Posterior reversible encephalopathy syndrome (PRES, or posterior leukoencephalopahty syndrome) is a neurological condition caused by reversible cortical/subcortical vasogenic brain edema secondary to hypertension, cytotoxic drugs, immunosuppressants, autoimmune diseases, renal disease, eclampsia or pre-eclampsia. It is characterized by acute neurological symptoms such as headache, seizures, visual disturbances, and impaired levels of consciousness. Brain imaging usually reveals bilateral,

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... al/subcortical vasogenic edema. Completely unilateral PRES constituted only 2.6% of the cases in a previous study. Here we report the case of a pediatric patient with completely unilateral PRES. A 13-year-old boy was admitted with acute gastroenteritis. On the fourth day of hospitalization, he started to complain of headache and vomiting. He then developed generalized tonic-clonic seizure 3 times. His blood pressure was 180/121 mmHg during the first seizure, 188/112 mmHg during the second seizure and 152/92 mmHg during the third seizure. T2-weighted imaging with fluid attenuation by inversion recovery (T2 FLAIR) demonstrated high-signal intensity in the cortical gyri of the left frontal, parietal, and occipital lobes. Followup magnetic resonance imaging (MRI) was performed 2 weeks after the seizure onset, which indicated a significant improvement in the patient's condition. Abdominal pelvic computed tomography (CT) and renal CT angiography showed abnormal narrowing of the left renal artery. In summary, we present a case report of unilateral PRES secondary to renovascular hypertension due to left renal arterial obstruction.