Interictal paroxysmal fast activity and functional connectivity in steroid responsive and non-responsive Lennox-Gastaut syndrome.

Objective: The aim of this study was to investigate the changes in interictal paroxysmal fast activity and functional connectivity before and after steroid pulse therapy in patients with Lennox-Gastaut syndrome (LGS).

Methods: The medical records of patients who visited the pediatric neurology clinics with LGS as their primary complaint and completed intravenous methylprednisolone therapy were reviewed. Effects of steroid therapy on clinical seizures and scalp EEG were analyzed. Generalized paroxysmal fast activity (GPFA) burden were detected and compared before and after treatment. As a measure of global functional connectivity, we calculated mutual information (MI) between all channels, which was then used to assess network topology.

Results: Steroid pulse therapy improved seizure control in 20 (27 %) patients. Fourteen (18.9 %) children became complete seizure-free, but 8 patients experienced relapses subsequently. The later age of disease onset, shorter duration of epilepsy, and definite cerebral structural etiology were found to advantageous for hormone response. A significant correlation was observed between GPFA burden and diary seizure number. Patients with higher GPFA burdens and higher MI values exhibited a poor response to steroid treatment. Patients who respond positively to steroids therapy demonstrated longer characteristic path length, higher modularity and lower global efficiency in high beta and gamma bands.

Conclusion: Add-on steroid therapy can be considered as an optional adjunct for LGS. GPFA could be utilized as a parameter to predict treatment effects and prognosis for LGS. The group that responded to steroids showed a high level of local clustering and low long-range network connectivity. This study provides real-world evidence regarding the effectiveness of steroid in refractory LGS.