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Posterior reversible encephalopathy syndrome (PRES) (also termed reversible posterior leukoencephalopathy syndrome) represents an entity with an underlying pathophysiological mechanism suggested to be vasogenic edema.1 Burrus and colleagues2 reported up to 48% PRES in patients with thrombotic thrombocytopenic purpura (TTP) and acute brain abnormalities. We agree that diffusion-weighted imaging and apparent diffusion coefficient mapping are indispensible to differentiation of vasogenic edema from cytotoxic edema in PRES. However, we have some concern regarding their definition of PRES.
Though PRES appeared common, as defined by the authors and others,3 we ascribe this prevalence to the misunderstanding of PRES. Reversible brain vasogenic edema may concomitantly occur with multiple disorders, including mitochondrial encephalopathy,4 cerebral ischemia,5 and hepatic encephalopathy.6 The reversibility of vasogenic edema, preferably involving posterior white matter, can unambiguously differentiate PRES, primarily arising from failure of cerebrovascular autoregulation at high blood pressure and ensuing disruption of the blood-brain barrier7 by said disorders. In this regard, it seems problematic to equate reversible brain vasogenic edema with PRES, as it might lead to overestimation of incidence of PRES.
In summary, PRES represents a neurological disorder characterized by reversible brain vasogenic edema primarily arising from failure of cerebrovascular autoregulation and disruption of the blood-brain barrier, mainly implicating posterior white matter. Definition of PRES by consensus remains imperative.
Correspondence: Dr Zhang, MD, Karolinska Institute, Department of Neurobiology, Care and Sciences Society, Novum, Plan 5, SE 141 86, Stockholm, Sweden (hongliang.zhang@ki.se).
Financial Disclosure: None reported.
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
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