High-altitude headache.

A human being's exposure to altitude, and the consequent hypobarism, entails a complex series of adaptive mechanisms that depend on the rate of ascent and the altitude reached. When these mechanisms fail, so-called acute mountain sickness (AMS) results, with headache as its predominant symptom. It has been observed, nonetheless, that well-acclimated mountaineers may have headache without symptoms of AMS. We consider that high altitude and ensuing hypobarism bring about three possibilities of cephalalgia: the first is covered by the set of AMS clinical manifestations and is undoubtedly the most frequent; the second occurs independently of acute mountain sickness and is probably due exclusively to hypoxia; and the third includes altitude-triggered migraine or migraine-like episodes. These are neurogenic problems secondary to hypoxia caused by hypobarism and, in all events, have a common denominator: hypoxia and a fundamental white organ, the brain.