Neuromagnetic high-frequency oscillations correlate with seizure severity in absence epilepsy

Objective: This study quantified the clinical correlation of interictal and ictal neuromagnetic activities from low- to very-high-frequency ranges in childhood absence epilepsy (CAE).

Methods: Twelve patients with clinically diagnosed drug-naïve CAE were studied using a 275-channel whole-head magnetoencephalography (MEG) system. MEG data were digitized at 6000 Hz and analyzed at both sensor and source levels with multi-frequency analyses.

Results: Neuromagnetic changes from interictal to ictal periods predominantly occurred in medial prefrontal cortex and parieto-occipito-temporal junction in absence seizures. The changes were statistically significant in low-frequency bands only (<30 Hz, p<0.0001). There was a significant correlation between the source strength of ictal high-frequency oscillations (HFOs) in 200-1000 Hz and the number of daily seizures (r=0.734, p<0.01).

Conclusions: CAE has focal neuromagnetic sources. The transition from interictal to ictal periods is associated with the elevation of low-frequency brain activities. The strength of HFOs reflects the severity of absence seizures.

Significance: Low- and high-frequency MEG signals reveal distinct brain activities in CAE. HFOs is a new biomarker for the study of absence seizures.