Purpose or Case Report: To evaluate multimodal magnetic resonance imaging (MRI) characteristics in pediatric patients diagnosed with posterior reversible encephalopathy syndrome (PRES).
Methods & Materials: A retrospective case series of five pediatric patients diagnosed with PRES based on clinical presentation and imaging findings is presented. Maximum blood pressure prior to imaging, presenting symptoms, and suspected etiology were recorded. MRI sequences included T1-weighted, T2-weighted, fluid attenuated inversion recovery (FLAIR), diffusion weighted (DWI) and apparent diffusion coefficient (ADC) maps, susceptibility weighted angiography (SWAN), and arterial spin labeling (ASL). Each study was reviewed by a pediatric neuroradiologist. Regions of interest were evaluated across multiple sequences to correlate regions of vasogenic edema with perfusion abnormalities and microhemorrhage.
Results: Clinical characteristics are summarized in the Table. All patients were found to have hyperintense FLAIR signal abnormalities in the occipital and parietal cortices, however, two patients had lesions in the temporal lobes and one patient had frontal lobe involvement. Correlating ASL signal, from which regional cerebral blood flow can be derived, with FLAIR signal abnormality yielded mixed results: Patient 1 demonstrated hyperperfusion in all areas of FLAIR signal abnormality, Patient 2 demonstrated hyperperfusion in most areas of FLAIR signal abnormality, however, also had hypoperfusion in an occipital lesion, Patient 3 demonstrated minimal FLAIR signal abnormality but extensive cortical hypoperfusion, Patient 4 demonstrated marked cortical hypoperfusion associated with areas of FLAIR signal abnormality, and Patient 5 demonstrated both intense hypoperfusion and hyperperfusion associated with hyperintense occipital FLAIR signal. In all patients, perfusion defects were found in areas of cerebral cortex that appeared normal on FLAIR sequences and ADC maps.
Conclusions: PRES is diagnosed based on both clinical presentation and imaging findings. The pattern of T2/FLAIR hyperintense lesions associated with vasogenic edema affecting primarily the occipital and posterior parietal cortex has been well-described in the pediatric population. However, perfusion defects in PRES have not been clearly described in children. This retrospective case series suggests that either hypo- or hyperperfusion defects identified on ASL imaging may be a more sensitive indicator of PRES than FLAIR or ADC abnormalities.