Abstracts

Rationale: Seizure is one of the most common clinical presentations in patients with posterior reversible encephalopathy syndrome (PRES). This syndrome is usually considered to be fully reversible and not a cause for chronic epilepsy or persistent cortical dysfunction. To date, the data of EEG findings in patients with PRES is limited. In this study, we retrospectively evaluated EEG characteristics in PRES patients in a single medical center. We also evaluated the long term outcome regarding seizures occurrence beyond the acute phase in these patients Methods: We searched the radiology database at the University of Minnesota from 1997-2011. We identified patients with radiologically diagnosed PRES. Among the patients with PRES, we reviewed MRI images, EEG finding, clinical manifestations including seizure occurrences and clinical outcome beyond the acute phase. Results: 75 patients were included in the study. 58/75 (77.3%) of patients with PRES had seizures. A total of 48 EEG studies were performed in 38 patients. 38/48 (79.1%) of EEG studies during PRES had generalized slowing of the background activity and other abnormalities, 25/48 (52.0%) had generalized slowing alone. 13/48 (27.1%) of EEG studies had sharps and/or spikes. 4/75 (5.3%) of these patients had seizures later than one month after the onset of 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: The most common EEG pattern in patients with PRES was generalized slowing. Many patients had sharp waves and/or spikes. Most patients who had spikes during PRES did not subsequently develop chronic epilepsy. No patient developed chronic epilepsy in the absence of spikes during PRES. PRES may infrequently cause partial epilepsy.