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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. If untreated, patients usually die within 48 hours, and those who receive treatment often take days or weeks to fully recover. It is a rare condition, occurring in less than one percent of people who ascend to . First described in 1913, little was known about the etiology of the condition until MRI studies were performed in the 1990s. ==Signs and symptoms== Early symptoms of high-altitude cerebral edema (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. Sufferers generally attempt to cease physical activities, regardless of their necessity for survival. Severe headaches develop and sufferers lose the ability to sit up. Retinal venous dilation occurs in 59% of people with HACE. Rarer symptoms include brisk deep tendon reflexes, retinal hemorrhages, blurred vision, extension plantar reflexes, and ocular paralysis. Cranial nerve palsies occur in some unusual cases. In the bestselling 1996 non-fiction book ''Into Thin Air: A Personal Account of the Mt. Everest Disaster'', Jon Krakauer describes the effects of HACE upon Dale Kruse, a forty-four-year-old dentist and one of the members of Scott Fischer's team: '' Kruse was having an incredibly difficult time simply trying to dress himself. He put his climbing harness on inside out, threaded it through the fly of his wind suit, and failed to fasten the buckle; fortunately, Fisher and Neal Beidleman noticed the screwup before Kruse started to descend. "If he'd tried to rappel down the ropes like that," says Beidleman, "he would have immediately popped out of his harness and fallen to the bottom of the Lhotse Face." "It was like I was very drunk," Kruse recollects. "I couldn't walk without stumbling, and completely lost the ability to think or speak. It was a really strange feeling. I'd have some word in my mind, but I couldn't figure out how to bring it to my lips. So Scott and Neal had to get me dressed and make sure my harness was on correctly, then Scott lowered me down the fixed ropes." By the time Kruse arrived in Base Camp, he says, "it was still another three or four days before I could walk from my tent to the mess tent without stumbling all over the place."'' Patients with HACE have an elevated white blood cell count, but otherwise their blood count and biochemistry is normal. If a lumbar puncture is performed, it will show normal cerebral spinal fluid and cell counts but an increase in pressure. In one study, CT scans of patients with HACE exhibited ventricle compression and low density in the cerebellum. Only a few autopsies have been performed on fatal cases of HACE; they showed swollen gyri, spongiosis of white matter, and compressed sulci. There was some variation between individuals, and the results may not be typical of HACE deaths. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「High-altitude cerebral edema」の詳細全文を読む スポンサード リンク
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