What causes posterior reversible encephalopathy syndrome (PRES)?

Causes of Posterior Reversible Encephalopathy Syndrome (PRES)

Posterior Reversible Encephalopathy Syndrome (PRES) is primarily caused by hypertension, pre-eclampsia/eclampsia, immunosuppressive medications, and certain systemic conditions that disrupt the blood-brain barrier, leading to vasogenic edema in the posterior brain regions. 1

Major Causes of PRES

Vascular/Hemodynamic Causes

• Hypertension and hypertensive encephalopathy - When blood pressure exceeds cerebral autoregulatory limits, particularly affecting posterior brain regions where sympathetic innervation is less pronounced 1, 2
• Pre-eclampsia and eclampsia - Common triggers in pregnant women 1, 3
• Renal impairment - Associated with fluid and electrolyte imbalances that can trigger PRES 1

Medication-Related Causes

• Immunosuppressive medications - Particularly cyclosporine, which is a well-documented trigger 1, 4
• Anticancer therapies - Various chemotherapeutic agents can cause endothelial injury 1
• Infliximab - Cases reported in Crohn's disease patients receiving this anti-TNF therapy 5

Systemic Conditions

• Autoimmune disorders - Various autoimmune conditions can predispose to PRES 1, 4
• Sepsis - Can trigger PRES through inflammatory mechanisms 1
• Allogenic stem-cell transplantation - Associated with higher risk of developing PRES 1
• Solid organ transplantation - Particularly when combined with immunosuppressive therapy 1

Less Common Causes

• Vasoactive substances - Including cannabis, antidepressants, and nasal decongestants 6
• Inadvertent dural puncture - Rare cases reported following spinal procedures 7
• Normotensive PRES - Uncommon but documented cases without hypertension 6

Pathophysiological Mechanisms

Two main theories explain the development of PRES:

1. Hypertension-induced autoregulatory failure - Severe hypertension exceeds cerebral autoregulation limits, causing breakthrough vasogenic edema, particularly in posterior brain regions 1, 3

2. Endothelial dysfunction - Direct injury to vascular endothelium from medications, autoimmune processes, or other triggers leads to blood-brain barrier disruption 1

Clinical Presentation

• Headache - Often severe and of sudden onset 3, 4
• Visual disturbances - Including blurred vision, hemianopia, or cortical blindness 8, 4
• Altered consciousness - Ranging from confusion to coma 1, 4
• Seizures - Often the presenting symptom, can be focal or generalized 1, 4

Diagnostic Imaging

• MRI findings - Characteristic hyperintensities on T2-weighted/FLAIR sequences in bilateral parietal-occipital regions, predominantly affecting white matter 1, 3
• CT scan - May show hypodensities in affected areas but less sensitive than MRI 1, 6

Common Pitfalls in Diagnosis

• Failure to recognize PRES in normotensive patients - While hypertension is common, PRES can occur without elevated blood pressure 6
• Mistaking PRES for other neurological conditions - Including stroke, demyelinating diseases, or encephalitis 1, 2
• Delayed diagnosis - Early recognition is crucial for prompt treatment and favorable outcomes 4

PRES typically follows a benign course with complete resolution when the underlying cause is promptly identified and addressed, highlighting the importance of early recognition and management 1, 4.