Climbers With Altitude Sickness Show Signs of Brain Bleeds Years Later
THURSDAY, Nov. 29 -- Mountain climbers who develop a potentially fatal type of high-altitude sickness can have traces of bleeding in the brain long after they recover, according to a new German study.
The study was expected to be presented Wednesday at the annual meeting of the Radiological Society of North America, in Chicago.
High-altitude cerebral edema is a condition that occurs when capillaries leak fluid and cause the brain to swell. It's "a life-threatening condition," said Dr. Michael Knauth, of the neuroradiology department at the University Medical Center Goettingen, in a society news release.
The condition typically affects mountain climbers, travelers, skiers and hikers above 7,000 feet. The condition causes many symptoms, including headache, loss of coordination and decreasing levels of consciousness.
"It usually happens in a hostile environment where neither help nor proper diagnostic tools are available," Knauth said. "It was previously thought that [high-altitude cerebral edema] did not leave any traces in the brains of survivors. Our studies show that this is not the case. For several years after, microhemorrhages or microbleeds are visible in the brains of survivors."
In conducting the study, the researchers compared brain MRI images of 36 mountain climbers. The climbers were placed into one of four groups according to their medical histories: well-documented cases of high-altitude cerebral edema, high-altitude illness, severe acute mountain sickness or isolated high-altitude pulmonary edema, a life-threatening altitude sickness that occurs when fluid builds up in the lungs.
Neuroradiologists who did not know the climbers' history of altitude illness examined the brain scans and scored them based on the number and location of small brain bleeds, or microhemorrhages.
"In most cases, these microhemorrhages are so small that they are only visible with a special MRI technique called susceptibility-weighted imaging," Knauth said. "With this technique, the microhemorrhages are depicted as little black spots."
The study showed the microhemorrhages occurred in eight of 10 climbers who had experienced high-altitude cerebral edema. Only two of the other 26 climbers had traces of bleeding in the brain.
The researchers also found that climbers with the most severe cases of high-altitude cerebral edema had the most significant brain bleeds. Most often, they pointed out, these microhemorrhages were found on the nerve fibers that connect the left and right sides of the brain, unlike other vascular diseases.
"The distribution of microhemorrhages is a new and sensitive MRI sign of [high-altitude cerebral edema] and can be detected years after," Knauth said. "We will further analyze our clinical and MRI data on patients with acute mountain sickness, which is thought to be a precursor of [the condition]."
Survivors of the condition do not need to stop climbing, the researchers said. "We cannot give such a strong recommendation," Knauth said. "However, mountaineers who have already experienced [high-altitude cerebral edema] once should acclimatize to the altitude very slowly."
Because this study was presented at a medical meeting, the data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.
Visit the U.S. National Institutes of Health to learn more about high-altitude cerebral edema.
Posted: November 2012