To determine the prevalence of arterial stenosis in PRES patients and demonstrate if patients with arterial stenosis define a subpopulation within PRES.

Posterior Reversible Encephalopathy Syndrome (PRES) is defined as reversible vasogenic cerebral edema in a characteristic posterior-dominant distribution in patients presenting with focal neurologic findings. It has been shown that some patients with PRES have transient arterial stenosis.

We searched patients with PRES in electronic health records at a single health system from January 2008 to December 2018. Inclusion criteria were age 18 years or older with clinical and radiographic evidence of PRES and arterial imaging (CT or MR angiography or cerebral angiogram.)  Age, presenting symptoms, comorbid conditions, and imaging findings were compared between those with arterial stenosis and those without.

Of 74 patients diagnosed with PRES, 46 had arterial imaging. Arterial stenosis was seen in 28.3% (13/46) of these patients. Stenoses improved in all 4 patients who had followup imaging, 3 with complete resolution. The arterial stenosis group was younger (median age 32 years with arterial stenosis vs 57.5 years without, p= 0.011.) Patients with arterial stenosis did not differ in frequency of presenting symptoms of seizure, encephalopathy, or focal neurologic deficits, nor did they differ in comorbid conditions of hypertension, immune suppression, eclampsia/preeclampsia, or antidepressant use.  There were no differences in ischemic stroke, intracerebral hemorrhage, subarachnoid hemorrhage, or frequency of diffusion restriction on MRI between the groups. The occurrence of >50% FLAIR reversibility was less frequent among those with arterial stenosis (40%) than in those without arterial stenosis (81%, p=0.04.)

A quarter of patients with PRES had transient arterial stenosis. These patients represent a subgroup within PRES patients who are younger age, but lower frequency of reversibility of parenchymal imaging abnormality.