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Kenji Yoshikawa

Publications and source records attributed to Kenji Yoshikawa.

12 recordsLinked to original sources
PubMed2006

Microbleeds in Alzheimer disease are more related to cerebral amyloid angiopathy than cerebrovascular disease.

Cerebral amyloid angiopathy (CAA) is one of the cardinal pathological features in the vascular components of Alzheimer's disease (AD). CAA itself results in disrupted microvasculature, mainly in the cerebral cortex, eventually leading to a brain cortical or subcortical hemorrhage in a population of elderly people, but clinically overt brain hemorrhages are not so frequent in AD patients. Here we assessed 50 AD patients and 26 controls to detect latent brain hemorrhages with gradient-echo T(2)*-weighted images, a sensitive magnetic resonance imaging technique to detect hemosiderin components in the brain. Microbleeds, demarcated as low-intensity spots in T(2)*-weighted images, were detected in 16.7% of AD patients without cerebrovascular disease (CVD) and in 12.5% of those with CVD, while no microbleeding was detected in the control subjects. No significant difference was observed between the microbleed-positive group and the microbleed-negative counterpart in their clinical background, such as hypertension, the use of antiplatelet drugs and smoking. In addition, white matter high intensities in the T(2)-weighted image were significantly more confluent in the microbleed-positive AD group than its negative counterpart. In conclusion, our evaluation of AD brains revealed that latent microbleeds in AD patients are more frequent than in normal controls. Microbleeds not being related to common hemorrhagic risk factors, but being significantly related to white matter pathologies suggested that microbleeds in AD may be associated with CAA, but not with hypertension or CVD.

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PubMed2005

Local tissue anisotropy decreases in cerebellopetal fibers and pyramidal tract in multiple system atrophy.

BACKGROUND: One of the cardinal features in multiple system atrophy (MSA) is the white matter pathology: loss of myelin, astrocytosis, and glial cytoplasmic inclusions. The pathological changes of tissue microstructure can modify the diffusion behavior of water molecules, which can be assessed by diffusion tensor imaging (DTI). OBJECTIVES: To explore the hypothesis of white matter degeneration in MSA. METHODS: We studied 11 patients with clinically probable MSA and 10 age-matched controls. DTI was performed in both groups to measure fractional anisotropy (FA) in various regions of interest: the inferior cerebellar peduncle (ICP), middle cerebellar peduncle (MCP), superior cerebellar peduncle (SCP), basis pontis, internal capsule, and corpus callosum. RESULTS: FA values in SCP and corpus callosum showed no significant difference between the MSA group and controls. By contrast, FA values decreased in the MSA group in the MCP, basis pontis and internal capsule. In addition, FA values in the MCP were negatively correlated with ataxia severity in the MSA group. CONCLUSION: The areas showing decreased tissue anisotropy in DTI corresponded well with pathologically vulnerable areas in MSA. In addition, the local tissue anisotropy of MCP decreased in accordance with functional disability. These observations implied that DTI is a feasible method for in vivo evaluation of the white matter pathology in MSA.

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PubMed2005

Effect of thin-section diffusion-weighted MR imaging on stroke diagnosis.

BACKGROUND AND PURPOSE: Diffusion-weighted (DW) imaging has limited spatial resolution, especially in the z direction. We decreased the section thickness of DW imaging to 3 mm to determine if this change improves the depiction of small infarcts and if it affects stroke diagnosis. METHODS: We studied conventional (5-mm section thickness, 1-mm intersection gap) and thin-section (3-mm section thickness, no intersection gap) DW imaging data in 49 patients with symptoms of acute cerebral ischemia. Two radiologists who were not aware of the clinical findings reviewed all images and diagnosed the stroke subtype according to the Trial of Org 10172 in Acute Stroke Treatment (TOAST) method. Accuracies of stroke diagnosis with an experienced neuroradiologist and with a second-year radiology resident were compared. To quantify lesion conspicuity, contrast-to-noise ratios (CNRs) were measured. The CNR of thin-section DW imaging was then divided by the CNR of conventional DW imaging to yield the relative CNR (rCNR). RESULTS: The experienced neuroradiologist made the correct final diagnoses in 78% of cases with conventional DW imaging, improving to 100% with thin-section DW imaging. The resident made the correct diagnoses in 71% of cases with conventional DW imaging, improving to 94% with thin-section DW imaging. Lesion conspicuity was improved on thin-section DW imaging (rCNR = 1.47 +/- 0.63), especially for supratentorial lesions (rCNR = 1.51 +/- 0.63). CONCLUSION: Compared with conventional DW imaging, thin-section DW imaging permitted better lesion conspicuity and more precise stroke diagnosis.

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PubMed2005

[A case of motor disturbance in upper limb by parietal lesion; limb kinetic apraxia without visual compensation?].

We report a 75-year-old right-handed man who showed limbkinetic apraxia in the left hand caused by brain infarction of the right parietal lobe including postcentral gyrus. The hand shaping and posture preceding grasping was not appropriate, and clumsiness of the hand was not corrected by visual guidance. Fiber-tracking of the sensorimotor tract on diffusion tensor MRI and electrophysiological studies revealed that the lesion involved the area 1, 2, 5, and 7 of the cortices in Brodmann's nomenclature. In the most cases with limbkinetic apraxia caused by posterior lesion in the center region, hand clumsiness in manipulation should be corrected by visual guidance, which did not function in this case due to coexisting disturbances of kinesthesia with relatively large lesion in the parietal cortex.

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PubMed2004

White matter loss in the splenium of the corpus callosum in a case of posterior cortical atrophy: a diffusion tensor imaging study.

There have been several functional imaging studies using PET and SPECT to investigate posterior cortical atrophy (PCA). These studies have suggested dysfunction of corticocortical connections which is consistent with the occipitoparietal stream. However, there are no reports suggesting disturbance of the white matter that interconnects the temporal, parietal and occipital cortices. We measured fractional anisotropy (FA) in the genu and splenium of the corpus callosum and created color maps using diffusion tensor imaging (DTI), which is a relatively new MRI technique that allows visualization of the directionality of water diffusion, in a patient with PCA and compared these findings with those in 5 typical Alzheimer disease (AD) patients. The PCA patient was a 75-year-old man presenting with progressive complex visual disorder who satisfied the clinical diagnostic criteria for PCA. In 5 typical AD patients, the FA index in the splenium was higher than that in the genu; however, in the PCA patient, the FA index in the splenium was significantly lower than that in the genu. A DTI-based color map of the PCA patient showed reduction of anisotropy and fiber volume in the splenium. These findings suggest that the splenium of the corpus callosum secondarily degenerated due to neuronal degeneration of the temporal, parietal and occipital cortices and suggest that reduction of the FA in the splenium is one of the characteristics of PCA.

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PubMed2004

Stroke patients' evolving symptoms assessed by tractography.

PURPOSE: To test the hypothesis that an interval evolution in the location of the depicted sensorimotor tract relative to the infarct (the "tract-infarct relationship") may be related to stroke victims' symptom progression. MATERIALS AND METHODS: Patients (N = 7) who underwent multiple diffusion-tensor imaging (DTI) studies during symptomatic progression were included in this study. DTI was performed using a single-shot echo-planar imaging (EPI) technique with a motion-probing gradient in six orientations, a b-value of 800 seconds/mm2, and six image averages. The total scan time was four minutes and 24 seconds. Fiber-tracking of the sensorimotor pathways was performed, and the locations of these tracts were retrospectively assessed in relation to the evolution of the symptoms. RESULTS: Five of the seven patients showed an interval enlargement of the infarct on diffusion-weighted (DW) images. In two of these cases the lesion enlarged to involve the sensorimotor tracts, while in three cases the lesion enlarged only so far to come into close proximity to the sensorimotor tract. In the remaining two cases there was no interval enlargement of the infarct, and therefore the tract-infarct relationship could not account for the evolution of the symptoms in these cases. CONCLUSION: A tract-infarct relationship can be observed with the use of a fiber-tracking technique, and the results may improve our understanding of the symptom progression seen in stroke victims.

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PubMed2004

[A case of brainstem and cerebellar infarctions related to basilar impression].

We report a 30-year-old man presenting with medial longitudinal fasciculus (MLF) syndrome after an afternoon nap. Magnetic resonance imaging revealed a right medial pontine tegmental infarction and right cerebellar infarctions. This patient was complicated with basilar impression detected on cervical X-ray and MRI. Three-dimensional CT angiography disclosed that the odontoid process migrated into the posterior fossa, thrusting the bilateral vertebral arteries postero-laterally. The mechanical stress on the bilateral vertebral arteries may have caused infarctions in the territories of the posterior circulation of this patient with basilar impression.

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PubMed2003

Fiber-tracking method reveals sensorimotor pathway involvement in stroke patients.

BACKGROUND AND PURPOSE: We tested the feasibility of a new MRI technique that provides visualization of the sensorimotor tracts in vivo in a group of stroke victims. SUMMARY OF REPORT: Fourteen patients with small infarctions involving the white matter of the supratentorial brain were evaluated. Sensorimotor tracts on the lesional and contralesional sides were successfully depicted in all cases. The position of the sensorimotor tracts relative to the infarct was in good agreement with clinical symptoms. The overall sensitivity and specificity for sensorimotor tract involvement were 100% and 77%, respectively. CONCLUSIONS: Our proposed fiber-tracking method was shown to be a clinically feasible technique that correlates well with clinical symptoms.

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PubMed2003

Improvement of sleep hypopnea by antiparkinsonian drugs in a patient with Parkinson's disease: a polysomnographic study.

An 80-year-old man was admitted to our hospital because of bradykinesia, muscle rigidity and respiratory dysfunction during sleep. Concerning bradykinesia and muscle rigidity, we diagnosed him as the early/moderate stage of Parkinson's disease without autonomic dysfunction. Polysomnography (PSG) showed a series of obstructive hypopneas and apneas. After administration of antiparkinsonian drugs, rigidity of the neck and trunk was diminished along with a drastic decrease in hypopnea on PSG. We consider that sleep hypopnea in this patient is caused by involvement of the striated musculature surrounding the upper-airway and/or rigidity in the trunk. These conditions are treatable with antiparkinsonian drugs.

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PubMed2002

Measurement of atmospheric NO2 concentrations in Antarctica with NO2 filter badge and tube.

Nitrogen dioxide (NO2) levels in Antarctica were monitored to determine background levels and distribution profile. The NO2 levels were higher than those reported from tropical remote areas. The NO2 concentrations gradually increased proceeding from the edge of the continent to the polar region, suggesting global pollutant transportation. To avoid artificial contamination of the data, a sled was used because motor vehicles discharge high levels of NO2. NO2 tubes and filter badges were selected as monitoring devices because of their convenience of transportation in Antarctica. They are small in size, light and easy-to-handle, and usually employed in personal NO2 exposure measurements. Because of severe Antarctica climate, the devices needed to be protected from the bitter cold. For that purpose, we designed an insulation container to shield the devices. The fixed NO2 monitoring site was Patriot Hill, located on the coast of the Weddell Sea. We also measured NO2 concentration along the expedition route from the fixed site to the South Pole, along with the 80 degrees west longitude. The survey periods were during November 1992 and January 1993. NO2 concentrations in Antarctica ranged from 1.0 to 2.8 ppb, which were relatively higher than previously reported background concentrations. The NO2 concentrations increased when nearing to the South Pole, supporting the theory that atmospheric circulation converges in the polar regions. This indicated that air pollutants discharged in populated regions were widely spread to isolated areas, like the South Pole.

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