Hyperpyrexia is an extreme elevation of body temperature which, depending upon the source, is classified as a core body temperature greater than or equal to 40.0 or 41.5 °C (104.0 or 106.7 °F).[31][32][33] Such a high temperature is considered a medical emergency, as it may indicate a serious underlying condition or lead to problems including permanent brain damage, or death.[34] The most common cause of hyperpyrexia is an intracranial hemorrhage.[5][33] Other possible causes include sepsis, Kawasaki syndrome,[36] neuroleptic malignant syndrome, drug overdose, serotonin syndrome, and thyroid storm.[34]