AbstractPosterior reversible encephalopathy syndrome (PRES) is a rare clinical disease that refers to the subcortical vasogenic edema involving bilateral parieto-occipital regions, with a usually reversible syndrome when causes are eliminated or controlled. Hypertension or blood pressure fluctuations are most common causes of PRES, but other contributors like chemotherapy and autoimmune disorders have also been reported. PRES has rapid onset of symptoms. Therefore, it is of major importance to determine whether blood pressure management plays an important role in prognosis. We presented two PRES patients who developed non-convulsive seizure but had normal baseline blood pressure at the time of presence of cause. The diagnosis of PRES was made by neurologists. The patients had no history of seizure or hypertension, but during the disease course they presented with temporal elevation of blood pressure with different durations. The second patients without instant blood pressure control developed residual symptoms of seizure at 90- and 120-day follow-up. Although the exact pathophysiology of PRES remains to be fully understood, primary and secondary prolonged blood pressure fluctuations may be associated with the prognosis of this syndrome. Early blood pressure management would be critical to favorable outcome.