High Altitude Brain Damage
The dangers of high altitude have been covered before on this
site, but permanent brain damage was not one of the risks looked
at. Unfortunately, recent evidence shows that this is a real
possibility, and at lower elevations than many would have guessed.
Although backpacking is not necessarily a high-altitude activity,
it can be, so consider this a warning.
Outside Magazine reported in their October 2009 issue on the
research done by Doctor Nicholas Fayed, a neuroradiologist in
Spain. He has been looking at MRI scans of the brains of climbers,
both before and after high altitude climbs. What he has found
is evidence of permanent brain damage occurring from single trips,
and much more commonly than scientists previously suspected.
There are three basic types of brain damage from exposure
to high altitude.
Cortical Atrophy - This is from the loss of neurons
in the cerebral cortex, the part of the brain that handles conscious
thought and perception. It has now been shown that single trips
to high enough elevations can cause a permanent damaging and
shrinkage of the cortex.
Enlarged Virchow-Robin Spaces - This widening of VR
spaces, the spaces around blood vessels in the brain, is normally
seen in age-related conditions like dementia, Alzheimer's and
general cognitive decline. It is now evident that high altitude
can also cause this.
Subcortical Lesions - These affect the white matter
underneath the cerebral cortex. Climbers suffer from this due
to small strokes resulting from clots in their thickened blood.
The damage can be widespread and permanent.
Dr. Fayed relates how one man forgot his phone number after
coming down from Aconcagua (22,800 feet), and had trouble remembering
what he went to a store for by the time he arrived there. A brain
scan confirmed the damage. This is permanent damage in most cases.
Perhaps most disturbing to those who merely hike or backpack
in the mountains is the story of seven trekkers who went to the
top of Mont Blanc in France in 1998. The summit is only 15,771
feet above sea level, and none of them reported any signs of
altitude sickness. But when their brains were scanned a few days
later, three were found to have damage. Two had enlarged Virchow-Robin
spaces, and one of those also had cortical lesions. One had cortical
atrophy - a permanent loss of gray matter that can make thinking
more difficult.
Before and after scans of the brains of those who climbed
to high altitude on other mountains has shown similar damage.
One study of 21 seasoned climbers showed that 60% of them showed
signs of cortical atrophy. Worse news: It is suspected that amateurs
are at greater risk due to improper acclimatization.
High Altitude - Good and Bad News
A study of seven Sherpas who climbed high but also lived relatively
high showed only one had signs of brain damage. This indicates
the importance of proper acclimatization.
Medical authorities who specialize in high altitude medicine
recommend a a day or so at 5,000 feet if you are coming from
sea level, and then ascending at just 2,000 feet per day once
above 9,000 feet. The more conservative advice (which is becoming
more common) is to keep it to 1,000 feet per day above 9,000
feet. That could be difficult for those who want to hike up the
fourteeners in Colorado, although if they live there they likely
have some acclimatization already (most of the state is above
4,000 feet).
There is more to this though. In the research done so far
it seems clear that...
High Altitude Brain Damage continues here...
Altitude.
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