Makindo Medical Notes

Related Subjects: |Hypertension |Hypertension in Pregnancy |Malignant Hypertension |PreEclampsia, Eclapsmia and HELLP

Note: In most cases, PRES resolves spontaneously, with clinical and radiological improvement. Severe cases, however, can be fatal.

Introduction

• First described by Hinchey in 1996 as a distinctive syndrome.
• Affects both children and adults sporadically.
• Characterized by vasogenic oedema in the posterior circulation on MRI, which typically resolves.

Aetiology

• Increased vessel permeability and breakdown of the blood-brain barrier.
• Vasogenic oedema visible on CT/MRI.
• Failure of cerebral autoregulation in the setting of hypertension or other triggers.
• May be associated with hormonal changes or toxic drug exposure.

Imaging

A trigger is typically identifiable, often acute hypertension (e.g., AKI, eclampsia, or illicit drug use) or related to sepsis, multi-organ failure, or autoimmune diseases.

Clinical Presentation

• Encephalopathy: Acute confusion, lethargy, and dull headache.
• Seizures: Occur in 90% of cases, usually tonic-clonic; status epilepticus may develop.
• Visual Symptoms: Occipital lobe involvement leads to hemianopia, visual hallucinations, or neglect.
• Headache: Typically bilateral and dull.
• Symptoms typically arise over 12-48 hours and often resolve within a week, though recovery may occasionally take longer.
• Hypertension is common but may be secondary to the PRES rather than causative.

Investigations

• Blood Tests: May show elevated LDH, low platelets, low magnesium, and raised LDH.
• CT Scan: Only helpful in about 50% of cases.
• MRI: Confirms diagnosis with bilateral vasogenic oedema, with hyperintensities on FLAIR in the parietal/occipital regions (sometimes in frontal, temporal, or cerebellar areas). Extensive lesions on T2-weighted images suggest a worse prognosis. DWI changes with restricted diffusion may occasionally be present.
• Angiography: May show reversible focal or diffuse abnormalities, including vasoconstriction and vasospasm.
• EEG: Non-specific findings, often diffuse slowing or focal delta waves.

Causes or Triggers of PRES

Differential Diagnoses

• Bilateral PCA Infarcts
• Venous Sinus Thrombosis or Intracranial Hemorrhage: Presents with headache, seizures, and focal signs. Non-contrast CT is diagnostic.
• Infective Encephalitis or Meningitis: Particularly herpes simplex encephalitis; initiate acyclovir and antibiotics pending diagnosis.
• Basilar Artery Thrombosis: May cause progressive neurologic deficits, tetraparesis, coma, or locked-in syndrome.
• Central Nervous System Vasculitis: Can mimic PRES but typically shows more diffuse and irreversible MRI changes.

Management

• Supportive Care: ABCs, monitor and manage blood pressure, and treat the underlying cause.
• Reversibility: As the name implies, PRES is often reversible, though haemorrhage can occur.
• Recovery: Most patients recover within weeks, with repeat MRI at 10 days showing improvement in most cases.
• Blood Pressure Control: Manage cautiously, avoiding nitroglycerin due to adverse reports.
• Seizures: Usually subside without the need for long-term antiepileptic drugs.
• Prognosis: Generally excellent, with outcomes largely dependent on the underlying cause.

Reviews and References

• Posterior Reversible Encephalopathy Syndrome. J Neurol (2017) 264:1608-1616
• Posterior Reversible Encephalopathy Syndrome: A Treatable Neurologic Illness. Peritoneal Dialysis International, Vol. 32, pp. 590-594