Previous studies (5,10,11) have shown that vasogenic edema is responsible for the changes seen in PRES, therefore, the hallmark of PRES is vasogenic edema in the territories of the posterior circulation, which can be differentiated from cytotoxic edema
in other etiologies by using DWI as well as apparent diffusion coefficient (ADC) map that shows elevated ADC values (22).
Another theory suggests that hypertension leads to cerebral autoregulatory vasoconstriction, ischemia and subsequent cytotoxic edema
and then extracellular edema (1), (17).
More recently, it has been hypothesized that when vasogenic edema becomes severe enough, it can result in reduced tissue perfusion and cytotoxic edema
because of irreversible ischemic changes that lead to white matter lesions.
A second theory posits that excessive arteriolar vasoconstriction results in decreased blood flow, ischemia, and cytotoxic edema
(Brubaker et al.
due to cell death was not definitively noted with our case.
leads to a narrowing of the extracellular matrix and, thus, to a reduction of Brownian molecular motion in the extracellular space.
The diffuse form of herpes encephalitis causes cytotoxic edema
that can mimic a hypoxic-ischemic type of injury on imaging.
Two pathophysiologic mechanisms have been proposed regarding cerebral autoregulation--cerebral vasospasm, which results in cytotoxic edema
, (4) and vasodilatation, which results in vasogenic edema.