EEG before and after total corpus callosotomy for pharmacoresistant infantile spasms: Fast oscillations and slow‐wave connectivity in hypsarrhythmia

Abstract

Objective We analyzed the features of fast oscillations (FOs) and connectivity in hypsarrhythmia to identify biomarkers for predicting seizure outcomes after total corpus callosotomy (TCC) in children with pharmacoresistant infantile spasms (IS). We hypothesize that the power of FOs and connectivity of slow waves in hypsarrhythmia would indicate the prognosis of IS. Method We retrospectively identified 42 children with pharmacoresistant IS who underwent TCC from 2009 to 2014 at Nagasaki Medical Center. We collected preoperative hypsarrhythmia for 200 seconds from each child. Children were categorized into three groups with interictal epileptic discharges on EEG at 6 months after TCC: group A, no epileptic discharge; group B, lateralized epileptic discharges; and group C; bilateral epileptic discharges. We analyzed spectral power and phase synchronization in preoperative hypsarrhythmia among the three groups. Results We found 10 children in group A, 10 children in group B, and 22 children in group C. All group A and 1 in group B achieved seizure freedom after TCC. Six (67%) of 9 group B children who underwent further surgeries achieved seizure freedom. Ten (45%) of group C children had seizure reduction >50% after TCC, and 13 (87%) of 15 children who underwent further surgeries had residual seizures. The clinical profiles of the three groups did not differ significantly. The power of FOs (≥45 Hz) in hypsarrhythmia was significantly stronger in group C at the midline and temporal regions than in groups B and A (P = .014). The connectivity of theta (4‐9 Hz) and FOs (29‐70 Hz) tended to increase in group C, compared with the increased connectivity of 1‐2 Hz in group A (P = .08). Significance The increased power and connectivity of FOs in hypsarrhythmia may correlate with pharmacoresistant and surgically resistant seizures in IS. The existence and connectivity of FOs are associated with unilateral/bilateral cortical epileptogenicity in hypsarrhythmia. Prominent slow waves and connectivity without FOs might correlate with seizure freedom after TCC. Modulation of the callosal system with subcortical/cortical epileptic discharges might play a role in generating hypsarrhythmia and IS.

Secondary epileptogenesis on gradient magnetic-field topography correlates with seizure outcomes after vagus nerve stimulation

“…After CC, the generalized discharges often disappear. In patients with hypsarrhythmia, which represents the most chaotic generalized/multifocal epileptic discharges, the interictal epileptiform discharges become either bilateral independent discharges or unilateral discharges, or none after CC (Baba et al 2019). In our present series, 5 patients required further VNS for their remaining generalized onset seizures.…”

“…CC is known to be effective for drop attacks caused by myoclonic, tonic, or atonic seizures (Tanriverdi et al 2009;Maehara and Shimizu 2001;Oguni et al 1991;Rossi et al 1996). In children with infantile spasms and hypsarrhythmia, the function of the corpus callosum in the chaotic bilateral fast and slow oscillations of hypsarrhythmia has been reported to be an essential part of the modulation of interhemispheric discharges (Baba et al 2019). In our present study, we evaluated patients for whom CC did not improve seizure control and further VNS was required.…”

Phase Lag Analyses on Ictal Scalp Electroencephalography May Predict Outcomes of Corpus Callosotomy for Epileptic Spasms

“…Previous studies on the analysis of the EEG power indicated that the emergence of gamma activity during interictal scalp EEG in patients with West syndrome positively correlated with intractableness of seizures or severity of hypsarrhythmia (17,18). Moreover, abnormal EEGs, defined as abnormal backgrounds Although the mean CPS in each patient tended to be higher in unfavorable outcome group in all frequency bands, significant differences were seen in the delta, theta, and gamma bands.…”

Corpus Callosotomy for Controlling Epileptic Spasms: A Proposal for Surgical Selection

“…Of these, three patients achieved seizure freedom with CC only, and two achieved seizure freedom through additional treatments [9]. In the patients with partial response in those previous studies, CC achieved reduction of seizure frequency and/or changed the ES into smaller ones, like head nodding or resolving drop attacks, unilaterally focal onset ES, or bilaterally independent focal onset-ES [3,4,6,[8][9][10][11][12]61,71]. Large data of long-term outcomes of CC for ES is unavailable.…”

“…In these cases, ictal EEG is visually bilateral and synchronous on slow waves [10]. Computed frequency analyses of presurgical scalp EEG recordings have shown small phase lags of ictal slow and beta waves among the bilateral hemispheres and less power and connectivity on interictal records [8,11]. caused predominantly by unilateral cortices and tend to show a uniformly lateralized seizure type.…”