What is PRES Syndrome?
Posterior Reversible Encephalopathy Syndrome (PRES) is a clinical-radiological syndrome characterized by acute neurological symptoms (altered consciousness, seizures, visual disturbances, headaches) and bilateral vasogenic edema predominantly in the parieto-occipital regions on MRI, triggered by conditions that disrupt the blood-brain barrier through endothelial injury. 1
Pathophysiology
The syndrome develops when abrupt blood pressure changes or endothelial toxins cause disruption of the blood-brain barrier, leading to vasogenic edema primarily affecting the posterior brain regions. 1 This occurs when blood pressure is markedly elevated and cerebral autoregulation fails, resulting in cerebral edema in posterior brain areas. 1
Clinical Presentation
Neurological symptoms include: 1, 2
- Altered consciousness or mental status changes
- Seizures (common during acute phase, though chronic epilepsy is rare)
- Visual disturbances including blurred vision or cortical blindness
- Headaches
- Focal neurological deficits
The presentation can be heterogeneous, with symptoms ranging from mild to severe. 3
Common Triggering Conditions
The most frequent precipitating factors are: 1, 2, 4
- Pre-existing arterial hypertension and hypertensive crises
- Renal impairment or renal failure
- Eclampsia or pre-eclampsia in pregnant patients
- Immunosuppressive medications, particularly cyclosporine
- High-dose chemotherapy or antineoplastic therapy
- Allogenic stem-cell transplantation or solid organ transplantation
- Autoimmune diseases
- Anti-TNF therapy (such as infliximab) 1
Diagnostic Imaging
MRI is the gold standard for diagnosis, showing increased signal intensity on T2-weighted or FLAIR imaging with hyperintensities in bilateral parietal-occipital lobes, predominantly affecting white matter. 1 CT scan can be useful to exclude intracranial hemorrhage when MRI is not immediately feasible. 1
Atypical imaging features can include: 2
- Involvement of other brain regions beyond parieto-occipital areas
- Cortical involvement
- Restricted diffusion
- Hemorrhage
- Contrast enhancement
Prognosis and Reversibility
Complete spontaneous remission occurs in most cases without sequelae, making the condition typically reversible with appropriate management. 1 However, early detection and prompt treatment are critical factors for rapid recovery and good outcomes. 1, 4
Factors associated with poor outcomes include: 2
- Altered sensorium
- Hypertensive etiology
- Hyperglycemia
- Longer time to control the causative factor
- Elevated C-reactive protein
- Coagulopathy
- Extensive cerebral edema
- Hemorrhage on imaging
While clinical and radiographic reversibility is common, long-standing morbidity and mortality can occur in severe forms, though aggressive care has markedly reduced mortality and improved functional outcomes in malignant forms of PRES. 2
Key Clinical Pitfall
The most critical error is failure to recognize PRES as a potential complication in patients with renal disease, hypertensive crisis, or those receiving immunosuppressive therapy, as delayed recognition can lead to irreversible brain injury despite the typically reversible nature of the syndrome. 3, 4