Focal electrical status (FES): a new finding associated with polymicrogyria

Polymicrogyria (PMG), a malformation of cortical organization, may, occasionally, be associated with electrical status epilepticus of sleep and focal electrical status. The aim of this study was to better characterize the latter association. This was an historic cohort study. Inclusion criteria were diagnosis of PMG on neuroimaging and presence of focal electrical status on EEG. Focal electrical status was considered when patients presented with continuous epileptiform abnormalities over a focal area on awakeness, which became bilateral and synchronous during sleep. Interictal EEGs lasted for at least 20 minutes and up to 4 hours and were performed during awakeness and sleep. Neuroimaging findings were classified as holosylvian PMG and hemispheric PMG. All patients, except one, had asymmetric neuroimaging findings, mostly on the right side. All patients had partial motor seizures, which were easily controlled with antiepileptic drugs in two of them. Despite seizure control, their EEGs still registered focal electrical status. The other four patients presented with atonic seizures and/or atypical absences. All patients showed awakeness focal electrical status that was activated by sleep. Focal electrical status is a different EEG pattern from other continuous electrographical patterns previously described, such as electrical status epilepticus of sleep, continuous epileptiform discharges, and rhythmic epileptiform discharges. Each one has its own peculiarity. Focal electrical status seems to be associated with asymmetric and extensive PMG.