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The descent is always the most dangerous part of the climb. Returning unharmed to base camp has stymied some of the most talented mountaineers in history. According to a new study by researchers at Miguel Servet University Hospital in Zaragoza, Spain, very few high-altitude climbers actually do return unharmed. The study, by doctors Nicolas Fayed, Pedro J. Modrego and Humberto Morales, scanned thirty-five high-altitude climbers’ brains with Magnetic Resonance Imaging (MRI) machines upon their return from their respective expeditions. Only one of the thirty-five climbers returned without measurable brain damage.

The sample, though not large, was represented by thirty-five men, aged 22-46, split between four expeditions, and all eschewing supplemental oxygen. All of the test subjects underwent general medical examination, standard blood tests, and MRI of the brain after they returned from their expeditions. MRI also was carried out in a control group of twenty healthy subjects, who did not climb at altitude.

The first group contained fourteen men attempting to summit Mt. Everest (8848m). Only one was defined as an amateur by the study. Of the fourteen member group, only one man did not have measurable damage.

The other three test groups contained twenty-two amateur mountaineers on trips to Mt. Aconcagua (6959m), Mont Blanc (4810m) and Mt. Kilimanjaro (5895m). All had some level of measurable damage.

Damage was measured by the presence of cerebral lesions on various parts of the brain, as well as atrophy and dilatation of Virchow-Robin spaces. VR spaces surround blood vessels as the enter the brain. They drain brain fluid and connect to the body’s lymph system. Widening of these VR spaces is seen in the elderly but very infrequently in younger people.

None of the control group subjects showed any signs of this type of damage.

One of the mountaineers in the study reported aphasia–problems with speech–from which he recovered six months later. Two complained of occasional memory loss and three others struggled with bradypsychia–slowed mental functioning.

The full implications and causes of this data awaits further research and investigation.

Read more at Scientific American.

Sources: The American Journal of Medicine, Scientific American,,