Extreme altitude transient aphasia.

Department of Physiological Sciences, Medical School, University of Barcelona, Spain Eduardo Garrido Casimiro Javierre Severe mountain sickness, cerebral oedema, or ischaemic infarcts may occur when humans ascend to high altitude. However, neurological symptoms can occasionally be atypical. Recently, we studied a highly experienced climber who had suffered difficulties in expressing himself verbally, emitting incomprehensible sounds during a strenuous ascent to 8000 m in the Himalayas. The speech disorder, which was not associated with other neurological impairments, disappeared following a short rest. Cranial magnetic resonance imaging, performed 40 days later, showed small high intensity signals in the posterior lobes. To our knowledge, the nearest neurological episode to this case is a self report by Shipton' in 1943. Cerebral blood flow is highly sensitive to changes in carbon dioxide tension. CO2 inhalation increases brain perfusion quickly reversing many high-altitude neurologic disturbances. Hackett et al.' reported six cases of altitude cortical blindness who showed excellent response to CO2 administration. A severe fall in the arterial Pco2 (at rest approximately 10 mm Hg at 8000 m) due to intense pulmonary gas exchange during fast ascents to extreme altitude can result in non-uniform vasoconstriction and tissue distribution. This mechanism, together with an increased blood viscosity and coagulability in a high mountain environment, would increase the hypoxic insult, especially in small vessel territories of the brain. Although the precise significance and future implications of these magnetic resonance findings are not clear, the presentation and clinical evolution of this case strongly suggest a selective vasospasm of brain speech areas. Nevertheless, these imaging findings may be related to cumulative cerebral damage, as we have observed in a large number of climbers after repeated exposure to extreme altitude.3 Indeed, the increasing popularity of attempting to conquer the world's highest summits without supplementary oxygen would lead us to conjecture that such autolimited neurological episodes occur more frequently than is reported in the mountain medicine literature.