Posterior Reversible Encephalopathy Syndrome

Posterior reversible encephalopathy syndrome (PRES) is a clinicoradiological syndrome of headache, seizures, visual disturbance and encephalopathy with reversible vasogenic oedema, predominantly posterior.

• Causes: hypertension (especially hypertensive emergency), eclampsia, immunosuppressants (tacrolimus, ciclosporin), chemotherapy, bevacizumab, renal failure, autoimmune disease (SLE), sepsis, sickle cell disease, thrombotic microangiopathy.

• Mechanism: endothelial dysfunction and failure of cerebral autoregulation causing vasogenic oedema.

• Usually reversible within days to weeks, but 10 to 20% suffer haemorrhage, infarction or permanent deficit.

• Acute headache, seizures (often generalised, in 70 to 90%), visual disturbance (blurred vision, cortical blindness), confusion, reduced consciousness.

• Focal deficits uncommon; status epilepticus possible.

• Hypertension in 70%, normal blood pressure in some.

• MRI brain: bilateral vasogenic oedema (T2/FLAIR hyperintensity, increased ADC) in parieto occipital white matter, also frontal, temporal, cerebellum, brainstem; contrast enhancement and microhaemorrhages may occur.

• CT may show hypodensity; MR angiography may show vasoconstriction.

• EEG: slowing, epileptiform discharges.

• Evaluate precipitants: blood pressure, renal function, drug levels (tacrolimus), pregnancy status (eclampsia), autoimmune markers.

• Exclude stroke, venous thrombosis, encephalitis, vasculitis, reversible cerebral vasoconstriction syndrome (overlap).

• Lower blood pressure promptly but gradually (by 20 to 25% in first hours): labetalol 20 to 80 mg IV bolus or 0.5 to 2 mg/min, nicardipine 5 to 15 mg/h, clevidipine; avoid precipitous falls.

• Remove or reduce the offending drug (tacrolimus, ciclosporin, chemotherapy), switch immunosuppressant (e.g. mycophenolate, sirolimus).

• Seizures: levetiracetam 500 to 1500 mg twice daily; benzodiazepines for status; continue for 3 to 6 months if recovery complete.

• Eclampsia: magnesium sulphate 4 g IV loading then 1 g/h, delivery of fetus.

• Treat the underlying cause (dialysis for renal failure, immunosuppression for SLE, exchange transfusion in sickle cell).

• ICU monitoring for encephalopathy; repeat MRI after 1 to 2 weeks to confirm resolution.

• Follow up for recurrent PRES, blood pressure control long term.