The cause of brain edema following HSES remains unclear, however, Unterberg et al. reported that brain edema of traumatic brain injury was associated with various mediators including cytokines, lactate, free oxygen radicals, etc. [30] . Brain edema in HSES patients seems to occur in such a situation. Because the serum levels of cytokines and lactate had increased, an increase in vascular permeability was suggested by our patients needing large amounts of fluids. Furthermore, large amounts of fluid-resuscitate within 24 hours of admission may lead to brain edema under the state of increasing vascular permeability.