Men’s Health has a piece on high-altitude cerebral edema. While the article is a novice’s account of climbing the Mexican volcano Pico de Orizaba, it provides great insight into how even the most physically trained people can fall victim.
High-altitude cerebral edema (HACE) can occur unpredictably at altitudes above 14,000 feet. Fluid fills the cavity between the brain and skull. The resulting pressure on gray matter induces headache, nausea, dizziness, emotionalism, seizures, disorientation, and, if left untreated (at higher altitudes, mostly), death. We all knew this. The best treatment is to head down the mountain. Immediately.