Cerebral edema can lead to coma. In severe cases, cerebral edema can lead to increased intracranial pressure, which can cause brain herniation leading to death, and may also cause impaired consciousness, including coma, lethargy, somnolence, and vegetative state, decortication, etc. Most of them are caused by intracerebral organic lesions. Common diseases include massive cerebral infarction, massive cerebral hemorrhage, subarachnoid hemorrhage, severe encephalitis, severe craniocerebral trauma, and cerebral parasitic infections. Hypertensive encephalopathy can be caused by patients with severe hypertension, which can also lead to impaired consciousness, toxic encephalopathy, and severe carbon monoxide poisoning. If the patient has toxic encephalopathy, it can also be caused by severe carbon monoxide poisoning. The patient should be treated for different causes, and the cranial pressure should be lowered and the brain should be awakened.