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I have completed bits of my EM training from India. Currently I am boarded with credentials from Christian Medical College, Vellore and also from the prestigious Royal College of Emergency Medicine, UK.  I am currently working in London as an A&E doctor, trying to appreciate the differences in the practise and culture of Emergency Medicine across different healthcare systems. I have always been an avid FOAMed supporter because FOAMed played an indispensable role during the days of my initial training. Through this blog, I aspire to disseminate knowledge and stay up to date with the EM literature. 

Monday, March 6, 2017

Posterior Reversible Encephalopathy Syndrome (PRES)

Posterior Reversible Encephalopathy syndrome PRES (also known as reversible posterior leukoencephalopathy syndrome) is a constellation of clinical and radiological findings which presents with rapid onset headache, seizures, altered consciousness, and visual disturbances. 

It strongly associated with with renal disease, vascular and autoimmune diseases, immunosuppressive medications, and organ transplantation. Nearly 3/4 patients with PRES are hypertensive, but others may have normal or only mildly elevated blood pressure.

Failure of Cerebral Autoregualtion, endothelial injury, disruption of blood brain barrier leading to Vasogenic edema is a proposed mechanism. However, the exact pathophysiology remains unclear. 

Prompt recognition of PRES is important to prevent permanent damage due to ongoing cerebral ischemia. Having a high index of suspicion is important. PRES must be added to our routine list of differentials of Posterior Circulation Stroke, SAH, Cerebral Venous Thrombosis. Focal neurologic deficits are uncommon in PRES and Seizures are the most common presentation. 

It is reasonable to start with CT Head in the Emergency Department to rule out other CNS Catastrophes. However, MRI is a better tool to diagnose PRES. Magnetic Resonance Imaging recordings showing white matter abnormalities without infarction. Classical MRI findings of vasogenic edema involving bilateral parietal-occipital lobes. 

PRES appears to be a misnomer as the syndrome is not always reversible, and it may not be localised to either the white matter or the posterior regions of the brain. Atypical features— including hemorrhage, asymmetrical changes, isolated involvement of the frontal lobes, and cortical lesions are common.


  • Rapid withdrawal of the trigger (Eclampsia, Drugs)
  • Prevent Seizures
  • Aggressive blood pressure management 

Take Home:

  • PRES should be considered in patients who present with seizures, altered consciousness, visual disturbances, or headache, particularly with acute hypertension.
  • PRES has been associated with chronic and acute kidney disease, solid organ transplantation, and use of immunosuppressive drugs.
  • Typical MRI findings include reversible, symmetrical, posterior subcortical vasogenic edema.
  • If recognized and treated promptly, the rapid-onset symptoms and radiologic features usually fully resolve within days to weeks.

  • Hinchey J, Chaves C, Appignani B, et al.  A reversible posterior leukoencephalopathy syndromeN Engl J Med. 1996;334(8):494-500
  • Hobson, E. V., Craven, I., & Blank, S. C. (2012). Posterior Reversible Encephalopathy Syndrome: A Truly Treatable Neurologic Illness. Peritoneal Dialysis International : Journal of the International Society for Peritoneal Dialysis32(6), 590–594. http://doi.org/10.3747/pdi.2012.00152
  • Fugate, J. E., Claassen, D. O., Cloft, H. J., Kallmes, D. F., Kozak, O. S., & Rabinstein, A. A. (2010). Posterior Reversible Encephalopathy Syndrome: Associated Clinical and Radiologic Findings. Mayo Clinic Proceedings85(5), 427–432. http://doi.org/10.4065/mcp.2009.0590
  • https://radiopaedia.org/articles/posterior-reversible-encephalopathy-syndrome-1

     Lakshay Chanana
     Speciality Doctor
     Northwick Park Hospital
     Department of Emergency Medicine



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