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Biomedical subjects

K Minematsu

Publications and source records attributed to K Minematsu.

At least 91 records · Page 5Linked to original sources
PubMed1992

New magnetic resonance techniques for evaluating cerebrovascular disease.

Magnetic resonance (MR) imaging of acute stroke has made important contributions to diagnosis. Several novel MR technologies, now in preclinical and clinical development, will contribute to stroke diagnosis and perhaps help to guide therapy. MR angiography is the most clinically advanced new MR technology and offers the clinician a method to image noninvasively the extra- and intracranial vasculature. Diffusion-weighted MR imaging can demonstrate ischemic lesions quantitatively within minutes of onset in experimental stroke models, and human application is proceeding. Perfusion MR studies can reveal the presence or absence of cerebral perfusion in specific arterial territories. MR spectroscopy can assess tissue metabolites in vivo and reveal changes in these metabolites associated with ischemic injury. The combination of these new MR techniques should provide a plethora of information about the extent of ischemic lesions, associated vascular and perfusion deficits, and metabolic consequences. This information will afford the clinician the opportunity to assess and subtype ischemic stroke patients more rapidly and could be used to monitor therapeutic responses.

Animals↗
PubMed1992

Sequential change of hemodynamic reserve in patients with major cerebral artery occlusion or severe stenosis.

To identify regional vasodilatory capacity and its sequential change, we evaluated prospectively a total of 78 acetazolamide tests in 51 patients with occlusion or greater than 75% stenosis of the carotid or middle cerebral arteries. The relative distribution of cerebral blood flow was determined by single photon emission computed tomography using N-isopropyl-p-[123I]-iodoamphetamine before and after intravenous injection of acetazolamide. Reduced vasodilatory capacity was demonstrated in 20 patients (38%), including 5 patients with hemodynamic transient ischemic attacks or infarction. Follow-up acetazolamide tests revealed asymptomatic progression of the arterial lesion (from stenosis to occlusion) in 1 patient and almost complete improvement of vasodilatory capacity in 5 patients, including 3 without surgical intervention. During an average follow-up period of 18.5 months, 4 patients died from cardiac causes or neoplasm; no neurovascular events occurred. Much larger numbers of patients with longer observation periods will be necessary to clarify the contribution of chronic hemodynamic failure to subsequent stroke. However, the present data indicate that the acetazolamide test is useful for assessing the course of high grade stenosis or occlusion of major cerebral arteries.

Acetazolamide↗
PubMed1992

Reversible focal ischemic injury demonstrated by diffusion-weighted magnetic resonance imaging in rats.

BACKGROUND AND PURPOSE: Diffusion-weighted magnetic resonance imaging (DWI) can quantitatively display focal brain abnormalities within minutes after the onset of ischemia. We performed the present study to determine the effects of 1 and 2 hours of temporary ischemia on DWI. METHODS: We examined DWI and T2-weighted magnetic resonance images (T2WI) during and after 1 and 2 hours of temporary middle cerebral artery occlusion in rats (n = 10 for each group). In a subgroup of four animals from each group, we employed perfusion magnetic resonance imaging to monitor cerebral perfusion. Neurological outcome and infarct size after survival for 24 hours were compared between the groups and correlated with DWI and T2WI studies. RESULTS: Perfusion studies qualitatively documented hypoperfusion and reperfusion during and after temporary occlusion. Lesion size on DWI during reperfusion was significantly less than that during ischemia for 1 (55% decline, p less than 0.02) but not 2 hours of occlusion. The DWI signal intensity ratio (intensity compared with that in the contralateral homologous area) just before withdrawal of the occluder was significantly less in regions where the hyperintensity disappeared after withdrawal than in regions with persistent hyperintensity (p less than 0.002). The T2WI studies revealed few or no abnormalities, except after 2 hours of occlusion. The neurological outcome was significantly better in the 1-hour than in the 2-hour group (p less than 0.05). Postmortem infarct volume was significantly smaller in the 1-hour group than in the 2-hour group (p less than 0.05). The postwithdrawal DWI accurately predicted infarct size (R = 0.96, p less than 0.0001). CONCLUSIONS: The present study indicates that DWI can rapidly display not only irreversible but also reversible ischemic brain damage and enhances the importance of DWI as a diagnostic modality for stroke.

Animals↗
PubMed1992

'Spectacular shrinking deficit': rapid recovery from a major hemispheric syndrome by migration of an embolus.

We studied the clinical features of a major hemispheric stroke syndrome with rapid recovery ("spectacular shrinking deficit" [SSD]) compared with stroke patients with the same major initial manifestations but without rapid recovery (non-SSD). There were 118 patients with an initial major hemispheric syndrome; 14 patients (12%) had SSD. All but one SSD patient met criteria for cardiogenic brain embolism. Angiographic examination within 24 hours after stroke onset demonstrated that the occlusion sites in SSD differed from those in non-SSD and suggested that rapid embolus migration had occurred in all SSD patients but in only five of 39 non-SSD. Infarcts in SSD were smaller and often scattered over the cortices and deeper structures. Hemorrhagic transformation was less frequent in SSD. In patients with a potential cardiac source of emboli, SSD was more likely to occur in nondiabetic men less than 60 years of age.

Aged↗
PubMed1992

Diffusion-weighted magnetic resonance imaging: rapid and quantitative detection of focal brain ischemia.

We examined serial changes of diffusion- (DWI) and T2-weighted (T2WI) magnetic resonance images 30 minutes to 3 hours after intraluminal suture occlusion of the middle cerebral artery (MCA) in eight rats and after sham occlusion in four. We correlated the abnormal areas on DWI and T2WI with postmortem areas of infarction determined by 2,3,5-triphenyltetrazolium chloride (TTC), 24 hours after the operation. The 30-minute DWI in each MCA-occluded rat demonstrated increased signal intensity in the ipsilateral MCA territory, while T2WI showed no changes. At 3 hours, the ipsilateral DWI signal intensity increased further and the area of abnormality slightly increased. In some animals, the 3-hour T2WI disclosed an area of hyperintensity significantly smaller than that seen on the 30-minute DWI. TTC staining demonstrated an extensive MCA infarction in all rats with permanent MCA occlusion, confirmed by hematoxylin and eosin staining. The percent infarcted area of coronal brain sections, as determined by TTC staining, correlated significantly with areas on similar DWI sections at both 30 minutes and 3 hours. Sham-occluded control animals did not display any changes on DWI, T2WI, or TTC staining. The present study suggests that DWI is a very sensitive modality for detecting early ischemic brain injury, being highly correlated with post-mortem area of infarction, and may be useful to assess pharmacologic intervention.

Animals↗
PubMed1991

[Long-term changes in cerebral blood flow in patients with atherothrombotic and embolic brain infarction].

Cerebral blood flow (CBF) was measured twice at years interval using xenon-133 inhalation technique in patients with atherothrombotic and embolic supratentorial brain infarction. The purpose of the study was to elucidate factors influencing long-term change in CBF in two subtypes of brain infarction of different mechanisms. Those patients were excluded from the study, who had bilateral hemispheric lesions, significant arterial lesion in the contralateral carotid axis and recurrent stroke before the second measurement of CBF. Of 46 patients studied, 23 (17 men and 6 women) were classified as atherothrombotic and 23 (15 men and 8 women) as embolic infarction based on the diagnostic criteria reported earlier. Their age at onset was 60.6 +/- 8.9 years old (mean +/- S.D.) for atherothrombotic patients, and 60.2 +/- 11.0 years old for embolic patients. The first measurement of CBF was performed between 31 and 87 days and the second measurement between 13 and 99 months after onset. In atherothrombotic group, mean hemispheric CBF (mCBF) of the affected side tended to be higher in patients examined at intervals shorter than 30 months, but tended to decrease in those at longer interval. The multivariate stepwise regression analysis indicated only "the interval between 2 measurements" to have a significant effect on reduction of mCBF, although in addition to the interval (p less than 0.05), infarct-size (p less than 0.01) and change in PaCO2 (p less than 0.05) were suggested to be possible factors by single regression analysis. In embolic group, an increase in hematocrit had a significant effect on reduction of mCBF, even when being evaluated with multivariate stepwise regression analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Hemorrhagic transformation in cerebral embolism.

We studied the mechanism of hemorrhagic infarction after acute cerebral embolism in 160 patients by brain computed tomography and angiography. Hemorrhagic infarction during the month after the embolic event was evident in 65 patients (40.6%). Initial angiography a median of 1.5 (range 1-60) days after the event revealed occlusion of the cerebral arteries in 117 of 142 patients (82.4%), and reopening of the vessels was observed in 56 (94.9%) of 59 patients who had follow-up angiography a median of 20 (range 3-47) days after the event. The incidence of hemorrhagic infarction was higher in patients greater than or equal to 70 years old (31 of 61, 50.8%) than in those aged 50-69 years (27 of 72, 37.5%) or less than 50 years (seven of 27, 25.9%) (greater than or equal to 70 vs. less than 50, p less than 0.05). In patients with moderate or large infarcts, hemorrhagic infarction developed in 50.0% or 51.5%, respectively, while in those with small infarcts it developed in only 2.9% (p less than 0.05). No correlation was found between hemorrhagic infarction and history of hypertension or blood pressure during the acute stage of stroke. Thrombolytic and/or anticoagulant therapy did not affect the incidence of hemorrhagic infarction (40.0% with vs. 40.7% without therapy) but tended to cause massive hematoma. Our results indicate that hemorrhagic transformation in cerebral embolism is caused not only by reopening of the occluded vessels but also by other factors such as age and size of the infarct. Hypertension per se seems to be less important for hemorrhagic infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Hemorrhagic infarct of the brain without a reopening of the occluded arteries in cardioembolic stroke.

We examined the brains of 14 patients (four men and 10 women, mean age 68.9 years) who died from brain herniation after cardioembolic stroke with persistent occlusion of the internal carotid-middle cerebral arterial axis. Our examination showed hemorrhagic infarct in seven patients and pale infarct in the other seven, contradicting the commonly proposed pathophysiologic mechanism for the development of hemorrhagic infarct that the opening of previously occluded vessels makes an infarct hemorrhagic. Analysis of blood pressure after stroke revealed one or more surges of arterial hypertension or rapid rise of blood pressure in patients with hemorrhagic infarct without a reopening of the occluded artery. Such arterial hypertension was not always present in patients with pale infarct. Hemorrhage into an infarct with persisting occlusion of the proximal artery is assumed to occur when the involved blood vessels are exposed to the force of arterial blood pressure from the leptomeningeal collaterals. This occurs when arterial blood pressure rises after stroke in the presence of efficient leptomeningeal collaterals and before occlusion of these collaterals by a swollen cerebral hemisphere containing a large infarct.

Adult↗
PubMed1989

[Differences in CT findings between embolic and thrombotic cerebral artery occlusion of the internal carotid arterial system].

Two hundred and one patients with embolic (EM) and 107 with thrombotic (TH) cerebral arterial occlusion of the internal carotid arterial system were subjected to the study. Diagnoses of EM and TH were made with our own diagnostic criteria, based on clinical and angiographic informations but not on CT findings, as previously described. Well-marginated hypodense areas in multiple vascular territories were observed only in patients with EM (13.9%). The following CT findings were more frequently seen in EM than in TH; a) a hypodense area involving the cortex, b) a sharply-marginated lesion, c) a shift of the mid-line structures and d) hemorrhagic infarction. Patients with TH were more frequently accompanied with watershed infarction, or infarct in the basal ganglia and/or deep white matter than those with EM. Watershed zone between cortical and perforating arteries was involved only by TH. Deep-seated infarct, however, was more likely to be embolic rather than thrombotic in nature, if it was sharply-marginated and accompanied with surrounding brain edema. Differences in CT findings of EM and TH appeared to reflect those of pathogenetic mechanisms such as rapidity of occlusive process, sites of occlusion, routes and availabilities of collateral circulation, presence of reopening of the previously occluded artery, etc. In the present study, it can be concluded that there is distinctive differences in CT findings between EM and TH, indicating the usefulness in differentiation of two diagnostic subtypes in the acute stage of cerebral infarction.

Arterial Occlusive Diseases↗
PubMed1989

[Aphasia and size of hematoma in patients with left putaminal hemorrhage].

Presence or absence of aphasic syndrome and its duration were related to the volume of hematoma calculated from CT in 27 consecutive non-surgical cases with left putaminal hemorrhage. In the present study, patients classified into three groups regardless of the types of aphasia; i.e. non-aphasics, transient aphasics and persistent aphasics. Transient aphasics were arbitrarily defined as cases who had presented with more or less evident aphasic syndrome in the acute stage, but almost completely recovered in the chronic stage. Volume of hematoma in non-aphasic patients ranged from 2 to 17 ml, with a mean of 7.7 ml and those in transient cases were from 11 to 23ml with a mean of 17ml. All but one case with persistent aphasia showed the hematoma volume larger than 25ml. This exceptional case was a 83 year-old female who showed marked cortical atrophy on CT. Consequently, the presence of aphasia and its persistence seem to be largely dependent on the size of hematoma in patients with left putaminal hemorrhage. Persistent aphasia may be caused by organic damage of subcortical white matter, when the volume of hematoma exceeds around 25ml.

Adult↗
PubMed1987

Effect of angiotensin converting enzyme inhibitor (captopril) on cerebral blood flow in hypertensive patients without a history of stroke.

The effect of the angiotensin converting enzyme inhibitor, captopril, on cerebral blood flow (CBF) was studied in 11 hypertensives without a history of stroke. Mean hemispheric CBF (mCBF) was measured in each patient by Xe-133 inhalation method before and after 7 days of captopril administration. Blood pressure (BP) both in the control state and at the time of CBF measurement decreased significantly after drug administration. mCBF, however, did not show any significant change. When percent changes in mCBF before and after the administration were plotted against those of mean arterial BP, significant inverse correlations were obtained in both hemispheres; the larger the BP decrease, the more increase in CBF was observed. It is concluded that captopril lowers systemic BP without concomitant decrease in CBF in hypertensive subjects with no history of stroke. Furthermore, the results suggest that captopril may have a vasodilating action on cerebral blood vessels.

Adult↗
PubMed1984

Clinical and neuroradiological analysis of thrombotic and embolic cerebral infarction.

The clinical and neuroradiological characteristics of cerebral thrombosis and cerebral embolism were established in 109 cases with nonembolic and 120 cases with embolic arterial occlusion of the brain. Cases with cerebral thrombosis due to occlusion of perforating branches were excluded from the study, to equalize the size of the involved arteries in the two groups. More than 60% of patients with cerebral embolism showed a level of consciousness lower than stupor, while less than 15% did so in the thrombotic group. Cortical signs such as aphasia, agnosia, conjugate deviation, etc., were more frequently seen in the embolic group. A mean size of the infarct on CT (Infarct-Index) was significantly larger, and a shift of the midline structure was more frequently noticed in the embolic group than in the thrombotic group. Accordingly, the patients with cerebral embolism showed more unfavorable outcome than those with thrombosis. Hyperdense area developed in 40% of cerebral embolism during the period of observation, while in only 2% of cerebral thrombosis. Recurrence of the attack was very common in cerebral embolism. Forty-four percent experienced more than two episodes of cerebral and/or systemic embolization; of these recurrences 51% (27% of all cases) occurred within 2 weeks before and/or after the present episode that caused the admission. The importance of atrial fibrillation as the source of emboli was reemphasized.

Adolescent↗
PubMedDate not supplied

Cerebral artery thrombosis as a cause of striatocapsular infarction. a histopathological case study.

Striatocapsular infarction is a distinct form of stroke, but few histopathological studies have been performed concerning acute lesions. We report the postmortem findings of a patient with an infarct who died shortly after onset. A 72-year-old man died of acute myocardial infarction 6 days after the onset of left-sided striatocapsular infarction. Autopsy revealed thrombus formation of the left middle cerebral artery (MCA) trunk. The lateral striate arteries irrigating the area of the infarct branched off distal to the arterial segment occluded with a thrombus. The cortical vessels were perfused by leptomeningeal collaterals. This report histopathologically confirmed thrombus formation of the MCA resulting in striatocapsular infarction.

Aged↗
PubMedDate not supplied

Transcranial Doppler of a paradoxical brain embolism associated with a pulmonary arteriovenous fistula.

We herein report the case of a patient who had paradoxical brain embolism owing to a pulmonary arteriovenous fistula (PAVF) who was diagnosed as having a right-to-left shunt by transcranial Doppler (TCD) with saline contrast medium. TCD with saline contrast medium failed to detect any high-intensity transient signals immediately after catheter embolization of the PAVF. Thus, TCD with saline contrast medium was useful for identifying the presence of a right-to-left shunt and for confirming that the shunt had been obliterated after endovascular treatment.

Arteriovenous Fistula↗