Three attributes of a good mountaineer are high pain threshold, bad memory, and ... I forget the third. —Joke in a mountaineering Internet chat room
In the late 1890s in a laboratory atop a 4,554-meter peak in the Monta Rosa range in the Italian Alps, physiologist Angelo Mosso made the first direct observations of the effects of high altitude on the human brain: by eye and with an apparatus he designed, Mosso peeked into the skull of a man whose brain had been partly exposed in an accident, observing changes in swelling and pulsation.
Now a similar experiment has been done with noninvasive brain imaging, and for those of us who love to climb the results are not elevating. Neurologist Nicolás Fayed and his colleagues in Zaragoza, Spain, performed MRI brain scans on 35 climbers (12 professionals and 23 amateurs) who had returned from high-altitude expeditions, including 13 who had attempted Everest. They found brain damage in virtually every Everest climber but also in many climbers of lesser peaks who returned unaware that they had injured their brain. It seems that climbers of high mountains, whether weekend warrior or seasoned professional, face returning from the high peaks with a brain that is not in the same condition it was in beforehand.
What Gives in a Climber’s Brain?
Although a person’s tolerance to hypoxia (lack of oxygen) varies according to differences in innate physiology and physical conditioning, no one is immune. Those effects can be acute, affecting you only while you are at altitude, or—as the Fayed study found—they can be longer-lasting.
The first acute stage is called, naturally enough, acute mountain sickness. It can cause headache, insomnia, dizziness, fatigue, nausea and vomiting. The next, more serious stage is high-altitude cerebral edema, also known as HACE, brain swelling that is potentially fatal.
Lack of oxygen can directly damage brain cells. In addition, the walls of blood capillaries begin to leak at high altitudes, and the leaked fluid can cause dangerous swelling, pressing the brain outward against the rigid skull. Sometimes the optic nerves swell so badly they bulge into the back of the eye, degrading vision and causing retinal hemorrhages. Meanwhile blood, concentrated from dehydration and thickened by increased numbers of red blood cells, clots more easily. This clotting, along with the hemorrhage from the thinned capillaries, can cause a stroke. A climber with HACE may experience amnesia, confusion, delusions, emotional disturbance, personality changes and loss of consciousness.
Severe cases of acute high-altitude disease have long been known to cause brain damage. But one of the sobering things about the Fayed study is that even when climbers showed no signs of acute sickness, the scans still found brain damage.
The results in the Everest climbers were the starkest. Of the 13 climbers, three had made the 8,848-meter summit, three had reached 8,100 meters, and seven had topped out between 6,500 and 7,500 meters. The expedition had no major mishaps, and none of the 12 professional climbers evinced any obvious signs of high-altitude illness; the only acute case of mountain sickness was a mild one in the expedition’s amateur climber. Yet only one of the 13 climbers (a professional) returned with a normal brain scan. All the scans of the other 12 showed cortical atrophy or enlargement of the Virchow-Robin (VR) spaces. These spaces surround the blood vessels that drain brain fluid and communicate with the lymph system; widening of these VR spaces is seen in the elderly but rarely in the young. The amateur climber’s brain had also suffered subcortical lesions in the frontal lobes.
How High Is Too High?
Of course, Everest is extreme. Fayed and his colleagues also studied an eight-person team that attempted Aconcagua, a 6,962-meter summit in the Argentine Andes. Two climbers reached the summit, five climbed to between 6,000 and 6,400 meters, and one reached 5,500 meters. Yet three members experienced acute mountain sickness, and two displayed symptoms of brain edema—probably because they ascended more rapidly from lower altitudes than the Everest climbers did.
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15 Comments
Add CommentMost interesting when you consider a pressurized aircraft cabin is standardized at 8000 ft/2440 meters. You are taken there rather quickly.
Reply | Report Abuse | Link to thisWhat about lower oxygen levels due to say poorly ventilated work spaces do they also cause brain damage? Something like apoxia can be experienced sometimes in a big mall or large buildings with lot of people
Reply | Report Abuse | Link to thisI recently talked with a flight attendant who worked for one of the large airlines. She said that she was retiring because the airline broke the 8000 foot requirement and now pressurized to an altitude of 15,000 feet to save money. She was afraid of having a stroke, something that she said that was becoming more and more frequent after flying.
Reply | Report Abuse | Link to thisWhat about people who pactice breath-holding exercises like yoga-practioners and free-divers?
Reply | Report Abuse | Link to thisThe dangers of hypoxia in aviation are well known, and in many situations, they are not subtle. "In the event of a loss of normal cabin pressure, oxygen masks will appear from the overhead compartments… if you are traveling with small children, please apply your own mask first and then tend to those who may need help." In other words, you have about 25 seconds to don the mask before there is a good chance you will lose consciousness.
Reply | Report Abuse | Link to thisPeople with respiratory or cardiac problems are at risk of suffering a dangerous drop in oxygen concentration in their blood (hypoxemia) in a commercial air plane. This is why doctors advise people with certain medical conditions not to fly, or to do so only while breathing supplemental oxygen. Still, a study in 2007 by Kelly, Hlavac, and Beckert, in Aviation Space Environ. Med, found that such passengers can still suffer significant hypoxic events, during light physical activity, such as going to the lavatory, resulting in shortness of breath and dizziness.
Healthy individuals on a normal commercial flight will experience a significant decrease in blood oxygen (Kelly, P.T. et al., Aviat. Space Environ Med., 2007). The amount of oxygen in blood of a healthy individual inside a commercial aircraft cabin decreases in proportion to a person's age (Muhm, J.M. Aviat. Space. Environ. Med 2005). However, children also experience effects of hypoxia during airline travel. The oxygen content in their blood declines and their heart rate increases to 105 beats per min in a 3 hr flight. (No wonder they kick the back of your seat.) Further decreases in oxygen and further increases in heart rate to 108 beats per min develop after 7 hrs in flight (Lee, Yamamoto and Relles, Pediatr. Emerg. Care 2002). The same study found no "acclimatization" on long flights--as any climber could have told you, acclimatization takes longer than 7 hrs—rather, the decline in oxygen concentration in the children's blood worsens on longer flights. Another study found that airline passengers can take a lesson from climbers who will acclimatize by "climbing high on the mountain, then descending low to sleep". By taking shorter flights with substantial layovers (Fatemian, et al., Pflugers. Arch, 2001), report that the body does acclimatize to hypoxia of airline travel. An 8 hour lay-over is required, but fortunately the airlines are becoming very accommodating in providing this situation to their customers (often without request).
Climbers suffer blood clots and strokes due to thickened blood. I guess everyone already knows about "deep vein thrombosis" on air flights, which can be fatal.
HACE, the dangerous high altitude illness of mountain climbers can be suffered in the "friendly skys", too. Zrinzo et al report two interesting cases in J. Neurosurgery 2006. A 22-year old man returned from a flight with a headache, which quickly developed into severe neurological problems, a Glasgow Coma Score of 13 and he was placed on an artificial respirator. "A CT scan revealed almost complete obliteration of the ventricular system [in his brain]…" The fellow had been just fine before the flight. The second case concerned a 55 yr old woman who was well before hand, but she suffered such severe brain injury from the commercial airline flight that, unfortunately, she died 24 hours later. These two people had pre-existing conditions that were triggered by the high-altitude. The authors conclude "Air crews may wish to consider the use of supplemental oxygen if passengers exhibit excessive drowsiness or abnormal behavior, including conduct resembling alcohol intoxication, well-described presentation of acute altitude sickness." (Humm…I think I may have witnessed that.)
The thing is, just like climbing, the standards for airline safety are focused on preventing sudden illness. No one gets a brain scan if they don't feel sick. Yet only 1 of 13 Everest climbers returned from the summit with a normal brain MRI. One difference, though: you can't change the air pressure on a mountain top, but inside an airplane, why are we flying around hypoxic at 8000 ft?
Finally, a sad personal note. I wonderful colleague of mine died suddenly during a flight across the country. She was exuberantly healthy when I last saw her the day before she departed. I do hope people are keeping statistics on these things. -R. Douglas Fields
Interesting article. I was an air rescue pilot flying mountain rescue in the Pacific Northwest for a number of years. It was not uncommon to go from sea level to 13,000 feet numerous times in one day. Our base was at sea level and missions often required extended time above 10,000 - 8 to 10 hours.
Reply | Report Abuse | Link to thisI now have brain lesions and have asked the doctors if this experience may have either contributed or caused the damage. This article may in fact point to a contributing factor for me.
I wonder if skiing can do a damage to your brain in the same way. I live in Houston, elevation 100 feet (30 meters) and whithin a day I may be on slopes in Taos, New Mexico, rapidly ascending and descending between 9,000 and 12,000 feet (3,000 to 4,000 meters). I remember that once I had to leave on the very first day of skiing because I got an intense headache (I seldom if ever get headaches), and the headache did not stop until I was back to 3,000 feet elevation (1,000 meters).
Reply | Report Abuse | Link to thisJano Mladonicky
I have lived for years in Colorado between 7 and 8K feet, so commercial flights are not a big change for me. You would think, perhaps, that the answer is to live high! The high life, alas, has its problems too. Living at higher altitudes, it seems, tends to damage the lungs and then the heart. Strokes are more likely due to thicker blood. Maybe I'll move to Death Valley. Or maybe I'll stay here and die happy.
Reply | Report Abuse | Link to thisIs this type of hypoxia similar to post op patients who may have respiratory depression caused by opiods
Reply | Report Abuse | Link to thisI am an extremely fortumate climber. In 06 at 23,000' on Everest i has a stroke. I lost the use of my left hand and some cognative thinking. With the assistance of two Sherpas I was able to down climb teh Lhotse face back to C2. After 24 hours i still could not get dressed with out the help of a Sherpa. Today i am 57 and my memory is challanged. Is it from being high or age? This event was a surpise sine in 02 my high point was 28,000. i did have visual problems at that elevation and question if that was from optic nerve swelling. My vision did return to normal. The Poisk system did not fit my face and i climbed with out 100% use of o2. i am considering going high again an meeting with docs in Denver with high altitude expertise. jack@winterparkjack.com
Reply | Report Abuse | Link to thisHi Dr. ! First of all, sorry my bad english... I read your article and I would to give my congratulations ! It's very clean and objective. In fact, I'm writing a text book (in portuguese) about High Altitude Climbing / Trekking, and I would to use your article (about brain damage) in my book. It's possible ? obviously I'll give all correct credits.
Reply | Report Abuse | Link to thisThanks in advance and best regards,
Davi Marski - Brazil
davi@marski.org
PS: I had some brain damages a couple of years ago.. I was climbing near 20000 feet and I've pneumonia... after a lot of time in hypoxia, with no oxygen, when I returned to Brazil I felt in myself all of symptons described in your text ;-)
With the major portion of the western population making commercial flights very frequently, a lot of people out there must have some form of brain damage.
Reply | Report Abuse | Link to thisThe first time I made an international flight I felt like a significantly different person; I felt that my brain had organically changed. On the ground, for the remainder of the time after the flight kinetic movement appeared different, things seemed to move at an artificial pace. I felt physically ill, and became depressed. I couldn't concentrate as well as before. Overall I felt compromised, skewed. Now, after multiple international flights I feel like a zombie. Initially my IQ was 190, now it's in the low hundred something. I feel devastated, and no one had forewarned me about this; I had no idea that this might happen. After you do it (international flying) once you're drawn to do it again and again. Sometimes you have to for business reasons, but often suffering comes from the pursuit of happiness - seeing new places, experiencing new cultures. The greatest minds in the world today are reclusive. They sequester themselves in oxygen rich environs and think and analyze and calculate and contrive and maintain a superb noggin. Frequent flyers become kooky - digress into dinosaurs, e.i. - bird brains.
It takes time to evaluate the repercussions of a given new technology and many more eons for our species to adjust to it, to evolve to handle it. Airplanes are detrimental to the ecosystem as well as the physiological intersystem. Most people don't climb mountains to get to the other side, but flight is a form of transportation that has become standard for traveling long distances and getting to the other side of oceans.
Dr. Fields - I know this is an old article but I had some questions for you. Would treatment with supplementary oxygen and dex earlier than normal help mitigate these effects? So instead of say using oxygen in the death zone, one would start earlier say at 6k meters? Or perhaps a gammow bag? Thanks.
Reply | Report Abuse | Link to thisok, Mountain Climbers, It is the physical world that you live in, if you climb above 10,000 feet without oxygen you will get brain damage. It is science, no amount of conditioning that you do will prevent this. It is a fact. You cannot walk in space without a space suit. The human body does not posses the ability to go to these heights without oxygen and not get damaged. If you think otherwise you obviously didn't get science in school. You cannot overcome the physics of the situation and this should not be a shock to you that you will damage your brain.
Reply | Report Abuse | Link to thisWinterPark Jack is not an extremely fortunate climber. Fortunate climbers do not suffer strokes. I'd guess his loss of cognitive ability may not be as temporary as he thinks, given his intent to head back up into the aethereal realms. But maybe the experience of extreme terrestrial elevations is worth the high risk. I, personally, understand that, but I really like being able to think, too. That may be further down Jack's list, especially now.
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