Depending on the degree of damage to brain tissue and the severity of cerebral edema, individualized differences vary, and the time from eye-opening coma to wakefulness due to cerebral edema in patients varies, but there are no accurate data. Cerebral edema refers to brain tissue lesions caused by a variety of intracranial and systemic diseases, such as cerebral hemorrhage, cerebral infarction, intracranial infections, brain tumors and cerebral ischemia and hypoxia, which are manifested by an abnormal increase in the amount of water in the brain tissues, an increase in the brain volume, and an increase in intracranial pressure. Generally, if the area of brain tissue damage is small and the degree of cerebral edema is light, the patient can recover consciousness soon after dehydration and symptomatic treatment. If the area of brain tissue damage is large and the degree of cerebral edema is heavy, the patient may be in a long-term or even permanent coma even after the cerebral edema subsides. Cerebral edema is characterized by rapid onset and rapid progression, which can lead to compression coma and serious complications such as cerebral hernia in a short period of time, endangering the patient’s life. Therefore, patients need to be actively treated, follow the medical advice, individualized medication, and quickly wake up in a few days and weeks, or may not be able to wake up permanently.