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Kensuke Shiga

Publications and source records attributed to Kensuke Shiga.

15 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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PubMed2006

Oculomotor nerve palsy evaluated by diffusion-tensor tractography.

INTRODUCTION: The aim of the study was to test the feasibility of the tractography technique based on diffusion-tensor imaging (DTI) for the assessment of small infarcts involving the brainstem. METHODS: A patient who presented with an isolated left third cranial nerve palsy underwent magnetic resonance examination. Images were obtained by use of a whole-body, 1.5-T imager. Data were transferred to an off-line workstation for fiber tracking. RESULTS: The conventional diffusion-weighted imaging (DWI) performed using a 5 mm slice thickness could only depict an equivocal hyperintensity lesion located at the left paramedian midbrain. An additional thin-slice DTI was performed immediately after the initial DWI using a 3 mm slice thickness and was able to delineate the lesion more clearly. Image postprocessing of thin-slice DTI data revealed that the lesion location involved the course of the third cranial nerve tract, corresponding with the patient's clinical symptoms. CONCLUSION: The tractography technique can be applied to assess fine neuronal structures of the brainstem, enabling direct clinicoradiological correlation of small infarcts involving this region.

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PubMed2005

Autosomal dominant leukodystrophy with axonal spheroids and pigmented glia: clinical and neuropathological characteristics.

We report two autopsy cases of siblings with adult-onset autosomal dominant leukodystrophy characterized by destruction of cerebral white matter, large numbers of axonal spheroids and pigmented glia in the fronto-temporal lobes. Both patients presented with motor and cognitive symptoms and aphasia, 2-3 years before death. At autopsy, the brain showed brown coloration and decreased volume of white matter in the frontal and temporal lobes as well as corpus callosum. Microscopically, marked loss of myelin and axons and abundant axonal spheroids without apparent neuronal loss were observed in the frontal and temporal lobes, which was consistent with hereditary diffuse leukodystrophy with spheroids (HDLS). In addition, glial cells, most consistent with macrophages and containing pigments that were stained by Sudan III and PAS, were found in the white matter lesions. The present cases showed overlapping features with HDLS and pigmentary type of orthochromatic leukodystrophy, suggesting that the pathomechanisms of these two diseases are closely related.

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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

Discrepancy between clinical and pathological diagnoses of CBD and PSP.

Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) are often clinically confused with each other. Moreover, the discrepancy between clinical and pathological diagnoses of CBD and PSP are still controversial. We report here two atypical cases of PSP and CBD. A 73-year old woman was admitted with right hand rigidity, limb kinetic apraxia and cortical sensory loss. Brain atrophy, hypoperfusion and hypometabolism predominantly in the left frontoparietal lobes indicated CBD clinically. Pathological studies revealed neuronal loss and spongy change without ballooned neurons (BN) in the cerebral cortex. Modified Gallyas-Braak (G-B) staining revealed neurofibrillary tangles (NFTs) and tufted astrocytes, indicating pathological diagnosis of PSP. A 75-year-old man admitted with vertical gaze palsy, neck dystonia, parkinsonism and dementia. Atrophy of the frontal lobes and tegmentum of the midbrain and symmetrical frontal hypoperfusion in SPECT indicated PSP. However, neuronal loss and BN in the frontal lobes and clusters of astrocytic plaques indicated CBD pathologically. The G-B staining was useful for differentiating between CBD and PSP, but our atypical cases bring up a new issue about differential diagnosis of CBD and PSP.

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PubMed2005

[Prognosis of patients with myasthenia gravis].

AIM: To study the correlation between therapy and outcome of patients with late adult onset and ocular type myasthenia gravis (MG). METHODS: The 58 MG patients admitted to our hospitals from 1991 to 2003 were classified into juvenile (younger than 20), early adult onset (20-64) and late adult onset (65 or older) groups, or also ocular and generalized types. We evaluated their therapeutic outcomes. RESULTS: The late adult onset group consisted of 11 patients, classified as 4 ocular and 7 generalized types. There were more women than men in both the late and early adult onset groups. Anti-acetylcholine receptor (anti-AchR) antibodies were positive in all patients. Four patients had thymus lesions. Ten patients received treatment as follows: steroid therapy in 6, thymectomy in 4 and only choline-esterase (ChE) inhibitor therapy in 4 patients. However 4 patients worsened after treatment because of inadequate steroid therapy, 2 of whom experienced myasthenic crisis. On the other hand 21 patients were ocular type, of whom anti-AchR antibodies were positive in 12. They received treatments of the 21, steroid therapy was given to 12, thymectomy was performed in 4 and only ChE inhibitor therapy was given to 8 patients. One ocular type patient progressed to the generalized type. Six of 16 improved patients showed distinct recovery. CONCLUSION: In the late adult onset group careful assessment concerning timings of administration and reduction of steroid are required to avoid side effects and complications. One ocular type patient progressed to the generalized type and most patients had a good outcome, which might be related to steroid therapy.

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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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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

[Riche-Cannieu anastomosis and a paradoxical preservation of thenar muscles in carpal tunnel syndrome: a case report].

A 72-year old woman had been suffered from a dysesthesia in the left median nerve distribution, followed by a dysesthesia in the right ulnar distribution. Neurological examination revealed weakness in the right intrinsic hand muscles with the ipsilateral thenar and hyothenar atrophy. Paradoxical preservation of the left thenar muscles was a clinical challenge. Nerve conduction studies disclosed bilateral carpal tunnel syndrome and the right cubital tunnel syndrome. In needle electromyography, however, the left abductor pollicis brevis and opponens pollicis muscles had normal motor unit potentials without denervation activity. The needle recording of the left abductor pollicis brevis muscle showed a good motor response with a negative deflection by the left ulnar nerve stimulation, indicating an ulnar to median nerve innervation, i.e., Riche-Cannieu anastomosis. A Riche-Cannieu anastomosis in a setting of a median or ulnar nerve injury can produce confusing clinical and electrodiagnostic findings. We reviewed clinical findings, electrophysiological data, and the impact of a Riche-Cannieu anastomosis in median nerve injury.

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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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