Electrographic patterns in patients with posterior reversible encephalopathy syndrome and seizures

Posterior reversible encephalopathy syndrome (PRES) is a neurotoxic encephalopathic state associated with reversible cerebral vasogenic edema. Seizures are a common clinical presentation in PRES, however its electroencephalographic and radiologic pattern correlation is limited in this subset of patients. The aim of this study is to analyze the origin of electrographic dysfunction according to the radiologic pattern in patients with PRES and seizures.

We retrospectively identified 46 cancer patients who developed PRES and seizures at The University of Texas MD Anderson Cancer Center between January 2006 and June 2012. Clinical, radiographic and electroencephalographic data were abstracted from their records and reviewed for our analysis.

The average age at presentation was 49.9±19.7years. Thirty-four (73.9%) patients were women. Twenty-two (47.8%) patients had a primary hematological malignancy whereas the rest had a solid tumor. Thirty-three (71.7%) patients had received some form of chemotherapy. The mean systolic blood pressure (SBP) variation was 23.7±16.4mmHg at onset of symptoms. On brain MRI, 32 (69.6%) patients had typical pattern while 14 (30.4%) had an atypical pattern. Thirty-seven (80.4%) patients had scalp electroencephalogram (EEG) evaluation. Thirty-three (89.2%) had abnormal EEG findings: diffuse theta/delta slowing (N=12, 36.4%), followed by diffuse slowing with focal dysfunction (N=8, 24.2%), focal dysfunction with epileptiform discharges (N=4, 12.1%), non-convulsive status epilepticus (N=4, 12.1%), focal seizure activity and burst suppression (N=2, 6.1% each). Lateralized Periodic Discharges (LPDs) were recorded in 1 case. Four patients had focal dysfunction localized to areas without conventional MRI signal changes. Four patients had recurrent seizures, of which 3 had an atypical PRES pattern.

PRES appears to be a diffuse neurotoxic encephalopathic state. Origin of seizures seen on scalp EEG may not correlate with the location of vasogenic edema/MRI signal changes raising the possibility of greater degree of dysfunction which may exist beyond those areas.