High-altitude cerebral edema is seen less frequently than high-altitude pulmonary edema but, owing to its higher mortality (up to 100 per cent without treatment), it is the most dangerous form of altitude-related disease. After ascent to high altitudes, cerebral blood flow increases more in subjects with acute mountain sickness than in healthy persons. In addition, elevated cerebral spinal fluid pressure has been reported in several cases of high-altitude cerebral edema. Magnetic resonance imaging and CT brain scans indicate the predominant involvement of the white matter in high-altitude cerebral edema. Possible pathogenetic factors for the development of high-altitude cerebral edema include (1) a depletion of ATP stores with concomitant reduction in the active outward sodium transport leading to cellular edema, (2) hydrostatic edema due to the increase in cerebral blood flow which causes an alteration in the Starling forces, favoring fluid extravasation, (3) a decrease in intracranial compliance, and (4) focal capillary compression by hypoxia-induced angiogenesis and osmotic swelling.
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