Clinical Picture of Posterior Reversible Encephalopathy Syndrome (PRES)
PRES presents with a characteristic tetrad of acute neurological symptoms: altered mental status/encephalopathy, seizures, visual disturbances, and headache, accompanied by bilateral parieto-occipital vasogenic edema on MRI. 1
Core Clinical Manifestations
Neurological Symptoms
- Altered consciousness and encephalopathy are the most common presenting features, ranging from confusion to coma in severe cases 1, 2
- Seizures occur frequently and may be the initial presenting symptom, often recurrent in nature 3, 4
- Visual disturbances including blurred vision, visual field defects, cortical blindness, and photophobia are characteristic 2, 4
- Headache is a prominent early symptom in most patients 3, 4
- Focal neurological deficits including hemiparesis can occur but are less common 5
Radiological Features
- MRI shows bilateral T2-weighted and FLAIR hyperintensities predominantly in the parieto-occipital lobes affecting subcortical white matter, which is the diagnostic hallmark 1, 4
- Atypical patterns include involvement of anterior cerebral regions, deep white matter, and brainstem 2
- Vasogenic edema is the underlying pathophysiological finding, distinguishing PRES from cytotoxic edema seen in infarction 1, 3
Common Triggers and Risk Factors
High-Risk Clinical Contexts
- Severe hypertension with failure of cerebral autoregulation is the most frequent precipitant 1, 6, 4
- Renal impairment and acute renal dysfunction 6, 5
- Immunosuppressive medications, particularly cyclosporine and tacrolimus (calcineurin inhibitors) 1, 5
- Solid organ and bone marrow transplantation 1, 5
- Eclampsia and pre-eclampsia 3, 5
- Cancer chemotherapy and high-dose antineoplastic therapy 1, 2
- Autoimmune diseases 1, 4
Medication-Associated PRES
- Immunotherapy agents including checkpoint inhibitors can trigger PRES as an immune-related adverse event 7, 1
- Infliximab (anti-TNF therapy) has been reported to cause PRES 1
Atypical Presentations and Complications
Hemorrhagic PRES
- Intracerebral or subarachnoid hemorrhage complicates PRES in a subset of patients, particularly those with underlying coagulopathy 5
- 85% of PRES-associated hemorrhage cases have underlying bleeding diathesis, thrombocytopenia (mean platelet count 82.1 × 10³/μL), or elevated INR (mean 2.18) 5
- Hemorrhagic PRES carries worse prognosis with higher mortality and only 40% achieving good functional outcomes (mRS ≤1) compared to typical PRES 5
Key Diagnostic Pitfalls
Critical Differentiating Features
- Distinguish from posterior circulation stroke by recognizing the characteristic bilateral symmetric distribution and vasogenic (not cytotoxic) edema pattern 1
- Rule out infectious/autoimmune meningoencephalitis through CSF analysis when clinical suspicion exists 8
- Exclude metabolic encephalopathies (uremic, hypoglycemic, thyroid disorders) through comprehensive metabolic panel 8
- Consider cerebral amyloid angiopathy-related inflammation in appropriate clinical contexts, particularly in patients on anti-amyloid monoclonal antibody therapy 8
Common Diagnostic Errors
- Failure to obtain MRI promptly delays diagnosis; MRI is the gold standard and CT may miss early changes 1
- Missing concomitant conditions such as sepsis, electrolyte disturbances, or medication toxicity that complicate management 1
- Overlooking coagulopathy in patients who develop hemorrhagic complications 5
Prognostic Considerations
- Complete spontaneous remission occurs in most cases when the triggering factor is removed and blood pressure is controlled 1, 2
- Clinical improvement typically occurs within days to weeks (5-7 weeks in eclampsia cases) with appropriate management 3
- Delayed diagnosis and treatment can lead to permanent neurological sequelae, emphasizing the importance of early recognition 2, 4
- Hemorrhagic transformation significantly worsens prognosis with increased mortality and morbidity 5