Kazuo Yamada

Nagoya City University, Nagoya, Aichi, Japan

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Publications (158)295.21 Total impact

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    ABSTRACT: The precise mechanism of carotid calcification formation and its clinical significance including the difference in outcomes compared with coronary artery have not been clearly elucidated yet. We applied the calcium score for analyzing carotid plaque calcification in focus on its relationship with symptoms and discuss the difference in transitional patterns and the clinical outcome in comparison with calcified coronary plaques. Multidetector row computed tomography angiography was performed preoperatively to determine the Agatston calcium score, volume score, and Hounsfield values for a total of 330 carotid arteries from 194 patients. Analysis focused on the relation of "the symptomatic rate" to calcium score, volume score, and Hounsfield value as well as the characteristics of calcified plaques and coexisting diseases. The symptomatic rate of carotid artery plaques in each range of the index was calculated as the percentage of the number of carotid arteries with plaques, which elicited symptoms of the contralateral limbs or the ipsilateral retina to the whole number of carotid arteries with plaques within the range. Calcified carotids with low symptomatic rate (<40%) tended to have calcification with significantly high calcium scores, high volume scores and mean/maximum Hounsfield values, high circularities, outer positions, positive remodeling, and carotid bulb/common carotid locations by univariate analysis, whereas high maximum Hounsfield value, high circularity, and outer position of calcification were significant independent predictors of low-symptomatic calcified carotid plaques by multivariate logistic regression analysis. When analyzed by calcium score, the rates for symptomatic carotids showed double peaks at calcium scores around 200-400 and 600-800 with a dip at 400-600. Significant independent predictors of low symptomatic carotid artery were high maximum Hounsfield value (odds ratio [OR], 5.70; P = .005), calcification encircling the carotid perimeter (OR, 7.18; P = .005), and the calcium location in the common carotid artery (OR, 6.62; P = .006) in comparing groups with low (0-400) and medium (400-600) calcium scores, whereas a high volume score (OR, .01; P = .003) alone was a significant independent determinant in the comparison between groups with high (600-1000) and medium calcium scores. Symptomatic rates of carotid plaque calcification were demonstrated to show double peaks with increasing calcium score and represent different features. Assessment of the 2 calcium-score parts might be helpful for appropriate comprehension of symptomatology and the complex process of carotid plaque calcification. We report a hypothesis for the mechanisms of the 2 different sections. Copyright © 2015 National Stroke Association. Published by Elsevier Inc. All rights reserved.
    No preview · Article · Mar 2015 · Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association
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    Full-text · Article · Jan 2015 · Scoliosis

  • No preview · Article · Nov 2014 · No shinkei geka. Neurological surgery
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    ABSTRACT: Background The aim of the study was to investigate the depiction of the carotid artery by fluorescein sodium (FS) videoangiography compared with indocyanine green (ICG) videoangiography, focusing on how the vasa vasorum of the carotid artery is depicted. Methods Thirty-five patients (19 FS patients, 16 ICG patients, mean age 69.4 ± 5.1 years, mean degree of stenosis 78.7% ± 11.7%) who underwent a carotid endarterectomy (CEA) were enrolled. FS (5-6 mg/kg) or ICG (.2-.3 mg/kg) was injected intravenously as a bolus before the arterectomy during the CEA. The intravascular fluorescence signal was recorded with a digital video camera integrated on a microscope. Magnetic resonance imaging black-blood (BB) T1-weighted imaging (WI) was preoperatively performed using a 1.5-T whole-body imager, and the signal intensity ratio relative to the ipsilateral sternocleidomastoid muscle on BB-T1WI (BB-SIR) was calculated. We also performed an immunohistochemistry study using CD31 and CD68 antibodies for plaque specimens. Results In the FS videoangiography series, the vasa vasorum of carotid adventitia was depicted first, followed by augmentation of FS of the wall and partially the inner lumen (pattern A) in 6 cases. Augmentation of FS of the wall and inner lumen prior or simultaneous to the depiction of the vasa vasorum of the carotid adventitia (pattern B) were observed in 13 cases. The average BB-SIR value of the pattern B cases was significantly higher than that in the pattern A group (P < .05). Most of the plaques with BB-SIR values higher than 1.25 also belonged to the pattern B group (90.9%). Microvessels stained by CD31 and macrophages stained by CD68 were more frequently observed in the high–BB-SIR plaques. In contrast, the ICG videoangiography uniformly showed pattern B in all 16 cases, because of the fluorolucency of the carotid wall revealed by the ICG. Conclusions The early depiction of adventitial vasa vasorum in FS videoangiography was inversely associated with the BB-SIR values of the plaques, along with many microvessels and macrophages that have been reported to have a tendency of intraplaque hemorrhage or symptoms. The present results may support the idea of an intimal origin of the neovascularization in vulnerable carotid plaques, and they demonstrated the potential of intraoperative plaque imaging by FS videoangiography.
    Full-text · Article · Nov 2014 · Journal of Stroke and Cerebrovascular Diseases
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    ABSTRACT: We classified the results of preoperative auditory brainstem response (ABR) in 121 patients with useful hearing and considered the utility of preoperative ABR as a preliminary assessment for intraoperative monitoring. Wave V was confirmed in 113 patients and was not confirmed in 8 patients. Intraoperative ABR could not detect wave V in these 8 patients. The 8 patients without wave V were classified into two groups (flat and wave I only), and the reason why wave V could not be detected may have differed between the groups. Because high-frequency hearing was impaired in flat patients, an alternative to click stimulation may be more effective. Monitoring cochlear nerve action potential (CNAP) may be useful because CNAP could be detected in 4 of 5 wave I only patients. Useful hearing was preserved after surgery in 1 patient in the flat group and 2 patients in wave I only group. Among patients with wave V, the mean interaural latency difference of wave V was 0.88 ms in Class A (n = 57) and 1.26 ms in Class B (n = 56). Because the latency of wave V is already prolonged before surgery, to estimate delay in wave V latency during surgery probably underestimates cochlear nerve damage. Recording intraoperative ABR is indispensable to avoid cochlear nerve damage and to provide information for surgical decisions. Confirming the condition of ABR before surgery helps to solve certain problems, such as choosing to monitor the interaural latency difference of wave V, CNAP, or alternative sound-evoked ABR.
    No preview · Article · Dec 2013 · Neurologia medico-chirurgica
  • Hiroyuki Katano · Kazuo Yamada
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    ABSTRACT: We compared patients who underwent carotid endarterectomy (CEA) using two-way and three-way internal shunts and discussed which shunt was more appropriate and effective for surgeons. Eighty-two patients (mean 69.5 ± 6.1 year old, mean degrees of stenosis 79.6 ± 10.4%) who had undergone CEA by our routine shunting policy were examined concerning the difference of Sundt and Pruitt-Inahara (P-I) shunts in clinical use. Carotid clamping time for the P-I shunt was over 2 minutes longer than that by Sundt in either split or conventional continuous arteriotomy (p < 0.001). The proportions of cases with multiple trials of either arteriotomy or insertion of a shunt tube, cases detected more than one high-intensity spot on diffusion-weighted images of magnetic resonance imaging after CEA, and cases detected postoperative intimal flaps detected by multi-detector CT angiography showed no significant differences between the two shunt groups. The two-way Sundt shunt was quicker than the three-way P-I shunt in placement with no remarkable problems. Split arteriotomy was not useful in shortening the placement time for either Sundt or P-I shunt tubes, compared with continuous arteriotomy. A simple two-way shunt with easy handling like the Sundt shunt would be also appropriate to choose in selective shunting under the unfamiliarity of treating shunts.
    No preview · Article · Dec 2013 · Neurologia medico-chirurgica
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    ABSTRACT: In surgery for subthalamic nucleus (STN) deep brain stimulation (DBS), precise implantation of the lead into the STN is essential. Physiological refinement with microelectrode recording (MER) is the gold standard for identifying STN. We studied single tract MER findings and surgical outcomes and verified our surgical method using single tract MER. The number of trajectories in MER and the final position of lead placement were retrospectively analyzed in 440 sides of STN DBS in 221 patients. Bilateral STN DBS yielded marked improvement in the motor score, dyskinesia/fluctuation score, and reduced requirement of dopaminergic medication in this series. The number of trajectories required to obtain sufficient activity of the STN was one in 79.0%, two in 18.2%, and three or more in 2.5% of 440 sides. In 92 sides requiring altered trajectory, the final direction of trajectory movement was posterior in 73.9%, anterior in 13.0%, lateral in 5.4%, and medial in 4.3%. In 18 patients, posterior moves were required due to significant brain shift with intracranial air caused by outflow of CSF during the second side procedure. Sufficient STN activity is obtained with minimum trajectories by proper targeting and precise interpretation of MER findings even in the single tract method. Anterior-posterior moves rather than medial-lateral moves should be attempted first in cases with insufficient recording of STN activity.
    No preview · Article · Oct 2013 · Neurologia medico-chirurgica
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    ABSTRACT: Patients with acoustic neuroma classified in Gardner and Robertson (GR) Class II should be considered to have useful hearing, and patients classified in Class III should be considered to have not-useful hearing. Therefore, it is important for acoustic neuroma surgery to distinguish between postoperative GR Class II and Class III patients by brainstem auditory evoked potentials (BAEPs). We evaluate which BAEP parameter is the best for predicting postoperative GR Class II or III in 36 preoperative GR Class II patients with unilateral acoustic neuroma. Delay in wave V latency, reduction ratio in wave V amplitude, and interaural difference of wave V (IT5) are evaluated by a receiver-operating characteristic (ROC) curve in this study. IT5 is the best distinguishing parameter between postoperative Class II and Class III. IT5 below 1.12 millisecond (msec) should be a good marker to preserve postoperative useful hearing. Thus, comparing the latency of wave V on both sides is important, and surgeons would be able to make more informed decisions during surgery by checking IT5 on BAEPs.
    No preview · Article · Oct 2013 · Journal of Neurological Surgery, Part B: Skull Base
  • Hiroyuki Katano · Kazuo Yamada
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    ABSTRACT: In carotid atherosclerotic lesions, calcified plaques are thought to be stable and to evoke very few symptoms. However, the molecular activity in calcified plaques and their clinical significance have not been fully clarified yet. Carotid plaques from 18 endarterectomy patients were classified into high- and low-calcified plaques on the basis of Agatston calcium score. Twelve plaques were investigated for the alteration of gene expression by microarray analysis and real-time polymerase chain reaction (PCR) and 6 other plaques underwent protein assessment to elucidate the difference in molecular biological activity between the groups. Microarray analysis demonstrated 93 angiogenesis or growth factor-related transcripts that are reliably expressed (175 probe sets). Among them, angiopoietin-like protein 4 (ANGPTL4) expression was significantly elevated, whereas fibroblast growth factor receptor 2 (FGFR2) expression was significantly suppressed. Quantitative messenger RNA analysis was performed with real-time PCR. Augmented or decreased protein expression of each gene was confirmed by Western blotting analysis and immunohistochemistry. In high-calcified plaques, ANGPTL4 might be upregulated for antiangiogenic modulating function together with the downregulation of FGFR2, contributing to the stability of the plaques.
    No preview · Article · Sep 2013 · Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association
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    ABSTRACT: Carotid endarterectomy (CEA) is an established surgical treatment for carotid stenosis. Recently, carotid artery stenting (CAS) has become aveilable as an alternative for treating the disease. However, which surgical method is the better choice is still controversial. Recent developments in medical treatment have brought remarkable improvement in the outcome of carotid stenosis. It is therefore time to reconsider the guidelines for carotid stenosis treatment based on the updated clinical evidence. © 2013, Japanese Congress of Neurological Surgeons. All rights reserved.
    No preview · Article · Sep 2013 · Japanese Journal of Neurosurgery
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    ABSTRACT: To investigate cerebral reactions to cognitive rehabilitation tasks, oxyhemoglobin changes were compared in 9 patients with cognitive impairments after traumatic brain injury (TBI) and 47 healthy controls using functional near infrared spectroscopy (fNIRS) during nine cognitive rehabilitation tasks employed at Nagoya City Rehabilitation Center. Forty-seven measurement channels were placed on the frontal to temporal cortices, and organized into seven channel regions. Oxyhemoglobin changes were normalized based on the mean oxyhemoglobin value at the resting state, and integrated throughout a task. Statistical analyses of the differences between the TBI patients and controls were performed with the two-sided Mann-Whitney U test. Oxyhemoglobin changes were high for both controls and TBI patients in the lateral frontal regions. Oxyhemoglobin changes in TBI patients tended to be higher than controls in the medial frontal regions for most training tasks, and significant differences (p < 0.05) were seen for two tasks in the medial frontal regions. Different regions were activated during the tasks in TBI patients compared to controls. fNIRS measurement is useful in the evaluation of changes of neuronal activities during rehabilitation tasks in TBI patients.
    No preview · Article · May 2013 · Neurologia medico-chirurgica
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    ABSTRACT: Background: In surgery of repair for spina bifida, various skin plastic techniques are sometimes necessary due to large skin defect or subsequent ulcers in cases when approximation on the midline is difficult. Case report: A baby was born with a large skin defect due to huge lumbar myeloschisis and kyphosis, which was repaired 2 days after birth using Limberg's skin flap at the peak of kyphosis. Skin ischemia around the tip of the flap gradually enlarged and resulted in a large skin ulcer. We performed negative pressure wound therapy (NPWT) using a Vacuum Assisted Closure (V.A.C.®) therapy system for 4 weeks which shrank the ulcer remarkably. Subsequently, a pedicle skin flap without graft was performed to cover the rest of the ulcer, which adapted well without CSF leakage postoperatively. Conclusion: A combination treatment of NPWT and skin plastic surgery was successfully performed for a very young infant with spina bifida. NPWT could be another useful option for the treatment of ulcer following spina bifida repair surgery, though surgeons should carefully confirm that there is no CSF leakage before and during the procedure.
    No preview · Article · May 2013 · Child s Nervous System

  • No preview · Article · Jan 2013 · Advances in Parkinson's Disease
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    ABSTRACT: Background: The aim of this study was to clarify both the present status of treatment for carotid stenosis with highly calcified plaques and the appropriate treatment. Methods: A total of 140 consecutive treatments for carotid stenoses (carotid endarterectomy [CEA]:carotid artery stenting [CAS] 81:59) were enrolled in the study. We classified the patients into low-calcified plaque (LCP) and high-calcified plaque (HCP) groups by calcium score, determined by a receiver operating characteristic analysis, and we compared the results after both treatments. Results: The mean degree of residual stenosis and improvement rates of the stenosis after CAS for the HCP group were 9.7% ± 13.3% and 87.0% ± 16.8%, respectively, whereas those for the LCP group were 1.7% ± 6.1% and 97.9% ± 7.9% (both P < .001). A multiple logistic regression analysis revealed that only the calcium score was an independent pre-CAS predictor of residual stenosis. Restenosis at 6 months was observed frequently in the HCP group after both CAS and CEA (18.8% and 20.0%, respectively). Cerebral hyperperfusion syndrome was observed in 2 cases of CAS, 1 for each plaque group. The 30-day and 6-month rates for any stroke or death after CAS were 2.3% and 12.5% for the LCP and HCP groups, respectively, whereas those after CEA were 1.6% and 0%. Conclusions: Carotid stenoses with HCP (calcium score ≥420) treated by CAS showed a disadvantage in the degree of stent expansion compared to carotid stenoses with LCP, suggesting that CEA may be recommended as a surgical option.
    No preview · Article · Dec 2012 · Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association
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    ABSTRACT: Objective: Chronic subdural hematoma (CSDH) after aneurysmal clipping is a rare complication, but its incidence and risk factors are not known in detail. We retrospectively reviewed our cases requiring surgery for CSDH after clipping. Methods: In our hospital, between January 2000 and December 2006, 794 patients (unruptured, 58.0%) underwent clipping surgery for aneurysm of the anterior circulation. We reviewed incidence and risk factors of CSDH after clipping. For the past 2 years, we reviewed all computed tomography scans for 163 unruptured aneurysms, and examined the relationship between an increase of subdural fluid collection (SFC) and development of CSDH. Results: Fifteen patients (1.9%) developed CSDH after clipping, which required evacuation. Among those, 13 had unruptured aneurysms (2.8%), a much higher percentage than for ruptured aneurysms (0.9%). On univariate statistical analysis, risk factors of CSDH were associated with advanced age (P = 0.0005), male gender (P = 0.04), and unruptured aneurysms (P = 0.02). Aneurysmal location was not related to the development of postoperative CSDH. Contralateral CSDH occurred in 3 patients, but no middle cerebral artery aneurysm developed contralateral CSDH. An increase in postoperative SFC during 1 week was a significant risk factor for CSDH (P = 0.001). Conclusions: In addition to the classic risk factors, this study showed that clipping for unruptured aneurysms carries a higher risk for CSDH compared to ruptured aneurysms. We suggest that an increase of SFC during 1 week postoperatively can be a factor in predicting CSDH after clipping.
    No preview · Article · Oct 2012 · World Neurosurgery
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    ABSTRACT: Background: Although acetazolamide-challenged single-photon emission CT (SPECT) is recommended before carotid endarterectomy (CEA) and carotid artery stenting (CAS), given the relationship between preoperative decreased cerebrovascular reserve (CVR) and postoperative cerebral hyperperfusion syndrome (CHS), it is controversial whether all cases should be checked. Methods: I-IMP-SPECT at rest was performed for 65 operative cases of carotid stenoses. At preoperative MR angiography we classified cases into two groups: G, featuring an anterior communicating artery with bilateral A1 with/without posterior communicating arteries; and P, a poor-escape-route group which did not match these criteria. Postoperative rCBF patterns were divided into two types: B, bilateral rCBF increase; and I, ipsilateral rCBF increase. Results: Cases with high postoperative increase rate of rCBF were most frequently found in Group P and the Type I cases (p < 0.001). All four cases with hyperemia or hyperperfusion belonged to Group P. Only two out of 48 patients in Group G were Type I, both demonstrating a preoperative rCBF decrease rate more than 10 % as compared to the contralateral side. Conclusions: From the present study, preliminary analysis of escape routes by preoperative MR angiography before surgical treatment of carotid stenosis is recommended and CVR investigation with acetazolamide-challenge SPECT should be considered for those relatively few cases with poor escape routes.
    No preview · Article · Sep 2012 · Acta Neurochirurgica
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    ABSTRACT: Background:Radioisotope cisternography (RICG) is useful for detecting cerebrospinal fluid (CSF) leakage in spontaneous intracranial hypotension (SIH) patients. However, RICG can cause iatrogenic CSF leakage (ICSFL) due to a lumbar puncture.Objectives:To compare the RICG findings of SIH and ICSFL.Methods:The presence of direct findings suggesting CSF leakage and indirect findings including early visualization of the bladder and absence of radioactivity over the brain convexities were evaluated in seven SIH and six ICSFL patients. Radioisotope clearance was assessed semi-quantitatively.Results:In contrast to the variety of anatomical levels at which direct findings were detected in the SIH patients, the ICSFL patients only displayed direct findings at the lumbosacral level. None of the ICSFL patients displayed direct findings at 1 hour after the tracer injection. Although early visualization of the bladder was depicted in all patients, no activity was visualized over the brain convexities in the SIH patients. In the semi-quantitative analysis, the tracer retention index at 24 hours was lower in the SIH patients than the ICSFL patients.Conclusions:The early appearance of direct findings above the lumbosacral level, the absence of radioactivity over the brain convexities and a low tracer retention index are suggestive of SIH.
    No preview · Article · Sep 2012 · Cephalalgia
  • Hiroyuki Katano · Shusaku Matsuo · Kazuo Yamada
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    ABSTRACT: Disproportionately large communicating fourth ventricle (DLCFV) is usually experienced in adults with no previous experience of shunting. We present a case of an infant with an enlarged fourth ventricle similar to isolated fourth ventricle (IFV) which appeared after shunting. The patient's brain stem symptoms and the abnormal appearance of the fourth ventricle were dramatically ameliorated simply by reducing the opening pressure of the adjustable valve of the ventriculo-peritoneal shunt. The present case suggests that in the present era, with adjustable or programmable valve shunt a common procedure, DLCFV may occur, at least temporarily, even in infants and even after shunting.
    No preview · Article · Mar 2012 · Acta neurologica Belgica
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    ABSTRACT: Since ventricular dilation and periventricular abnormal intensities are commonly seen in patients with idiopathic normal pressure hydrocephalus (INPH) on magnetic resonance imaging (MRI), dysfunction of white matter may have an important role in the mechanism causing symptoms of INPH. To clarify the pathophysiology of INPH, we analyzed axonal water dynamics using diffusion tensor MRI. Thirty-six patients with possible INPH were included. Regional fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were measured in several white matter regions before and 24 h after a cerebrospinal fluid tap test (CSF-TT). The patients were divided into two groups: patients who showed significant improvements in neurological status after the CSF-TT (positive, n = ;17) and those with no neurological improvement (negative, n = 19). After CSF-TT, ADC values were significantly decreased in the frontal periventricular region and the body of the corpus callosum in the positive group (p < 0.05), whereas no significant change was shown in the negative group. FA values were significantly increased in the body of the corpus callosum in both groups after CSF-TT (p < 0.05). After CSF-TT, water molecules at the extracellular space could move to the intraventricular space, resulting in decreased ADC values. This suggests that changes of water dynamics in white matter may have a role in the mechanism causing symptoms of INPH.
    No preview · Article · Jan 2012 · Acta neurochirurgica. Supplement
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    ABSTRACT: Selective impairment of executive function has been shown in Parkinson's Disease (PD) patients undergoing Deep Brain Stimulation (DBS) of the Subthalamic Nucleus (STN). However, some patients experience difficulties in daily life, such as dissension in interpersonal relationships or a loss of lifestyle balance, in the short term after surgery. Our hypothesis is that these difficulties might be related to executive dysfunction. To elucidate the involvement of executive dysfunction in these difficulties, we assessed motor and executive function in the short term and long term after surgery. We examined motor function and executive function in 30 patients who underwent bilateral STN-DBS for medically refractory PD. Patients were evaluated for executive function 1 month before surgery, 1 month after surgery, and 12 months after surgery using the Trail Making Test (TMT), the Modified Stroop Color Word Interference Test (MST) and tests of Verbal Fluency (VF). TMT-B, TMT (B/A), MST-B, VF-phonemic and VF-semantic scores were significantly poorer 1 month after STN-DBS. TMT-B, TMT (B/A) and VF-phonemic recovered to preoperative levels by 12 months after surgery. A reduction in dopaminergic medication 1 month after surgery was significantly correlated with deterioration of TMT (B/A). Temporary deterioration of executive function may occur in the short term after STN-DBS, whereas motor function is usually improved. PD patients undergoing STN-DBS should be managed during this period to better predict temporary executive dysfunction. Excessive reduction of dopaminergic medication after surgery might, at least in part, result in this deterioration of executive function.
    No preview · Article · Dec 2011 · Clinical neurology and neurosurgery

Publication Stats

2k Citations
295.21 Total Impact Points


  • 1996-2014
    • Nagoya City University
      • • Graduate School of Medical Sciences
      • • Department of Neurosurgery
      Nagoya, Aichi, Japan
  • 1992-1994
    • Kinki University
      • Department of Neurosurgery
      Ōsaka, Ōsaka, Japan
  • 1985-1994
    • Osaka University
      • Division of Neurosurgery
      Suika, Ōsaka, Japan