Usually, fever is divided into low fever, moderate fever, high fever and super high fever, and high fever is when the body temperature exceeds 39℃, which can easily affect the brain. In addition, when the body temperature exceeds 41℃, it is particularly likely to affect the brain. Usually, damage to neurons in the brain or damage to brain cells is caused by a lack of oxygen, or a lack of ATP energy and glucose release in the brain. When the body temperature is highly elevated, above 39°C for more than 24 hours, the body’s energy metabolism will be relatively slowed down and a transient ischemia and hypoxia of the cerebral vessels will occur. In the case of ischemia and lack of oxygen in brain cells, secondary brain neuron damage will occur if it exceeds 24 hours, so if the body temperature exceeds 39℃, it is especially likely to cause affect the brain.