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K Minematsu

Publications and source records attributed to K Minematsu.

At least 73 records · Page 4Linked to original sources
PubMed1997

Limb salvage using distraction osteogenesis. A classification of the technique.

We report the results of distraction osteogenesis (callotasis) for the reconstruction of extensive defects after the excision of skeletal tumours in the limbs. Bone transport was performed in ten patients (five osteosarcomas and five giant-cell tumours), shortening-distraction in three (two osteosarcomas and one Ewing's sarcoma), and distraction osteogenesis combined with an intramedullary nail to reduce the time of external fixation in six (three osteosarcomas, two chondrosarcomas, and one malignant fibrous histiocytoma). The mean length of the defects after excision of the lesion was 8.4 cm. The mean external fixation index was 39.5 days/cm for the group treated by bone transport, 34.1 days/cm for the shortening-distraction group, and 24.0 days/cm for the group treated by distraction and an intramedullary nail. Functional evaluation gave excellent results in 12 patients, good in five and fair in two. There were ten complications in 19 patients, all of which were successfully treated. We also classified reconstruction using distraction osteogenesis into five types based on the location of the defects after resection of the tumour: type 1, diaphyseal; type 2, metaphyseal; type 3, epiphyseal; type 4, subarticular reconstruction; and type 5, arthrodesis. Our results suggest that reconstruction using distraction osteogenesis provides bone which will develop sufficient biomechanical strength and durability. It is beneficial in patients with an expectation of long-term survival and in growing children.

Adolescent↗
PubMed1996

The competitive NMDA antagonist, CGS-19755, improves postischemic hypoperfusion in selectively vulnerable regions in gerbils.

We attempted to clarify the effects of an NMDA antagonist on postischemic hypoperfusion in gerbils with 10 min forebrain ischemia and to relate it to postischemic metabolic recovery. We administered 10 mg/kg of CGS-19755, a competitive NMDA antagonist, or the same volume of saline intraperitoneally 30 min before the vascular occlusion. In 26 gerbils, we measured local cerebral blood flow (LCBF) 60 min after the reperfusion using [14C]iodoantipyrine autoradiography. In 20 gerbils, the effects on metabolic recovery were determined by serial measurements of intracellular pH, adenosine triphosphate (ATP) and the ratio between phosphocreatine and inorganic phosphate (PCr/Pi) until 60 min after reperfusion using 31P-magnetic resonance spectroscopy. In another group of 24 gerbils, we determined histopathological damage 24 h after the ischemia. The LCBF autoradiograms in the control group consistently demonstrated a typical postischemic hypoperfusion, i.e. homogeneous 50-75% reduction of blood flow in all forebrain structures. In contrast, CGS-19755 pretreatment animals showed highly heterogeneous LCBF declines, and significantly higher LCBF values were observed in the frontoparietal cortex and thalamus both of which were the most vulnerable area in this model. No significant LCBF change was observed in sham operated animals with or without CGS-19755 pretreatment. The postischemic recovery of PCr/Pi in gerbils pretreated with CGS-19755 was significantly better than that in the control animals. No significant differences in the recovery of ATP and intracellular pH were observed. The histological damage in the CGS-19755-treated group was less extensive than those in the saline-treated group. CGS-19755 pretreatment improved postischemic hypoperfusion and PCr/Pi recovery in the 10-min forebrain ischemia model in gerbils. The improvement of postischemic hypoperfusion in selectively vulnerable regions suggests that the activation of NMDA receptors may be related to the mechanism of developing postischemic hypoperfusion.

Animals↗
PubMed1996

Medial medullary infarction: analyses of eleven patients.

Of 2,130 consecutive patients admitted to two hospitals with acute brain infarction, we examined 11 patients (0.52%) with medial medullary infarction. The infarcts documented by MRI were unilateral in 9 patients and bilateral in 2 patients, and located in the anteromedial arterial territory of the upper or middle part of the medulla. Atherosclerosis of the vertebral arteries was the predominant vascular pathology. The vertebral artery was occluded at its terminal portion in 7 patients. Nine patients had hypertension, and 8 of these had additional risk factors. Male gender (10 patients) and smoking habits (7 patients) were more prevalent compared with patients with pontine infarction. One patient had a medial medullary infarction attributed to dissection of the vertebral arteries following blunt head injury. Limb weakness was the major symptom in all patients, and gaze-evoked nystagmus was also frequent (6 patients). Tongue weakness ipsilateral to the infarct, the classic sign of medial medullary syndrome, was evident in only 3 patients. The outcome was usually excellent.

Adult↗
PubMed1996

The Ilizarov method in the management of giant-cell tumours of the proximal tibia.

We have used the Ilizarov technique for the management of subarticular defects after the excision of giant-cell tumours in the proximal tibia in five patients. The defect was reconstructed with a segment of 5 to 6 cm obtained from the diaphysis of the affected tibia and by autogenous bone graft from the iliac crest. The newly developed defect in the diaphysis was reconstructed by distraction using the Ilizarov apparatus. Bone grafting at the docking site was performed soon after positioning the bone segments. The mean length of the bone defect was 5.7 cm and the mean duration of external fixation was 233 days. The relative blood flow in the leg measured by 99mTc angiography increased by 1.7 to 2.3 times that of the control level during distraction and consolidation. When seen at a mean of 43 months all patients showed a normal range of motion in the knee and ankle with no collapse of the articular surfaces.

Adolescent↗
PubMed1996

[Erythromycin-induced hearing loss in a patient with Listeria monocytogenes meningo-ventriculitis].

We report a 43-year-old woman who suffered from Listeria monocytogenes meningitis. She was admitted to our hospital because of headache, nausea, vomiting, and fever. On admission she had no abnormal neurological signs except for severe nuchal stiffness. Cerebrospinal fluid (CSF) examination on the day of admission revealed pleocytosis and increased total protein level. The CSF culture demonstrated Listeria monocytogenes. Because ampicillin therapy was not effective, erythromycin (8 g/day) was added. After 12 hours of erythromycin therapy, the patient complained of moderate hearing difficulty. Erythromycin was then stopped on the next day. Her hearing improved and became normal within 48 hours after discontinuation of erythromycin. Contrast MRI of the brain revealed enhancement of the ependyma of the lateral ventricle, suggesting the presence of ventriculitis. By parenteral administration of ampicillin and cephazolin, clinical symptoms improved quickly, and abnormal CSF and MRI findings were normalized. Listeria meningitis accompanied with ventriculitis has been reported in neonates and infants, but not in adults. In addition, this is the first case with erythromycin-induced hearing loss in the Japanese literature. Hearing should be regularly examined in patients who are treated with high-dose erythromycin (> or = 4 g/day), and the drug should be immediately discontinued when the patient develops hearing loss.

Adult↗
PubMed1995

Nylon monofilament for intraluminal middle cerebral artery occlusion in rats.

BACKGROUND AND PURPOSE: In rat middle cerebral artery (MCA) occlusion models with an intraluminal nylon monofilament, lesion volume and its reproducibility vary among laboratories. These variations may be caused by differences in the properties of nylon monofilaments. We performed the present study to compare the effects of two different types of 4-0 nylon monofilament on neurological and morphological outcomes in this model. METHODS: We randomly and blindly used two types of 4-0 nylon monofilament (Ethilon, n = 15, and Nitcho, n = 15) to permanently occlude the ostium of the right MCA intraluminally in rats. Neurological outcome and lesion size were compared 24 hours after MCA occlusion between the two groups. The diameter, tensile strength, and extensibility of each filament were measured. RESULTS: Neurological outcome was not different between the groups. The mortality within 24 hours was 13% (2/15) in the Ethilon group and 0% in the Nitcho group. Total lesion volume in the former was 295.9 +/- 97.2 mm3 (mean +/- SD), significantly larger and more reproducible than that in the latter (190.3 +/- 144.7 mm3, P = .026). The Ethilon filament had a significantly larger diameter (Ethilon, 0.193 +/- 0.001 mm; Nitcho, 0.180 +/- 0.001 mm; P < .0001), poorer tensile strength, and better extensibility than the other. CONCLUSIONS: Exact diameter and quality are not always the same among nylon monofilaments, even if they meet the standard for the designation 4-0. The present study indicates that slight differences of filament characteristics significantly affect lesion volume and its reproducibility. This result may explain some conflicting observations in this MCA occlusion model.

Animals↗
PubMed1995

[The pathogenesis of brain infarction in the posterior cerebral artery territory].

In order to clarify the etiology of brain infarction in the posterior cerebral artery (PCA) territory, we investigated 85 patients (29 women and 56 men, mean age: 63.6 years old) with PCA territory infarction confirmed by computed tomography or magnetic resonance imaging. Patients with thalamic infarction alone were excluded from the present study. Cerebral angiography was performed in 72 subjects. The diagnosis of the mechanism of brain infarction was made on the basis of cerebral angiographic and echocardiographic (presence of cardiac disease as a potential embolic source) findings. Embolism was inferred when the presence of the patent PCA ipsilateral to the infarction, reopening of the occluded PCA or intraluminal filling defect was demonstrated by angiographic studies. In addition, we divided these patients into three groups according to potential source of emboli; cardiogenic, atherothrombotic (so-called artery-to-artery embolism) and embolism of undetermined origin. We diagnosed the patient to have thrombotic mechanism, when an occlusion of the PCA was demonstrated without presence of an embolic source (heart diseases or stenotic arterial lesions proximal to the occluded PCA). When the mechanism (embolic or thrombotic) could not be clearly distinguished, we categorized them "unclassified". When other apparent mechanisms such as arterial dissection, moyamoya disease etc, were demonstrated, we classified them in "miscellaneous". According to the above criteria, 50 patients (59%) were diagnosed as having embolism, only two patients (2%) had definite thrombosis, 28 patients (33%) "unclassified", and five patients (6%) "miscellaneous" (2 arterial dissection, 1 radiation vasculopathy, 1 migraine, 1 moyamoya disease).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

[Diffusion MRI for evaluating cerebrovascular disease].

There are several new magnetic resonance (MR) technologies, which will provide data about the pathogenesis, circulatory state and cellular effects of ischemic stroke. Among them, diffusion MRI is the most promising one. This technology clearly reveals, within minutes of stroke onset, ischemic lesions which ultimately progress to infarct. The early ischemic lesions demonstrated by diffusion MRI represent regions with slower water diffusions perhaps due to intracellular water accumulation or shrinkage of the extracellular spaces resulting from ionic pump failure, spreading depression, or other mechanisms. The diffusion MRI can show not only irreversible but also reversible ischemic lesions, and therefore has a potential to discriminate salvageable tissues from irreversibly damaged tissues before a therapeutic intervention with thrombolytic and/or cytoprotective agents. The diffusion MRI can highlight only a fresh lesion, because water diffusion is decreased during several days after stroke onset. Diffusion MRI is extremely prone to motion artifacts, a major concern against clinical application. This problem can be solved by combination with an ultrafast technique, echo planar (EP) imaging. The EP diffusion MRI will become a rapid, reliable, objective and essential emergency diagnostic test in a clinical setting that will guide the development and application of acute therapeutic intervention.

Animals↗
PubMed1994

Radioactive microsphere validation of a volume localized continuous saturation perfusion measurement.

Detre et al. (Magn. Reson. Med. 23, 37-45 (1992)) and Zhang et al., (Magn. Reson. Med. 25, 362 (1992)) have recently demonstrated a technique for the measurement of regional cerebral blood flow (rCBF) based on the continuous saturation (or inversion) of the arterial blood supply to the brain in rats at 4.7 T. In the work reported here, we combined this technique with volume localized (PRESS) readouts to benefit from recording "perfusion" signals averaged over a larger volume, resulting in rapid acquisition of data with sufficient signal-to-noise ratio for application at 2.0 T. In 10 baseline flow measurements, the mean error between the NMR technique and the microsphere flow measurement was -1.5% with a standard deviation of 15.2%. For five measurements obtained with occlusion of the middle cerebral artery, the mean error was -32.4 +/- 20.2%. Perfusion measurements from a single animal under hypercapnic conditions indicated that the NMR technique could underestimate rCBF at high flow rates. An error analysis of the NMR perfusion model is also presented, along with results for typical parameters encountered at 2.0 T.

Animals↗
PubMed1994

Long-term changes in cerebral blood flow according to different types of ischemic stroke.

Recurrence of ischemic stroke may be related to chronic hemodynamic failure of the brain. Long-term changes in cerebral blood flow (CBF) remain undetermined for each ischemic stroke subtype. We performed the present study to clarify this issue. The study group consisted of 77 unilateral, hemispheric, ischemic stroke patients who had a single stroke episode; atherothrombotic stroke in 34, cardioembolic in 26 and lacunar in 17. We measured baseline CBF in the affected and unaffected hemispheres 1.0-3.4 months after stroke onset, then repeated the measurements 10 months to 10 years later (mean 43.7 months), with the xenon-133 inhalation method. We analyzed changes in CBF in relation to other clinical characteristics. CBF in the affected hemisphere changed differently among the stroke subtypes (P < 0.01); increased in the atherothrombotic group, particularly within 40 months of stroke; remained unchanged in the cardioembolic group; and decreased in the lacunar group, especially later than 40 months of stroke. In the atherothrombotic group, CBF increased in hypertensive patients but decreased in normotensives (7.9 +/- 2.4% and -3.6 +/- 3.9%, respectively; P < 0.05). Present results suggest that long-term changes in CBF depend on ischemic stroke subtype. Development of collateral circulation may occur after several years in atherothrombotic stroke patients. The findings raise doubts about the significance of chronic hemodynamic failure as a cause of stroke recurrence.

Adult↗
PubMed1994

Acetazolamide reactivity on 123I-IMP single photon emission computed tomography in patients with major cerebral artery occlusive disease: correlation with positron emission tomography parameters.

Single photon emission computed tomography (SPECT) with acetazolamide challenge has increasingly been used for evaluating hemodynamic reserve in stroke patients. The accuracy of this test, however, has not been validated with positron emission tomography (PET). In 14 patients who had occlusive disease of the internal carotid artery or the trunk of the middle cerebral artery (MCA) with minimal or no infarction on computed tomography (CT) and magnetic resonance imaging (MRI), we compared acetazolamide reactivity on SPECT with N-isopropyl-p-[123I]-iodoamphetamine to hemodynamic parameters determined with gas inhalation labeled 15O steady-state PET studies. The asymmetry index (AI)--i.e., the percentage of the activity rate of the ischemic MCA territory versus the contralateral one, was determined by SPECT. Acetazolamide reactivity expressed as delta AI, or change in AI after acetazolamide challenge, was significantly lower in seven patients than -8.4%, the lower limit of the 95% confidence interval for the normal reactivity. Values of ipsilateral CBF, cerebral blood volume (CBV)/CBF, and oxygen extraction fraction (OEF) and contralateral OEF were significantly different between patients with normal and reduced acetazolamide reactivity. Values of delta AI were correlated with OEF (r = -0.87; p < 0.001) and CBV/CBF (r = -0.56; p < 0.05). All patients with OEF > 0.52, the mean + 2 SD calculated from five normal volunteers, also had reduced acetazolamide reactivity, while the patients with normal OEF values had normal reactivity. The present study has demonstrated that SPECT studies with an acetazolamide challenge can detect the Stage II hemodynamic failure.

Acetazolamide↗
PubMed1994

[Effects of CDP-choline on dynamic changes in LCBF and cognitive function in demented subjects--an H2 15O-PET study].

We studied correlations of serial changes in local cerebral blood flow (LCBF) after single intravenous (i.v.) injection of cytidine diphosphate choline (CDP-choline) to changes in cognitive function in demented subjects after its daily administration for one week. The study group consisted of 7 patients with dementia of vascular origin (VD group; mean age 65.0 years) and 3 patients with dementia of non-vascular origin (non-VD group; 64.7 years). Cognitive function was evaluated with the Japanese version of the Cross Cultural Cognitive Examination (CCCE). After i.v. injection of CDP-choline, mean supratentorial LCBF increased with the maximum value at 40 minutes post-injection in the VD-group, but decreased in the non-VD group (Type, n.s.; Time, n.s.; Type x Time, p < 0.01; ANOVA). The number of the pass-tasks in CCCE increased significantly after the 7 days-injection of CDP-choline only in the VD group (p < 0.05), while it was fairly stable in 15 control patients, who were matched in age and severity of dementia to the study patients. In this group, a change in the number of pass-tasks was significantly correlated with those in LCBF at ROIs in the left and right temporal cortices and the right thalamus. In the non-VD group, there were no significant changes of mean supratentorial LCBF and of the number of pass-tasks in CCCE. These results may be attributable to difference in availability of the acetylcholine neurotransmitter system in the brain between VD- and non-VD patients.

Aged↗
PubMed1993

Apparent diffusion coefficient mapping of experimental focal cerebral ischemia using diffusion-weighted echo-planar imaging.

Diffusion-weighted, echo-planar imaging (EPI) was used to map regional changes in the apparent diffusion coefficient (ADC) during experimental focal ischemia in the rat brain following permanent middle cerebral arterial occlusion (MCAO). Sixteen 64 x 64 diffusion-weighted EPIs were acquired in 32 s with successively increasing amplitudes of the diffusion-sensitive gradient pulses. A linear least-squares regression algorithm was used to fit 15 of the 16 two-dimensional matrices, on a pixel-by-pixel basis, to solve for the slope from which the ADC value was calculated. The correlation coefficient of the fit, R2, was used to filter the final ADC maps, and the ADCs were then scaled appropriately to be displayed in a 256 gray level format. Ranges (bins) of 0.05 x 10(-3) mm2/s were then grouped and color coded to qualify and quantify the evolution of ischemia in the MCA territory. The percentage of area in the ischemic and contralateral hemispheres in seven ADC bins were calculated at 30, 60, and 120 min after MCAO for 10 animals and demonstrated a significant increase in ADC bins below 0.45 x 10(-3) mm2/s and a decrease in bins above 0.50 x 10(-3) mm2/s over time. The postmortem infarct area, as measured by TTC staining, was highly correlated with the portion of the ischemic hemisphere falling below ADC values of 0.55 x 10(-3) mm2/s at 2 h after stroke onset. These studies suggest that focally ischemic brain tissue can be quantitatively subdivided according to ADC values and that ADC values below 0.55 x 10(-3) mm2/s 2 h following ischemia highly predict infarction in a rat permanent occlusion stroke model.

Algorithms↗
PubMed1993

The J-curve phenomenon in stroke recurrence.

BACKGROUND AND PURPOSE: The relation of poststroke blood pressure to stroke recurrence remains undetermined, and the optimal control of blood pressure has not been established. We performed the present study to resolve these issues. METHODS: We analyzed 368 stroke patients with a history of hypertension (mean age, 62 years) who were admitted within 3 months after stroke onset and observed for 6 months or more. We determined stroke recurrence rate in relation to baseline (or initial) blood pressure, mean values of poststroke blood pressure, stroke subtypes, age, antihypertensive treatment, and other clinical features. RESULTS: The recurrence rate had a J-curve relation to poststroke diastolic blood pressure but not to poststroke systolic blood pressure and baseline diastolic and systolic blood pressures. The stroke recurrence rate was 3.8% per patient-year in 94 patients who had a poststroke diastolic blood pressure of 80 to 84 mm Hg, significantly lower than the rates of 9.2% per patient-year (P < .05) and 11.4% per patient-year (P < .01) in those with a lower and higher poststroke diastolic blood pressure, respectively. The range of poststroke diastolic blood pressure accompanying the lowest stroke recurrence rate was higher in patients with atherothrombotic (85 to 89 mm Hg) than in those with lacunar infarction (80 to 84 mm Hg). Neither antihypertensive therapy nor patients' age affected this phenomenon. CONCLUSIONS: The present study suggests that lower blood pressure does not always result in favorable effects on stroke recurrence. The effects of poststroke blood pressure and antihypertensive therapy on stroke recurrence may be complicated by the J-curve phenomenon.

Aged↗
PubMed1993

Diffusion and perfusion magnetic resonance imaging studies to evaluate a noncompetitive N-methyl-D-aspartate antagonist and reperfusion in experimental stroke in rats.

BACKGROUND AND PURPOSE: Diffusion magnetic resonance imaging (MRI) can quantitatively detect focal ischemic injury within minutes of onset, and perfusion MRI can evaluate the brain's microcirculation. N-Methyl-D-aspartate (NMDA) antagonists and reperfusion can reduce lesion size in stroke models. We used diffusion and perfusion MRI to evaluate the in vivo effects of a noncompetitive NMDA antagonist, CNS 1102, in a temporary ischemia model. METHODS: Sixteen Sprague-Dawley rats underwent suture occlusion of the middle cerebral artery. Fifteen minutes after occlusion, animals were randomly assigned to treatment with CNS 1102 (n = 10) or placebo (n = 6), receiving a bolus of 1.13 mg/kg at that time and an infusion of 0.785 mg.kg-1.h-1 for the next 165 minutes. The placebo group received a saline bolus and infusion. Diffusion MRI studies by a spin-echo technique were initiated 30 minutes after occlusion and repeated every 30 minutes for the next 3 hours. Perfusion MRI studies were obtained using echo-planar imaging after injection of superparamagnetic iron oxide particles, immediately before and 15 minutes after withdrawal of the occluder at 3 hours after middle cerebral artery occlusion. At 24 hours, the animals were clinically evaluated (scale of 0 to 5) and electively killed, and the brain was stained with triphenyltetrazolium chloride to evaluate infarct size. RESULTS: Diffusion imaging demonstrated markedly reduced ischemic lesion area in the CNS 1102 group during occlusion--10.5 +/- 7.3% (mean +/- SEM) of the ischemic hemisphere (optic chiasm slice) at 30 minutes after occlusion versus 50.0 +/- 2.7% of the hemisphere in controls (P < .02). With reperfusion after 3 hours of temporary ischemia, diffusion imaging documented an additional 29% reduction of the ischemic lesion area in the CNS 1102-treated group (P < .01) compared with the prereperfusion ischemic lesion area, with no change in the placebo group. During occlusion, perfusion imaging demonstrated a relative signal intensity decline of 31.5 +/- 7.7% in controls and 83.4 +/- 7.6% in the CNS 1102 group (P < .005), indicating better perfusion in the latter group. After removal of the occluder, perfusion improved in both groups and was not significantly different. Post mortem infarct volume was 53.8 +/- 20.0 mm3 in the CNS 1102 group and 216.8 +/- 16.1 mm3 in the controls (P < .0001). Clinical outcome at 24 hours was 1.1 +/- 0.4 in the CNS 1102 group and 4.0 +/- 0.5 (scale of 0 to 5) in the controls (P < .005). CONCLUSIONS: This study demonstrates that CNS 1102 reduces early postischemic injury as documented by diffusion MRI and improves perfusion as documented by perfusion MRI and that reperfusion confers additional reduction of ischemic lesion size.

Animals↗
PubMed1993

Effects of a novel NMDA antagonist on experimental stroke rapidly and quantitatively assessed by diffusion-weighted MRI.

We employed diffusion-weighted MRI (DWI) to identify regions of focal brain ischemia during the first 3 hours after permanent occlusion of the middle cerebral artery in rats. Using DWI as early as 30 minutes after the onset of ischemia, it was possible to identify the areas of brain destined to progress to infarction over the next 24 hours in untreated animals, as demonstrated by postmortem evaluation. DWI studies revealed the cerebroprotective effects of a noncompetitive N-methyl-D-aspartate receptor antagonist, CNS 1102, administered 15 minutes postocclusion, both on the cortical and caudoputaminal regions during the initial 3 hours of ischemia. Although the treatment effect lessened over the next 21 hours in a few animals with lower plasma drug levels at 3 hours, postmortem studies demonstrated a 66% reduction in the total volume of infarcted tissue with the treatment and confirmed the DWI results. T2-weighted MRI obtained at similar times revealed little or no abnormality. These results suggest that DWI provides a sensitive in vivo measure of focal cerebral ischemic injury and can assess the beneficial effects of cytoprotective therapy. DWI may be useful in the early evaluation of human stroke patients and in monitoring the effects of cerebroprotective therapies in the clinical setting.

Animals↗