science

High-altitude cerebral edema

High-altitude cerebral edema is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand High-altitude cerebral edema rather than just read about it. In short: 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.

Key takeaways

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Reference excerpt

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. Severe headaches develop and people 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, Fischer 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 are 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.

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Illustrations

Worked examples

Example 1 — a first encounter with High-altitude cerebral edema

Start with the simplest possible case. Write down what High-altitude cerebral edema claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to High-altitude cerebral edema before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about High-altitude cerebral edema ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of High-altitude cerebral edema

In research: High-altitude cerebral edema appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses High-altitude cerebral edema in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: High-altitude cerebral edema is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cerebrum, Mountaineering and health, so understanding it makes those chapters shorter.
In everyday life: Look for High-altitude cerebral edema outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study High-altitude cerebral edema in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what High-altitude cerebral edema means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain High-altitude cerebral edema out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is High-altitude cerebral edema in simple terms?

Why does High-altitude cerebral edema matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study High-altitude cerebral edema?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on High-altitude cerebral edema.