To assess the possibility that climbing to extremely high altitude may result in hypoxic injury to the brain, we performed neuropsychological and physiologic testing on 35 mountaineers before and 1 to 30 days after ascent to altitudes between 5488 and 8848 m, and on 6 subjects before and after simulation in an altitude chamber of a 40-day ascent to 8848 m. Neuropsychological testing revealed a decline in visual long-term memory after ascent as compared with before; of 14 visual items of information on the Wechsler Memory Scale, fewer were recalled after ascent by both the simulated-ascent group (a mean [±SD] of 10.14±1.68 items before, as compared with 7.00±3.35 items after; P<0.05) and the mountaineers (12.33±1.96 as compared with 11.36±1.88; P<0.05). Verbal long-term memory was also affected, but only in the simulated-ascent group; of a total of 10 words, an average of 8.14±1.86 were recalled before simulated ascent, but only 6.83±1.47 afterward (P<0.05). On the aphasia screening test, on which normal persons make an average of less than one error in verbal expression, the mountaineers made twice as many aphasie errors after ascent (1.03±1.10) as before (0.52±0.80; P<0.05). A higher ventilatory response to hypoxia correlated with a reduction in verbal learning (r = -0.88, P<0.05) and with poor long-term verbal memory (r = -0.99, P<0.01) after ascent. An increase in the number of aphasie errors on the aphasia screening test also correlated with a higher ventilatory response to hypoxia in both the simulated-ascent group (r = 0.94, P<0.01) and a subgroup of 11 mountaineers (r = 0.59, P<0.05). We conclude that persons with a more vigorous ventilatory response to hypoxia have more residual neurobehavioral impairment after returning to lower elevations. This finding may be explained by poorer oxygenation of the brain despite greater ventilation, perhaps because of a decrease in cerebral blood flow caused by hypocapnia that more than offsets the increase in arterial oxygen saturation. (N Engl J Med 1989; 321:1714–9.), BOTH transient and long-lasting neurobehavioral impairments have been found in a group of young, fit mountaineers after an expedition to climb Mount Everest (altitude, 8848 m; barometric pressure, about 34 kPa [253 mm Hg]).1 Before and after the expedition, these climbers were given a variety of neuropsychological tests known to be sensitive to the integrity of cortical function. The transient effects from exposure to extremely high altitude were found to include mild deterioration in the ability to learn, remember, and express information verbally. These impairments were present during the first three days after the return to low altitude but not….
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