AMS may represent early BBB disruption without frank edema
AMS-HACE continuum supported by MRI evidence
Not all AMS progresses to HACE
Therapeutic Considerations
Evidence base for treatments
Dexamethasone evidence
Reduces vasogenic edema via multiple anti-inflammatory mechanisms
Wilderness Medical Society Grade 1C recommendation for HACE treatment
Does not facilitate acclimatization (symptoms recur without true acclimatization)
Descent evidence
Gold standard treatment across all altitude illness guidelines
Every 300 m descent raises barometric pressure and alveolar PO2
Grade 1A recommendation in all society guidelines
Acetazolamide mechanism
Carbonic anhydrase inhibition
Produces bicarbonate diuresis and mild metabolic acidosis
Stimulates respiratory drive (corrects central sleep apnea at altitude)
Accelerates ventilatory acclimatization
Prophylactic efficacy established; therapeutic role in HACE limited
Primarily prevents AMS from progressing to HACE
Does not reverse established HACE
Gamow bag mechanism
Increases ambient pressure surrounding patient
Raises partial pressure of inspired oxygen
Equivalent to descent of 1,500–2,500 m physiologically
Limitation: symptoms recur on removal at same altitude
Temporizing measure only
Must be combined with pharmacologic therapy
Patient Discharge Instructions
copy discharge instructions
Diagnosis explanation
You were treated for High Altitude Cerebral Edema (HACE)
HACE is a life-threatening brain swelling caused by traveling to high altitude too quickly
Your brain did not have enough time to adjust to lower oxygen levels at altitude
You received dexamethasone (a steroid) and oxygen to reduce brain swelling
You have been moved to a lower altitude where you can recover safely
Medication instructions
Continue prescribed dexamethasone exactly as directed
Do not stop the steroid suddenly without physician guidance
Take with food to reduce stomach irritation
Acetazolamide if prescribed
Take with plenty of water
May cause increased urination and tingling in fingers and toes
Activity restrictions
No further ascent to high altitude until fully cleared by a physician
Do not attempt to return to altitude while still on dexamethasone
Minimum 2–3 days fully symptom-free before any future altitude attempt
Avoid strenuous physical activity for 1–2 weeks
Rest until all neurologic symptoms fully resolved
Follow-up instructions
Neurology follow-up within 1–2 weeks
MRI of the brain may be recommended to confirm full recovery
Cognitive assessment if experiencing memory or concentration problems
Primary care within 1 week for steroid taper management
Future altitude safety
Future ascents require slower ascent profile
Sleep altitude increase no more than 300–500 m per night above 3,000 m
Take one rest day for every 600–900 m of altitude gain above 3,000 m
Discuss acetazolamide prophylaxis for future altitude trips with your physician
Personal susceptibility is established; you are at higher risk for recurrence
Return to emergency department immediately if
Severe headache that does not respond to pain medication
Especially if worsening or different from usual headaches
Confusion, disorientation, or unusual behavior
Difficulty walking or loss of balance
Difficulty breathing or shortness of breath at rest
Coughing up pink or frothy sputum
Seizures
Loss of consciousness
Any new neurologic symptoms
Weakness on one side of the body
Slurred speech or vision changes
References
Guidelines and key sources
Wilderness Medical Society Clinical Practice Guidelines 2024
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 and Environmental Medicine 2024
Provides Grade 1A recommendation for descent in HACE
Grade 1C recommendation for dexamethasone in HACE
Acetazolamide 125–250 mg q12h for prophylaxis
Wilderness Medical Society Clinical Practice Guidelines 2019
Luks AM, Auerbach PS, Freer L, et al.
Wilderness and Environmental Medicine 2019
Microhemorrhage documentation and long-term HACE sequelae
CDC Yellow Book 2025
Hackett PH and Shlim DR
High-Altitude Travel and Altitude Illness
2025 edition; comprehensive traveler guidance
Landmark clinical studies
Bärtsch P, Swenson ER
Acute High-Altitude Illnesses
New England Journal of Medicine 2013
Comprehensive review of AMS, HACE, and HAPE pathophysiology and management
Hackett PH, Roach RC
High-Altitude Illness
New England Journal of Medicine 2001
Foundational pharmacologic treatment evidence
Hackett PH, Yarnell PR, Hill R, et al.
High-Altitude Cerebral Edema Evaluated With MRI: Clinical Correlation and Pathophysiology
JAMA 1998
Established T2/FLAIR corpus callosum splenium as MRI hallmark
Hackett PH, Yarnell PR, Weiland DA, Reynard KB
Acute and Evolving MRI of HACE: Microbleeds, Edema, and Pathophysiology
AJNR American Journal of Neuroradiology 2019
Characterized microhemorrhage pattern and "HACE footprint" on SWI
Additional references
Luks AM, Hackett PH
Medical Conditions and High-Altitude Travel
New England Journal of Medicine 2022
Comorbidities, special populations, and altitude-specific management
Gatterer H, Villafuerte FC, Ulrich S, et al.
Altitude Illnesses
Nature Reviews Disease Primers 2024
Current epidemiology, pathophysiology, and therapeutics
Wilson MH, Newman S, Imray CH
The Cerebral Effects of Ascent to High Altitudes
Lancet Neurology 2009
Neuroimaging and cerebrovascular mechanisms
Basnyat B, Murdoch DR
High-Altitude Illness
Lancet 2003
Clinical spectrum and management overview
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.