Which imaging finding is associated with posterior reversible encephalopathy syndrome (PRES)?

The imaging finding associated with posterior reversible encephalopathy syndrome (PRES) is positive vasogenic edema on MRI. PRES is characterized by a pattern of edema primarily affecting the posterior regions of the brain, notably the occipital lobes and the parietal lobes. This edema is due to a breakdown of the blood-brain barrier, leading to the accumulation of fluid in the interstitial space, which is referred to as vasogenic edema.

When an MRI is performed for a patient suspected of having PRES, these areas of hyperintensity can be observed on fluid-attenuated inversion recovery (FLAIR) sequences and T2-weighted images. The condition is often reversible with appropriate treatment, and early identification through imaging plays a crucial role in managing the patient's symptoms and preventing long-term neurological damage.

The other options provided do not accurately reflect the characteristic imaging findings of PRES. Increased ventricular size would suggest a different pathology, hyperintensities in the anterior brain are not typically seen in PRES, and white matter atrophy on CT scan does not correlate with the acute edema seen in this syndrome. Thus, the identification of positive vasogenic edema on MRI directly ties to the clinical manifestation of PRES, making it the appropriate answer.