Atypical Edema in Posterior Reversible Encephalopathy Syndrome: Clinical Associations and Outcome

Posterior reversible encephalopathy syndrome (PRES) is a neurotoxic state with characteristic imaging findings. While classic PRES typically involves parieto-occipital edema, atypical cases present with variable involvement of deep gray nuclei, brainstem, cerebellum, and corpus callosum, which may complicate diagnosis. This study aims to characterize the neuroimaging features of "atypical" PRES in a large cohort and evaluate relationships with clinical variables and outcomes.

We retrospectively analyzed neuroimaging data from patients diagnosed with PRES, identifying cases with atypical edema patterns. Relationships between MRI findings, clinical variables, and outcomes were assessed with univariable and multivariable regression analyses.

A total of 184 PRES cases were analyzed. 71.7% had "atypical" imaging findings. Atypical edema was associated with older age (odds ratio [OR] 2.96 ≥52 years, p = 0.002) and negatively associated with pregnancy (OR 0.20, p<0.001). These associations were seen in a subset of atypical locations, particularly those supplied by the posterior circulation. Additionally, certain atypical edema patterns were correlated with prolonged hospital stays and reduced clinical reversibility, suggesting a potential impact on patient outcomes.

In this large series of PRES cases, atypical imaging findings were common. Atypical edema, including a posterior circulation pattern, was seen more commonly in older patients, less commonly in pregnancy, and may represent a more severe form of this syndrome with worse outcomes. Recognizing these atypical imaging patterns is crucial for timely intervention and improved patient outcomes.