Possible bad news for some Mount McKinley climbers. A new medical study suggests that high altitude cerebral edema does long-term damage to the brain. The findings in some ways parallel what has become known about concussions in recent years, namely that brain injuries leave scars.
Exactly how many McKinley climbers suffer HACE is unclear, but acute mountain sickness, a precursor, hits 50 percent of them, according to one study. The treatment for both mountain sickness and HACE is the same -- get back down to lower altitude quickly. Climbers who do that usually recover rapidly.
It had long been thought they recovery fully, too. The new study questions that. It concluded that those who develop serious brain swelling at altitude appear to suffer lasting damage. Researchers who scanned their brains found evidence of small hemorrhages.
The medical website MedPage Today reported that "in a single-center MRI (magnetic resonance imaging) study of 36 mountaineers, patients who'd had high altitude cerebral edema (HACE) had microbleeds in their corpus callosum, while those with other forms of altitude sickness largely did not, Michael Knauth, MD, PhD, of the University Medical Center Goettingen in Germany, and colleagues reported during a press briefing at the Radiological Society of North America meeting...."
The good news for climbers was that those who suffered only acute mountain sickness suffered none of those microbleeds, a good argument for aborting an assent at the first sign of big problems with altitude. Why altitude affects people in different ways, and the same people in different ways at different times, is unclear, as the researchers noted.
"It's not like you can say that at 8,000 [feet] they'll have so many [microbleeds] and at Everest they'll have double," Knauth told MedPage. "But those who have the most severe HACE – the ones that almost died -- have the most severe changes on MRI as well."
The long-term consequences of this damage remains unclear. Researchers said that those with damaged brains showed no clinical signs of mental impairment, but researchers don't know what the damage means over the long term. Knauth appeared hopefully the long-term conclusion would be that while HACE permanently damages the brain it doesn't do as much damage as a concussion.
"The neuropsychological consequences are unclear, but at the present there are no data to support the hypothesis that they are impaired," he said. "They work normally, but subtle testing of their mental capabilities is still to be performed. But it probably [will show] nothing."
Research on traumatic brain injury has concluded human responses vary greatly by individual, making it impossible to broadly categorize the consequences of brain injuries. But the evidence points to cumulative impacts from even small limited brain injuries, which might suggest that if you've suffered HACE once you might want to be extra careful with your brain on future climbs.
Contact Craig Medred at craig(at)alaskadispatch.com