How long it takes for a patient to die from a brain hernia cannot be generalized and depends on the type of hernia, the patient’s underlying medical condition, and the type of treatment taken. The more severe cases of foramen magnum herniation may be fatal at any time without effective treatment. Brain tissue is squeezed and displaced by intracranial hypertension, and when the displacement exceeds a certain threshold, a brain hernia is formed. In general, the specific survival time of the patient varies depending on the type of herniation. When subfalx herniation occurs, if the lesion can be removed in a timely manner by surgery, the patient can return to a normal state and survive for a long time. In the case of cerebellar tegmental herniation, if the lesion can be released in a short time, the patient also has a hope of recovery. The most serious case is subungual herniation of the cerebellum, also known as foramen magnum herniation, in which the patient usually suffers respiratory and cardiac arrest rapidly after the onset of herniation due to brainstem compression. Brain herniation is a sign of critical condition, so the patient’s breathing, pulse, temperature, blood pressure and pupil changes should be closely monitored during the acute phase of the disease to detect brain herniation early and treat it actively to reduce the morbidity and mortality rate.