Spatial relationship between fast and slow components of ictal activities and interictal epileptiform discharges in epileptic spasms

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

In 1940, van Wagenen and Herren first proposed the corpus callosotomy (CC) as a surgical procedure for epilepsy. CC has been mainly used to treat drop attacks, which are classified as generalized tonic or atonic seizures. Epileptic spasms (ESs) are a type of epileptic seizure characterized as brief muscle contractions with ictal polyphasic slow waves on an electroencephalogram and a main feature of West syndrome. Resection surgeries, including frontal/posterior disconnections and hemispherotomy, have been established for the treatment of medically intractable ES in patients with unilaterally localized epileptogenic regions. However, CC has also been adopted for ES treatment, with studies involving CC to treat ES having increased since 2010. In those studies, patients without lesions observed on magnetic resonance imaging or equally bilateral lesions predominated, in contrast to studies on resection surgeries. Here, we present a review of relevant literature concerning CC and relevant adaptations. We discuss history and adaptations of CC, and patient selection for epilepsy surgeries due to medically intractable ES, and compared resection surgeries with CC. We propose a surgical selection flow involving resection surgery or CC as first-line treatment for patients with ES who have been assessed as suitable candidates for surgery.

Strong coupling between slow oscillations and wide fast ripples in children with epileptic spasms: Investigation of modulation index and occurrence rate

OBJECTIVE

Epileptic spasms (ES) often become drug-resistant. To reveal the electrophysiological difference between children with ES (ES+) and without ES (ES-), we compared the occurrence rate (OR) of high-frequency oscillations (HFOs) and the modulation index (MI) of coupling between slow and fast oscillations. In ES+, we hypothesized that (1) pathological HFOs are more widely distributed and (2) slow oscillations show stronger coupling with pathological HFOs than in ES-.

METHODS

We retrospectively reviewed 24 children with drug-resistant multilobar onset epilepsy, who underwent intracranial video electroencephalography prior to multilobar resections. We measured the OR of HFOs and determined the electrodes with a high rate of HFOs by cluster analysis. We calculated MI, which reflects the degree of coupling between HFO (ripple/fast ripple [FR]) amplitude and 5 different frequency bands of delta and theta activities (0.5-1 Hz, 1-2 Hz, 2-3 Hz, 3-4 Hz, 4-8 Hz).

RESULTS

In ES+ (n = 10), the OR_(FRs) , the number of electrodes with high-rate FRs, and the MI_{(FRs & 3-4 Hz)} in all electrodes were significantly higher than in ES- (n = 14). In both the ES+ and ES- groups, MI_{(ripples/FRs & 3-4 Hz)} was the highest among the 5 frequency bands. Within the good seizure outcome group, the OR_(FRs) and the MI_{(FRs & 3-4 Hz)} in the resected area in ES+ were significantly higher than in ES- (OR_[FRs] , P = .04; MI_{[FRs & 3-4 Hz]} , P = .04).

SIGNIFICANCE

In ES+, the larger number of high-rate FR electrodes indicates more widespread epileptogenicity than in ES-. High values of OR_(FRs) and MI_{(FRs & 3-4 Hz)} in ES+ compared to ES- are a signature of the severity of epileptogenicity. We proved that ES+ children who achieved seizure freedom following multilobar resections exhibited strong coupling between slow oscillations and FRs.

Fast (40-150Hz) oscillations are associated with positive slow waves in the ictal EEGs of epileptic spasms in West syndrome

OBJECTIVE

To elucidate the generative mechanisms of epileptic spasms (ESs) in West syndrome, we investigated the temporal relationship between scalp fast (40-150Hz) oscillations (FOs) and slow waves in the ictal electroencephalograms (EEGs) of ESs.

METHODS

In 11 infants with WS, ictal FOs were detected in a bipolar montage based on spectral and waveform criteria. Their temporal distribution was analyzed in terms of the positive peaks (trough point, T_T) of identical EEG data in a referential montage. Among six EEG data sections defined according to T_T, the number of FOs, peak power values, and peak frequencies were compared.

RESULTS

We identified a total of 1014 FOs (946 gamma and 68 ripple oscillations), which clustered closely at T_T. The number of gamma oscillations in the 1s epoch including T_T was significantly higher than those in the prior and subsequent phases. Peak power values and frequencies tended to be higher in these positive phase sections.

CONCLUSIONS

The temporal association of FO clustering and positive slow waves in the ictal EEGs of ES indicated that active neuronal firing related to FOs underlies the generation of ESs and their ictal slow waves.