Magnetoencephalography source analysis in epilepsy-aphasia spectrum

Epilepsy-aphasia spectrum (EAS) represents the most common group of childhood epilepsy syndromes, however, the precise source localization of epileptiform discharges remains undetermined. This study aimed to localize and compare the sources of epileptiform discharges across different EAS subtypes using magnetoencephalography (MEG).

In this prospective MEG-based study, we recruited 70 patients with EAS, including 52 with self-limited epilepsy with centrotemporal spikes (SeLECTS), 12 with atypical benign partial epilepsy (ABPE), 3 with Landau-Kleffner syndrome (LKS), and 3 with Epileptic Encephalopathy with continuous Spike-and-Waves during sleep (EE-SWAS). Ten independent epileptiform discharges per patient were analyzed using distributed source modeling with standardized low-resolution electromagnetic brain tomography (sLORETA). The spike source density was quantified as current amplitude, and source locations were mapped according to the Desikan-Killiany atlas.

The source locations of epileptiform discharges differed significantly across EAS subtypes. EE-SWAS exhibited the highest overall current source density, followed by ABPE, whereas SeLECTS and LKS showed the lowest values. Lobar analysis revealed frontal-predominant discharges in EE-SWAS and ABPE, contrasting with temporal-predominant discharges in SeLECTS and LKS. Moreover, patients with secondary generalized tonic‑clonic seizures exhibited higher current source densities than those with only focal seizures, consistent with broader EEG discharge spread.

This first systematic MEG source analysis across the full EAS reveals a hierarchical gradient from temporo-centric to fronto-centric distribution, paralleling the clinical severity gradient. Our findings highlight the potential of MEG source imaging for phenotyping and pathophysiological stratification in EAS.