High altitude cerebral edema

High altitude cerebral edema (or HACE) is a severe (frequently fatal) form of altitude sickness. HACE is the result of swelling of brain tissue from fluid leakage. Symptoms can include headache, loss of coordination (ataxia), weakness, and decreasing levels of consciousness including disorientation, loss of memory, hallucinations, irrational behavior, and coma. It generally occurs after a week or more at high altitude, but symptoms of mild HACE can sometimes show up even after few hours at higher altitudes. Severe instances can lead to death if not treated quickly. Immediate descent is a necessary life-saving measure (2,000 - 4,000 feet). There are some medications (e.g. dexamethasone) that may be prescribed for treatment in the field, but these require proper medical training in their use. Anyone suffering from HACE must be evacuated to a medical facility for proper follow-up treatment. A Gamow bag can sometimes be used to stabilize the sufferer before transport or descending.

Climbers may also suffer high altitude pulmonary edema (HAPE).