Kensuke Kawai

The University of Tokyo, Edo, Tōkyō, Japan

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Publications (37)79.42 Total impact

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    ABSTRACT: Objective Resective surgery for mesial temporal lobe epilepsy (MTLE) with a correspondent lesion has been established as an effective and safe procedure. Surgery for temporal lobe epilepsies with bilateral hippocampal sclerosis or without correspondent lesions, however, carries a higher risk of devastating memory decline, underscoring the importance of establishing the memory-dominant side preoperatively and adopting the most appropriate procedure. In this study, we focused on high gamma activities (HGAs) in the parahippocampal gyri and investigated the relationship between memory-related HGAs and memory outcomes after hippocampal transection (HT), a hippocampal counterpart to neocortical multiple subpial transection. The transient nature of memory worsening after HT provided us with a rare opportunity to compare HGAs and clinical outcomes without risking permanent memory disorders.Methods We recorded electrocorticography from parahippocampal gyri of 18 patients with temporal lobe epilepsy while they executed picture naming and recognition tasks. Memory-related HGA was quantified by calculating differences in power amplification of electrocorticography signals in a high gamma range (60–120 Hz) between the two tasks. We compared memory-related HGAs from correctly recognized and rejected trials (hit-HGA and reject-HGA). Using hit-HGA, we determined HGA-dominant sides and compared them with memory outcomes after HT performed on seven patients.ResultsWe observed memory-related HGA mainly between 500 and 600 msec poststimulus. Hit-HGA was significantly higher than reject-HGA. Three patients who had surgery on the HGA-dominant side experienced transient memory worsening postoperatively. The postoperative memory functions of the other four patients remained unchanged.SignificanceParahippocampal HGA was indicated to reflect different memory processes and be compatible with the outcomes of HT, suggesting that HGA could provide predictive information on whether the mesial temporal lobe can be resected without causing memory worsening. This preliminary study suggests a refined surgical strategy for atypical MTLE based on reliable memory lateralization.
    Epilepsia 08/2014; · 3.96 Impact Factor
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    ABSTRACT: How visual object categories are represented in the brain is one of the key questions in neuroscience. Studies on low-level visual features have shown that relative timings or phases of neural activity between multiple brain locations encode information. However, whether such temporal patterns of neural activity are used in the representation of visual objects is unknown. Here, we examined whether and how visual object categories could be predicted (or decoded) from temporal patterns of electrocorticographic (ECoG) signals from the temporal cortex in five patients with epilepsy. We used temporal correlations between electrodes as input features, and compared the decoding performance with features defined by spectral power and phase from individual electrodes. While using power or phase alone, the decoding accuracy was significantly better than chance, correlations alone or those combined with power outperformed other features. Decoding performance with correlations was degraded by shuffling the order of trials of the same category in each electrode, indicating that the relative time series between electrodes in each trial is critical. Analysis using a sliding time window revealed that decoding performance with correlations began to rise earlier than that with power. This earlier rise time was replicated by a model using phase differences to encode categories. These results suggest that activity patterns arising from interactions between multiple neuronal units carry additional information on visual object categories.
    NeuroImage 12/2013; · 6.25 Impact Factor
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    ABSTRACT: Recognition of faces and written words is associated with category-specific brain activation in the ventral occipitotemporal cortex (vOT). However, topological and functional relationships between face-selective and word-selective vOT regions remain unclear. In this study, we collected data from patients with intractable epilepsy who underwent high-density recording of surface field potentials in the vOT. "Faces" and "letterstrings" induced outstanding category-selective responses among the 24 visual categories tested, particularly in high-γ band powers. Strikingly, within-hemispheric analysis revealed alternation of face-selective and letterstring-selective zones within the vOT. Two distinct face-selective zones located anterior and posterior portions of the mid-fusiform sulcus whereas letterstring-selective zones alternated between and outside of these 2 face-selective zones. Further, a classification analysis indicated that activity patterns of these zones mostly represent dedicated categories. Functional connectivity analysis using Granger causality indicated asymmetrically directed causal influences from face-selective to letterstring-selective regions. These results challenge the prevailing view that different categories are represented in distinct contiguous regions in the vOT.
    Cerebral Cortex 11/2013; · 8.31 Impact Factor
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    ABSTRACT: Object Meningiomas treated by subtotal or partial resection are associated with significantly shorter recurrence-free survival than those treated by gross-total resection. The Simpson grading system classifies incomplete resections into a single category, namely Simpson Grade IV, with wide variations in the volume and location of residual tumors, making it complicated to evaluate the achievement of surgical goals and predict the prognosis of these tumors. Authors of the present study investigated the factors related to necessity of retreatment and tried to identify any surgical nuances achievable with the aid of modern neurosurgical techniques for meningiomas treated using Simpson Grade IV resection. Methods This retrospective analysis included patients with WHO Grade I meningiomas treated using Simpson Grade IV resection as the initial therapy at the University of Tokyo Hospital between January 1995 and April 2010. Retreatment was defined as reresection or stereotactic radiosurgery due to postoperative tumor growth. Results A total of 38 patients were included in this study. Regrowth of residual tumor was observed in 22 patients with a mean follow-up period of 6.1 years. Retreatment was performed for 20 of these 22 tumors with regrowth. Risk factors related to significantly shorter retreatment-free survival were age younger than 50 years (p = 0.006), postresection tumor volume of 4 cm(3) or more (p = 0.016), no dural detachment (p = 0.001), and skull base location (p = 0.016). Multivariate analysis revealed that no dural detachment (hazard ratio [HR] 6.42, 95% CI 1.41-45.0; p = 0.02) and skull base location (HR 11.6, 95% CI 2.18-218; p = 0.002) were independent risk factors for the necessity of early retreatment, whereas postresection tumor volume of 4 cm(3) or more was not a statistically significant risk factor. Conclusions Compared with Simpson Grade I, II, and III resections, Simpson Grade IV resection includes highly heterogeneous tumors in terms of resection rate and location of the residual mass. Despite the difficulty in analyzing such diverse data, these results draw attention to the favorable effect of dural detachment (instead of maximizing the resection rate) on long-term tumor control. Surgical strategy with an emphasis on detaching the tumor from the affected dura might be another important option in resection of high-risk meningiomas not amenable to gross-total resection.
    Journal of Neurosurgery 09/2013; · 3.15 Impact Factor
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    ABSTRACT: Vagus nerve stimulation (VNS) is a palliative treatment for intractable epilepsy. Therapeutic mechanisms of VNS have not been elucidated. In this study, we measured the local field potential (LFP) with high-spatial resolution using a microelectrode array in adult rats, and analyzed VNS-evoked phase modulation at a local network level. Eight adult Wistar rats (270 - 330 g) were used. Each rat underwent implantation of VNS system (Cyberonics, Houston, TX., USA) under 1.5% isoflurane anesthesia. One week after implantation, right temporal craniotomy was performed under the same as previous anesthesia. Subsequently, a microelectrode array was placed in the temporal lobe cortex, and LFP was recorded with sampling rate of 1000 Hz. Phase-locking value (PLV) between all pairs of electrodes in varied frequency bands was calculated in order to evaluate the effect of VNS in terms of synchrony of neuronal activities. PLV was calculated both in a normal state and in an epileptic state induced by kainic acid. VNS increased PLV in a normal state, particularly in high-γ band. In an epileptic state, VNS increased PLV in high-γ band, and decreased in d and low-β bands. VNS modulates synchrony in a band-specific and state-dependent manner. VNS might keep cortical synchrony within the optimal state.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 07/2013; 2013:5348-5351.
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    ABSTRACT: BACKGROUND:: There has been a growing interest in clinical single-neuron recording, to better understand epileptogenicity and brain function. It is crucial to compare this new information, single-neuronal activity, with that obtained from conventional intracranial electroencephalographyduring simultaneous recording. However, it is difficult to implant microwires and subdural electrodes during a single surgical operation, since the stereotactic frame hampers flexible craniotomy. OBJECTIVE:: We describenewly designed electrodes as well as surgical techniques to implant these with subdural electrodes that enable simultaneous recording from hippocampal neurons and broad areas of the cortical surface. METHODS:: We designed a depth electrode that does not protrude into the dura and pulsates naturally with the brain. The length and the tract of the depth electrode were determined preoperatively between the lateral subiculum and the lateral surface of the temporal lobe. A frameless navigation system was used to insert the depth electrode. Surface grids and ventral strips were placed before and after the insertion of the depth electrodes, respectively. Finally, a microwire bundle was inserted into the lumen of the depth electrode. We evaluated the precision of implantation, the recording stability, and therecording rate with microwire electrodes. RESULTS:: Depth-microwire electrodes were placed with a precision of 3.6mm. The mean successful recording rate of single- or multiple-unit activity was 14.8%, which was maintained throughout the entire recording period. CONCLUSION:: We achieved simultaneous implantation of microwires, depth electrodes and broad-area subdural electrodes. Our method enabled simultaneous and stable recording of hippocampal single-neuron activities and multi-channel intracranial electroencephalography.
    Neurosurgery 04/2013; · 2.53 Impact Factor
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    ABSTRACT: BACKGROUND: Vagus nerve stimulation (VNS) is a palliative treatment for drug resistant epilepsy for which the efficacy and safety are well established. Accumulating evidence suggests that ascending vagal signals modulate abnormal cortical excitability via various pathways. However, there is no direct evidence for an ascending conduction of neural impulses in a clinical case of VNS. OBJECTIVE: We recorded and analyzed the short-latency components of the vagus nerve (VN) evoked potential (EP) from the viewpoint of determining whether or not it is a marker for the ascending neural conduction. METHODS: EPs within 20 ms were prospectively recorded simultaneously from a surgical wound in the neck and at multiple scalp sites during implantation surgery in 25 patients with drug-resistant epilepsy. Electrical stimulation was delivered using the clinical VNS Therapy system. A recording was made before and after a muscle relaxant was administered, when changing the rostrocaudal position of stimulation, or when stimulating the ansa cervicalis instead of the VN. RESULTS: The short-latency components consisted of four peaks. The early component around 3 ms, which was most prominent in A1-Cz, remained unchanged after muscle relaxation while the later peaks disappeared. Rostral transition of the stimulation resulted in an earlier shift of the early component. The estimated conduction velocity was 27.4 ± 10.2 m/s. Stimulation of the ansa cervicalis induced no EP. CONCLUSIONS: The early component was regarded as directly resulting from ascending neural conduction of A fibers of the VN, probably originating around the jugular foramen. Recording of VN-EP might document the cause of treatment failure in some patients.
    Brain Stimulation 10/2012; · 4.54 Impact Factor
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    ABSTRACT: High gamma activity (HGA) has been shown to be positively correlated with blood oxygenation level-dependent (BOLD) responses in the primary cortices with simple tasks. It is, however, an open question whether the correlation is simply applied to the association areas related to higher cognitive functions. The aim of this study is to investigate quantitative correlation between HGA and BOLD and their spatial and temporal profiles during semantic processing. Thirteen patients with intractable epilepsy underwent fMRI and electrocorticography (ECoG) with a word interpretation task to evoke language-related responses. Percent signal change of BOLD was calculated at each site of ECoG electrode, which has power amplification of high gamma band (60-120Hz) activity. We transformed locations of individual electrodes and brains to a universal coordination using SPM8 and made the quantitative comparisons on a template brain. HGAs were increased in several language-related areas such as the inferior frontal and middle temporal gyri and were positively correlated with BOLD responses. The most striking finding was different temporal dynamics of HGAs in the different brain regions. Whereas the frontal lobe showed longer-lasting HGA, the HGA-intensity on the temporal lobe quickly declined. The different temporal dynamics of HGA might explain why routine language-fMRI hardly detected BOLD in the temporal lobe. This study clarified different neural oscillation and BOLD response in various brain regions during semantic processing and will facilitate practical utilization of fMRI for evaluating higher-order cognitive functions not only in basic neuroscience, but also in clinical practice.
    NeuroImage 09/2012; · 6.25 Impact Factor
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    ABSTRACT: Despite the recent advances in microsurgical techniques, reconstruction of extensive skull base defects using free flaps in pediatric patients presents a surgical challenge, and reports on skull base reconstruction in infants is quite limited. We present a case of reconstruction of an extensive anterior skull base defect using a rectus abdominis (RA) myocutaneous flap in a 1 year-old (14 months) infant. Sufficient coverage of the intracranial contents, good aesthetic results, and minimal growth disturbance at the donor site were achieved by the muscle-sparing RA flap transfer. To the best of our knowledge, this was among the youngest case of skull base reconstruction using a free flap. The feasibility of free flap transfer and flap selection in pediatric skull base reconstruction is discussed. © 2012 Wiley Periodicals, Inc.
    Microsurgery 09/2012; · 1.62 Impact Factor
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    ABSTRACT: We compared electrocorticography (ECoG) with invasive intracranial noninvasive functional MRI using language-related tasks. Twenty patients underwent bilateral implantation of subdural electrodes (more than 80 channels) for diagnosing intractable epilepsy. Before implantation of the electrodes, language-related fMRI was performed, and the fMR images were superimposed on individual brain images. Brain mapping with electrocortical stimulation was performed on the basis of the fused fMR and brain MR images, and the specificity and sensitivity of language-related fMRI was calculated. For careful interpretation of spatial and temporal ECoG changes with semantic tasks, we developed a software to visualize semantic-ECoG dynamics in the brain. Semantic-ECoG was recorded during word, figure, and face recognition as well as memory tasks. The raw ECoG data were processed by averaging and time-frequency analysis, and the functional profiles were projected onto the individual brain surface. Acquired ECoG was classified using Support Vector Machine and Sparse Logistic Regression to decode brain signals. Because of variations in electrode locations, we normalized the ECoG electrodes by using SPM8. Although fMRI has 90% sensitivity, its specificity is only up to 50%. The basal temporal-occipital cortex was activated within 250 ms after visual object presentation. Compared to other stimuli, face stimulation evoked significantly higher ECoG amplitudes. Among different brain regions, the hippocampus was predominantly activated during the memory task. The prediction rate of ECoG classification was 90%, which was sufficient for clinical use. Semantic-ECoG is a powerful technique to detect and decode human brain functions.
    Brain and nerve = Shinkei kenkyū no shinpo 09/2012; 64(9):1001-12.
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    ABSTRACT: OBJECTIVE: This study aims to elucidate differences in preoperative cerebral glucose metabolism between patients who did and did not become seizure free after unilateral mesial temporal lobe epilepsy (mTLE) surgery. We hypothesized that regional glucose metabolism on preoperative fluorodeoxyglucose positron emission tomography (FDG-PET) in patients with seizure-free outcomes differed from that in patients who were not seizure free after appropriate epilepsy surgery for unilateral mTLE. In this study, we compared preoperative FDG-PET findings between these two patient groups by applying a statistical analysis approach, with a voxel-based Asymmetry index (AI), to improve sensitivity for the detection of hypometabolism. METHODS: FDG-PET scans of 28 patients with medically refractory mTLE, of whom 17 achieved a seizure-free outcome (Engel class 1 a-b) during a postoperative follow-up period of at least 2 years, were analyzed retrospectively. Voxel values were adjusted by the AI method as well as the global normalization (GN) method. Two types of statistical analysis were performed. One was a voxel severity analysis with comparison of voxel values at the same coordinate, and the other was extent analysis with comparison of the number of significant voxels in the anatomical areas predefined with Talairach's atlas. RESULTS: In the voxel severity analysis, significant hypometabolism restricted to the ipsilateral temporal tip and hippocampal area was detected in the postoperative seizure-free outcome group as compared to controls. No significant area was detected in the non-seizure-free group as compared to controls (family-wise error corrected, p < 0.05). With extent analysis using a low threshold, the extents of hypometabolism in the ipsilateral hippocampal, frontal and thalamic areas were larger in the seizure-free than in the non-seizure-free group (p = 0.01, 0.03 and 0.01, respectively.) On the other hand, in the contralateral frontal and thalamic areas, extents of hypometabolism were smaller in the seizure-free than in the non-seizure-free group (p = 0.01 and 0.01). CONCLUSIONS: We found the preoperative distribution of hypometabolism to differ between the two patient groups. Severe hypometabolism restricted to the unilateral temporal lobe, with ipsilateral dominant hypometabolism including mild decreases, may support the existence of an epileptogenic focus in the unilateral temporal lobe and a favorable seizure outcome after mTLE surgery.
    Annals of Nuclear Medicine 07/2012; · 1.41 Impact Factor
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    ABSTRACT: OBJECTIVE: We developed a novel technique of spatial normalization of subdural electrode positions across subjects and assessed the spatial-temporal dynamics of high-gamma activity (HGA) in the dominant hemisphere elicited by three distinct language tasks. METHODS: The normalization process was applied to 1512 subdural electrodes implanted in 21 patients with intractable epilepsy. We projected each task-related HGA profile onto a normalized brain. RESULTS: The word interpretation task initially elicited HGA augmentation in the bilateral fusiform gyri at 100ms after stimulus onsets, subsequently in the left posterior middle temporal gyrus, in the left ventral premotor cortex at 200ms and in the left middle and left inferior frontal gyri at 300ms and after. The picture naming task elicited HGA augmentation in few sites in the left frontal lobe. The verb generation task elicited HGA in the left superior temporal gyrus at 100-600ms. Common HGA augmentation elicited by all three tasks was noted in the left posterior-middle temporal and left ventral premotor cortices. CONCLUSIONS: The spatial-temporal dynamics of language-related HGA were demonstrated on a spatially-normalized brain template. SIGNIFICANCE: This study externally validated the spatial and temporal dynamics of language processing suggested by previous neuroimaging and electrophysiological studies.
    Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 07/2012; · 3.12 Impact Factor
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    ABSTRACT: This is a report of two cases of spontaneous temporal encephalocele: one was anteroinferior and presented with epilepsy; the other was posteroinferior and presented with facial neuritis and labyrinthitis. Spontaneous temporal encephalocele is relatively rare and apparently not familiar to a majority of primary physicians. It may present with a variety of symptoms according to its anatomical location, including cerebrospinal fluid fistulas, recurrent meningitis, chronic otitis media, hearing loss, facial nerve palsy and medically intractable epilepsy. Attention should be paid to this disease entity, as it is easily overlooked in imaging studies and can leave serious neurological deficits.
    Journal of Neuroradiology 05/2012; · 1.24 Impact Factor
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    ABSTRACT: Techniques for the surgical treatment of meningioma have undergone many improvements since Simpson established the neurosurgical dogma for meningioma surgery in his seminal paper published in 1957. This study aims to assess the clinical significance and limitations of the Simpson grading system in relation to modern surgery for WHO Grade I benign meningiomas and to explore the potential of the cell proliferation index to complement the limitations in predicting their recurrence. The surgical records of patients who underwent resection of intracranial meningiomas at the University of Tokyo Hospital between January 1995 and August 2010 were retrospectively analyzed. The authors investigated the relationships between recurrence-free survival (RFS) and Simpson grade or MIB-1 labeling index value. A total of 240 patients harboring 248 benign meningiomas were included in this study. Simpson Grade IV resection was associated with a significantly shorter RFS than Simpson Grade I, II, or III resection (p<0.001), while no statistically significant difference was noted in RFS between Simpson Grades I, II, and III. Among meningiomas treated by Simpson Grade II and III resections, however, multivariate analysis revealed that an MIB-1 index of 3% or higher was associated with a significantly shorter time to recurrence. The clinical significance of the different management strategies related to Simpson Grade I-III resection may have been diluted in the modern surgical era. The MIB-1 index can differentiate tumors with a high risk of recurrence, which could be beneficial for planning tailored optimal follow-up strategies. The results of this study appear to provide a significant backing for the recent shift in meningioma surgery from attempting aggressive resection to valuing the quality of the patient's life.
    Journal of Neurosurgery 05/2012; 117(1):121-8. · 3.15 Impact Factor
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    ABSTRACT: It has been suggested that a difference in signal intensity (SI) between the resection cavity and normal cerebrospinal fluid (CSF) on fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) in partially resected gliomas indicates subsequent or coincident tumor progression. We considered that this would hold true for resected meningiomas as well. Hence, we aimed to assess whether or not such a difference in the SI during the follow-up evaluation helps predict residual or recurrent tumor in resected meningiomas. We evaluated 63 patients with resected meningiomas. The SI within the resection cavity observed on FLAIR images was qualitatively and quantitatively assessed during follow-up. Qualitative analysis comprised visual comparison of the SI in the resection cavity with that of normal CSF by neuroradiologists. The SI in the resection cavity was quantitatively assessed by region of interest (ROI) analysis and normalized against the background noise and CSF SI. Normalized SI recorded during follow-up was compared with that recorded immediately after resection. Tumor progression was defined as a 20% or greater increase in the diameter of the longest residual or recurrent meningioma (Response Evaluation Criteria in Solid Tumors). The sensitivity and specificity of the elevated SI in the resection cavity for indicating residual or recurrent tumor were calculated. Qualitative analysis by FLAIR MRI showed that patients with remnant tumor following surgery had a prolonged SI increase in the resection cavity. Further, SI increase could not always be observed before recurrence, and both SI increase and regrowth remnant/recurrence could be detected in the same MRI examination. In resected meningiomas, leakage of tumor elements into the resection cavity, presumably tumor cells, manifests as an SI increase on FLAIR images and indicates residual or recurrent tumor. However, unlike the previous reports on partially resected gliomas, we concluded that the SI change does not always precede tumor progression or recurrence.
    The neuroradiology journal. 05/2012; 25(2):163-71.
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    ABSTRACT: Despite the controversy over the clinical significance of Gamma Knife surgery (GKS) for refractory mesial temporal lobe epilepsy (MTLE), the modality has attracted attention because it is less invasive than resection. The authors report long-term outcomes for 7 patients, focusing in particular on the long-term complications. Between 1996 and 1999, 7 patients with MTLE underwent GKS. The 50% marginal dose covering the medial temporal structures was 18 Gy in 2 patients and 25 Gy in the remaining 5 patients. High-dose treatment abolished the seizures in 2 patients and significantly reduced them in 2 others. One patient in this group was lost to follow-up. However, 2 patients presented with symptomatic radiation necrosis (SRN) necessitating resection after 5 and 10 years. One patient who did not need necrotomy continued to show radiation necrosis on MRI after 10 years. One patient died of drowning while swimming in the sea 1 year after GKS, before seizures had disappeared completely. High-dose treatment resulted in sufficient seizure control but carried a significant risk of SRN after several years. Excessive target volume was considered as a reason for delayed necrosis. Drawbacks such as a delay in seizure control and the risk of SRN should be considered when the clinical significance of this treatment is evaluated.
    Journal of Neurosurgery 03/2012; 116(6):1221-5. · 3.15 Impact Factor
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    ABSTRACT: Inter-ictal (18)F-2-fluoro-deoxy-D: -glucose-positron emission tomography (FDG-PET) is widely used for preoperative evaluation to identify epileptogenic zones in patients with temporal lobe epilepsy. In this study, we combined statistical parametric mapping (SPM) with the asymmetry index and volume-of-interest (VOI) based extent analysis employing preoperative FDG-PET in unilateral mesial temporal lobe epilepsy (MTLE) patients. We also evaluated the detection utility of these techniques for automated identification of abnormalities in the unilateral hippocampal area later confirmed to be epileptogenic zones by surgical treatment and subsequent good seizure control. FDG-PET scans of 17 patients (9 males, mean age 35 years, age range 16-60 years) were retrospectively analyzed. All patients had been preoperatively diagnosed with unilateral MTLE. The surgical outcomes of all patients were Engel class 1A or 1B with postoperative follow-up of 2 years. FDG-PET images were spatially normalized and smoothed. After two voxel-value adjustments, one employing the asymmetry index and the other global normalization, had been applied to the images separately, voxel-based statistical comparisons were performed with 20 controls. Peak analysis and extent analysis in the VOI in the parahippocampal gyrus were conducted for SPM. For the extent analysis, a receiver operating characteristic (ROC) curve was devised to calculate the area under the curve and to determine the optimal threshold of extent. The accuracy of the method employing the asymmetry index was better than that of the global normalization method for both the peak and the extent analysis. The ROC analysis results, for the extent analysis, yielded an area under the curve of 0.971, such that the accuracy and optimal extent threshold of judgment were 92 and 32.9%, respectively. Statistical z-score mapping with the asymmetry index was more sensitive for detecting regional glucose hypometabolism and more accurate for identifying the side harboring the epileptogenic zone using inter-ictal FDG-PET in unilateral MTLE than z-score mapping with global normalization. Moreover, the automated determination of the side with the epileptogenic zone in unilateral MTLE showed improved accuracy when the combination of SPM with the asymmetry index and extent analysis was applied based on the VOI in the parahippocampal gyrus.
    Annals of Nuclear Medicine 02/2012; 26(4):319-26. · 1.41 Impact Factor
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    ABSTRACT: A 20-year-old woman presented with a rare case of intraorbital mesenchymal chondrosarcoma manifesting as a 6-month history of progressive ptosis and exophthalmos of her left eye. Computed tomography and magnetic resonance imaging revealed a partially calcified round mass occupying the postbulbar space. Partial removal of the tumor via a left fronto-orbital approach was performed. The histological diagnosis was mesenchymal chondrosarcoma, and additional intraorbital exenteration was performed. Neither chemotherapy nor radiotherapy was performed. She was free from tumor recurrence at the 6-year follow-up examination. Radical resection, including exenteration if possible, is recommended for intraorbital mesenchymal chondrosarcoma.
    Neurologia medico-chirurgica 01/2012; 52(10):747-50. · 0.49 Impact Factor
  • Kensuke Kawai, Kenichi Usami, Nobuhito Saito
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    ABSTRACT: Vagus nerve stimulation is the first electrical stimulation therapy for epilepsy. While its clinical use was approved by the European Union in 1994 and by the United States in 1997, it was approved last year and coverage by public insurance started last July in Japan. Owing to less invasiveness and broad indication, it is expected that vagus nerve stimulation will be increasingly used in Japan as well. Its efficacy for refractory partial seizures in patients older than 13 years was validated by two randomized control trials. Although it has been used for children and generalized seizures broadly, the efficacy for these subpopulations of patients has not been validated by randomized control trials, necessitating those studies in the near future. Afferent neural impulses generated by vagus nerve stimulation transmit to the solitary tract nucleus, then via multiple pathways including the monoamine system, vagus nerve stimulation affects the excitability of the cortical neurons. It likely exerts the anti-epileptic and anti-seizure effects using these pathways, but the detailed mechanisms underlying the effect remains to be elucidated further in future.
    Rinshō shinkeigaku = Clinical neurology. 11/2011; 51(11):990-2.
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    ABSTRACT: BACKGROUND: Tumor-to-tumor metastasis is a rare but well-known phenomenon. Among the more than 100 intracranial tumors reported, meningiomas are the most common type, whereas schwannoma is extremely rare. CASE DESCRIPTION: We describe a 75-year-old woman with a lung adenocarcinoma that metastasized to a vestibular schwannoma. Tumor-to-tumor metastasis was indicated by preoperative [(18)F]-fluorodeoxyglucose positron emission tomography. CONCLUSIONS: [(18)F]-fluorodeoxyglucose positron emission tomography is effective in the preoperative diagnosis of rapidly growing cerebellopontine angle tumors in patients with a history of malignancy.
    World Neurosurgery 11/2011; · 1.77 Impact Factor

Publication Stats

186 Citations
79.42 Total Impact Points

Institutions

  • 2002–2014
    • The University of Tokyo
      • Department of Neuroscience
      Edo, Tōkyō, Japan
  • 2013
    • Niigata University
      Niahi-niigata, Niigata, Japan
  • 2012
    • Asahikawa Medical University
      • Department of Neurosurgery
      Asakhigava, Hokkaidō, Japan
  • 2004–2012
    • Tokyo Medical University
      • Department of Neurosurgery
      Tokyo, Tokyo-to, Japan