Evidence for cytotoxic edema
in the pathogenesis of cerebral venous infarction.
Therefore, in most cases, PRES represents vasogenic and not cytotoxic edema
12 In our study, as similar to the literature, DWI was found to be superior due to cytotoxic edema
in early stage in most of the patients, and FLAIR images were superior in late- stage because it was replaced by vasogenic edema.
In contrast, arterial infarct presents with cytotoxic edema
with blurring of the gray and white matter interface from edema distal from the point of occlusion (Figure 5).
However, as in a recently reported case  our patients MRI showed bilaterally, symmetrical basal ganglia hyperintensity without any mass effect, cytotoxic edema
, and calcification.
Nevertheless, some small regions of cytotoxic edema
can also be detected in the central parts by DWI.
23) So a pattern of persistent cytotoxic edema
suggests fulminant necrotizing changes and poor prognosis, whereas a pattern of vasogenic edema represents mild pathological changes and better prognosis.
Vasospasm theory: severe hypertension promotes cerebral overregulation, vasoconstriction, ischemia, infarction and cytotoxic edema
Diffusion-weighted MRI (DWI) has been shown to be a reliable method in distinguishing vasogenic edema in PRES from cytotoxic edema
seen in cerebral ischemia (10,11).
Although the lesions were increased in distribution, no evidence of cytotoxic edema
was found on DWI (Figure 2b, 2c).
But this technique provides detailed information about the makeup of lesions, showing vasogenic and cytotoxic edema
, as well as location in the superficial or deep structures in both gray and white matter.
One is vasogenic edema, which occurs as a result of breakdown of the endothelial blood-brain barrier leading to interstitial brain edema; the other is cytotoxic edema
caused by swelling of astrocytes as a result of altered intracellular osmotic balance or dysfunctional cellular membrane (8).
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.
The diffuse form of herpes encephalitis causes cytotoxic edema
that can mimic a hypoxicischemic type of injury on imaging.