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Acute mountain sickness and high altitude cerebral edema

Scott A Gallagher, MD
Peter Hackett, MD
Section Editor
Daniel F Danzl, MD
Deputy Editor
Jonathan Grayzel, MD, FAAEM


Anyone who travels to high altitude, whether a recreational hiker, professional mountain climber, or rescue worker, is at risk of developing high altitude illness. Acute mountain sickness (AMS) and high altitude cerebral edema (HACE) represent a continuum of one form of such illness.

The pathophysiology, clinical presentation, treatment, and prevention of AMS and HACE are reviewed here. Other forms of high altitude illness are discussed separately. (See "High altitude pulmonary edema" and "High altitude illness: Physiology, risk factors, and general prevention".)


Acute mountain sickness (AMS) and high altitude cerebral edema (HACE) are generally considered to represent two points along a single spectrum of disease, with the same underlying pathophysiology. Although several aspects of this pathophysiology remain unclear, the concept that AMS/HACE represents a continuum, and that AMS can progress to fatal HACE, fits with clinical experience and is helpful for management. A full discussion of the pathophysiology of AMS and HACE is beyond the scope of this review, but may be found in the attached references [1,2].

Cerebral edema is consistently found in neuroimaging and at autopsy in patients with severe AMS or HACE [1,3,4]. MRI studies reveal reversible vasogenic brain edema, with characteristic T2 signal increase in the splenium of the corpus callosum and subcortical white matter. These findings indicate increased blood-brain barrier (BBB) permeability.

Some hypotheses to explain this increased cerebral vascular permeability emphasize the role of increased intravascular pressure. Increased cerebral blood flow and the loss of autoregulation of intracranial pressure may contribute to such an increase. Chemical factors (eg, vascular endothelial growth factor, nitric oxide, cytokines) may also play a role by altering endothelial permeability [5,6].

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Literature review current through: Nov 2017. | This topic last updated: Mar 03, 2016.
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