HACE is a severe form of acute mountain sickness characterized by ataxia, fatigue, and altered mental status. It results from cerebral edema caused by hypoxia-induced vasodilation and disruption of the blood-brain barrier at high altitudes. Treatment requires immediate descent to lower altitude, use of portable hyperbaric chambers or supplemental oxygen, and medications like dexamethasone and acetazolamide to reduce swelling and inflammation in the brain. Left untreated, HACE can rapidly progress to coma and death from brain herniation.

1. High Altitude Cerebral Edema
- Acute Mountain Sickness -
Ade Wijaya, MD – December 2018

2. Introduction
• HACE is a severe and potentially fatal manifestation of high altitude
illness and is often characterized by ataxia, fatigue, and altered
mental status
• An extreme form/end-stage of Acute Mountain Sickness (AMS)
• It may progress rapidly to coma and death as a result of brain
herniation within 24 hours, if not promptly diagnosed and treated
• 0.5-1% at altitudes of 4000-5000 m

3. Risk Factors
• Prior history of high altitude illness
• Lack of acclimatization
• Heavy physical exertion
• Rapid rate of ascent
• Abrupt ascent from lower altitudes

4. Pathophysiology (1)
• Altitude elicits neuro-hormonal (VEG-F, Nitric Oxide, reactive
cytokines, free radicals) and hemodynamic responses resulting in
hypoxia-induced cerebral vasodilation leading to over perfusion of
microvascular cerebral beds.
• This leads to intracranial hypertension with elevated capillary
pressure and capillary leakage. The disruption of the blood-
brain barrier from these stressors leads to subsequent cerebral
edema

5. Pathophysiology (2)
• Hypoxia induces free radical formation causing damage/failure of the
Na+/K+ ATPase Pump with resultant astrocyte swelling from osmotic-
oxidative stress, with subsequent cytotoxic edema.

6. Clinical Presentation
• Ataxia
• Severe headache
• Difficulty speaking
• Lassitude
• A decline in the level of consciousness
• Focal neurological deficits
• Seizures
• Preceded by AMS symptoms: headache, fatigue, nausea, insomnia,
and/or lightheadedness

7. Evaluation
• Elevated WBC
• Lumbar puncture: elevated opening pressure
• Neuroimaging: cerebral edema

8. Differential Diagnosis
• Dehydration
• Hypoglycemia
• Hypothermia
• Hyponatremia

9. Management
• Immediate descent of at least 1000m or until symptoms improve
(with assistance)
• Portable hyperbaric chamber and/or supplemental oxygen
• Dexamethasone 8mg for one dose, followed by 4mg every 6 hours
should be given to adults via PO, IM, or IV routes. Pediatric dosing is
0.15 mg/kg every 6 hours.
• Acetazolamide is 250 mg PO, given twice daily

10. Summary
• HACE is a severe form of AMS with potentially fatal neurological
symptoms
• Ataxia, fatigue, and altered mental status
• Treatment: immediate descent, hyperbaric chambers (portable),
supplemental oxygen, dexamethasone, acetazolamide

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