Biomedical subjects

Kensuke Kawai

Publications and source records attributed to Kensuke Kawai.

17 recordsLinked to original sources

PubMed2006

Hippocampal transection for treatment of left temporal lobe epilepsy with preservation of verbal memory.

Despite good seizure outcome with temporal lobectomy, postoperative impairment of verbal memory remains unsolved. To address this problem we developed a new method, applying the rationale of multiple subpial transection (MST) to the hippocampus. The inferior ventricle is accessed without disrupting the neuronal pathways related to verbal memory. Intraoperative electrocorticography is recorded over the hippocampus and amygdala. After the extent of the epileptic area is determined, multiple transections of the pyramidal layer under the alveus is performed using specially designed ring transectors. After this procedure, epileptic discharges from the hippocampus can be completely abolished. Of 21 cases undergoing this operation, 12 left-sided and nine right-sided, 17 were followed up for more than one year. Fourteen (82%) are seizure free, two (12%) have rare seizures, and one (6%) has significantly improved. Of eight patients who underwent a battery of neuropsychometric tests both before and after left hippocampal transection, postoperative verbal memory was completely preserved in seven cases, and one transiently worsened patient recovered within 6 months. However, these results are still preliminary as the number of patients is small and the follow-up time short. The accumulation of cases and follow-up of greater duration will be necessary to precisely confirm the efficacy of this new technique.

Electroencephalography↗

PubMed2005

High frequency activities in the human orbitofrontal cortex in sleep-wake cycle.

We recorded human orbitofrontal electrocorticogram during wakefulness and sleep in epileptic patients using subdural electrodes. During wakefulness and rapid eye movement (REM) sleep, we observed beta activity in the raw orbitofrontal signals. Power spectral analysis demonstrated beta enhancement during wakefulness and REM sleep when compared to slow wave sleep (SWS). During the phasic REM periods, the beta power was significantly lower than during the tonic REM periods. Gamma enhancement manifested itself in four out of six subjects during the phasic periods. This study is the first that has focused on electrical activity in the human orbitofrontal cortex. Although the role of the orbitofrontal cortex during sleep still remains unclear, high frequency activities give us important suggestions in elucidating the human sleep mechanism.

Adult↗

PubMed2005

Functional monitoring for visual pathway using real-time visual evoked potentials and optic-radiation tractography.

OBJECTIVE: It has been difficult to obtain anatomic and functional information about the visual pathway during neurosurgical operations. The aim of this study was to combine the information of the visual evoked potentials (VEPs) and the anatomic navigation of the optic radiation by diffusion tensor imaging-based tractography for functional monitoring of the visual pathway. METHODS: The subjects were two patients with brain lesions adjacent to the visual pathway. Diffusion tensor imaging-based tractography of the optic radiation was performed by selecting appropriate regions of interest and by fractional anisotropy. During surgery, cortical VEPs were recorded continuously under general anesthesia with sevoflurane. In Patient 2, the results of optic radiation tractography were imported to a neuronavigation system to better understand the spatial relationships between the lesions and the visual pathway (functional neuronavigation). RESULTS: In Patient 1, the lesion did not seem to be attached to the optic radiation, and VEP profiles remained stable during resection. In Patient 2, who had a lesion adjacent to the posterior horn of the lateral ventricle, VEPs suddenly diminished when resection reached the optic radiation as illustrated on the neuronavigation system. As a result, complete left hemianopia developed after surgery in Patient 2. CONCLUSION: We confirmed functional correlations of the results of diffusion tensor imaging-based tractography by monitoring intraoperative VEPs. The combination of continuous VEP and optic-radiation tractography is reliable to monitor the visual function and is helpful in performing neurosurgical planning near the visual pathway.

Adult↗

PubMed2004

Theta oscillation in the human anterior cingulate cortex during all-night sleep: an electrocorticographic study.

Ten epileptic patients each with subdural electrodes surgically attached to the anterior cingulate cortex (ACC; two cases), the orbitofrontal cortex (OFC; seven cases), or both (one case) were included in this study. We recorded each patient's ACC or OFC electrocorticogram (ECoG) during the time period that the patient was awake and naturally asleep. We performed a Fast Fourier Transformation (FFT) power spectral analysis on each ECoG to examine its frequency component. We found that the ACC showed regular and continuous theta oscillation (5-7Hz) during wakefulness and rapid eye movement (REM) sleep, but not during slow wave sleep. Theta waves observed in REM sleep were not as distinct as those found in wakefulness. We also discovered that the orbitofrontal signals represented spectral peaks in the theta band only during wakefulness. This suggests the coexistence of theta oscillation in the ACC. Considering our previous observations of gamma and beta oscillations in the human hippocampus, we hypothesize that the human limbic system manifests two oscillatory activities. The results obtained in this study suggest that electrophysiological activity in the ACC could be related to particular psychological functions in wakefulness and in REM sleep. These results are useful in elucidating the human brain mechanism.

Adult↗

PubMed2004

Usefulness of [11C]methionine PET in the diagnosis of dysembryoplastic neuroepithelial tumor with temporal lobe epilepsy.

PURPOSE: We assessed the diagnostic value of [11C]methionine (MET) positron emission tomography (PET) in the differential diagnosis of dysembryoplastic neuroepithelial tumors (DNETs) among benign tumors associated with temporal lobe epilepsy (TLE). METHODS: This series consisted of seven TLE patients with benign tumors in the temporal lobe. After MET-PET study, all seven patients underwent tumor resection along with focus excision. The uptake of tracers was evaluated by the lesion-to-contralateral ratio (L/C ratio) and the standardized uptake value (SUV). We also assessed the relation between MET uptake and proliferation capacity observed in the surgical specimens. RESULTS: Whereas four patients with DNETs did not show high MET uptake visually, the ganglioglioma and gliomas of the remaining three patients were identified as high-MET-uptake lesions. In the DNETs, the SUV ranged from 1.03 to 1.41, and the L/C ratio ranged from 0.99 to 1.14. MET uptake was significantly lower in the patients with DNETs than in the patients with ganglioglioma and brain gliomas (SUV, p = 0.045; L/C ratio, p = 0.0079). The Ki-67 labeling index was 4% in one patient with DNET and 5% in one patient with pleomorphic xanthoastrocytoma (higher labeling index). The higher labeling index was not related to high MET uptake based on the SUV (p = 0.91) and L/C ratio (p = 0.38). CONCLUSIONS: Negative MET uptake in benign temporal lobe tumors with TLE is consistent with a preoperative diagnosis of DNET.

Adolescent↗

PubMed2004

Proximal occlusion of the middle cerebral artery in C57Black6 mice: relationship of patency of the posterior communicating artery, infarct evolution, and animal survival.

OBJECT: The intraluminal suture model for focal cerebral ischemia is increasingly used, but not without problems. It causes hypothalamic injury, subarachnoid hemorrhage, and inadvertent premature reperfusion. The patency of the posterior communicating artery (PCoA) potentially affects the size of the infarct. In addition, survival at 1 week is unstable. The authors operated on C57Black6 mice to produce proximal middle cerebral artery occlusion (MCAO) so that drawbacks with the suture model could be circumvented. METHODS: The MCA segment just proximal to the olfactory branch was occluded either permanently or temporarily. After 1 hour of MCAO the infarct volume was significantly smaller than that found after 2 hours or in instances of permanent MCAO. The differences were assessed at 24 hours and 7 days after surgery (p < 0.05 and p < 0.001, respectively). The patency of the PCoA, as visualized using carbon black solution, did not correlate with the infarct size. Neurologically, the 1- and 2-hour MCAO groups displayed significantly less severe deficits than the permanent MCAO group on Days 1, 4, and 7 (p < 0.005 and p < 0.01, respectively). Although the infarct size, neurological deficits, and body weight loss were more severe in the permanent MCAO group, the survival rate at Day 7 was 80%. CONCLUSIONS: This model provides not only a robust infarct size (which is not affected by the patency of the PCoA), but also a better survival rate.

Animals↗

PubMed2004

Clinical outcomes after corpus callosotomy in patients with bihemispheric malformations of cortical development.

OBJECT: Epilepsy in patients with bihemispheric malformations of cortical development (MCD) is typically medically intractable. Focal resection has been reported to be ineffective. Corpus callosotomy has been advocated as a treatment option, but the results have been reported only in several case reports. The authors describe a series of 10 patients with bihemispheric MCDs who underwent total corpus callosotomy. METHODS: The MCDs in these patients included lissencephaly, band heterotopia, perisylvian polymicrogyria, and tuberous sclerosis. Preoperatively all patients suffered disabling drop attacks or intense head drop seizures that caused frequent physical injuries. The follow-up period ranged from 1.4 to 5.8 years (median 3.2 years). Seizure outcome, parental assessment of daily function, and parental satisfaction with outcome were assessed postoperatively. Drop attacks disappeared completely during the entire follow-up period in eight patients and decreased to less than 10% of baseline in one. Other types of seizures were resolved completely in one patient and decreased in seven. Overall daily function improved and parents were satisfied with the surgery-related results in all patients except one who experienced a recurrence of drop attacks. There were no signs of significant and persistent neurological deficits in any case. CONCLUSIONS: Results of total corpus callosotomy in patients with bihemispheric MCDs were favorable in most cases. The procedure was particularly effective against drop attacks causing physical injuries and impaired quality of life in these patients.

Cerebral Cortex↗

PubMed2004

[Surgical treatment for temporal lobe epilepsy with preservation of postoperative memory function].

Temporal lobe epilepsy is frequently drug-resistant in adult epilepsy. However, its surgical treatment is very effective and about 70% of operated patients become seizure-free. As preoperative evaluation, analysis of seizure characteristics, scalp EEG with sphenoidal lead, and neuroimaging are most important. When these noninvasive examinations are concordant in focus localization, surgical treatment without prolonged recording by intracranial electrodes become feasible. In spite of good seizure outcome after temporal lobectomy, postoperative impairment of verbal memory has remained to be a long-standing problem. To cope with this ominous complication, we developed a new surgical method of hippocampal transection, based on the principle of multiple subpial transection (MST). Placing a small corticotomy on the anterior part of superior temporal gyrus, the inferior ventricle is opened through suctioning the temporal stem. Intraoperative electrocorticography (ECoG) is recorded over the hippocampus. After the extent of the epileptic area is determined, the alveus is cut with microscissors and the pyramidal layer is transected in parallel with neuronal fibers by a specially designed ring transector. With this procedure, epileptic discharges from the hippocampus can be completely abolished. In all 7 cases undergoing left hippocampal transection, postoperative verbal memory was preserved with excellent seizure outcome.

Adult↗

PubMed2003

Sleep spindles in human prefrontal cortex: an electrocorticographic study.

To investigate the sleep spindle activity of the human prefrontal cortex (PFC), we simultaneously recorded whole nights of polysomnographic and electrocorticographic (ECoG) activities during the natural sleep of epileptic patients. Subjects were nine patients with intractable epilepsy who had subdural electrodes surgically attached to the orbital (seven cases), medial (three cases), or dorsolateral (two cases) PFC, and in one case to the frontal pole. To examine spindle frequencies, fast Fourier transformation (FFT) and auto-correlation analyses were performed on the PFC ECoG and Cz EEG data, primarily on epochs of stage 2 sleep. Lower sigma band ECoG oscillations of about 12 Hz were widely distributed across all prefrontal cortical areas including the frontal limbic regions, but none of the PFC sigma frequency peaks coincided with the faster (about 14 Hz) Cz EEG sleep spindles. Combining our results with anatomical and electrophysiological facts, it is suggested that the thalamofrontal circuit involving the rostral reticular and the mediodorsal nucleus of the thalamus is responsible for the generation of 12 Hz frontal spindles in humans.

Adult↗

PubMed2003

Theta oscillation in the anterior cingulate and beta-1 oscillation in the medial temporal cortices: a human case report.

In previous studies we observed gamma (30-150 Hz) and beta-1 (10-20 Hz) oscillations in the medial temporal lobe (MTL) using subdural electrodes. The beta-1 was present during wake and REM sleep while gamma was present in all states. Recently we studied a patient (35 years M) with electrodes attached to the anterior cingulate cortex (ACC). This structure showed regular theta (5-6 Hz) oscillations. In the first recording, electrodes were attached to the MTL, that demonstrated the beta-1 and gamma oscillations. Two months later, electrodes were placed on orbitofrontal and ACC and an all night sleep recording was carried out. The ACC exhibited a highly regular and continuous theta oscillation during wakefulness and REM sleep, but not during NREM sleep. Since this same subject showed beta-1 oscillations in the MTL, it is probable that the theta in the ACC is independent of beta-1 in the MTL. This single case suggests the existence of two different frequency oscillators in the human limbic system. Elucidating their functional roles will be an interesting challenge for future studies.

Adult↗

PubMed2002

Lectin cytochemical demonstration of glucose- and mannose-containing glycoconjugates on human reactive astrocytes.

Lectin cytochemistry of the human autopsy cases of Creutzfeldt-Jakob disease and old cerebral infarction was performed on formalin-fixed, paraffin-embedded sections using 15 lectins. Reactive astrocytes showed a positive reaction with concanavalin A (Con A), Lens culinaris agglutinin (LCA) and Pisum sativum agglutinin (PSA), with common specificity for both mannose and glucose. However normal astrocytes demonstrated no or little cytochemical reaction for any of the lectins. Reactivity for the lectins in control sections was obviously reduced using the blocking sugars (0.1 mol/l D-mannose and 0.5 mol/l D-glucose for Con A, LCA, and PSA, and 0.5 M mol/l alpha-methyl mannopyranoside for Con A). The present data provide suggestive evidence that the reactivity for Con A, LCA, and PSA is increased in reactive astrocytes.

Aged↗

PubMed2002

Cardiac arrest cerebral ischemia model in mice failed to cause delayed neuronal death in the hippocampus.

Global cerebral ischemia models for genetically engineered mice are of particular importance for the study of delayed neuronal death, but have been complicated by variability of vascular anatomy. Here we developed a 5-min cardiac arrest model that was not affected by vascular anatomy, and evaluated the hippocampal neuronal injury in BL/6 and SV129 mice. Despite prolonged anoxic depolarization for approximately 7 min, however, no consistent ischemic neuronal injury was noted in the CA1 sector of the hippocampus in both strains. Thus, our observations suggested that murine hippocampal neurons are relatively resistant to ischemia compared with those in other rodents.

Animals↗

PubMed2002

Preservation of nigral neurons in Pick's disease with Pick bodies: a clinicopathological and morphometric study of five autopsy cases.

Many reports have described loss of neurons in the substantia nigra in Pick's disease (PiD). In those reports, however, "Pick's disease" includes PiD without Pick bodies (PB), and there is only limited data available on regional nigral pathology in PiD with PB. To elucidate the pathological changes of the substantia nigra in PiD with PB, we examined five cases and 12 age-matched controls by morphometry. The number and size of pigmented and nonpigmented neurons, as well as the area of the substantia nigra were examined. The area of the substantia nigra was significantly reduced in PiD with PB. The pigmented and nonpigmented neuron counts in PiD with PB were not statistically different from those in controls. There was a significant reduction in the size of pigmented neurons in PiD with PB to 82% with that in the controls. In addition, after reviewing 48 cases of PiD with PB reported in the literature, we found that none of the cases with typical frontotemporal lobe symptoms exhibited parkinsonism until the terminal stage. These data are useful for discriminating PiD with PB from other diseases showing frontotemporal characteristics, including the frontal lobe degeneration type and the motor neuron disease type of frontotemporal dementia.

Adult↗

PubMed2002

Postoperative development of children after hemispherotomy.

We studied the postoperative development of 14 children with cortical dysgenesis who underwent modified functional hemispherectomy (hemispherotomy) at the age of 6 years or younger. At follow-up of 24-72 months (median of 47 months), six (43%) were seizure-free, six achieved>90% reduction, one achieved 50-90% reduction, and one achieved 0-50% reduction in seizure frequency. At the preoperative and final postoperative examinations, mean scores of developmental quotient (DQ) were as follows: 25.5 and 31.9 in total DQ, 26.0 and 33.7 in intellectual DQ, and 27.4 and 22.9 in motor DQ. Children scoring >50 points in preoperative intellectual DQ score obtained near-normal intellectual DQ postoperatively, while, those scoring <10 DQ preoperatively remained at a low developmental level. Among children with DQ scores in the range from 10 to 50, two children who obtained seizure-free outcome and were operated upon in the first 3 years of life achieved marked developmental progress. The present study indicated that high preoperative intellectual DQ and cessation of seizures seem to be associated with better postoperative intellectual development. However, long-term observation of postoperative development and an accumulation of more cases will be needed before we can reach a firm conclusion.

Cerebral Cortex↗

PubMed2002

Pathological effect of seizures on the hippocampus in cases with temporal lobe epilepsy caused by brain tumors.

The cause of Ammon's horn sclerosis in temporal lobe epilepsy has not yet been clarified. In the present study, the pathological effect of epileptic seizures on the hippocampus was investigated in surgically treated patients with brain tumor-induced temporal lobe epilepsy. Tumors involving the hippocampus were identified as the foci of epilepsy in 13 patients (seven male and six female) and resected after epileptic discharges were found at the hippocampus on intraoperative electrocorticogram. The mean age at operation was 29.8 +/- 11.5 years and the mean age of seizure onset was 19.9 +/- 10.8 years. Because only three of the 13 patients who underwent temporal lobectomy for brain tumors involving the hippocampus had Ammon's horn sclerosis pathologically, it was concluded that it was very unlikely that the Ammon's horn sclerosis was produced by the epileptic seizures. Two of the three patients with pathological signs of Ammon's horn sclerosis had episodes of coma, covulsion, high fever and cyanosis in their past histories that might have portended the appearance of Ammon's horn sclerosis later in their lives.

Adolescent↗

PubMed2002

Outcome of long-term vagus nerve stimulation for intractable epilepsy.

The outcome of long-term vagus nerve stimulation (VNS) was evaluated in 13 Japanese patients with intractable epilepsy, all followed up for more than 4 years (48-91 months, median 56 months). VNS achieved a long-lasting and cumulative seizure-control effect in nine of 13 patients. The mean reduction of seizure frequency in the 1st to 4th year was 28%, 47%, 54%, and 63%, respectively. The percentage of patients with >60% seizure reduction in the 1st to 4th year was 15%, 46%, 54%, and 69%, respectively. One patient did not respond to the treatment at all. No patient became completely free from seizure or free from medication, but the number and/or dosage of antiepileptic drugs was reduced in five patients. Ten patients underwent exchange of the generator and continued treatment, and two patients underwent removal of the generator because of the unsatisfactory result. VNS controlled more disabling seizures earlier and more efficiently than less disabling seizures in seven patients. The cumulative reduction of seizures was partly associated with changes in the device setting toward increased stimulation. These effects were similar in patients with or without previous resective surgery. Long-term VNS therapy achieved a favorable outcome in a significant proportion of patients with intractable epilepsy.

Adult↗

PubMedDate not supplied

Impulse response function based on multivariate AR model can differentiate focal hemisphere in temporal lobe epilepsy.

The purpose of this study is to propose and investigate a new approach for discriminating between focal and non-focal hemispheres in intractable temporal lobe epilepsy, based on applying multivariate time series analysis to the discharge-free background brain activity observed in nocturnal electrocorticogram (ECoG) time series. Five unilateral focal patients and one bilateral focal patient were studied. In order to detect the location of epileptic foci, linear multivariate autoregressive (MAR) models were fitted to the ECoG data; as a new approach for the purpose of summarizing these models in a single relevant parameter, the behavior of the corresponding impulse response functions was studied and described by an attenuation coefficient. In the majority of unilateral focal patients, the averaged attenuation coefficient was found to be almost always significantly larger in the focal hemisphere, as compared to the non-focal hemisphere. Also the amplitude of the fluctuations of the attenuation coefficient was significantly larger in the focal hemisphere. Moreover, in one patient showing a typical regular sleep cycle, the attenuation coefficient in the focal hemisphere tended to be larger during REM sleep and smaller during Non-REM sleep. In the bilateral focal patient, no statistically significant distinction between the hemispheres was found. This study provides encouraging results for new investigations of brain dynamics by multivariate parametric modeling. It opens up the possibility of relating diseases like epilepsy to the properties of inconspicuous background brain dynamics, without the need to record and analyze epileptic seizures or other evidently pathological waveforms.

Adult↗