General description

High altitude cerebral edema (HACE) is a rare but severe condition that can occur following acute mountain sickness (AMS), which is characterized by symptoms such as headache, nausea, insomnia, and fatigue. HACE typically manifests 1–5 days after rapid ascent to high altitudes, usually above 3,000 meters, and presents with symptoms of altered consciousness, ataxia, and progressive cerebral edema. If left untreated, it can rapidly progress to coma and death, sometimes within 2–3 hours. The most critical factor contributing to its onset is the speed of ascent, with increases of more than 600 meters within 24 hours posing significant risk. HACE is often accompanied by retinal hemorrhages and is considered the most severe form of AMS.

The underlying mechanism of HACE involves vasogenic and cytotoxic edema caused by hypoxia. Without timely treatment, brain herniation can occur, leading to fatal outcomes. In some cases, after the resolution of AMS through descent or treatment, patients may experience delayed neuropsychiatric symptoms, sometimes after a lucid interval of up to a month. These symptoms can include personality changes (apathy, indecision, lack of motivation), cognitive impairments, and Parkinsonism.

Radiographic features

MRI shows T2WI hyperintensity in the cerebral white matter, along with T2WI hyperintensity in the splenium of the corpus callosum in all cases. Follow-up MRI reveals the resolution of these findings, indicating reversible cerebral vasogenic edema. Microbleeding in the splenium of the corpus callosum may also be observed, appearing as hypointensity on T2*WI and SWI.

In patients with neuropsychiatric symptoms following HACE, MRI shows T2WI hyperintensity in the globus pallidus, suggesting irreversible necrotic changes.