A lot of the mountaineers I know have trouble remembering the small stuff — where their keys are, where they live, things like that. I always attributed it to post-summit celebrations, but now comes some scary research indicating that high-altitude climbing causes significant brain damage. Even more frightening is the fact that damage appeared in climbers who hadn't suffered any ill effects from pulmonary edema, cerebral edema, or acute mountain sickness.
Neurologists in Spain performed fMRI brain scans on 35 professional and amateur climbers after they returned from high-altitude mountaineering expeditions, including 13 who attempted Everest. The results are particularly dire for Himalayan climbers: Nearly all the Everest climbers showed some form of brain damage. Only one climber had a mild case of AMS, yet all of them except one — a pro — showed cortical atrophy or an enlargement of the spaces that surround the blood vessels that drain fluid from the brain. One of the amateurs also suffered from subcortical lesions in the frontal lobes. These symptoms are sometimes observed in the elderly, but rarely in the young and fit.
But lower-altitude climbers don't get off any easier. The scientists also scanned the brains of eight climbers after Aconcagua expeditions and seven after Mont Blanc attempts. All eight Aconcagua climbers showed signs of cortical atrophy, while two of the Mont Blanc climbers returned with enlarged spaces around the blood vessels of the brain. Unfortunately, the damage seems permanent: The neurologists reexamined the same climbers three years later (with no intervening high-altitude climbs), and could still identify brain injuries on fMRI scans.
Amateurs seem to be at greater risk for sudden brain damage, since they are more prone to suffering from AMS, HAPE, or HACE. But the cumulative cost of high-altitude acclimation weighs heaviest on the brains of professional guides: Pro climbers had greater overall amounts of cortical atrophy. Their long periods of acclimation make them feel stronger, but it leads to more long-term brain damage.
I imagine this news will arrive as a huge bummer for aspiring mountaineers who have dreams of conquering 8,000-meter peaks, but I doubt it will deter them. Many will no doubt happily recount their tales of returning from high peaks without any discernible symptoms or signs of brain damage. I've even tackled a few high peaks in my time, and so far hothing's nappened to by mrain.
Wait, what were we talking about? — Ted Alvarez
Into Thin Air: Mountain Climbing Kills Brain Cells (Scientific American)