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Biomedical subjects

A Ochi

Publications and source records attributed to A Ochi.

At least 19 recordsLinked to original sources
PubMed2001

Malignant rolandic-sylvian epilepsy in children: diagnosis, treatment, and outcomes.

OBJECTIVE: To describe the diagnosis, treatment, and outcomes in children with malignant rolandic-sylvian epilepsy (MRSE), defined as a form of epilepsy characterized by sensorimotor seizures, medical refractoriness, normal MRI, frontocentrotemporal EEG spikes, rolandic-sylvian spike sources on magnetoencephalography (MEG), and cognitive problems. METHODS: A retrospective chart analysis of seven patients who had shown these characteristics and undergone extensive diagnostic testing, including MEG and intracranial video-EEG was performed. RESULTS: Interictal scalp EEG spikes were seen over the frontocentrotemporal regions bilaterally (6) and unilaterally (1). MEG showed spike sources in the perisylvian region in two patients (both bilateral) and in the perirolandic fissure in five (two bilateral). Three patients required bilateral subdural strips to lateralize seizures before electrocorticography. Final electrocorticograms showed an ictal onset zone around the rolandic (four cases) and rolandic-sylvian regions (three cases). Six patients showed neuropsychological deficits. After cortical excision and multiple subpial transection, three were seizure free and four had seizures rarely (30 months' mean follow-up). No child had a permanent deficit in sensorimotor or cognitive functions, although two showed exacerbation of preexisting attentional deficits. Tissue analysis showed definite evidence of neuronal migration disorders (3) and gliosis (2). CONCLUSIONS: MEG was helpful for localizing both malignant rolandic-sylvian neuronal activities and functional cortex. Successive neuropsychological assessments are necessary to detect cognitive deterioration and indicate remedial programming. If, after careful observation over at least 5 years, surgery is considered to control refractory seizures, intracranial video-EEG is needed to localize the epileptogenic zone.

Adolescent↗
PubMed2001

MEG predicts epileptic zone in lesional extrahippocampal epilepsy: 12 pediatric surgery cases.

PURPOSE: To discover whether the spatial distribution of spike sources determined by magnetoencephalography (MEG) provides reliable information for planning surgery and predicting outcomes in pediatric patients with lesional extrahippocampal epilepsy. METHODS: We retrospectively studied 12 children with extrahippocampal epilepsy secondary to cortical dysplasia (CD), tumor, or porencephalic cyst. We compared interictal MEG spike source locations and somatosensory evoked fields derived from equivalent-current dipole modeling with intraoperative or extraoperative electrocorticography (ECoG). RESULTS: MEG spike sources were found in proximity to the lesion in all patients and extended from lesions in five patients with CD. Marginal spike sources were noted in three patients with tumors, one patient with a cyst, and one with CD, and extramarginal sources in three patients with tumors. Three patients with tumors underwent lesionectomy only; two had further cortical excisions. One patient with CD underwent lesionectomy only, three had lesionectomy and cortical excisions, and two had lesionectomy and multiple subpial transection. Asymmetric MEG spike sources correlated with ECoG findings in all patients. Residual epileptiform discharges on postexcisional ECoG corresponded to spike sources in three patients with tumors and one patient with a cyst. Eleven patients have been seizure free for 1-6 years (mean, 4 years). One patient had residual seizures after incomplete excision of right temporal CD. CONCLUSIONS: MEG delineated asymmetric epileptogenicity surrounding lesions and the eloquent cortex. Complete tumor resection produced favorable outcomes despite residual postexcisional ECoG spikes and extramarginal MEG spike sources. CD characterized by clusters of MEG spike sources within and extending from lesions seen on magnetic resonance imaging (MRI) should be removed to prevent seizures.

Adolescent↗
PubMed2001

Dipole localization for identification of neuronal generators in independent neighboring interictal EEG spike foci.

PURPOSE: We evaluated dipole localizations of independent neighboring interictal spike foci using scalp electroencephalogram (EEG) to identify neuronal generators of epileptic discharges. METHODS: Three pediatric patients with extratemporal lobe epilepsy who had two independent neighboring interictal spike foci on scalp EEG were studied. Prolonged video EEG was digitally recorded from 19 scalp electrodes, whose positions were registered using a three-dimensional digitizer. Interictal spikes were visually selected based on negative phase reversals on bipolar montages. We analyzed the dipole position and moment of each spike using a single moving dipole and three-shell spherical head model. The dipoles were overlaid onto magnetic resonance (MR) images and divided into two groups based on two spike foci. RESULTS: The dipoles of the two groups were oriented either tangentially or radially to the scalp in close proximity to each other. The dipoles oriented radially were located underneath the electrode with a negative peak; those oriented tangentially were between electrodes with a negative and positive peak. The positions of tangential dipoles were more concentrated than those of radial dipoles. The epileptogenic regions corresponded to the dipole localizations. Surgical excisions were performed based on the results of electrocorticography. After surgery, two patients were seizure free, and one had rare seizures (follow-up period, 13-31 months). CONCLUSIONS: We showed that dipoles in close proximity but with different orientations projected two negative maxima on scalp EEG in three patients with extratemporal localization-related epilepsy. Equivalent current dipole analysis of individual interictal spikes can provide useful information about the epileptogenic zone in these patients.

Adolescent↗
PubMed2001

Image-guided, frameless stereotactic sectioning of the corpus callosum in children with intractable epilepsy.

Corpus callosotomy is an effective neurosurgical procedure for children with intractable atonic or drop attack seizures. While this procedure has not changed significantly over the past three decades, some technical issues remain to be resolved. These include the intraoperative determination of the extent of the callosotomy, the need to stage the procedure, as well as side of approach of craniotomy. We report our 8-year experience with corpus callosotomy using a frameless stereotactic image-guided system (ISG Viewing Wand). Seventeen children with atonic seizures underwent sectioning of the corpus callosum. The mean patient age was 10.5 years. Six children underwent complete callosotomy while 11 underwent resection of the anterior two-thirds. MRI 3D reconstruction of the sagittal sinus and draining cerebral veins was undertaken in all cases. The side of the craniotomy was determined on the basis of favorability of the draining veins with respect to the extent of the callosotomy. The extent of the callosotomy was determined by intraoperative feedback using the ISG Viewing Wand((R)). Nine of 11 patients in the partial callosotomy group and 4 of 6 patients in the complete callosotomy group showed significant improvement in atonic seizures. We conclude that the use of frameless stereotaxy can function as an important adjunct in the planning and conduction of successful sectioning of the corpus callosum in children with intractable seizures.

Adolescent↗
PubMed2001

Comparison of electroencephalographic dipoles of interictal spikes from prolonged scalp video-electroencephalography and magnetoencephalographic dipoles from short-term recording in children with extratemporal lobe epilepsy.

We retrospectively compared electroencephalographic (EEG) dipoles of interictal spikes from prolonged video-EEG monitoring with magnetoencephalographic dipoles from short-term recording in four children with extratemporal lobe epilepsy. We analyzed both sets of dipoles using individual interictal spikes and single moving dipole modeling and evaluated the profiles of spike appearance, dipole position, and orientation in EEG and magnetoencephalography. We obtained more than 100 magnetoencephalographic spikes in two patients who manifested frequent interictal EEG spikes throughout both day and night but fewer than 40 magnetoencephalographic spikes in two patients who had interictal EEG spikes mainly during sleep. The dipole positions of EEG and magnetoencephalography were in close proximity and included in the surgical resection area. Most of the dipoles between EEG and magnetoencephalography were oriented perpendicularly. A combination of EEG dipole analysis from prolonged video-EEG monitoring and magnetoencephalographic dipole analysis provides complementary information for presurgical evaluation in children with intractable extratemporal lobe epilepsy.

Adolescent↗
PubMed2000

Systematic approach to dipole localization of interictal EEG spikes in children with extratemporal lobe epilepsies.

OBJECTIVES: To assess the reliability of dipole localization based on residual variances (RV), using equivalent current dipole analysis of interictal EEG spikes in children with extratemporal lobe epilepsy. METHODS: Four pediatric patients with extratemporal lobe epilepsy were studied. Digital EEG was recorded from 19 scalp electrodes. Computer programs for spike detection and clustering analysis were used to select spikes. Dipoles were calculated 5 times for each spike using different initial guesses by the moving dipole model. Standard deviation (SD) of the dipole positions was calculated at each time point in the 5 trials. RESULTS: We analyzed the dipoles at 1097 time points from 4 patients. Among 106 time points with RV < 2%, the SD was < 1 mm in 78 (74%), while in those with SD > 1 mm the dipole positions varied between 2.8 and 52.6 mm. Of dipoles with RV < 1%, 26 of 27 (96%) had an SD < 1 mm; the one dipole with SD > 1 mm varied within 2.5 mm. The dipole localizations with RV < 2% corresponded to the epileptogenic zones identified on intracranial invasive video EEG and intraoperative ECoG. CONCLUSIONS: The systematic approach of equivalent current dipole analysis using spike detection, clustering analysis, and an RV < 2% as a standard is useful for identifying extratemporal epileptic regions.

Adolescent↗
PubMed2000

Cross-talk between NO and oxyradicals, a supersystem that regulates energy metabolism and survival of animals.

Mammalian tissues have large amounts of available ATP which are generated by oxidative phosphorylation in mitochondria. For the maintenance of the human body, a large amount of oxygen is required to regenerate these ATP molecules. A small fraction of the inspired oxygen is converted to superoxide radical and related metabolites even under physiological conditions. Most reactive oxygen species react rapidly with a variety of molecules thereby interfering with cellular functions and induce various diseases. Nitric oxide (NO) is an unstable gaseous radical with high affinity for various molecules, such as hemeproteins, thiols, and related radicals. NO easily penetrates through cell membrane/lipid bilayers, forms dissociable complexes with these molecules and modulates cellular metabolism and functions. Because NO has an extremely high affinity for the superoxide radical, the occurrence of the latter might decrease the biological function of NO. Thus, superoxide radicals in and around vascular endothelial cells play critical roles in the pathogenesis of hypertension and vasogenic tissue injury. Because NO also reacts with molecular oxygen, it rapidly loses its biological activity, particularly under ambient atmospheric conditions where the oxygen tension is unphysiologically high. Thus, biological functions of NO are determined by the local concentrations of molecular oxygen and superoxide radicals.

Animals↗
PubMed1999

Bacterial superantigens induce down-modulation of CC chemokine responsiveness in human monocytes via an alternative chemokine ligand-independent mechanism.

Staphylococcal superantigens (SAgs) are very potent T cell mitogens, but they can also activate monocytes by binding directly to MHC class II molecules in a manner independent of TCR coengagement. Induction of proinflammatory cytokines and chemokine expression in monocytes by superantigens has recently been reported. Here we report that superantigen stimulation of human peripheral blood monocytes results in a rapid, dose-dependent, and specific down-regulation of chemokine (macrophage inflammatory protein-1alpha (MIP-1alpha), monocyte chemotactic protein-1 and MIP-1beta) binding sites (e.g., CCR1, CCR2, and CCR5), which correlates with a concomitant hyporesponsiveness of human monocytes to these CC chemokine ligands. This down-regulation occurs 15-30 min following superantigen stimulation and is specific to chemokine receptors, in that binding and responsiveness of monocytes to the chemoattractant formyl-tripeptide FMLP are not affected. We further demonstrate that SAg-induced down-modulation of chemokine binding and monocyte hyporesponsiveness to the chemokines MIP-1alpha, monocyte chemotactic protein-1, and MIP-1beta is mediated through cellular protein tyrosine kinases, and the down-modulation can be mimicked by an MHC class II-specific mAb. Additionally, our observations indicate that SAg-induced loss of chemokine binding and monocyte responsiveness is probably mediated by secreted serine proteinases. Bacterial SAg-induced down-modulation of chemokine responsiveness represents a previously unrecognized strategy by some bacteria to subvert immune responses by affecting the intricate balance between chemokine and chemokine receptor expression and function.

Antigens, Bacterial↗
PubMed1999

Characteristics of symptomatic chronic subdural haematomas on high-field MRI.

We studied the frequency of various features of the appearances on high-field MRI in symptomatic patients with chronic subdural haematomas (CSDH). The ability to predict recurrence after treatment with one burr-hole procedure using MRI was evaluated. A total of 40 patients with symptomatic CSDH underwent MRI at 1.5 T. All haematomas were evacuated within a few days of the MRI examination. Symptomatic CSDH were divided into five groups according to the MRI findings: group A (11 cases), isointense or low signal on T1- and low signal on T2-weighted images; group B (18 cases), high signal on T1- and low signal on T2-weighted images; group C (5 cases), high signal on both T1- and T2-weighting; group D (1 case), low signal on T1- and high signal on T2-weighted images; group E (5 cases), heterogeneous intensity on T1- and T2-weighting throughout the haematoma cavity. The mean interval between onset of symptoms and MRI for group A was 5.0 +/- 4.1 days, which was significantly shorter than that for group B (9.4 +/- 4.4 days, P < 0.02), group C (27.8 +/- 20 days, P < 0.005) or group E (17.8 +/- 12.2 days, P < 0.01). Recurrence was seen in three haematomas of group A and one of group B. Reoperation was most closely correlated with diffuse low signal on T2-weighted images but not with a multiloculated appearance. Low signal on T2 weighting was surprisingly high (72.5%) and the age of the haematomas as estimated on the MRI correlated well with the interval between the onset of symptoms and MRI. Our findings support the causative role of recurrent bleeding in the enlargement of CSDH.

Adult↗
PubMed1999

Utility of digital camera-derived intraoperative images in the planning of epilepsy surgery for children.

OBJECTIVE: This study was undertaken to assess the utility of digital camera-derived intraoperative images in the planning of neurosurgery for children with epilepsy. METHODS: A hand-held digital camera was used to capture the exposed surgical field at the time of craniotomy for 11 children with medically intractable seizure disorders. Intraoperative somatosensory evoked potential recordings of phase reversals and direct cortical stimulation were used to map areas of eloquent brain tissue. Digital camera images were obtained to mark regions of functional brain tissue with respect to cortical surface landmarks and subdural grid placement. The digital camera images were then immediately downloaded, in the operating room, to a laptop computer, which was placed next to the electroencephalographic recording device. Using computer software, the epileptologist highlighted the primary and secondary zones of epileptogenesis, as well as the functional brain areas identified during the monitoring period, on the digital camera images on the computer screen. A neurosurgical map was thus created to aid the neurosurgeon and the epileptologist with the proposed cortical resections and multiple subpial transections. RESULTS: With the images obtained using the digital camera, the epilepsy team was able to observe the contacts of the grid electrodes with the brain during the procedure. Color printouts of the images served as references during the period of invasive monitoring. Zones of primary and secondary epileptogenesis, as well as areas of functional brain tissue, were identified and plotted on the digital camera images. Other benefits of the digital camera-derived images included the ability to accurately reposition the grids or letters marking eloquent brain tissue if they were inadvertently shifted during the procedure, the ease with which the images could be obtained and manipulated, the ability to assess postresection epileptiform activity of the surrounding brain tissue with images obtained while an electrocorticographic array was in place, the ability to provide the entire epilepsy team with updated information on the neurosurgical field while minimizing movement in the operating room, and facilitation, with neurosurgical maps, of discussions with the patients and their families concerning proposed cortical resections. CONCLUSION: Digital camera images have become essential components for the planning of cortical resections for children with intractable epilepsy at our institution. We envision widespread application of this technology to other neurosurgical fields.

Adolescent↗
PubMed1999

[Somatosensory evoked potential (SEP) to posterior tibial nerve stimulation in children with cerebral palsy].

We investigated the possible usefulness of SEP to the posterior tibial nerve in children with cerebral palsy. Sixty-four children with cerebral palsy, aged between 6 months to 20 years, were studied. Twelve patients had hemiplegia (H), 24 spastic diplegia who were able to walk (SDW), 17 spastic diplegia who were impossible to walk (SDNW) and 11 spastic quadriplegia (SQ), respectively. We also studied with 40 normal controls. Informed consent was obtained from subjects and parents. A significant difference was found in an appearance rate of P37 between the control and cerebral palsy groups. Absent and shortening of P37 were recognized in 10 among 18 recordings in the paralytic side of patients with hemiplegia. The central conduction time was shortened gradually with age in the control group. There was difference in the central conduction velocity between SDW, SDNW or SQ. These results suggested that P37 was the first cortical response, and that it was useful for the diagnosis of cause of paralysis.

Adolescent↗
PubMed1998

Superclustering of B cell receptor and Fc gamma RIIB1 activates Src homology 2-containing protein tyrosine phosphatase-1.

Fc gamma RIIB1 (CD32) is a receptor that binds the Fc domain of Ag-complexed IgG. Coaggregation of B cell receptor (BCR) and Fc gamma RIIB1 generates a dominant negative signal that inhibits B cell activation. In Ag-specific Id-positive B cells, the co-cross-linking of BCR and Fc gamma RIIB1 by anti-Id Ab resulted in the association of both Src homology 2-containing protein tyrosine phosphatase (SHP-1) and Src homology 2-containing inositol phosphatase (SHIP) with the Fc gamma RIIB1; however, only SHIP activity was detected. "Superclustering" of the BCR and Fc gamma RIIB1 complex induced by stimulation with anti-Id Ab plus polyvalent Ag synergistically activated SHP-1. The degree of co-cross-linking between BCR and Fc gamma RIIB1 may determine the activation status of SHP-1 and SHIP.

Animals↗
PubMed1998

The mitogen-activated protein kinase pathway inhibits ceramide-induced terminal differentiation of a human monoblastic leukemia cell line, U937.

This communication describes an extracellular signal-regulated kinase kinase (MEK)-dependent signal transduction pathway that prevents the terminal differentiation of a hemopoietic cell line. Both PMA and the cell-permeable ceramide, C2-ceramide, caused differentiation of U937 cells, but with distinct cell morphology and CD11b/CD14 surface expression. While PMA activated extracellular signal-regulated kinase (ERK), a downstream kinase of Raf-MEK signaling, C2-ceramide activated c-Jun NH2-terminal kinase (JNK), an anchor kinase of stress-induced signaling. Furthermore, only C2-ceramide stimulated an induction of cell cycle arrest that was associated with stable expression of p21CIP1 and retinoblastoma nuclear phosphoprotein dephosphorylation. Expression of p21CIP1 and JNK activation were also observed in sphingosine-treated cells, whereas sphingosine did not induce detectable differentiation. Concomitant stimulation with C2-ceramide and PMA resulted in the PMA phenotype, and cell cycle arrest was absent. ERK activation was enhanced by C2-ceramide plus PMA stimulation, whereas the activation of JNK was aborted. Strikingly, the inhibition of MEK with PD98059 altered the phenotype of C2-ceramide- and PMA-stimulated U937 cells to that of cells treated with C2-ceramide alone. Thus, ERK and JNK pathways deliver distinct signals, and the ERK pathway is dominant to the JNK cascade. Furthermore, differentiation and cell cycle arrest caused by C2-ceramide rely on independent signaling pathways, and JNK is an unlikely signaling element for this differentiation. Importantly, during C2-ceramide and PMA costimulation, the JNK pathway is not simply blocked by ERK activation; rather, cross-talk between these MAP kinase pathways acts to simultaneously augment ERK activity and down-regulate JNK activity.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1998

Development of an ultra-fast data-acquisition system for a two-dimensional microstrip gas chamber.

A high-performance data-acquisition system has been developed in order to obtain time-resolved sequential images from a two-dimensional microstrip gas chamber (MSGC). This was achieved using fully digital processing with a synchronized pipeline method. Complex logical circuits for processing large numbers of signals are mounted on a small number of complex programmable logic devices. The system is operated with a 10 MHz synchronous clock, and has the capability of handling more than 3 x 10(6) counts s(-1) for asynchronous events. The system was examined using a 5 x 5 cm MSGC and the recently developed 10 x 10 cm MSGC (1024 outputs); the anticipated performances were achieved.

Journal Article↗
PubMed1998

X-ray polarimetry with the microstrip gas chamber.

A two-dimensional microstrip gas chamber (MSGC) with a 5 cm x 5 cm detection area has been developed. It has 254 anodes and 255 back strips, both with 200 micro m pitches. Using this MSGC, linear polarization of X-rays was successfully measured in the energy range 6-14 keV. In addition, the performance of the MSGC as an X-ray imaging polarimeter has been simulated using the EGS4 program (Electron Gamma Shower, Version 4) modified for this purpose. In this article, the results of both the polarization measurement and the simulation are reported.

Journal Article↗
PubMed1998

Development of a MicroStrip Gas Chamber as a Time-Resolved Area Detector.

A two-dimensional microstrip gas chamber (MSGC) has been developed with a 10 cm-square detection area and an ultrafast read-out system. The MSGC was made using multi-chip module (MCM) technology, and has a very thin substrate of 17 micro m and many anodes and back strips, both with 200 micro m pitches. The new read-out system, in which the hit addresses of the electrodes were sequentially encoded to the hit positions by a synchronous clock, handles data rates of up to 10(7) events s(-1) from MSGCs. This enables the acquisition of fast and sequential digital images. Furthermore, since the MSGC is a real photon-counting detector, the timing of the photons, to an accuracy of a few tens of nanoseconds, and energy can be recorded. Here, the performance of the MSGC system as a real-time area detector is reported, and the abilities of this system are discussed.

Journal Article↗