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Posterior reversible encephalopathy syndrome (PRES) is a neurotoxic process that typically occurs in the setting of immune dysregulation. In contrast to the characteristic pattern involving parieto-occipital and posterior frontal regions, predominant involvement of the infratentorial brain occurs in a minority of PRES patients. We examined six patients with infratentorial predominant posterior reversible encephalopathy syndrome (IPPRES) relative to those with typical PRES in terms of clinical factors of toxicity and outcomes. We review the current understanding of PRES pathophysiology. An institutional database of PRES patients was created through an IRB-approved search of the electronic record from 2007 to 2012. MR images were reviewed and classified by two neuro radiologists. Clinical data including laboratory data, blood pressure, and discharge outcome were collected through review of existing electronic medical records. Characteristics of the two groups were compared. Six cases among 80 PRES patients displayed an atypical distribution of signal abnormality predominantly involving the infratentorial brain. In IPPRES patients, signal abnormalities within the supratentorial brain, when present, showed a predominantly central distribution rather than the typical peripheral distribution. IPPRES patients showed higher rates of extreme hypertension, renal dysfunction, abnormal serum calcium, and abnormal serum magnesium relative to typical PRES patients. Outcomes were similar between the two groups. In our small series, IPPRES differs from typical PRES patients not only in the distribution of imaging abnormalities but also in rates of extreme hypertension and several laboratory indices. Despite these differences, clinical outcome in the IPPRES group was similar to that of typical PRES.