MEG may reveal hidden population of spikes in epilepsy with porencephalic cyst/Encephalomalacia

Porencephalic cyst/encephalomalacia is often associated with intractable epilepsy. A limited number of studies reported magnetoencephalography's (MEG's) potential to help construct treatment strategy for epilepsies associated with porencephalic cyst/encephalomalacia. The authors present here simultaneous electroencephalography (EEG) and MEG findings in three adult patients with pediatric-onset epilepsy due to porencephalic cyst/encephalomalacia. There were two types of spikes: one type was detected by MEG only (EEG2/MEG1), and the other detected by both EEG and MEG (EEG1/MEG1). Both types were seen in all three cases. The EEG2/MEG1 spikes all formed tight clusters; in contrast, the majority of EEG1/MEG1 spikes formed loose clusters. These data suggest that MEG may be helpful to better identify spike populations in epilepsy patients with porencephalic cyst/encephalomalacia. If hidden spike populations were to be found by MEG, this information would affect the interpretation of patient's pathophysiology and planning of intracranial electrode placement.