Takushi Inoue

Very Fast Rhythmic Activity on Scalp EEG Associated with Epileptic Spasms

Summary:  Purpose: Very fast activity was investigated on the ictal EEGs of epileptic spasms to elucidate the pathophysiology of West syndrome (WS) and related disorders from a novel point of view.

Scalp‐recorded high‐frequency oscillations in childhood sleep‐induced electrical status epilepticus

Because high‐frequency oscillations (HFOs) may affect normal brain functions, we examined them using electroencephalography (EEG) in epilepsy with continuous spike‐waves during slow‐wave sleep (CSWS), a condition that can cause neuropsychological regression. In 10 children between 6 and 9 years of age with epilepsy with CSWS or related disorders, we investigated HFOs in scalp EEG spikes during slow‐wave sleep through temporal expansion of the EEG traces with a low‐cut frequency filter at 70 Hz as well as through time‐frequency power spectral analysis. HFOs (ripples) concurrent with spikes were detected in the temporally expanded traces, and the frequency of the high‐frequency peak with the greatest power in each patient’s spectra ranged from 97.7 to 140.6 Hz. This is the first report on the detection of HFOs from scalp EEG recordings in epileptic patients. We speculate that epileptic HFOs may interfere with higher brain functions in epilepsy with CSWS.

High-frequency oscillations in idiopathic partial epilepsy of childhood

Purpose:  We explored high‐frequency oscillations (HFOs) in scalp sleep electroencephalography (EEG) studies of patients with idiopathic partial epilepsy (IPE) of childhood in order to obtain a better understanding of the pathologic mechanisms underlying IPE.

Rasmussen encephalitis associated with SCN1A mutation

Mutations in the SCN1A gene, encoding the neuronal voltage‐gated sodium channel α1 subunit, cause SMEI, GEFS+, and related epileptic syndromes. We herein report the R1575C‐SCN1A mutation identified in a patient with Rasmussen encephalitis. R1575C were constructed in a recombinant human SCN1A and then heterologously expressed in HEK293 cells along with the human β1 and β2 sodium channel accessory subunits. Whole‐cell patch‐clamp recording was used to define biophysical properties. The R1575C channels exhibited increased channel availability and an increased persistent sodium current in comparison to the wild‐type. These defects of electrophysiological properties can result in neuronal hyperexitability. The seizure susceptibility allele may influence the pathogenesis of Rasmussen encephalitis in this case.

Spectral characteristics of EEG gamma rhythms associated with epileptic spasms

To elucidate the pathophysiology of epileptic spasms, unaveraged time-frequency spectra of spasm-associated EEG gamma rhythms were investigated in 15 patients with West syndrome or related disorders. Using these unaveraged spectra, we were able to investigate in detail various aspects of the structure of ictal gamma rhythms that could not be examined using averaged spectra. The characteristics of the ictal gamma peaks (peak frequency, power, duration, and the number of peaks in each brain-region for each spasm) were statistically evaluated with respect to their differences among the brain regions and over the time-course of the clusters. Our findings were as follows: (1) Gamma peaks were clearly detected in most spectra and generally had a similar pattern in each spasm, which repeated in clusters. (2) The mean frequency of gamma peaks was 69.2+/-16.8Hz, and the number of peaks in each brain region of each spasm was 1.83+/-1.16. (3) The occipitoparietal gamma peaks had significantly greater power and longer duration than the frontocentral peaks. (4) The frequency of the gamma peaks was higher in the mid phase of clusters than in the ending, and it tended to have a positive correlation with its latency from the preceding beta peak. An analysis of the ictal gamma rhythms might give some insight into the generative mechanism of spasms.

EEG dipole characteristics in Panayiotopoulos syndrome

Summary:  Purpose: Panayiotopoulos syndrome (PS) is a type of benign childhood partial epilepsy that is frequently associated with abundant multifocal spikes other than main occipital spikes on the EEG. In this study, we investigated the characteristic features of dipoles in PS.

Characteristics of Slow Waves on EEG Associated with Epileptic Spasms

Summary:  Purpose: The high‐voltage slow waves (HVSs) on EEG associated with epileptic spasms were investigated to clarify their characteristics and their relation to the pathophysiology of spasms in West syndrome and related disorders.

Spectral analysis of EEG gamma rhythms associated with tonic seizures in Lennox–Gastaut syndrome

PURPOSE EEG gamma rhythms, which are found in association with epileptic spasms in infants with West syndrome, were explored in the ictal EEGs of tonic seizures in older patients with Lennox-Gastaut syndrome (LGS) to investigate the pathophysiology of the disease. METHODS The subjects were 20 patients with LGS (11 males, 9 females; age range: 3 years 1 month to 29 years 3 months) who had at least one digitally recorded tonic seizure with minimal artifacts. A time-frequency analysis was applied to each patients ictal EEG data. RESULTS A total of 54 seizures were analyzed, excluding spasms in clusters. The ictal EEGs of the tonic seizures showed only diffuse desynchronization in 10 seizures, and desynchronization followed by rhythmic activity in 21. The ictal discharges started as rhythmic activity of varying amplitude without initial desynchronization in 23 seizures. In a total of 25 seizures from 13 patients, gamma rhythms with frequencies ranging from 43 to 101.6Hz were detected by temporal expansion of the ictal EEG traces and spectral analysis. In 24 (96%) of these seizures, gamma rhythms were observed at seizure onset corresponding to visually identified desynchronization. In the remaining seizure, gamma rhythms were found in association with transient suppression of high-amplitude rapid discharges. CONCLUSION The detection of gamma rhythms in the ictal EEGs of tonic seizures indicated that some tonic seizures might have generative mechanisms in common with epileptic spasms, and that these mechanisms are possibly related to desynchronization at seizure onset.

Epilepsy development in infancy with epileptic discharges

As a part of the study to prevent West syndrome (WS) by early treatment, we assessed what kind of epilepsy developed in infants who showed epileptic discharges in early infancy. EEG examinations were performed on 116 infants born from 1997 to September 2004, both before and after 3 months of corrected age (CA). We divided 45 infants who showed epileptic discharges in early infancy into two groups according to the existence of periventricular leukomalacia (PVL) and retrospectively performed the course observation at the survey point on April 1 in 2005. Out of 45 infants showing epileptic discharges in early infancy, 26 developed WS. Compared with infants without PVL, infants with PVL were more likely to develop WS than infants without PVL. Furthermore, infants with PVL were more likely to develop WS than other types of epilepsy. Namely, 11 out of 17 infants with PVL developed WS at the survey point. All infants with WS showed initial epileptic discharges before 5 months of corrected age (CA), and most of them (except for five) had initial epileptic discharges before 3 months of CA. There were two infants who once developed hypsarrhythmia on EEG; however, after starting VPA therapy, they did not develop WS with the improvement of EEG findings, and one was presented here in detail. We proposed that preterm infants with PVL who showed epileptic discharges before 3 months of CA should be treated by antiepileptic drugs to prevent the onset of WS syndrome.

Inhalation of 10% carbon dioxide rapidly terminates Scn1a mutation-related hyperthermia-induced seizures

The aim of this study was to assess the anticonvulsant effect of carbon dioxide (CO2) on Scn1a mutation-related febrile seizures. We examined physiological changes in the blood gas levels after the induction of hyperthermia-induced seizures (HISs), which were associated with the Scn1a missense mutation. We determined the efficacy of inhalation of 5% or 10% CO2 to treat HISs. HISs were evoked in Scn1a mutant and wild-type (WT) rats by hot water baths. To determine the anticonvulsant effect of CO2 inhalation, rats were placed in a chamber filled with air or mixed gas containing 5% CO2 or 10% CO2 for 3 min, immediately after the induction of HISs. We also analyzed the blood gas levels at the end of inhalation of CO2. Hot water bathing induced a significant reduction in the partial pressure of CO2 (pCO2) and respiratory alkalosis in the WT and Scn1a mutant rats. HISs were evoked in 100% of the Scn1a mutant rats within 5 min, but in none of the WT rats. The Scn1a mutant rats demonstrated a higher HISs susceptibility associated with respiratory alkalosis than the WT rats. Inhalation of 10% CO2 shortened the seizure duration from 62.6±12.1 s to 15.5±1.0 s. Blood gas analysis after the inhalation of 10% CO2 demonstrated an elevated pCO2 level and respiratory acidosis. Inhalation of 10% CO2 demonstrated a potent and fast-acting anticonvulsant effect against HISs.