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S Ohtahara

Publications and source records attributed to S Ohtahara.

At least 19 recordsLinked to original sources
PubMed1996

Investigation of bilateral synchronous spike-wave discharge by EEG topography.

To investigate the generator mechanism of the generalized discharge in childhood epilepsy, we studied its voltage field distribution using linked ear reference (L + R), common averaged reference (CA), and source derivation methods (SD). Two cases of epilepsy with clinical lapse of consciousness, and diffuse EEG spike-wave burst were divided into primary bilateral synchrony (PBS) and secondary bilateral synchrony (SBS), using coherence-phase analysis. Spike topograph images were shown by three different references. The difference in spike voltage between CA and SD was also investigated (CA-SD). By all three different references, PBS spike topography showed a broad symmetrical voltage gradient. In SBS, a left frontal focal negativity was shown with a steep voltage gradient in the topographic images of spikes by L + R, CA and SD. This asymmetry disappeared gradually at the end of the spike-wave burst. Both patients showed almost identical broad symmetrical voltage gradients on CA-SD topogram. EEG topography using various references suggested that the potential fields produced by deep generators were identical for PBS and SBS, although those generated by surface generators were different. These findings support the hypothesis that SBS may be projected from the subcortical system, and activated by cortical firing.

Brain↗
PubMed1996

Effects of high-dose antiepileptic drugs on event-related potentials in epileptic children.

N200 and P300 of event-related potentials (ERPs) were recorded from 22 epileptic children receiving high-dose antiepileptic drugs. The patients were undergoing monotherapy with supratherapeutic serum level and were not mentally retarded. P300 latency was prolonged in 5 of 8 patients (62.5%) of the carbamazepine (CBZ) group and in 4 of 7 patients (57.1%) of the phenytoin (PHT) group. Only one child of the PHT group showed abnormality in brain-stem auditory evoked potentials (BAEPs). Abnormality of P300 was more frequent than that of BAEP. In patients of the PHT group who underwent examinations consecutively before and after changing the dose, P300 latency was prolonged rapidly when the PHT level exceeded 30 micrograms/ml. This suggested that the prolongation was dose dependent. In all patients of the valproic acid (VPA) group, P300 latency was normal. Only 2 patients of the PHT group had P300 prolongation simultaneously with clinical signs of intoxication. Others demonstrated changes in P300 without symptoms of side effects.

Adolescent↗
PubMed1996

Partial seizures in West syndrome.

PURPOSE: To study the occurrence of partial seizures (PS) and elucidate the characteristics of patients with West syndrome (WS) with PS. METHODS: We investigated the electroclinical and radiologic features in 92 children with WS who were older than 3 years at follow-up. RESULTS: Thirty-six (39.1%) children had PS at some time during the course of the disease. They had a significantly high incidence of asymmetric spasms, hemiparesis, and asymmetric hypsarrhythmia. Their seizure prognosis was significantly less favorable. PS appeared only before spasms (group A, six children), concomitant with spasms (group B, 18 children), and only after spasms ceased (group C, 12 children). Five children in group B had PS after spasms stopped. PS in group A and during the period of active spasms in group B showed high seizure frequency and variability of both seizures and EEG manifestations. The PS and EEG epileptiform discharges were mainly in parietal-posterior temporal-occipital, and central regions. Late PSs in group B and PSs in group C were characterized by stereotyped manifestations and relatively low seizure frequency. These PSs originated mostly from frontal regions. CONCLUSIONS: In some children with WS, cortical lesions can induce both PS and spasms in series, whereas in others, both types of seizures occur with abnormally increased excitability throughout the cortex rather than as the result of a single cortical lesion. These findings suggest caution in interpreting focal discharges, which may fluctuate and are not necessarily indicative of a surgically accessible lesion. When the discharges are stable and correlate with an equally stable clinical pattern, the likelihood of an underlying cortical lesion is greater.

Age of Onset↗
PubMed1995

Simple and rapid analysis of lamotrigine, a novel antiepileptic, in human serum by high-performance liquid chromatography using a solid-phase extraction technique.

A simple and rapid method for the quantitation of concentrations of lamotrigine, a novel antiepileptic, in human serum was developed with high-performance liquid chromatography, using a solid-phase extraction technique. The mobile phase was composed of acetonitrile-10 mM phosphate buffer (pH 3.5) containing 5 mM sodium octanesulphonate (27:73, v/v), and components were detected at 265 nm. Retention times of acetanilide as an internal standard and lamotrigine were 3.4 and 10.3 min, respectively. The coefficients of variation were 3.1-4.5% and 4.4-9.8% for the within-day and between-day precision estimates, respectively. The extraction recovery of lamotrigine added to blank serum was 86-107%. The quantitation limit of lamotrigine was ca. 0.2 microgram/ml in 100 microliters of serum. These results suggest that the method employed in this study is useful for the routine monitoring of serum concentrations of lamotrigine in epileptic patients.

Anticonvulsants↗
PubMed1995

Spike dipole analysis using SEP dipole as a marker.

UNLABELLED: In dipole localization analysis many problems remain which affect the accuracy of localization. We performed dipole estimation of spikes and SEP components in identical patients. The subjects are 8 cases of benign childhood epilepsy with centrotemporal spikes (BCECS), and two cases of temporal lobe epilepsy (TLE). In 8 of 10 cases, we also investigated dipoles using a 3-layer model in addition to a single layer (homogenous) model. RESULTS: 1) In 8 cases of BCECS, the spike dipoles were concentrated at the central line near the SEP dipoles, at a slightly fronto-lateral-downward position to the latter. The spike dipoles seemed to be situated at the bottom of the sensory cortex. 2) In two cases of TLE, the spike dipoles were located at the same coronal plane with the SEP dipoles, and more deeply seated mesially. The spike dipoles seemed to be at the bottom of the mesial temporal area. 3) Using 3-layer models, both the spike dipoles and the SEP dipoles located more superficially, while conserving the positional relationship with each other. CONCLUSION: It is possible to more accurately define spike dipoles by using the SEP dipole as a marker.

Brain↗
PubMed1995

Monozygotic twin patients with congenital ichthyosis, microcephalus, spastic quadriplegia, myoclonus, and EEG abnormalities.

A pair of monozygotic twins manifested widespread ichthyosis on the trunk and extremities, mainly on the extensor surface of the lower legs. Both patients had severe developmental retardation, microcephalus, spastic quadriplegia, myoclonus, and hearing impairment. Cranial computed tomography and magnetic resonance imaging revealed diffuse cortical atrophy. Electroencephalography documented diffuse slow wave dysrhythmia and marked epileptic discharges, namely bilateral occipital dominant, and low-voltage multifocal spikes which appeared asynchronously as a burst, mainly during sleep. Skin biopsy revealed hyperkeratosis with parakeratosis. Granular cell layer was not thickened and diminished. Papillomatosis was absent. Electron microscopy did not reveal any distinctive abnormalities. Sjögren-Larsson syndrome and other known ichthyosis syndromes were excluded because of the difference in localization of skin lesions, skin manifestations, lack of papillomatosis, the nature and severity of neurologic symptoms and marked electroencephalographic abnormalities.

Diseases in Twins↗
PubMed1995

Lennox-Gastaut syndrome: a new vista.

Lennox-Gastaut syndrome (LGS) is regarded as a model of the epileptic syndrome because of its specific clinicoelectrical manifestation. However, a close investigation reveals that its outline is somewhat vague, having the borderland around it. Precise diagnosis in an individual case is not always easy. In this paper, the diagnostic criteria of LGS are described. According to these criteria, cases with LGS were subclassified into the typical and the atypical cases, and also cases in the borderland of LGS were reviewed. On the other hand, our prospective long-term follow-up study revealed that cortical mechanisms played an important role in the pathophysiology, clinical features and refractoriness of LGS. Secondary bilateral synchrony (SBS) is supposed to be a mode of expression of cortical mechanisms of LGS. A newly developed method with coherence and phase analysis demonstrated that the pathophysiology was based on SBS in 33% of the typical LGS cases. This finding is not only crucial for the choice of rational treatment including epilepsy surgery, such as callosotomy, but also contributes to a more refined subclassification of LGS.

Child↗
PubMed1995

Neuroepidemiological study of childhood epilepsy by application of international classification of epilepsies and epileptic syndromes (ILAE, 1989).

A population-based survey of childhood epilepsy was made in 1975 on the total population of children aged < 10 years living in Okayama Prefecture (n = 2,378 patients). Using the data obtained, we attempted to reclassify the various types of epilepsy according to the international classification (ILAE, 1989). Reclassification was possible in 1,872 (78.7%) of the 2,378 cases. The 1,872 cases consisted of 1,045 (55.8%) with localization-related epilepsies, 824 (44.0%) with generalized epilepsies, and 3 (0.2%) with epilepsies undetermined whether focal or generalized. Classification of the epilepsies in a population-based survey using the international classification involves difficulties, because both clinical and EEG findings are essential. However, if an appropriate area is selected, classification of epilepsies and epileptic syndromes in a population-based survey is possible by referring to all medical records stored at every hospital and practitioner's clinic that administers treatment to patients with epilepsy in the area.

Age Factors↗
PubMed1994

Infantile hypotonia and paroxysmal dystonia: a variant of alternating hemiplegia of childhood?

We report 2 children with early onset of hypotonia and frequent episodes of paroxysmal dystonia. The episodes were abolished even by brief naps. One of the children developed alternating hemiplegia in the second decade. These children seem to have a variant of the now well-recognized syndrome of alternating hemiplegia of childhood. In that disorder, episodes of alternating hemiplegia develop before the age of 18 months. This syndrome must be considered in the differential diagnosis of paroxysmal dystonia in childhood.

Adolescent↗
PubMed1993

Clinical application of spike averaging to dipole tracing method.

As part of our studies on localization of epileptic foci, dipole analysis using averaged spikes were compared with that using individual spikes for 25 patients with localization related epilepsy. Our results are as follows. 1) In the group which showed stable dipoles from individual spikes, dipole localization from averaged and individual spikes were similar, although the former showed a higher dipolarity and more stable location, for the entire spike discharge including the peak, trough and wave. The high dipolarity was due to improved signal to noise ratio obtained from averaging. 2) The cases with centrotemporal spike focus including benign childhood epilepsy with centrotemporal spikes showed more reliable dipoles. In the cases with frontal lobe epilepsy, reliable dipoles were rarely obtained even with averaged spikes. Each method provided independent information, so they are of complementary value.

Adolescent↗
PubMed1993

The effects of age on the N200 component of the auditory event-related potentials.

This study was undertaken to determine the effects of development and aging on N200 of event-related potentials from childhood to adulthood. Event-related potentials were recorded from 164 normal subjects ranging in age from 4 to 77 years. A total of 127 of the 164 subjects demonstrated N200 peaks. N200 showed marked developmental changes. During childhood, the N200 latency decreased rapidly with age to the minimum (217 +/- 17.3 ms) at 16 years of age, while it was prolonged gradually with age during adulthood. The latency/age slope in the subjects from 5 to 15 years of age was -9.03 ms/year, while +0.97 ms/year in those from 16 to 77. The N200-P300 interpeak latency remained constant in all age groups and showed no age-related changes. The N200 amplitude decreased as age increased. Nineteen young cases showed N200 peaks to the frequent stimuli. Their ages ranged from 5 to 17 years. Our study suggests that N200 is valuable in evaluating the developmental and aging processes in the central nervous system. The results of this study could be used as normative data in clinical practices.

Acoustic Stimulation↗