What are Symptoms of High Altitude Cerebral Edema?

High Altitude Cerebral Edema: Key Signs, Causes & Treatment

High-altitude cerebral edema (HACE) is a rare but crucial condition in which the brain expands because of a lack of oxygen at higher elevations. If your body isn't able to adjust properly, fluid leaks into the brain, increasing the pressure within the skull.

The first signs are extreme headache, nausea, fatigue, dizziness, and trouble sleeping. These symptoms are similar to acute mountain sickness (AMS). As HACE advances, the patient may become unstable (ataxia) and be confused or behave strangely, as well as speak with confusion and experience fatigue.

In the most severe instances, the person's consciousness can diminish, and coordination deteriorates. Medical attention and immediate descent are essential.

Read on to know the symptoms, causes, and treatment of high-altitude cerebral edema!

What are the Signs of High Altitude Cerebral Edema?

High-altitude cerebral edema (HACE) is a severe, life-threatening form of altitude sickness. It causes the brain to swell due to low oxygen levels at high elevations. This usually develops after 2–5 days at altitudes above 4,000 m (13,100 ft) and often follows milder altitude sickness symptoms, such as headache, nausea, or dizziness.

Common HACE symptoms are:

1. Severe Headache: A pounding or persistent head pain that doesn’t improve with rest or medication.
2. Loss of Coordination (ataxia): Difficulty walking, stumbling, or losing balance, often the first clear neurological sign.
3. Extreme Tiredness or Weakness: Feeling unusually exhausted or unable to do even simple tasks.
4. Confusion or Altered Thinking: Trouble focusing, memory lapses, disorientation – you might even seem “off” to others.
5. Slurred Speech: Difficulty communicating clearly; words may come out jumbled.
6. Dizziness, Nausea, or Vomiting: Feeling lightheaded, sick to your stomach, or actually vomiting.
7. Drowsiness or Decreased Alertness: Feeling overly sleepy, lethargic, or very slow to respond.
8. Visual Changes or Hallucinations: Blurred vision, seeing things that aren’t there.
9. Seizures or Loss of Consciousness: In extreme cases, seizures may occur, or the person may collapse or fall unconscious.

HACE is rare, affecting less than 1% of people above 4,000 m, but it can rapidly become fatal within 24 hours if not treated. At the first signs of the symptoms above, descent to a lower altitude and urgent medical care are essential.

What are the Causes of High Altitude Cerebral Edema?

The causes of high-altitude cerebral edema are as follows:

1. Rapid Ascent to High Elevations: Reaching altitudes above 2,500–4,000 m too quickly overwhelms the body’s natural ability to adapt.
2. Insufficient Acclimatisation: Without spending enough time at intermediate stages, low oxygen (hypoxia) stresses the brain and circulatory system.
3. Primary Altitude Sickness: HACE often develops after acute mountain sickness (AMS); symptoms like headache and nausea precede brain swelling.
4. Hypoxia-Induced Brain Vessel Widening: Low oxygen causes cerebral blood vessels to dilate and leak fluid through the blood–brain barrier, raising pressure in the skull.
5. Microvascular Stress and Barrier Breakdown: Swelling occurs when tiny blood vessels in the brain lose integrity under increased pressure, allowing fluid to enter brain tissue.
6. Individual Vulnerability: Genetics, past altitude problems, strenuous physical activity, and fast climbing pace all increase risk.

How to Treat High Altitude Cerebral Edema?

High-altitude cerebral edema is treated as follows:

1. Immediate Descent: The top priority is to descend promptly, ideally by at least 300 m (1,000 ft), aiming for a 300–1,000 m lower elevation, until symptoms improve.
2. Supplemental Oxygen: Provide oxygen to maintain blood saturation above 90%; it helps reduce brain swelling and supports symptom relief.
3. Dexamethasone Administration: Administer dexamethasone (e.g., 8 mg initially, then 4 mg every 6 hours) to quickly reduce cerebral edema. It offers swift symptom relief, though it doesn’t aid acclimatisation.
4. Portable Hyperbaric Chamber (If Descent Isn’t Possible): Use a Gamow-style bag to simulate descent by 1,000–3,000 m when evacuation isn’t feasible; it should be seen as a temporary measure.
5. Acetazolamide and Prevention Strategies: Though not useful during an acute HACE attack, acetazolamide helps acclimatisation and reduces future risks when used early.

High‑altitude cerebral edema is a rare but life-threatening brain swelling caused by rapid ascent and inadequate acclimatisation. Immediate descent, oxygen, and corticosteroids are essential for recovery.

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