Margaret A.WinkerMD, Deputy EditorIndividualAuthorPhil B.FontanarosaMD, Interim CoeditorIndividualAuthor
Copyright 1999 American Medical Association. All Rights Reserved.
Applicable FARS/DFARS Restrictions Apply to Government Use.1999
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
Hackett P, Yarnell P. High-Altitude Cerebral Edema—Reply. JAMA. 1999;281(19):1794. doi:10-1001/pubs.JAMA-ISSN-0098-7484-281-19-jbk0519