Critical Cases - PRES

History: A 64-year-old woman presents to the ED via EMS after a witnessed seizure lasting less than 1 minute. The patient appeared post-ictal for EMS but is currently alert and oriented. She does not recall what happened. She has no history of seizures or syncope. She has a past medical history that includes hypertension.

Physical Exam

BP 201/106   HR 126   T 97.7   RR 20   SpO2 97%

  • Patient appears slightly confused with absent recent memory, but she is alert to person, place, and time
  • Her cranial nerves are intact, her reflexes are 2+, sensation and strength are intact
  • Finger-to-nose and heel-to-shin are within normal limits

Differential diagnosis

  • Hypertensive emergency
  • Intracranial mass
  • Stroke
  • Syncope
  • Migraine
  • Drug use
  • Head injury
  • Metabolic
  • Idiopathic


  • CTH without contrast
  • Blood pressure control with IV antihypertensives-reduce SBP by 25% in the first hour
  • Neurology consult
  • Patients with sequala including status epilepticus, stroke, or intracranial hemorrhage often require ICU for invasive BP monitoring



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Radiology read this as: “Ill-defined hypoattenuation involving the bilateral cerebellar hemispheres, right side greater left, nonspecific but may be secondary to acute to subacute ischemia. No acute intracranial hemorrhage.”



  • PRES has a variety of vague neurologic symptoms from headache to encephalopathy to seizure
  • There are multiple theories regarding the etiology and pathophysiology
  • One theory is that a rapid increase in arterial blood pressure leads to vascular leakage and vasogenic edema
  • Another theory is that cytotoxic agents or immunosuppressants can cause PRES (mechanism unknown)
  • CT or MRI (more sensitive) may show bihemispheric distribution of vasogenic edema in the posterior portion of the brain
  • There is no established diagnostic criteria for PRES but acute onset of neurologic findings, vasogenic edema on radiologic imaging, and reversibility have been suggested as criteria
  • Treatment is geared towards eliminating the trigger
  • Consider starting antiepileptics in consultation with neurology


Bottom line

  • PRES can often be a diagnosis of exclusion, consider it in patient with new and acute onset of neurologic findings with high blood pressure
  • Get a CT and consider MRI for further evaluation 



Fischer M, Schmutzhard E. Posterior reversible encephalopathy syndrome. J Neurol. 2017;264(8):1608-1616. doi:10.1007/s00415-016-8377-8