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.
Zhang H, Mao X, Zheng X, Wu J. Posterior Reversible Encephalopathy Syndrome: Imperative to Define. Arch Neurol. 2010;67(12):1535. doi:10.1001/archneurol.2010.313