain, and if the lesion is infratentorial, it can cause a herniation of the foramen magnum. The common lesions that cause brain herniation are: (1) various intracranial hematomas caused by injury, such as acute epidural hematoma, subdural hematoma and intracerebral hematoma; (2) various intracranial tumors, especially those located in one cerebral hemisphere and posterior cranial fossa; (3) intracranial abscess; (4) intracranial parasitic diseases and other chronic granulomas. If some artificial factors are added to the above mentioned lesions, such as the release of excessive cerebrospinal fluid by lumbar puncture, which increases the pressure difference between the cranial cavity and the vertebral canal, and between the supratentorial and infratentorial cavities, the formation of cerebral herniation can be promoted. This kind of brain herniation caused by medical factors should be avoided by clinicians. What are the symptoms of cerebral herniation (a) cerebellar herniation 1. symptoms of increased intracranial pressure: severe headache and frequent vomiting, the degree of which is more aggravated than before cerebral herniation, and irritability. 2. changes in consciousness: drowsiness, shallow coma or even coma, and dull or absent response to external stimuli. 3. pupillary changes: unequal pupils on both sides, slightly narrowed pupil on the sick side at the beginning, slightly dulled light response, and later The pupil on the sick side is gradually dilated, slightly irregular, and the direct and indirect light response disappears, but the pupil on the opposite side can still be normal, which is due to the compression and pulling of the articular nerve on the affected side. In addition, the affected side may also have ptosis and exophthalmos. If the brain herniation continues to develop, the pupils may become dilated bilaterally and the light response may disappear, which is caused by the malfunction of the nucleus accumbens in the brainstem. 4. The continued development of brain herniation causes the symptoms to spread bilaterally, resulting in decreased muscle strength of the limbs or intermittent head and neck tilting back, straightening of the limbs, and dorsal hyperextension of the torso in the form of coracocephaly, which is a characteristic manifestation of severe brainstem damage. 5. In severe cases, blood pressure may be high and low, respiration may be fast and slow, sometimes the face is flushed and sweating profusely, sometimes it turns pale and sweating closed, the body temperature may be as high as 41℃ or more, or it may be as low as 35℃ or less without rising, and finally the respiration stops, and finally the blood pressure drops and the heart stops and death occurs. (ii) Occipital foramen hernia: the patient often has only severe headache, repeated vomiting, disturbance of vital signs and neck tonicity, pain, late onset of consciousness changes, no pupil changes and early onset of respiratory arrest. (c) Subfalx herniation: It causes softening and necrosis of the brain tissue in the compressed part of the medial side of the cerebral hemisphere on the side of the disease, and symptoms such as mild paralysis of the contralateral lower limb and urinary disorder appear.