title: Seizure outcomes of posterior reversible encephalopathy syndrome and correlations with electroencephalographic changes.
abstract: BACKGROUND
  Seizures are among the most common clinical presentations of posterior reversible encephalopathy syndrome (PRES). This syndrome has rarely been reported to cause chronic epilepsy or persistent cortical dysfunction. The prognostic value of EEG findings during PRES is unknown. We retrospectively evaluated EEG characteristics in patients with PRES in a single medical center. We also evaluated the long-term outcome regarding seizure occurrence beyond the acute phase in these patients.
  
  
  METHODS
  We searched a radiology database at the University of Minnesota from 1997 to 2012 to identify patients with clinically and radiologically diagnosed PRES. Among the patients with PRES, we reviewed MRI images, EEG findings, clinical manifestations including seizure occurrences, and clinical outcomes beyond the acute phase.
  
  
  RESULTS
  Seventy-five patients were included in the study. Fifty-eight out of seventy-five (77.3%) patients with PRES had seizures. A total of 48 EEG studies were performed in 38 patients. Generalized slowing was the most common EEG pattern. Among the 38 patients who had EEGs, 37 (97.3%) patients had diffuse or focal slowing of the background, and 11 (28.9%) patients had IEDs. Four out of seventy-five (5.3%) patients had seizures later than one month beyond their hospitalization for PRES. None of these 4 patients had seizures before the episode of PRES. Two patients developed chronic epilepsy, with seizures occurring later than one year after the PRES.
  
  
  CONCLUSIONS
  Most patients who had seizures or who had epileptiform activities in EEG during PRES did not subsequently develop chronic epilepsy. No patient developed chronic epilepsy in the absence of clinical seizures during PRES. Posterior reversible encephalopathy syndrome may infrequently be associated with subsequent development of symptomatic epilepsy.
authors.affiliation: Department of Neurology, University of Minnesota Medical School, Minneapolis, MN, USA. Electronic address: zysha@umn.edu.
authors.forename: Zhiyi
authors.initials: Z
authors.lastname: Sha
authors.affiliation: Department of Neurology, University of Minnesota Medical School, Minneapolis, MN, USA.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Moran
authors.affiliation: Department of Radiology, University of Minnesota Medical School, Minneapolis, MN, USA.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: McKinney
authors.affiliation: Department of Neurology, University of Minnesota Medical School, Minneapolis, MN, USA.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Henry
mesh_terms: D000328:Adult; D000368:Aged; D001927:Brain Diseases / Q000150:complications* / Q000473:pathology*; D058256:Brain Waves / Q000502:physiology*; D004569:Electroencephalography; D004827:Epilepsy / Q000150:complications; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009778:Occipital Lobe / Q000473:pathology; D010296:Parietal Lobe / Q000473:pathology*; D054038:Posterior Leukoencephalopathy Syndrome; D011379:Prognosis; D012189:Retrospective Studies; D012640:Seizures / Q000175:diagnosis / Q000209:etiology*
keywords: EEG; Epilepsy; MRI; Posterior reversible encephalopathy syndrome (PRES)