Contributor: Jorge Chalit-Hernandez, OMS3

Educational Pearls:

Acute mountain sickness (AMS) is the term given to what is otherwise colloquially known as altitude sickness
High altitude cerebral edema (HACE) is a severe form of AMS marked by encephalopathic changes
Symptoms begin at elevations as low as 6500 feet above sea level for people who ascend rapidly

Occurs in everyone ascending to high altitudes but is more pronounces in those that develop symptoms
The reduced partial pressure of oxygen induces hypoxic vasodilation in the brain, which results in edema and, ultimately, HACE in some patients

Headache, nausea, and sleeping difficulties occur within 2-24 hours of arrival at altitude
HACE may occur between 12-72 hours after AMS and presents with ataxia, confusion, irritability, and ultimately results in coma if left untreated

Clinical presentation may be mistaken for simple exhaustion, so clinicians should maintain a high index of suspicion

Notably, if symptoms occur more than 2 days after arrival at altitude, clinicians should seek an alternative diagnosis but maintain AMS/HACE on the differential

Adjunctive oxygen and descent to lower altitude
Acetazolamide is used as a preventive measure but is not helpful in acute treatment
+/- dexamethasone

References

Burtscher M, Wille M, Menz V, Faulhaber M, Gatterer H. Symptom progression in acute mountain sickness during a 12-hour exposure to normobaric hypoxia equivalent to 4500 m. High Alt Med Biol. 2014;15(4):446-451. doi:10.1089/ham.2014.1039
Levine BD, Yoshimura K, Kobayashi T, Fukushima M, Shibamoto T, Ueda G. Dexamethasone in the treatment of acute mountain sickness. N Engl J Med. 1989;321(25):1707-1713. doi:10.1056/NEJM198912213212504
Luks AM, Beidleman BA, Freer L, et al. Wilderness Medical Society Clinical Practice Guidelines for the Prevention, Diagnosis, and Treatment of Acute Altitude Illness: 2024 Update. Wilderness Environ Med. 2024;35(1_suppl):2S-19S. doi:10.1016/j.wem.2023.05.013

Summarized & Edited by Jorge Chalit, OMS3

Episode 942: Acute Mountain Sickness and High Altitude Cerebral Edema

Emergency Medical Minute