Posterior reversible encephalopathy syndrome with obstructive hydrocephalus. A case report.

We describe an unusual presentation of posterior reversible encephalopathy syndrome (PRES) with predominant posterior fossa edema, causing ascending transtentorial herniation, tonsillar herniation, and obstructive hydrocephalus. MR imaging with additional MR spectroscopy and MR perfusion helped discriminate PRES from infiltrative tumor, and supported the pathogenesis of hydrostatic edema. Infusion of an antihypertensive drug was promptly administered. Diversion of cerebrospinal fluid by ventriculostomy was subsequently performed. However, the patient developed thalamic hemorrhage and secondary intraventricular hemorrhage with contralateral hemiparesis. Awareness of this rare cause of obstructive hydrocephalus with aggressive treatment of high blood pressure may help obviate the need of ventriculostomy and may prevent the hemorrhagic complication.