Cerebral edema (CE), or "brain swelling," can also occur with severe DKA. It is unclear what causes CE in children with DKA. Proposed mechanisms include changes in blood flow to the brain, inflammatory mediation, and alteration in the intracellular and extracellular fluid composition in the brain. CE can be "clinically apparent" or "subclinical" in terms of symptomatology. Children with clinically apparent DKA-related CE present with neurologic deficits and altered mental status. These children are at risk for herniation of the brain stem due to elevated pressures in and around the brain, and ultimately death. The neurologic manifestations of clinically apparent DKA-related CE typically occur 4-12 hours after the initiation of medical therapy. However, cases have been reported to occur prior to initiation of therapy. Although clinically apparent DKA-related CE is rare, occurring in 0.5-1% of children with DKA, subclinical DKA-related CE is much more common with estimates suggesting that up to 54% of children with DKA have underlying CE that goes clinically undetected. Early identification of both clinically apparent and subclinical DKA-related CE is critical as the time between initial neurologic symptoms and clinical deterioration can be as little as 3 hours. Moreover, early identification of subclinical DKA-related CE may lead to differences in medical therapy.