Hiromitsu Naka

Hiroshima University, Hiroshima-shi, Hiroshima-ken, Japan

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Publications (19)45.31 Total impact

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    ABSTRACT: The hyperintense vessel sign (HVS) on fluid-attenuated inversion recovery images can frequently be detected in patients with acute cerebral infarction attributable to large artery stenosis or occlusion. The prognostic values and clinical characteristics of HVS remain to be elucidated. The aim of this study was to evaluate the association of HVS with ischemic lesions and severity of neurologic deficit. A total of 96 consecutive acute ischemic stroke patients (54 women, median age 76.5 [range 39-97] years), who had symptomatic severe stenosis or occlusion in the proximal middle cerebral artery that was detected with magnetic resonance angiography within 24 hours of onset, were enrolled. The extent of HVS was graded by a systematic quantitative scoring system (the HVS distribution score) based on Alberta Stroke Program Early Computed Tomographic Score. An HVS was detected in 89 patients (93%) at admission, and the patients who displayed wider HVS distribution scores exhibited more severe neurologic deficits at admission (P < .05). The follow-up magnetic resonance imaging, which was obtained in 79 patients (82%), was performed an average of 13 days. The association between HVS distribution score and final ischemic lesions was strongly observed (n = 67, P < .05) but not in the patients with intravenous thrombolysis (n = 12, P = .06). Although the distribution of HVS reflected final ischemic lesion, this association might not apply to the patients with the thrombolysis treatment. The interpretation of HVS distribution score with acute ischemic stroke patients should be discussed dependent on thrombolysis.
    Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association 01/2014;
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    ABSTRACT: We hypothesized that leukocytes have 2 opposing effects on patients with ischemic stroke treated with recombinant tissue plasminogen activator (rtPA). Patients with ischemic stroke treated with rtPA were divided into 2 groups using the peripheral leukocyte count: high leukocyte group (HLG) and low leukocyte group (LLG) and were evaluated with the National Institutes of Health stroke scale (NIHSS) during the first 24 hours. We defined significant improvement (SI) as NIHSS improving by more than 50% from the baseline, and deterioration following improvement (DFI) as the achievement of SI within 24 hours but its subsequent loss at 24 hours. Fifty-three patients were enrolled, and the rate of SI within 24 hours was higher in HLG than in LLG (85.2% vs 42.3%, P = .0011). However, the rate of DFI was significantly higher in HLG than in LLG (29.6% vs 7.7%, P = .0413). We found that leukocytes might have not only deleterious but also beneficial effects in intravenous rtPA treatment.
    Clinical and Applied Thrombosis/Hemostasis 07/2012; · 1.58 Impact Factor
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    ABSTRACT: BACKGROUND: Although brain microbleed has been reported to be a risk factor for antiplatelet-associated intracerebral hemorrhage, data on the use of specific antiplatelet agents are lacking. In this study, we examined the associations between specific antiplatelets and brain microbleeds in order to help select antiplatelet agents in patients with microbleeds. METHODS: We evaluated 1914 consecutive acute stroke patients, including 412 patients with intracerebral hemorrhage and 1502 patients with ischemic stroke. The associations between the presence of microbleeds and antiplatelet use were evaluated, including specific antiplatelet agents (aspirin, clopidogrel, cilostazol, and ticlopidine). RESULTS: Antiplatelet use was associated with the presence of microbleeds in patients with intracerebral hemorrhage (odds ratio [OR] 2.418; 95% confidence interval [CI] 1.236-4.730; P = .0099), but not in patients with ischemic stroke. The use of a single antiplatelet medication was not associated with the presence of microbleeds. In patients with intracerebral hemorrhage, aspirin (OR 2.160; 95% CI 1.050-4.443; P = .0364) but not clopidogrel, cilostazol, or ticlopidine was associated with microbleeds. In these patients, dividing brain microbleeds into deep microbleeds and lobar microbleeds revealed an association only between antiplatelet use and the presence of deep microbleeds (OR 2.397; 95% CI 1.258-4.567; P = .0079). None of the antiplatelet agents were associated with the presence of deep microbleeds, although aspirin had a trend of association (OR 1.986; 95% CI 1.000-3.946; P = .0501). CONCLUSIONS: Attention to microbleed-positive patients is necessary for the safe use of aspirin in order to avoid antiplatelet-associated hemorrhages, but prospective studies are needed to verify our results.
    Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association 07/2012;
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    ABSTRACT: The etiology of transient global amnesia (TGA) is not well understood. MR studies, including studies using diffusion-weighted imaging (DWI), have been used to investigate the pathophysiology of TGA, and focal hippocampal lesions have been detected in some studies. The aim of this study was to investigate serial changes in MR images from the patients with TGA. In seven TGA patients, serial MRI scans (from the same day of the onset to several days after the onset of symptoms) using a 1.5-T MR unit were prospectively evaluated. In four patients, the duration of TGA was over 12 hr. Three of those patients showed small punctate hippocampal hypersensitivity with decreased ADC values on DW images. These lesions were detected in the postacute phase (a time window of 24 - 48 hr after the onset of symptoms). In follow-up studies performed several days after the onset of symptoms, DWI lesions had disappeared in the subacute phase (7-10 days after the TGA episode). The delayed hippocampal lesion on DW images with 1.5-T MRI in patients with TGA appears to be associated with longer duration of symptoms, to persist for several days and to disappear in the chronic phase.
    Hiroshima journal of medical sciences 12/2010; 59(4):77-81.
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    ABSTRACT: Cerebral microbleeds (MB) are potential risk factors for intracerebral hemorrhage (ICH), but it is unclear if they are a contraindication to using antithrombotic drugs. Insights could be gained by pooling data on MB frequency stratified by antithrombotic use in cohorts with ICH and ischemic stroke (IS)/transient ischemic attack (TIA). We performed a systematic review of published and unpublished data from cohorts with stroke or TIA to compare the presence of MB in: (1) antithrombotic users vs nonantithrombotic users with ICH; (2) antithrombotic users vs nonusers with IS/TIA; and (3) ICH vs ischemic events stratified by antithrombotic use. We also analyzed published and unpublished follow-up data to determine the risk of ICH in antithrombotic users with MB. In a pooled analysis of 1460 ICH and 3817 IS/TIA, MB were more frequent in ICH vs IS/TIA in all treatment groups, but the excess increased from 2.8 (odds ratio; range, 2.3-3.5) in nonantithrombotic users to 5.7 (range, 3.4-9.7) in antiplatelet users and 8.0 (range, 3.5-17.8) in warfarin users (P difference=0.01). There was also an excess of MB in warfarin users vs nonusers with ICH (OR, 2.7; 95% CI, 1.6-4.4; P<0.001) but none in warfarin users with IS/TIA (OR, 1.3; 95% CI, 0.9-1.7; P=0.33; P difference=0.01). There was a smaller excess of MB in antiplatelet users vs nonusers with ICH (OR, 1.7; 95% CI, 1.3-2.3; P<0.001), but findings were similar for antiplatelet users with IS/TIA (OR, 1.4; 95% CI, 1.2-1.7; P<0.001; P difference=0.25). In pooled follow-up data for 768 antithrombotic users, presence of MB at baseline was associated with a substantially increased risk of subsequent ICH (OR, 12.1; 95% CI, 3.4-42.5; P<0.001). The excess of MB in warfarin users with ICH compared to other groups suggests that MB increase the risk of warfarin-associated ICH. Limited prospective data corroborate these findings, but larger prospective studies are urgently required.
    Stroke 06/2010; 41(6):1222-8. · 6.16 Impact Factor
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    ABSTRACT: Although MBs, ICH, and LI are secondary to cerebral microangiopathy, it remains unclear whether the location of subsequent ICH/LI corresponds to the previous location of MBs. We performed this study to clarify the positional relationship between recurrent ICH/LI and previously detected MBs. We evaluated patients with recurrent ICH/LI who had MBs, as shown on prior T2*-weighted MR imaging. We assessed retrospectively whether the location of recurrent ICH/LI corresponded to that of the prior MB. Patients with ICH were divided into the deep ICH group and the lobar ICH group, and the positional relationship between hematoma and previously detected MBs was evaluated. A total of 55 patients, including 34 with recurrent ICH and 21 with recurrent LI were evaluated. Although the location of the LI corresponded to prior MBs in only 1 patient (4.8%), the location of ICH corresponded to prior locations of MBs in 21 patients (61.8%) (OR, 32.3; 95% CI, 3.86-270.3; P < .001). Among the patients with ICH, the correspondence ratio was higher in the deep ICH group (19 of 24 patients, 79.2%) than in the lobar ICH group (2 of 10 patients, 20%) (OR, 15.2; 95% CI, 2.42-95.3; P < .002). The close positional association between recurrent ICH and prior MBs suggests that MBs represent hemorrhage-prone microangiopathy. In addition, different correspondence ratios between the deep ICH group and the lobar ICH group may be attributable to their different pathogenesis.
    American Journal of Neuroradiology 05/2010; 31(8):1498-503. · 3.17 Impact Factor
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    ABSTRACT: Although accumulating evidence suggests the presence of microbleeds as a risk factor for intracerebral hemorrhage (ICH), little is known about its significance in anticoagulated patients. The aim of this study was to determine whether the presence of microbleeds is associated with recurrent hemorrhagic stroke in patients who had received warfarin following atrial fibrillation-associated cardioembolic infarction. A total of 87 consecutive patients with acute recurrent stroke, including 15 patients with ICH and 72 patients with cerebral infarction, were enrolled in this study. International normalized ratios (INRs), vascular risk factors, and imaging characteristics, including microbleeds on T2*-weighted MR images and white matter hyperintensity (WMH) on T2-weighted MR images, were compared in the 2 groups. Microbleeds were noted more frequently in patients with ICH than in patients with cerebral infarction (86.7% versus 38.9%, P = .0007). The number of microbleeds was larger in patients with ICH than in patients with cerebral infarction (mean, 8.4 versus 2.1; P = .0001). INR was higher in patients with ICH than in patients with cerebral infarction (mean, 2.2 versus 1.4; P < .0001). The frequency of hypertension was higher in patients with ICH than in patients with cerebral infarction (86.7% versus 45.8%, P = .0039). Multivariate analysis revealed that the presence of cerebral microbleeds (odds ratio, 7.383; 95% confidence interval, 1.052-51.830) was associated with ICH independent of increased INR and hypertension. The presence of cerebral microbleeds may be an independent risk factor for warfarin-related ICH, but more study is needed because of strong confounding associations with elevated INR and hypertension.
    American Journal of Neuroradiology 05/2008; 29(8):1483-6. · 3.17 Impact Factor
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    ABSTRACT: We report a case of a 52-year-old woman with Behcet's disease who presented with dysarthria and right-sided hemiparesis. T2-weighted and diffusion-weighted images (DWI) showed a hyperintense lesion in the left pons with a relatively decreased apparent diffusion coefficient (ADC). Imaging showed almost complete resolution of the lesion after treatment with prednisolone. The atypical DWI and ADC findings in this case may reflect cytotoxic edema due to excitotoxic brain injury. This case thus illustrates the radiological diversity of neuro-Behcet's lesions.
    Internal Medicine 02/2008; 47(23):2073-6. · 0.97 Impact Factor
  • International Journal of Cardiology - INT J CARDIOL. 01/2008; 125.
  • Nippon rinsho. Japanese journal of clinical medicine 11/2006; 64 Suppl 7:478-81.
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    ABSTRACT: Previous studies have shown microbleeds to be a risk factor for intracerebral hemorrhage and white matter hyperintensity (WMH) to be a risk factor for ischemic stroke. This study was performed to determine whether combinations of the presence or absence of microbleeds and advanced WMH are risk factors for subsequent recurrent stroke types. In 266 patients with stroke, microbleeds on T2*-weighted MR images were counted, and WMH on T2-weighted images was graded. Patients were divided into 4 groups by the combinations of the presence or absence of microbleeds and advanced WMH and were followed up for stroke recurrence. During a mean follow-up period of 564.8 +/- 220.5 days, 26 patients developed recurrent strokes, including 10 intracerebral hemorrhages and 16 ischemic strokes. Patients with microbleeds without advanced WMH (n = 42) developed only intracerebral hemorrhages (n = 8), and the recurrence rate of intracerebral hemorrhage in those patients estimated by the Kaplan-Meier method was the highest in the 4 groups (14.3% in 1 year and 21.2% in 2 years). In contrast, patients with advanced WMH without microbleeds (n = 39) developed only ischemic strokes (n = 6), and the estimated recurrent rate of ischemic stroke in those patients was the highest in the 4 groups (10.5% in 1 year and 17.4% in 2 years). Cox proportional hazards regression analysis revealed that microbleeds were associated with intracerebral hemorrhage (hazard ratio [HR], 85.626; 95% confidence interval [CI], 6.344-1155.649) and that advanced WMH was negatively associated with intracerebral hemorrhage (HR, 0.016; 95% CI, 0.001-0.258). Advanced WMH was associated with ischemic stroke (HR, 10.659; 95% CI, 2.601-43.678). It appears that patients at high risk of subsequent intracerebral hemorrhage or ischemic stroke can be identified by combinations of the presence or absence of microbleeds and advanced WMH.
    American Journal of Neuroradiology 05/2006; 27(4):830-5. · 3.17 Impact Factor
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    ABSTRACT: Both leukoaraiosis and asymptomatic microbleeds are associated with small-artery diseases. Although an association between hyperhomocysteinemia and leukoaraiosis has been reported, no studies have evaluated the association between total homocysteine (tHcy) level and presence of microbleeds in stroke patients. We evaluated the association between tHcy level and leukoaraiosis or microbleeds in stroke patients. In 102 patients with stroke (69.5 +/- 10.3 years old, 54 men and 48 women), microbleeds on T2*-weighted MR images were counted, leukoaraiosis on T2-weighted images was graded and fasting plasma tHcy concentrations were measured. Plasma tHcy level was significantly higher in patients with advanced leukoaraiosis than in those without advanced leukoaraiosis (13.9 +/- 4.6 micromol/l vs. 10.2 +/- 3.4 micromol/l, P < 0.0001). Plasma tHcy level was not significantly different in patients with microbleeds and those without microbleeds (11.3 +/- 4.1 micromol/l vs. 11.4 +/- 4.3 micromol/l, P = 0.9441). Elevated tHcy level is significantly and independently associated with advanced leukoaraiosis [odds ratio (OR), 1.330; 95% CI, 1.130-1.565] but not with the presence of microbleeds. Elevated tHcy level appears to be associated with ischemic small-artery disease rather than with bleeding-prone small-artery disease.
    European Journal of Neurology 04/2006; 13(3):261-5. · 4.16 Impact Factor
  • Nihon Naika Gakkai Zasshi 12/2004; 93(11):2424-6.
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    ABSTRACT: Spinocerebellar ataxia type 6 (SCA6) is an autosomal dominant cerebellar ataxia caused by CAG trinucleotide expansion. The characteristics of regional cerebral blood flow (rCBF) in SCA6 patients have not been established, whereas it has been reported that decreased rCBF in the cerebrum seems to be a remote effect of cerebellar impairment in other cerebellar disorders. To clarify the characteristics of rCBF, including cerebro-cerebellar relationship, and its correlation with clinical manifestations in patients with genetically confirmed SCA6 using quantitative assessment of rCBF by brain single-photon emission computed tomography (SPECT). Technetium Tc 99m ethyl cysteinate dimer SPECT study using a Patlak plot. Patients Hiroshima University Hospital, Hiroshima, Japan. Ten patients with SCA6 and 9 healthy controls. Main Outcome Measure The rCBF of the cerebellar vermis, cerebellar hemisphere, and frontal lobes. In SCA6 patients, rCBF was decreased only in the cerebellar vermis and hemisphere compared with healthy controls, and this was inversely correlated with duration of illness. The rCBF in the frontal lobes was slightly correlated with duration of illness without statistical significance. The rCBF in the vermis was inversely correlated with severity of dysarthria, but there was no significant correlation with CAG repeated expansions. Decrease in rCBF was found only in the cerebellum and was associated with duration of illness, dysarthria and ataxia, and cerebellar atrophy. No remote effect of cerebellar hypoperfusion was found in the SCA6 patients.
    JAMA Neurology 07/2004; 61(6):933-7. · 7.58 Impact Factor
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    ABSTRACT: Asymptomatic microbleeds shown by T2*-weighted MR imaging are associated with small-artery diseases, especially with intracerebral hemorrhage. Few studies have focused on the prevalence of microbleeds in patients with recurrent stroke. We investigated frequency of microbleeds in patients with recurrent stroke and association of presence of microbleeds with a combination of stroke subtypes and severity of leukoaraiosis. The study population consisted of 102 patients with primary stroke and 54 patients with recurrent stroke. Microbleeds were counted and classified by using T2*-weighted MR imaging with a 1.0-T system. Patients with recurrent stroke showed a significantly higher prevalence of microbleeds (68.5%) than did patients with primary stroke (28.4%) (P <.0001). Among patients with recurrent stroke, the highest frequency of microbleeds occurred in those with intracerebral hemorrhage alone (92.3%), with the next highest frequency occurring in those with a combination of intracerebral hemorrhage and ischemic stroke (76.5%) and then those with ischemic stroke alone (50.0%) (P <.05). Leukoaraiosis was more severe in patients with recurrent stroke than in patients with primary stroke, and correlations between grade of microbleeds and severity of leukoaraiosis were found in patients with primary stroke (r = 0.367, P <.001) and in patients with recurrent stroke (r = 0.553, P <.0001). Logistic regression analysis identified recurrent stroke (odds ratio, 4.487; 95% confidence interval, 1.989-10.120) and leukoaraiosis (odds ratio, 5.079; 95% confidence interval, 2.125-12.143) as being significantly and independently associated with microbleeds. Asymptomatic microbleeds are observed to occur frequently in patients with recurrent stroke, either hemorrhagic or ischemic stroke, and are closely associated with the severity of leukoaraiosis.
    American Journal of Neuroradiology 06/2004; 25(5):714-9. · 3.17 Impact Factor
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    ABSTRACT: To determine whether magnetization transfer imaging (MTI) demonstrates abnormalities in the brain structures of patients with multiple system atrophy (MSA), we examined 12 patients with clinically probable MSA and 11 control subjects. We calculated magnetization transfer ratios (MTRs) using region of interest analysis from MTI and assessed abnormal signal changes on T2-weighted images. MTRs of the base of the pons, middle cerebellar peduncle, putamen, and white matter of the precentral gyrus were significantly lower in the MSA patients than in the controls. Abnormal signal changes on T2-weighted images were observed in the base of the pons (n = 6), middle cerebellar peduncle (n = 7), and putamen (n = 7). MTRs of regions with abnormal signals were significantly lower than those of regions without abnormal signals and those in the controls. Even the MTRs of the regions without abnormal signals were lower than those in the controls. MTRs of the pyramidal tract, including white matter of the precentral gyrus, posterior limb of the internal capsule, cerebral peduncle, and base of the pons, were significantly lower in patients with pyramidal tract sign (n = 7) than in the controls. Patients with asymmetrical parkinsonism (n = 5) showed significantly lower MTRs in the putamen contralateral to the predominant side of parkinsonian symptoms than the ipsilateral side, although asymmetry of abnormal signal changes on T2-weighted images was not evident in more than half of those patients. This study showed that MTI demonstrates abnormalities in the brains of patients with MSA that seem to reflect underlying pathological changes and that the pathological changes detected by MTI seem to give rise to clinical symptoms. This study also showed that the abnormalities are detected more sensitively and over a larger area by MTI than by conventional magnetic resonance imaging.
    NeuroImage 12/2002; 17(3):1572-8. · 6.25 Impact Factor
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    ABSTRACT: We reviewed MRI findings in 29 patients with probable multiple system atrophy (MSA) to see whether there were common and or less common neuroradiological findings in the various clinical subtypes. We divided the patients into three clinical subtypes according to initial and predominant symptoms: 14 with olivopontocerebellar atrophy (OPCA), eight with the Shy-Drager syndrome (SDS) and seven with striatonigral degeneration (SND). The patients showed atrophy of the brain stem and cerebellum, high signal on T2-weighted images of the base of the pons and middle cerebellar peduncles, high and low signal on T2-weighted images of the putamen and atrophy of frontal and parietal lobes. The degree of atrophy of the middle cerebellar peduncle and cerebellum was greater in OPCA patients and a high-signal lateral rim to the putamen more frequent in SND. However, all findings were observed in all subtypes, and the degrees of atrophy of the putamen and pons and the frequency of high signal in the base of the pons were similar in the subtypes. We also found atrophy of the cerebral hemispheres, especially the frontal and parietal lobes, but its degree was not significantly different in the various subtypes. Our findings suggest that, although MSA can be divided clinically into three subtypes, most of the features on MRI are common and overlap in the subtypes, independently of the clinical presentation.
    Neuroradiology 04/2002; 44(3):204-9. · 2.70 Impact Factor
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    ABSTRACT: To determine whether patients with myotonic dystrophy (MyD) have structural changes in the cerebral white matter, we performed magnetization transfer (MT) imaging of the cerebral white matter in 14 MyD patients and 11 age-matched normal controls. We calculated MT ratios in both the white matter lesions (WMLs) and the normal-appearing white matter (NAWM) of MyD patients using region of interest (ROI) analysis. MT ratios in WMLs were markedly decreased, and all ROIs in NAWM also showed significantly lower MT ratios in MyD patients than in normal controls. The average MT ratio of all ROIs in WMLs and NAWM in each patient showed a significant negative correlation with duration of illness, but not with the patient's age or age at onset. The results of the present study indicate not only the presence of pathological changes in WMLs but also the widespread involvement of NAWM in MyD patients. The results also suggest that structural changes in the white matter may be progressive during the clinical course of MyD.
    Journal of the Neurological Sciences 02/2002; 193(2):111-6. · 2.24 Impact Factor
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    ABSTRACT: Folic acid (folate) levels were measured in the serum of patients with various neurological diseases in Japan. Thirty-six patients showed decreased serum folate levels among 343 consecutive neurological patients (10.5%). Folate administration (15 mg/d) to folate-deficient patients improved neurological symptoms in 24 of 36 cases (67%). Serum folate levels were significantly lower in female than in male folate-deficient patients. Folate-deficient patients showed predominantly axonal neuropathy, which responded to folate supplementation more markedly. Male patients more frequently exhibited neuropathy, especially demyelinating and motor-dominant neuropathy, than females. Anemia was correlated with male sex and low serum folate levels. Male patients were more responsive than females to folate treatment. More male patients had taken excess alcohol or received gastrectomies than females. Neurological symptoms were more frequently improved by folate supplementation in patients with neuropathy than exclusive encephalopathy. Serum folate levels were lower in patients with encephalopathy, especially those with dementia, while folate therapy was more effective in neurological patients without dementia. Dysgeusia and anemia improved in all patients after folate administration. Neurological patients with malabsorption or treated with continuous drip infusion were resistant to folate therapy. Since folate-responsive neuroencepahlopathies are not rare among patients with neurological diseases in Japan, the serum folate level would serve as a valuable indicator for folate supplement therapy.
    Journal of Nutritional Science and Vitaminology 07/2001; 47(3):181-7. · 0.99 Impact Factor