PRES is a syndrome that is characterized by symptoms including a headache, seizures, altered consciousness, visual disturbances, and occasionally focal neurologic signs. It is commonly, but not always associated with acute hypertension, transplantation, chemotherapy and preeclampsia/eclampsia. Typically, MRI brain typically shows bilateral occipital, parietal, frontal cortex and subcortical white matter T2/FLAIR hyperintensities. However, atypical patterns of PRES are being increasingly recognized where DWI images and ADC maps show restricted diffusion. 

We will describe the first reported cases, to our knowledge, of typical and atypical PRES following oral medication containing phenylephrine and review its significance.

One female and one male, ages 61 and 89, respectively, presented with visual disturbances and altered mental status. Additionally, the male presented with seizure like activity and focal neurological deficits, while the female presented with headache. In both cases, they underwent MRI brain that showed bilateral occipital white matter hyperintensities on FLAIR in additional to hemosiderin staining on GRE. One had bilateral vasogenic edema which is the pattern typically seen with PRES, while the other had an atypical presentation of PRES that consisted of DWI changes which suggestive cytotoxic edema and possibly infarction. The latter had a prolong hospitalization and worse outcome. 

While PRES is a common syndrome that manifests in different ways, the progression of vasogenic edema into cytotoxic edema and infarction remains elusive. There have been reports linking phenylephrine to ischemic and hemorrhagic stroke, and intracerebral hemorrhage, however, there have been no report linking it to PRES. This case series shows that sympathomimetic such as phenylephrine is associated with both typical and atypical presentation of PRES. Larger studies are needed to determine if typical and atypical pattern of PRES are cause by the same pathophysiology.