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Findings

CT shows diffuse subcortical and deep white matter hypodensity most prominent in the posterior frontal and parieto-occipital regions.

MRI shows corresponding hyperintensity on FLAIR and T2 weighted imaging

Predominantly increased signal on the ADC map images with a punctate focus of diffusion restriction

Foci of signal drop-out on the gradient-echo images compatible with areas of punctate hemorrhage

Differential diagnosis

Posterior reversible encephalopathy syndrome (PRES) / hypertensive encephalopathy

Post radiation changes

Acute cerebral ischemia

Progressive multifocal leukoencephalopathy

Metabolic derangement

Acute demyelinating disease

Gliomatosis

PRES / Hypertensive encephalopathy

Disorder of cerebrovascular autoregulation with multiple etiologies, most of which result in acute hypertension

Acute hypertension damages vascular endothelium

Breakthrough of autoregulation causes BBB disruption, resulting in vasogenic edema

Arteriolar dilatation with cerebral hyperperfusion and extravasation of fluid secondary to elevated hydrostatic pressure

Predilection for parietal and occipital lobes (posterior circulation is sparsely innervated by sympathetic nerves)

Generally reversible with blood pressure normalization

Permanent infarction rare

Most common presentation is with headache, seizure, altered mental status

Children may be normotensive or with only mildly elevated BP

Schwartz R et al: Preeclampsia-eclampsia: Clinial and neuroradiographic correlates and insights into the pathogenesis of hypertensive encephalopathy. Radiology 2000; 217:371-76.