Posterior reversible encephalopathy syndrome

Overview

Posterior reversible encephalopathy syndrome (PRES) is a rare but serious neurological condition characterized by sudden onset of symptoms such as headaches, seizures, altered mental status, and visual disturbances. It is associated with reversible vasogenic edema (swelling) in the posterior regions of the brain, particularly the parietal and occipital lobes. Despite the name, PRES is not always confined to the posterior brain regions and, in some cases, may involve the frontal lobes, cerebellum, or brainstem.

Prompt recognition and management are crucial because, although the condition is potentially reversible, delays in diagnosis and treatment can lead to permanent neurological damage or even death. PRES is often triggered by acute elevations in blood pressure or exposure to certain medications or systemic conditions.

Causes

The exact pathophysiology of PRES is not completely understood, but it is believed to involve failure of cerebral autoregulation in response to acute hypertension, leading to endothelial dysfunction and blood-brain barrier breakdown. This results in fluid leakage and vasogenic edema. Common causes and risk factors include:

• Acute hypertension or hypertensive crisis – Often due to eclampsia, renal disease, or sudden blood pressure spikes.

• Pre-eclampsia and eclampsia – Common obstetric causes of PRES, particularly in the third trimester or postpartum period.

• Renal failure or chronic kidney disease – Impaired blood pressure regulation increases risk.

• Autoimmune diseases – Such as systemic lupus erythematosus (SLE) and vasculitis.

• Immunosuppressive or cytotoxic medications – Including cyclosporine, tacrolimus, and chemotherapy agents.

• Sepsis or systemic infections – Can lead to endothelial injury and inflammatory cytokine release.

• Organ transplantation – Especially in the setting of immunosuppressive therapy.

Symptoms

The clinical presentation of PRES is acute or subacute, often developing over hours to days. The symptoms can be varied and may include:

• Headache – Often severe and diffuse.

• Seizures – Generalized or focal seizures, including status epilepticus in severe cases.

• Visual disturbances – Such as blurred vision, visual field deficits, or cortical blindness.

• Altered mental status – Confusion, agitation, lethargy, or decreased level of consciousness.

• Nausea and vomiting – Related to increased intracranial pressure.

• Motor deficits – Hemiparesis or coordination issues in rare cases.

The severity and combination of symptoms vary depending on the extent and location of cerebral involvement. In pregnant women, symptoms may overlap with those of eclampsia.

Diagnosis

Diagnosis of PRES requires a combination of clinical evaluation and neuroimaging. Early identification is key to initiating treatment and improving outcomes.

• Clinical history and physical exam: Identification of risk factors such as high blood pressure, kidney disease, or medication use. Neurological examination helps assess mental status, vision, and motor function.

• Magnetic Resonance Imaging (MRI): The gold standard for diagnosis. T2-weighted and FLAIR sequences typically show symmetrical hyperintense signals indicating vasogenic edema, predominantly in the parieto-occipital lobes.

• Computed Tomography (CT): May be used initially but is less sensitive. Can show hypoattenuation in affected areas.

• Electroencephalogram (EEG): May be useful in evaluating seizures or altered consciousness.

• Laboratory tests: To evaluate kidney function, complete blood count, liver function, and rule out infections or autoimmune activity.

• Blood pressure monitoring: Essential to identify and control hypertensive episodes.

Differential diagnoses include stroke, central nervous system infection, toxic/metabolic encephalopathy, and demyelinating diseases.

Treatment

Management of PRES focuses on addressing the underlying cause, controlling symptoms, and preventing complications. Treatment is generally supportive but must be prompt to prevent permanent damage.

Blood Pressure Control

• Antihypertensive therapy: Gradual reduction of blood pressure using intravenous agents such as labetalol, nicardipine, or hydralazine. Avoid overly rapid decreases to prevent cerebral ischemia.

Withdrawal or Adjustment of Offending Medications

• Immunosuppressants or cytotoxic drugs may need to be reduced or discontinued.

Seizure Management

• Antiepileptic drugs (AEDs): Used to control acute seizures. Long-term AED use is typically not required unless seizures persist.

Supportive Care

• Monitoring in an ICU setting may be necessary for severe cases.

• Management of fluid and electrolyte balance, especially in patients with renal dysfunction.

Treatment of Underlying Conditions

• Such as addressing eclampsia, renal failure, sepsis, or autoimmune disease.

Prognosis

The prognosis for posterior reversible encephalopathy syndrome is generally favorable with timely diagnosis and management. Most patients experience significant improvement or complete resolution of symptoms within days to weeks.

Key factors that influence prognosis include:

• Speed and effectiveness of blood pressure control.

• Timely withdrawal of triggering medications or treatment of underlying conditions.

• Severity and duration of symptoms before treatment begins.

While the condition is termed “reversible,” in some cases—particularly when diagnosis is delayed—permanent neurological deficits, cerebral hemorrhage, or death may occur. Follow-up imaging is often done to confirm resolution of brain edema.

With appropriate care, most patients recover fully and do not experience long-term neurological issues.