Dynamic magnetic source imaging of absence seizure initialization and propagation: A magnetoencephalography study

• The dMSI is particularly useful in visualizing epileptic discharges.
• The paper adds information about onset and propagation of absence seizures.
• The anterior and posterior cortical activity form main propagative pattern.
• The default mode network is strongly involved in absence seizures.

SummaryPurposeThe present study aims to determine the initialization and propagation of typical absence seizures using magnetoencephalography (MEG).MethodFourteen drug-naïve children with childhood absence epilepsy (CAE) were studied using a 275-Channel MEG system. The spectral signatures of epileptic activity were assessed using Morlet continuous wavelet transform. Magnetic sources were volumetrically localized using dynamic magnetic source imaging (dMSI) with a slide window at a millisecond temporal resolution.ResultThe initial portion of ictal activity was predominantly located to the left frontal and posterior cortices. The frontal sources were in the left medial prefrontal cortex (MPFC), the pre-supplementary motor area (pre-SMA), the primary motor cortex, and the lateral prefrontal cortex. The posterior cortical sources were predominantly localized to the left precuneus (pC) and the medial occipital cortices (MOC). The ictal activity after the initialization showed involvement of the MPFC and pC of all patients (14/14) and recursive propagation between the frontal (MPFC) and posterior cortices (pC and MOC) via either the medial portion of the brain (9/14) or the thalamus (5/14), respectively.ConclusionThe left frontal and posterior (pC and MOC) cortices play a key role in the initialization of epileptic activity in absence seizures. The thalamus plays a key role in the propagation of absence seizures between the frontal and posterior cortical sources. Considering the MPFC and pC are the nodes of the default mode network (DMN), our results support involvement of the DMN in absence seizures.