Scientific American Mind Article

The Scientific American Mind article, “Into thin air: Altitude’s toll on the brain” introduced by David Dobbs speaks of a neuroscientist’s study of examining the effects that one-time and cumulative high-altitude climbing have on the human brain. The article, “Brain Cells into Thin Air”, written by R. Douglas Fields describes the research of fellow neurologist Nicholas Fayed and colleagues ("Evidence of Brain Damage After High-Altitude Climbing by Means of Magnetic Resonance Imaging”).

Current technology has allowed for noninvasive brain imaging. In the study, thirty-five climbers, including twelve professionals and twenty-three amateurs, who had returned from high-altitude trips were given MRI brain scans. Of the thirty-five climbers, thirteen people had attempted Mt. Everest. Of the thirteen climbers, three had trudge 8480 meters, three had gone 8100 meters, and the last seven made it as far as 6500 to 7500 meters. Those who had attempted Mt. Everest had the most severe results except for one climber who had a normal MRI scan. The remaining twelve brain scans showed that the climbers had suffered “cortical atrophy,” a wasting away and decrease in size of the cerebral cortex, and “enlargement of the Virchow-Robin spaces.” Virchow-Robin spaces (VRS) are the perivascular spaces surrounding blood vessels in the cerebral cortex. These vessels drain fluid and communicate with the lymph system. An MRI can clearly demonstrate these spaces. Patients of all ages express a relatively small perivascular space but these spaces tend to increase in size and frequency with progressive age. Usually these spaces are 2 or 3 mm in diameter but can grow to become quite large (5 to 20 mm). Within the group, the brains of the amateur climbers also had showed sub-cortical lesions in the frontal lobes.

The article goes on to address a person’s tolerance to hypoxia or lack of oxygen. It had stressed that hypoxia “varies according to differences in innate physiology and physical conditioning.” These differences “can help the body and brain to better tolerate exertion and physiological stresses of high-altitude mountaineering” though it cannot be eliminated.

The first stage of high altitude sickness is called acute mountain sickness (AMS). AMS is caused by a lack of oxygen when traveling to higher elevations (usually over 2,100 m). When climbers do not have a chance to acclimate to the altitude, they can experience “headache, insomnia, dizziness, fatigue, nausea, and vomiting”. Stage two is called high-altitude cerebral edema (HACE). HACE is a potentially fatal form of AMS where the brain swells and stops functioning in the normal way. Symptoms of this includes confusion, fatigue, changes in behavior, ataxia (staggering), difficulty speaking, vomiting, hallucinations, blindness, paralysis of a limb, seizure, unconsciousness, total paralysis, and coma. Furthermore, an insufficient amount of oxygen to the brain can directly impair and cause damage to brain cells. Accordingly, “the walls of blood capillaries in the brain and elsewhere begin to leak at high altitude, and this leakage causes dangerous swelling, pressing the brain outward against the rigid skull.”

The study of Nicholas Fayed and colleagues explained that none of the Mt. Everest climbers experienced HACE and only one amateur climber experienced a mild case of AMS. However, all of the experienced climbers showed “lasting brain damage” prior to the Mt. Everest attempt and their MRI scans were unchanged following the climb.

In another experiment, Fayed and colleagues studied an eight-member team who attempted Aconcagua, a 6926-meter mountain in the Andes. Two of the climbers had reached the summit point while five had gone 6000 to 6400 meters and the last one had gone as far as 5500 meters. In this group, three had experienced AMS and two had suffered HACE. The MRI results showed that all of the climbers suffered cortical atrophy, seven of the eight climbers had enlargement of the Virchow-Robin spaces, and four of the climbers showed many subcortical lesions. Several of the climbers also experienced a range of harmful symptoms. Three years after the expedition, all of the climbers were re-examined to determine if the brain had recovered from the stresses of mountaineering Aconcagua. The results showed that the brain damage was still apparent through the MRI scans. In another case, researchers found that seven climbers who reached the summit of Mount Blanc, a 4810-meter summit in the Alps, showed enlarged Virchow- Robin spaces.

Overall, the research shows that amateur climbers are at greater risk to AMS or HACE being inexperienced while professional climbers are at greater risk of cumulative high-altitude stresses. In the study, professional climbers experienced a greater cortical atrophy over the amateur climbers. This only goes to show that there is a price to pay to live dangerously…literally!