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Biomedical subjects

Kazumi Kimura

Publications and source records attributed to Kazumi Kimura.

At least 19 recordsLinked to original sources
PubMed2006

Microembolic signals within 24 hours of stroke onset and diffusion-weighted MRI abnormalities.

BACKGROUND: The clinical relevance of the microembolic signals (MES) detected by transcranial Doppler sonography (TCD) in acute stroke remains unclear. In a prospective study the authors analyzed the relationship between MES and the findings on diffusion-weighted magnetic resonance imaging (DWI) in acute stroke patients. METHODS: We performed TCD for a period of 30 min to detect MES in patients within 24 h of stroke onset, and DWI was done within the initial 7 days. MES were assessed from Doppler waves obtained from the middle cerebral artery contralateral to the side of the neurological deficits. The acute ischemic lesions observed on DWI were classified by their diameter (small, medium or large) and by their site (cortical, superficial perforator territory, internal borderzone or deep perforator territory). RESULTS: We obtained Doppler waves from 39 vessels in 37 patients; 2 patients had bilateral deficits. MES were detected in 12 vessels (MES-positive group) and not detected in 27 vessels (MES-negative group). No significant differences in clinical features were observed between the 2 groups. The number of small lesions was significantly higher in the MES-positive group than in the MES-negative group (p = 0.02). The numbers of cortical and superficial perforator infarcts were significantly higher in the MES-positive group than in the MES-negative group (p = 0.002 and 0.02, respectively). CONCLUSION: In acute ischemic stroke, MES detected by TCD in the acute phase may produce small cortical and subcortical lesions found on DWI.

Acute Disease↗
PubMed2006

Spontaneous recanalization at subacute phase of stroke may be dramatic: A case report.

Spontaneous recanalization of the occluded cerebral arteries has occasionally occurred in an acute phase of stroke patients. We report a stroke patient with recanalization at 7 days of onset detected by using continuous transcranial Doppler (TCD) monitoring. After the presence of microembolic signals on TCD display, dynamic flow changes of the middle cerebral artery (MCA) occurred, which represented recanalization of the occluded MCA.

Adult↗
PubMed2006

Characteristics of in-hospital onset ischemic stroke.

BACKGROUND AND PURPOSE: The aim of the present study was to clarify the clinical characteristics of in-hospital onset stroke. MATERIAL AND METHODS: We analyzed 15,815 patients with acute brain infarction registered in the Japan Multicenter Stroke Investigators' Collaboration (J-MUSIC) registry. RESULTS: The in-hospital onset group included 694 (4.4%) patients and the out-of-hospital group included 15,121 (95.6%) patients. Atrial fibrillation (AF) was more common in the in-hospital onset group (34.6%) than in the out-of-hospital group (20.4%, p < 0.001). The admission NIHSS score (median, in-hospital 13 vs. out-of-hospital 5, p < 0.0001) and the mortality rate at discharge were higher in the in-hospital group than in the out-of-hospital group (in-hospital 19.2% vs. out-of-hospital 6.8%, p < 0.0001). On multivariate logistic regression analyses, female gender (OR 1.1, 95% CI 1.1-1.3), older age (OR 1.0, 95% CI 1.02-1.03), AF (OR 4.4, 95% CI 4.0-4.8), history of stroke (OR 1.3, 95% CI 1.2-1.4) and in-hospital stroke onset (OR 3.3, 95 %CI 2.7-3.9) were independent factors associated with severe stroke (NIHSS score > or =11), and older age (OR 1.03, 95% CI 1.02-1.04), the presence of AF (OR 1.21, 95% CI 1.0-1.5), in-hospital stroke onset (OR 1.01, 95% CI 1.01-1.02) and NIHSS score at initial evaluation (OR 1.15, 95% CI 1.14-1.17) were independent factors associated with death at discharge. CONCLUSION: In-hospital stroke onset was not uncommon. The neurological deficits in patients with in-hospital onset stroke were severer and the outcome was worse than in those with out-of-hospital stroke. Therefore, a strategy to reduce in-hospital stroke onset should be implemented.

Aged↗
PubMed2006

First impression at stroke onset plays an important role in early hospital arrival.

BACKGROUND: Treatment for acute ischemic stroke should be administered as soon as possible after symptom onset. The aim of this study was to investigate whether or not the patient's and bystander's first impression at stroke onset was associated with hospital arrival time. METHODS: To investigate the factors influencing the prehospital delay, we prospectively interviewed consecutive stroke patients and bystanders about their first impression at the stroke onset and assessed the methods of transportation, and clinical characteristics. Early arrival was defined as a hospital arrival of within 2 h from stroke onset. RESULTS: One hundred thirty patients were enrolled: 82% were ischemic stroke and 18% were cerebral hemorrhage. The median interval between symptom onset and the hospital arrival was 7.5 h and 30% of patients presented within 2 h of stroke onset. First impression of stroke (odds ratios [OR] 4.56, 95% confidence interval [CI] 1.54-13.5, p=0.006), presence of consciousness disturbance (OR 4.29, CI 1.39-13.3, p=0.011), arrival through other facilities (OR 0.25, CI 0.08-0.76, p=0.015), a history of diabetes (OR 0.23, CI 0.06-0.80, p=0.028) and nocturnal onset (OR 0.19, CI 0.04-0.88, p=0.042) independently contributed to the early arrival. CONCLUSIONS: The first impression of patients and bystanders at stroke onset is important in order to reach hospital earlier in Japan. Public educational systems such as those, which advertise stroke warning signs, are necessary.

Aged↗
PubMed2006

Transcranial doppler and carotid duplex ultrasonography findings in Bow hunter's syndrome.

Bow hunter's syndrome (BHS) is caused by transient vertebro-basilar ischemia on head rotation. We report a patient with BHS who was identified from dynamic changes to blood flow velocities in the posterior cerebral, basilar and vertebral arteries using carotid duplex ultrasonography and transcranial Doppler, simultaneously. Neurosonology appears to be useful for diagnosing and evaluating BHS.

Blood Flow Velocity↗
PubMed2005

Crystal structure of a ribonuclease P protein Ph1601p from Pyrococcus horikoshii OT3: an archaeal homologue of human nuclear ribonuclease P protein Rpp21.

Ribonuclease P (RNase P) is a ribonucleoprotein complex involved in the removal of 5' leader sequences from tRNA precursors (pre-tRNA). The human protein Rpp21 is essential for human RNase P activity in tRNA processing in vitro. The crystal structure of Ph1601p from the hyperthermophilic archaeon Pyrococcus horikoshii OT3, the archaeal homologue of Rpp21, was determined using the multiple anomalous dispersion (MAD) method with the aid of anomalous scattering in zinc and selenium at 1.6 A resolution. Ph1601p comprises an N-terminal domain (residues 1-55), a central linker domain (residues 56-79), and a C-terminal domain (residues 80-120), forming an L-shaped structure. The N-terminal domain consists of two long alpha-helices, while the central and C-terminal domains fold in a zinc ribbon domain. The electrostatic potential representation indicates the presence of positively charged clusters along the L arms, suggesting a possible role in RNA binding. A single zinc ion binds the well-ordered binding site that consists of four Cys residues (Cys68, Cys71, Cys97, and Cys100) and appears to stabilize the relative positions of the N- and C-domains. Mutations of Cys68 and Cys71 or Cys97 and Cys100 to Ser destabilize the protein structure, which results in inactivation of the RNase P activity. In addition, site-directed mutagenesis suggests that Lys69 at the central loop and Arg86 and Arg105 at the zinc ribbon domain are strongly involved in the functional activity, while Arg22, Tyr44, Arg65, and Arg84 play a modest role in the activity.

Amino Acid Sequence↗
PubMed2005

Hyperacute diffusion-weighted imaging abnormalities in transient ischemic attack patients signify irreversible ischemic infarction.

BACKGROUND: To characterize the frequency and clinical features of diffusion-weighted imaging (DWI) abnormalities in the hyperacute phase of transient ischemic attacks (TIAs). METHODS: We performed DWI in 21 consecutive patients with TIA (mean age 64 years; 17 men and 4 women) during both the hyperacute phase (within 6 h after onset) and subacute phase (within 2-9 days after onset). RESULTS: DWI abnormalities were present in the hyperacute phase in 11 patients (positive group) and absent in the other 10 patients (negative group). These groups could not be differentiated based on the clinical characteristics. In the subacute phase, all 11 patients from the positive group had abnormalities on MRI including T2-weighted and fluid attenuation inversion recovery images as well as DWI, with lesions being located in regions similar to those observed in the hyperacute phase. Of the 10 patients in the negative group, new DWI abnormalities were noted in 2 during the subacute phase. CONCLUSIONS: Approximately half of TIA patients in whom MRI was performed in the hyperacute phase had DWI abnormalities, all of which persisted in the subacute phase. The findings suggest that essentially all hyperacute DWI abnormalities in TIA patients may indicate irreversibility and signify the presence of brain infarction.

Adult↗
PubMed2005

Diagnosis of middle cerebral artery occlusive lesions with contrast-enhanced transcranial color-coded real-time sonography in acute stroke.

It is useful to evaluate the occlusive lesions of middle cerebral artery (MCA) occlusion with transcranial color-coded real-time sonography (TCCS). However, TCCS criteria for locating the site of the MCA occlusion has, as yet, remained unclear. The aim of the present study was to establish TCCS criteria for MCA occlusive lesions. We prospectively performed contrast-enhanced TCCS (CE-TCCS) in 75 consecutive acute stroke patients within 24 h of digital subtraction angiography. Patients were divided into four groups: occlusion of the MCA stem (MO group, n=12); occlusion of the MCA branch (MBO group, n=10); stenosis of the MCA stem (MS group, n=9); and no occlusive or stenotic lesions (control group, n=44). The following parameters were measured: peak systolic velocity (PSV) and end diastolic velocity (EDV) of bilateral MCA stems, and ED-ratio (the side-to-side ratio of the EDV). We establish the CE-TCCS criteria for MCA occlusive lesions using the sensitivity-specificity curve analysis. A PSV of 170 cm/s distinguished MCA stenosis from other groups (positive and negative predictive values and the accuracies were 100%, 99.0% and 99.1%, respectively). An EDV of 26 cm/s differentiated MO or MBO from the other groups (positive and negative predictive values and the accuracies were 84.6%, 100% and 96.5%, respectively). An ED-ratio of 2.5 discriminated MO from the MBO group (positive and negative predictive values and the accuracies were 88.9%, 85.7% and 87.5%, respectively). Measurement of MCA stem flow velocity with CE-TCCS can identify MCA stem stenosis and occlusion, as well as MCA branch occlusion.

Aged↗
PubMed2005

A case-control analysis of intra-arterial urokinase thrombolysis in acute cardioembolic stroke.

BACKGROUND: Intra-arterial urokinase (IA-UK) thrombolysis is frequently given in Japan to selected patients with acute cerebral artery occlusion. However, it is not clear whether or not IA-UK thrombolysis has an efficacy for acute stroke patients. The purpose of this study was to assess the effects of IA-UK thrombolysis in acute cardioembolic stroke patients, by performing a case-control analysis using data from Japan's Multicenter Stroke Investigator's Collaboration (J-MUSIC). METHODS: 16,922 acute ischemic stroke patients were enrolled into J-MUSIC. From these patients, we selected 91 patients (UK group) who met the following criteria: treatment with IA-UK; 20-75 years of age; cardioembolic stroke; presenting with a carotid stroke; admission within 4.5 h of symptom onset, and a National Institutes of Health Stroke Scale (NIHSS) score of 5-22 points on admission. A control group of 182 patients without IA-UK treatment and matched to the NIHSS score, gender, and age was chosen. We compared the modified Rankin scale (mRS) score at discharge and the mortality between the 2 groups. RESULTS: In both groups, the mean age was 65 +/- 8 years, and the median NIHSS score was 14. The mean interval between symptom onset and UK administration was 3.4 +/- 1.3 h, and the IA-UK dose was 392,000 +/- 200,000 units. The mRS score at discharge was lower in the UK group than in the control group (mean, SD, median; 2.8, 2.9, 2 in UK group vs. 3.3, 1.8, 4, in the control, respectively p = 0.031). A favorable outcome (mRS of 0-2) was more frequently observed in the UK group (50.5%) than in the control group (34.1%, p = 0.0124). No difference in the mortality rate was seen between the UK group (11.0%) and the control group (13.3%). As well, there was no difference in the length of hospital stay between the UK group (46 +/- 41 days, mean +/- SD) and the control group (42 +/- 42 days, mean +/- SD). CONCLUSIONS: IA-UK thrombolytic therapy may improve the outcome in hyperacute cardioembolic stroke patients.

Acute Disease↗
PubMed2005

Mortality and cause of death after hospital discharge in 10,981 patients with ischemic stroke and transient ischemic attack.

BACKGROUND: The aim of this study was to examine the 1-year cumulative mortality rate and cause of death, and to identify the predictive factors for death after hospital discharge following ischemic stroke and transient ischemic attack (TIA) using data from the Japan Multicenter Stroke Investigators' Collaboration study. METHODS: We prospectively registered 16,922 consecutive patients with acute ischemic stroke or TIA from May 1999 to April 2000 in 156 Japanese hospitals. We mailed a questionnaire to the 15,322 patients who were alive at hospital discharge. RESULTS: 10,981 patients (6,945 men, 4,036 women, age 70 +/- 11 years, median 71, range 19-100 years) were enrolled in the follow-up study. The mean follow-up period was 271 +/- 110 days (median 272 days; range 1-487 days). The 1-year cumulative mortality was 6.8% (7.0% for 10,234 stroke patients and 3.5% for 747 TIA patients). The causes of death were: cerebrovascular disease, 24.1%; pneumonia, 22.6%; heart disease, 18.1%; cancer, 11.0%, and miscellaneous causes, 24.1%. Multivariate analysis suggested that male gender, age, diabetes mellitus, atrial fibrillation, history of stroke, nonlacunar stroke, functional disability and transfer to another hospital or nursing home on discharge were significant independent predictors of death during the follow-up period. CONCLUSIONS: The major causes of death after hospital discharge were found to be cerebrovascular diseases, pneumonia and heart diseases. Thus, in order to improve survival after hospital discharge, in addition to appropriate management of vascular risk factors following stroke, it appears to be important to take measures to prevent pneumonia and to discharge patients to their own home, if possible.

Age Distribution↗
PubMed2005

Transoral carotid ultrasonography for evaluating internal carotid artery occlusion.

BACKGROUND AND PURPOSE: Transoral carotid ultrasonography (TOCU) has enabled the assessment of the distal portion of the extracranial internal carotid artery (ICA). We evaluated the ultrasonographic features of ICA occlusion using TOCU. METHODS: We studied 50 occluded ICAs in 42 stroke patients. The mechanism of ICA occlusion was embolic (group E) in 14 arteries and thrombotic (group T) in the other 36 arteries. We used a color flow imaging system equipped with special convex array transducers, and placed the probe on the postero-lateral pharyngeal wall to identify the distal extracranial ICA. We evaluated intraluminal echodensity (lucent or opaque) and measured the diameter of the ICA. Then, we examined the relationship of these early (<1 week after onset) and chronic (>4 weeks after onset) phase TOCU findings to the mechanism of ICA occlusion and the site of occlusion. RESULTS: In the early phase of a stroke, the intraluminal echodensity was more frequently lucent (9/11, 81.8%) in group E than in group T (5/20, 20%, p<0.05). In the chronic phase, echodensity became opaque in both groups. In the early phase, the lucent echodensity was more frequently seen in patients with distal occlusion than in those with proximal occlusion. Thus, it may represent blood or fresh thrombus formation. In patients with unilateral ICA occlusion, the occluded ICA was significantly smaller in diameter than the non-occluded contralateral artery both in the early and chronic phases. CONCLUSION: The echodensity and diameter of the extracranial ICA distal portion as found on TOCU can help to identify the mechanism of ICA occlusion.

Aged↗
PubMed2004

Variation in ischemic stroke frequency in Japan by season and by other variables.

BACKGROUND AND PURPOSE: It is unclear whether acute ischemic stroke exhibits a seasonal pattern in Japan. The aim of the present study was to elucidate seasonal differences in acute ischemic stroke. METHODS: Our study enrolled 12,660 patients with ischemic stroke (7943 men, 4717 women; mean age, 70.1 years, S.D. 11.5; median 70; range 18-107). We divided the year into four parts: spring (March-May); summer (June-August); fall (September-November); and winter (December-February). Time of stroke onset was divided into three subgroups: daytime (08:00-16:00), evening (16:00-24:00), and night (24:00-08:00). We examined the association between clinical characteristics, season, and time of stroke onset. RESULTS: Stroke occurred least frequently in spring (22.9%), followed by winter (25.3%), fall (25.8%), and summer (26.0%) (P<0.001). No differences in age, National Institutes of Health Stroke Scale (NIHSS) score, modified Rankin Scale (m-RS) score, history of stroke/transient ischemic attack (TIA), or risk factors for stroke were observed among the four seasons. Stroke in men (63.8% vs. 62.4%; P<0.01), lacunar stroke (LS) (41.2% vs. 39.4%, P<0.01), atherothrombotic stroke (ATS) (34.0% vs. 32.3%; P<0.01), and nighttime stroke (26.5% vs. 24.8%; P<0.05) were observed more frequently in summer compared to other seasons. This contrasts with the findings for stroke in women (39.0% vs. 36.7%; P<0.05), cardioembolic stroke (CES) (23.4% vs. 20.6%; P<0.05), and daytime stroke (47.4% vs. 45.0%; P<0.05), which were more frequent in winter. CONCLUSIONS: Acute ischemic stroke displays seasonal characteristics according to gender, stroke subtype, and time of stroke onset. These results may have important clinical implications in ischemic stroke prevention.

Adolescent↗
PubMed2004

Analysis of 16,922 patients with acute ischemic stroke and transient ischemic attack in Japan. A hospital-based prospective registration study.

OBJECTIVE: The purpose of the present study was to clarify the present status of stroke medicine in Japan using a hospital-based, prospective registration study of 156 hospitals from all over Japan. METHODS: Consecutive patients with acute ischemic stroke and transient ischemic attack (TIA) who presented to hospital within 7 days of onset from May 1999 to April 2000 were enrolled in this study. A common protocol was applied in every participating hospital. RESULTS: A total of 16,922 patients (TIA, 6.4%) with a mean age of 70.6 +/- 11.5 years (median 71 years, range 18-107 years) were enrolled in the study. Lacunar stroke was the most frequent stroke subtype (38.8%), followed by atherothrombotic (33.3%), cardioembolic (21.8%) and other stroke (6.1%). NIH stroke scale score on admission was 8.0 +/- 7.9 (median 5; 25th to 75th percentile, 2-11). 36.8% arrived at hospital within 3 h of symptom onset, and 49.5% within 6 h. The ambulance was used for 70.2% of patients arriving within 3 h after onset, but in only 29.9% of patients visiting the hospital later than 3 h after onset (p < 0.0001). 60.8% displayed good outcome (modified Rankin Scale score of 0-2 at discharge), while 32.3% displayed poor outcome (score 3-5), and mortality rate was 6.9%. CONCLUSIONS: More than half of the acute stroke patients arrived at hospital later than 6 h after onset. Establishment of ideal emergency systems is needed for better management of stroke and for improvement of patient outcome, in particular, in the future after approval of intravenous recombinant tissue plasminogen activator for acute ischemic stroke by the Japanese government.

Adult↗
PubMed2004

Vertebral artery occlusion in duplex color-coded ultrasonography.

BACKGROUND AND PURPOSE: To establish the diagnostic criteria for the site of occlusion in the vertebral arteries (VAs) using duplex color-coded ultrasonography. METHODS: In 128 consecutive patients who underwent conventional cerebral angiography, we prospectively measured the diameter, mean flow velocity (MV), peak systolic flow velocity, and end-diastolic flow velocity of both VAs. The diameter-ratio (diameter of contralateral VA divided by that of target VA) and MV-ratio (MV of contralateral VA divided by that of target VA) were determined. Based on the angiographic findings, we classified the VAs into 4 types (5 groups) as follows: (1) the origin of VA occlusion (Origin group: n=9); (2) VA occlusion before branching into the posterior inferior cerebellar artery (PICA) (Before group: n=10); (3A) symptomatic VA occlusion after branching into the PICA (After group: n=12); (3B) asymptomatic or hypoplastic occlusive VA after branching into the PICA (PICA end group: n=15); and (4) no significant occlusive lesions in the VA (Control group: n=194). RESULTS: No flow signals in the VAs apparently indicated the Origin group. Preserved peak systolic flow velocity but end-diastolic flow velocity of zero cm/s indicated the Before group. MV <18 cm/s and MV-ratio > or =1.4 indicated the PICA end group or After group. Furthermore, these groups could be distinguished as follows: a diameter-ratio <1.4 indicated the After group. A diameter-ratio > or =1.4 indicated the PICA end group. Either MV > or =18 cm/s or MV <18 cm/s in combination with MV-ratio <1.4 indicated the Control group. CONCLUSIONS: Duplex color-coded ultrasonography can accurately diagnose the site of VA occlusion.

Angiography, Digital Subtraction↗
PubMed2004

Early neurological deterioration represents recurrent attack in acute small non-lacunar stroke.

The aim of this study was to identify the frequency and possible pathogenic mechanisms of early neurological deterioration in patients with acute small non-lacunar infarction. We studied 46 patients (35 men, 11 women; age, 70.3+/-10.4 years) with acute small non-lacunar infarction. Small non-lacunar infarction was diagnosed using diffusion-weighted magnetic resonance imaging (DWI) as being <15 mm in diameter and located in the cortex and centrum ovale in the middle cerebral artery territory. The patients were divided into two groups; Group D (n=6) had neurological deterioration within 7 days after symptom onset, while Group N (n=40) did not have any neurological deterioration. In Group D, the interval from symptom onset to clinical deterioration was 3.3+/-1.5 days (range 2-6 days). Blood pressure on admission was higher in Group D than in Group N (p<0.05). In Group D, four of these five patients with follow-up DWI had new acute small ischemic lesions in addition to the initial lesions, indicating recurrent attacks of brain infarction. Neurological deterioration occurred within 7 days after symptom onset in 13% of patients. Neurological deterioration was frequently caused by recurrent infarction detected by DWI.

Acute Disease↗