HACE is caused by the swelling of the brain from the dilation of the oxygen starved blood vessels and fluid leakage.

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The first symptom of HACE is loss of balance and muscular coordination, scientifically known as ataxia, this can progress to loss of mental function, hallucination, weakness on one side of the body and blurred vision.

The symptoms can develop over a few hours to a couple of days, a headache and nausea or vomiting are also very common amongst sufferers of HACE in addition to the combined symptoms of HAPE and if left untreated, HACE can become very serious leading to a coma and/or death.

Furthermore, a fast rate of ascent and extreme exertion can cause HAPE or HACE to develop suddenly without the progression from AMS.

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The risk factors associated with HACE could also affect much younger people, as there is less space within their skull for brain swelling to occur or in those who suffer head injuries at altitude.

The treatments for HACE are very similar to those of HAPE:

1. Descent should always be the first action taken, as then the symptoms to usually subside quicker are; the confusion and mental function
2. Where decent is not immediately possible the use of a hyperbaric bag will provide the same effect. When inflated, the hyperbaric bag produces a pressure that is equivalent to a decent of 1000m. This treatment can be used for up to 6 hours for sufferers of HACE. When signs of improvement occur ever effort should be taken to descend the patient.
3. Supplementary oxygen should be given, if possible, to any sufferers of HACE, for early HACE an oxygen flow of 2 to 4 litres per minute is recommended. However, for more severe cases an oxygen flow of 8 to 10 litres per minute is necessary .
4. The drug Dexamethasone can be taken to treat HACE, 8 to 10mg should initially be taken via the mouth followed by 4mg every 6 hours. If the patient enters or is in a coma, the airways must be managed to prevent further risk and medication should then be administered via injection.

‍References:

Barry, P.W. and Pollard, A.J. (2003) “Altitude illness”, British Medical Journal, 326(7395), pp.915-919.

Bezruchka, S. (2005) Altitude illness: Prevention & Treatment, Seattle: Mountaineers Books.

Luks, A.M., Auerbach, P.S., Freer, L., Grissom, C.K., Keyes, L.E., McIntosh, S.E., Rodway, G.W., Schoene, R.B., Zafren, K. and Hackett, P.H. (2019) “Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness: 2019 Update”, Wilderness & environmental medicine, 30(4), pp.3-18.