Posterior Reversible Encephalopathy Syndrome (PRES)

Posterior reversible encephalopathy syndrome (PRES) is a clinico-radiological syndrome characterized by vasogenic edema predominantly in the posterior parieto-occipital white matter, presenting with acute headache, seizures, visual disturbances (cortical blindness, hemianopia, blurred vision), and altered mental status. The pathophysiology involves failure of cerebral autoregulation, most commonly from acute severe hypertension exceeding the upper autoregulatory limit (MAP greater than 150-160 mmHg), causing forced dilation of cerebral arterioles, breakdown of the blood-brain barrier, and extravasation of plasma proteins and fluid into the brain parenchyma (vasogenic edema). The posterior circulation is preferentially affected because it has less sympathetic innervation and therefore less autoregulatory capacity than the anterior circulation. Common triggers include hypertensive emergency, eclampsia, immunosuppressive medications (cyclosporine, tacrolimus, which cause endothelial toxicity), and cytotoxic chemotherapy. The nurse monitors blood pressure continuously, administers IV antihypertensive therapy with a target of gradual reduction (25% in the first hour), monitors for seizures and implements seizure precautions, performs serial neurological assessments including visual acuity and field testing, monitors for recurrence, and coordinates with the medical team regarding dose adjustment or discontinuation of offending immunosuppressive agents.