Various Imaging Manifestations of Posterior Reversible Encephalopathy Syndrome (PRES) on Magnetic Resonance Imaging (MRI)

Posterior reversible encephalopathy syndrome (PRES), also called the acute hypertensive encephalopathy and reversible posterior leukoencephalopathy syndrome (RPLS), is a neurotoxic syndrome of cerebral vasoregulation classically characterized by bilaterally symmetrical parieto-occipital edema. However, the imaging findings are variable and may occur in other locations such as the frontal lobes, thalami, basal ganglia and brainstem. Most commonly, PRES presents with hyperintense signals on T2 and FLAIR sequences. Restricted diffusion and hemorrhage are rare. This study presents the typical and atypical manifestations of PRES on 3T MR images. It is a retrospective study analyzing a radiology report database and MR images of 92 patients with a clinical and radiological diagnosis of PRES. The brain MRI images of these patients were evaluated. The regions involved and the signal intensity of the affected areas on T1, T2, FLAIR and DW sequences were recorded. The location of the abnormal signal intensity as well as the presence or absence of atypical features such as diffusion restriction and hemorrhage were also recorded. The most commonly affected region was the parieto-occipital lobes (100%), however, other atypical regions involved were the frontal lobes (30.4%), temporal lobes (8.69%), basal ganglia (22%), cerebellum(17.39%), brainstem(9%) and thalamus(4%). Some of the cases showed restricted diffusion (43%) and hemorrhage (9%). The involvement of the parieto-occipital, frontal and temporal lobes is common in PRES. Occasionally, there may be an involvement of the basal ganglia, cerebellum and brainstem, with or without hemorrhage and restricted diffusion. Radiologists should be aware of the typical and atypical imaging manifestations of PRES in order to make an accurate diagnosis.