Posterior Reversible Encephalopathy Syndrome (PRES)

Overview

Posterior reversible encephalopathy syndrome (PRES) is a condition in which fluid builds up and swelling develops in parts of the brain, most often the back (posterior) regions. "Encephalopathy" means a disturbance in brain function, and "reversible" reflects that, with prompt treatment, symptoms and brain changes often resolve completely.

PRES is usually triggered by a sudden, severe rise in blood pressure or by certain medications and conditions that affect the brain's small blood vessels. It is a medical emergency: although typically reversible, untreated PRES can lead to lasting damage such as bleeding or stroke. Quick recognition and treatment of the underlying cause are key to a good outcome.

Symptoms

Symptoms usually develop over hours to a few days and may include:

• Headache, often severe
• Seizures, sometimes the first sign
• Visual disturbances, such as blurred vision, partial vision loss, or seeing things that are not there
• Confusion, drowsiness, or altered alertness
• Nausea and vomiting
• Weakness in some cases

PRES is an emergency. Sudden severe headache with seizures, vision changes, or confusion, especially with very high blood pressure, needs immediate medical attention.

Causes

PRES is thought to result from a failure of the brain's normal regulation of blood flow, leading to leakage of fluid and swelling. Common triggers include:

• Severe or rapidly rising high blood pressure
• Preeclampsia and eclampsia in pregnancy
• Certain medications, including some used for cancer treatment and to suppress the immune system after transplants
• Kidney disease
• Autoimmune conditions
• Severe infections such as sepsis

Risk Factors

• Poorly controlled or rapidly fluctuating blood pressure
• Pregnancy with preeclampsia or eclampsia
• Treatment with certain chemotherapy or immunosuppressant drugs
• Kidney disease, including those on dialysis
• Autoimmune diseases such as lupus
• Organ or stem cell transplant

Diagnosis

Diagnosis combines the clinical picture with brain imaging:

• MRI of the brain is the most useful test, typically showing swelling in the back parts of the brain on both sides.
• CT scan may be used first in an emergency to look for bleeding or other causes.
• Blood pressure measurement and review of medications and recent illnesses to identify the trigger.
• Blood and urine tests to assess kidney function, look for preeclampsia, and check for other causes.
• EEG if seizures occur.

Treatment

Treatment focuses on removing the trigger and supporting the brain, usually in hospital and often in intensive care:

• Lowering blood pressure carefully and steadily when it is the cause.
• Controlling seizures with anti-seizure medication.
• Stopping or adjusting the responsible medication when a drug is the trigger.
• Treating the underlying condition, such as delivering the baby in eclampsia or managing infection or kidney problems.
• Supportive care and close monitoring.

With prompt treatment, most people recover fully over days to weeks, and follow-up imaging often shows the brain changes have resolved.

Prevention

• Keep blood pressure well controlled, especially if you have kidney disease or are pregnant
• Attend prenatal care so preeclampsia is caught and treated early
• Follow monitoring plans if you take chemotherapy or immunosuppressant medicines
• Report severe headaches, vision changes, or seizures promptly, particularly if at higher risk

When to See a Doctor

Seek emergency care immediately for:

• A seizure, especially a first-time seizure
• Sudden severe headache with vision changes or confusion
• Very high blood pressure with neurological symptoms
• In pregnancy, severe headache, vision changes, or upper abdominal pain with high blood pressure

Rapid treatment improves the chance of full recovery and prevents complications such as bleeding or stroke.

Related Topics

Frequently Asked Questions

References

1. National Institute of Neurological Disorders and Stroke (NINDS).
2. National Organization for Rare Disorders (NORD). Posterior reversible encephalopathy syndrome.
3. MedlinePlus, U.S. National Library of Medicine.
4. American College of Obstetricians and Gynecologists (ACOG).