Abstracts

Rationale: The onset and mechanism of epileptic spasms (ES) have still under discussed. Recently, the analysis of modulation index (MI) that reflecting the degree of coupling between high frequency oscillations (HFO) and slow waves in the electrocorticography could contribute to find out the epileptic foci in patients with ES. Pathological HFO coupled with 3-4Hz and physiological HFO coupled with 0.5-1Hz. However, the reported method was invasive and we had better to detect meaningful MI even in scalp EEG. Analyzing of scalp EEG cannot detect HFO. Therefore, we tried to analyze the interictal epileptic discharges (IEDs) in scalp EEG by using the phase-amplitude coupling between the detectable gamma oscillations and the slow waves in a patient with ES. Methods: We reviewed a case of 5-year-old girl with Sturge-Weber syndrome who had a leptomeningeal angioma in the right temporo-parieto-occipital regions. Her seizure semiology was ES. EEG demonstrated IEDs originated from the contralateral hemisphere. We performed posterior corpus callosotomy (PCC) as the 1^stsurgery. After PCC, EEG presented IEDs originated from the ipsilateral hemisphere. We performed posterior quadrantectomy (PQT) as the 2^ndsurgery. After PQT, EEG demonstrated seldom IEDs and consequently resulted seizure free. We recorded scalp EEG at a sampling rate of 500Hz. MI was calculated at each electrode using EEGLAB Toolbox PACTv.0.17 in MATLAB. We measured MI between the following fast oscillations; ranging from 30 to 50Hz (low gamma oscillations [LGO]), 50 to 80Hz (high gamma oscillations [HGO]) amplitude and the two slow wave phases (0.5-1Hz, 3-4Hz) in total, anterior and posterior areas. We calculated reduction rate of MI in total, anterior and posterior areas after PCC and PQT. We compared MI and reduction rate of MI between each area.  Results: After PCC, MI(LGO & 3-4Hz) in the ipsilateral posterior area was significantly higher than that in the contralateral posterior area (p‹0.01). After PCC, MI(HGO & 3-4Hz) in the ipsilateral total and posterior area were significantly higher than those in the contralateral total and posterior area (p=0.02, p=0.03). After PCC, reduction rate of MI(LGO & 3-4Hz) and MI(HGO & 3-4Hz) in the contralateral total and posterior area were significantly higher those in the ipsilateral total and posterior area (p=0.04, p‹0.01). After PQT, reduction rate of MI(LGO & 3-4Hz) and MI(HGO & 3-4Hz) in the ipsilateral posterior area were significantly higher than those in the contralateral posterior region (p=0.03, p=0.04). Both after PCC and PQT, there were no significant differences of MI(HGO/LGO & 0.5-1Hz). Conclusions: This is the first study that analyzing the phase-amplitude coupling in scalp EEG demonstrate the dynamic changes of the epileptogenicity of ES. Corpus callosum exaggerate the symptomatic severity and electrophysiological activity in ES. Disconnection of both the commissural and association fibers could attribute to the improvement of ES.  Funding: None