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May 19, 1999

High-Altitude Cerebral Edema—Reply

Author Affiliations

Margaret A.WinkerMD, Deputy EditorIndividualAuthorPhil B.FontanarosaMD, Interim CoeditorIndividualAuthor

JAMA. 1999;281(19):1794. doi:10-1001/pubs.JAMA-ISSN-0098-7484-281-19-jbk0519

In Reply: We entirely agree with Dr Basnyat that HACE is a clinical diagnosis generally not requiring MRI, which is expensive and often unavailable. Magnetic resonance imaging may be helpful, however, when the diagnosis is unclear. The purpose of our study was to use MRI to understand the pathophysiology, not to advocate MRI as essential for diagnosis.

The findings published by Dr Surks 33 years ago have been confirmed in many subsequent studies. The mechanism of this shift of fluid from the vascular space on ascent to high altitude and the exact division of the fluid between the intracellular and interstitial spaces are not as clear. Nor is it known whether the brain participates in this fluid translocation to the same extent as other tissues. The studies done by Surks et al were in persons without altitude illness. In those who are ill with acute mountain sickness, a net fluid retention or antidiuresis also takes place, which would aggravate any fluid shift into the brain that might be taking place and contribute to cerebral edema. However, the fluid shift from the vascular space does not, in itself, provide a clue as to whether and to what extent the brain is involved, and as to whether the brain edema is cytotoxic (intracellular) or vasogenic (blood-brain barrier leak of proteins and water).