Fig. 1. Pathophysiology of acute mountain sickness (AMS). This schema emphasizes a role for blood–brain barrier opening (BBB), brain swelling and cerebrospinal compliance (CSC). Although highly speculative at present, new non-invasive and sensitive techniques will allow measurement of the variables necessary to evaluate this hypothesis (see text for more detail). pCap, cerebral capillary perfusion pressure; cCSF, cranial cerebrospinal fluid; ICP, intracranial pressure; CBV, cerebral blood volume; CBF, cerebral blood flow.