Epidemiology
HACE occurs in 0.5% to 1% of people who climb or trek between 4,000 metres (13,000 ft) and 5,000 metres (16,000 ft). In some unusual cases, up to 30% of members of expeditions have had the condition. The condition is seldom seen below 3,000 metres (9,800 ft), but in some rare cases it has developed as low as 2,500 metres (8,200 ft). The condition generally does not occur until an individual has spent 48 hours at an altitude of 4,000 metres (13,000 ft). History
HACE was first described by a medical officer stationed in Chile in 1913, but few took note of it. Later, access to air travel made the condition more common because it allowed more people access to high mountains, such as those in the Himalayas. One early description of HACE may have been published in 1969 after a group of Indian soldiers made a rapid ascent to almost 6,000 metres (20,000 ft). It is not definitely established whether they had HACE or acute decompression sickness. MRI has been used to study the effects of high altitude on the brain, providing the best evidence about the condition. A 1998 MRI study of nine climbers with HACE clearly demonstrated vasogenic edema.Data about HACE are lacking because it generally occurs in remote areas, far from hospitals and is generally rare. It is uncommon for doctors to be able to study victims within six days of the conditions development. Animal models of HACE have not been developed.
High-altitude cerebral edema (HACE) is a medical condition in which the brain swells with fluid because of the physiological effects of traveling to a high altitude. It generally appears in patients who have acute mountain sickness and involves disorientation, lethargy, and nausea among other symptoms. It occurs when the body fails to acclimatize while ascending to a high altitude. It appears to be a vasogenic edema (fluid penetration of the blood–brain barrier), although cytotoxic edema (cellular retention of fluids) may play a role as well. Individuals with the condition must immediately descend to a lower altitude or coma and death can occur. Patients are usually given supplemental oxygen and dexamethasone as well. HACE can be prevented by ascending to heights slowly to allow the body more time to acclimatize. Acetazolamide also helps prevent the condition. Untreated patients usually die within 48 hours. Those who receive treatment may take weeks to fully recover. It is a rare condition, occurring in less than one percent of people who ascend to 4,000 metres (13,000 ft). Although it was first described in 1913, little was known about the cause of the condition until MRI studies were performed in the 1990s. Signs and symptoms
Early symptoms of HACE generally correspond with those of moderate to severe acute mountain sickness (AMS). Initial symptoms of HACE commonly include confusion, loss of consciousness, fever, ataxia, photophobia, rapid heart beat, lassitude, and an altered mental state. Those affected generally attempt to cease physical activities, regardless of their necessity for survival.