Which MRI finding is most characteristic of PRES?

Which MRI finding is most characteristic of PRES?

• A. Focal restricted diffusion with cytotoxic edema.
• B. Symmetric vasogenic edema in the posterior white matter, particularly the parieto-occipital regions.
• C. Hippocampal sclerosis.
• D. Mass in temporal lobe.

Answer: (B)

PRES is driven by a disruption of cerebral autoregulation that leads to vasogenic edema. The most characteristic MRI finding is symmetric edema in the posterior white matter, especially in the parieto-occipital regions. On MRI this appears as T2/FLAIR hyperintensities in those areas, and the edema is vasogenic, so diffusion imaging typically shows no marked restriction (often increased ADC), distinguishing it from cytotoxic edema seen in infarcts. Other choices suggest different conditions—cytotoxic edema points to acute infarction; hippocampal sclerosis and a temporal lobe mass indicate chronic or neoplastic processes, not PRES.

PRES is driven by a disruption of cerebral autoregulation that leads to vasogenic edema. The most characteristic MRI finding is symmetric edema in the posterior white matter, especially in the parieto-occipital regions. On MRI this appears as T2/FLAIR hyperintensities in those areas, and the edema is vasogenic, so diffusion imaging typically shows no marked restriction (often increased ADC), distinguishing it from cytotoxic edema seen in infarcts. Other choices suggest different conditions—cytotoxic edema points to acute infarction; hippocampal sclerosis and a temporal lobe mass indicate chronic or neoplastic processes, not PRES.