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Yukio Miki

Publications and source records attributed to Yukio Miki.

At least 19 recordsLinked to original sources
PubMed2007

Evaluation of pituitary macroadenomas with multidetector-row CT (MDCT): comparison with MR imaging.

INTRODUCTION: It is important to have information on cavernous sinus extension and bony destruction in pituitary macroadenomas before surgery, but magnetic resonance (MR) imaging cannot always depict them. In the present study we sought to determine whether multidetector-row computed tomography (MDCT) could provide preoperative information in addition to that provided by MR imaging in pituitary macroadenoma. METHODS: The subjects comprised 33 consecutive patients (15 women, 18 men; mean age 50 years) with surgically proven macroadenoma. For MDCT, using the soft-tissue window and bone window, three orthogonal multiplanar reconstruction images were generated from venous-phase contrast-enhanced 0.5-mm isotropic voxel data. MDCT and MR images were evaluated with regard to: (1) clarity of tumor margins; (2) identification of the normal pituitary gland; (3) identification of erosion or destruction of the sellar floor; and (4) visualization of the adjacent optic pathways. RESULTS: MDCT more clearly demonstrated the lateral tumor margin than MR imaging (P = 0.002). No significant differences in visualization of the normal pituitary gland were noted between MDCT and dynamic MR imaging (P = 0.7). MDCT more clearly demonstrated sellar floor erosion or destruction at the sphenoid sinus than MR imaging (P < 0.001). MR imaging was superior to MDCT for visualizing the adjacent optic pathways (P < 0.001). CONCLUSION: MDCT is superior to MR imaging for assessing lateral tumor margin and the sellar floor at the sphenoid sinus. MDCT offers useful preoperative information in addition to that obtained from MR imaging.

Adenoma↗
PubMed2006

Clinicoradiological factors influencing the reversibility of posterior reversible encephalopathy syndrome: a multicenter study.

PURPOSE: The aim of this retrospective study was to clarify the relation between the reversibility of posterior reversible encephalopathy syndrome (PRES) with three factors: the anatomical region of the brain involved, the background clinical cause, and the diffusion weighted image (DWI) intensity of PRES lesions. MATERIAL AND METHODS: This multicenter study, conducted by the PRES Study Group of the Neuroradiology Workshop, involved 52 cases from 28 institutions. Initial and follow-up magnetic resonance imaging were compared regarding the reversibility of PRES lesions according to anatomical location and clinical background. Initial DWI and apparent diffusion coefficient (ADC) maps were reviewed in 20 cases. RESULTS: Reversibility was significantly lower (P < 0.01) in the brain stem (44%) and deep white matter (47%) compared to the other cortical and subcortical areas (76%-91%). The reversibility was greater in the eclampsia subgroup followed by the hypertension and chemotherapy subgroups. DWI, even with ADC maps, had limitations in predicting the outcome of PRES lesions. CONCLUSION: The typical cortical and subcortical PRES lesions showed reversibility, whereas the brain stem and deep white matter lesions showed less reversibility. PRES due to eclampsia showed maximum reversibility compared to hypertension- and drug-related PRES. DWI, even with ADC maps, had limitations in predicting the course of PRES.

Adolescent↗
PubMed2006

Fibers from the dorsal premotor cortex elicit motor-evoked potential in a cortical dysplasia.

OBJECTIVE: To identify the fibers originating from the dorsal premotor cortex (dorsal PMC) that contribute to motor-evoked potentials (MEP), we have applied integrated functional neuronavigation and awake surgery during removal of an epileptic cortical dysplasia located in the right premotor cortex. METHODS: Chronic subdural electrodes were employed for functional mapping during a routine invasive evaluation for intractable epilepsy. After the fibers originating from the dorsal PMC were plotted into the tractography-integrated functional neuronavigation, subcortical MEPs and clinical symptoms were examined during resection of the epileptogenic dorsal PMC. RESULTS: During removal of the epileptogenic area, MEPs were elicited by electrical stimulation of the fibers originating from the dorsal PMC, which were separated from the pyramidal tracts from the precentral gyrus. Resection of the dorsal PMC and its fibers caused a transient dysmetric movement of the left toe without motor weakness. CONCLUSION: Functional corticospinal tract fibers originating from the dorsal PMC can be defined and removed safely under local anesthesia with the aid of integration of functional neuronavigation and subcortical electrical stimulation.

Adolescent↗
PubMed2006

Corticospinal tract localization: integration of diffusion-tensor tractography at 3-T MR imaging with intraoperative white matter stimulation mapping--preliminary results.

Institutional review board approval and written informed consent were obtained. The purpose of this study was to prospectively validate usefulness of diffusion-tensor (DT) fiber tractography of the corticospinal tract at 3-T magnetic resonance imaging, in combination with the subcortical motor-evoked potential (MEP) technique, as a tool for tractography-guided neurosurgery. DT imaging and corticospinal tractography were performed at 3 T in eight patients (four men, four women; mean age, 41 years; age range, 23-58 years) with intracranial space-occupying lesions. Tractography data were transferred to a neuronavigation system, and tractography-guided neurosurgery was performed. During lesion resection, subcortical MEPs were recorded. Positive MEP response was observed in four patients. No patients developed new motor weakness postoperatively. Complementary use of tractography and MEP may be useful for intraoperative depiction of corticospinal tracts.

Adult↗
PubMed2006

Comparison of 3.0- and 1.5-T three-dimensional time-of-flight MR angiography in moyamoya disease: preliminary experience.

PURPOSE: To prospectively compare 3.0- and 1.5-T three-dimensional (3D) time-of-flight (TOF) magnetic resonance (MR) angiography in patients with moyamoya disease, with special emphasis on the visualization of abnormal netlike vessels (moyamoya vessels). MATERIALS AND METHODS: Study protocols were approved by the local ethics committee; written informed consent was obtained from all patients. The study included 24 consecutive patients with moyamoya disease (four male and 20 female patients). Patients ranged in age from 17 to 66 years (mean age, 41 years). Moyamoya disease had been diagnosed in all patients before they were entered into the study. All patients underwent 3D TOF MR angiography at both 3.0 and 1.5 T; imaging examinations were performed within 14 days of each other. Maximum intensity projections (MIPs) obtained with MR angiography performed at both 3.0 and 1.5 T were evaluated by two neuroradiologists; the visualization of moyamoya vessels was graded according to a 4-point scale. For both 3.0- and 1.5-T imaging, the number of high-signal-intensity areas and the summation of cross-sectional areas of high signal intensity on source images obtained at the same level of MR angiography were compared quantitatively by using the Wilcoxon matched-pair signed-rank test. RESULTS: Moyamoya vessels were better visualized on MIPs obtained with 3.0-T imaging than on MIPs obtained with 1.5-T imaging (P < .001). At the identical level of the source image, 3.0-T imaging depicted more high-signal-intensity areas than did 1.5-T imaging. Wider cross-sectional areas of moyamoya vessels were visualized with 3.0-T imaging than with 1.5-T imaging (P < .001). CONCLUSION: Moyamoya vessels are better depicted with MR angiography at 3.0 T than at 1.5 T.

Adolescent↗
PubMed2006

Diffusion-tensor fiber tractography: intraindividual comparison of 3.0-T and 1.5-T MR imaging.

PURPOSE: To prospectively evaluate the depiction of brain fiber tracts at 3.0- versus 1.5-T diffusion-tensor (DT) fiber tractography performed with parallel imaging. MATERIALS AND METHODS: Institutional review board approval was obtained, and each subject provided written informed consent. Subjects were 30 healthy volunteers (15 men, 15 women; mean age, 28 years; age range, 21-46 years). Single-shot spin-echo echo-planar magnetic resonance (MR) sequences with parallel imaging were applied. Four fiber tracts were reconstructed: corticospinal tract (CST), superior longitudinal fasciculus (SLF), corpus callosum (CC), and fornix. Two neuroradiologists compared 3.0- and 1.5-T tractography in terms of fiber tract depiction by using five depiction scores (scores 0-4) and numbers of reconstructed tract fibers and in terms of lateral asymmetry in the CST by using numbers of reconstructed fibers. The Wilcoxon signed rank test was applied for statistical analysis. RESULTS: Visual scores for both CST hemispheres (P < .001), the right SLF (P = .005), the CC (P = .01), and the right fornix (P = .04) were higher at 3.0-T DT tractography. Larger numbers of CST (right, P = .008; left, P < .001), SLF (right, P = .001; left, P = .02), and fornix (bilaterally, P = .02) tract fibers were depicted at 3.0 T. The asymmetry index for the CST was lower (P < .001) at 3.0 T. Visual scores for the left SLF and the left fornix and numbers of CC tract fibers were not significantly different. CONCLUSION: Depiction of most fiber tracts was improved at 3.0-T DT tractography compared with depiction at 1.5-T tractography.

Adult↗
PubMed2006

Small artery dementia in Japan: radiological differences between CADASIL, leukoaraiosis and Binswanger's disease.

CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy) is a hereditary small artery disease which is phenotypically similar to Binswanger's disease (BD), a nonhereditary form of small artery disease. Recent studies have indicated that lesions in the temporopolar, medial frontopolar areas and external capsule are frequently seen in Caucasian patients with CADASIL. However, it remains unclear whether magnetic resonance (MR) imaging findings are helpful in diagnosing small artery disease outside countries with Caucasian populations, since CADASIL is rare despite the high prevalence of small artery disease in Japan. We examined 58 patients with small artery disease, all of whom were devoid of major vessel occlusion or severe stenosis. These patients included 7 patients from 3 families with CADASIL, 27 nondemented patients with extensive leukoaraiosis (LA) and 24 patients with BD. On T(2)-weighted MR images, hyperintensities in the temporopolar areas were observed in all 7 patients with CADASIL, whereas these lesions were observed in only 1 subject from each of the nondemented LA and BD groups. Hyperintensities in the medial frontopolar areas were seen in 4 of the 7 patients with CADASIL (57%) and in 14 of the 24 patients with BD (58%), and were more frequent than in the nondemented LA group (4 of the 27 patients; 15%). In contrast, hyperintensities in the external capsule were frequently observed in all groups. Therefore, temporopolar lesions can also serve as diagnostic markers for CADASIL in non-Caucasian patients.

Adult↗
PubMed2006

MR imaging of Liliequist's membrane.

Liliequist's membrane is an arachnoid structure well-known to neurosurgeons. However, the importance of this membrane had been lost until the development of endoscopic third ventriculostomy (ETV). ETV is superior in its minimal invasiveness, but in some subgroups of hydrocephalus, the effectiveness of ETV may be reduced. Liliequist's membrane may block the cerebrospinal fluid (CSF) flow from the defect of the third ventricle floor, which may cause failure of ETV. Liliequist's membrane can be visualized on magnetic resonance (MR) imaging in normal healthy individuals, however, its visibility is different among individuals. CSF artifacts exist to varying degrees, but do not impede visualization of Liliequist's membrane in most subjects. Since Liliequist's membrane is a cisternal structure, the three-dimensional (3D) constructive interference in steady state (CISS) sequence is useful. The outcome of ETV could be predicted with MR imaging findings of Liliequist's membrane in a patient with obstructive hydrocephalus. High-field (> or =3 Tesla) MR imaging of Liliequist's membrane also offers superior resolution and is expected to provide additional information about Liliequist's membrane.

Arachnoid↗
PubMed2006

Early experience with 3-T magnetic resonance tractography in the surgery of cerebral arteriovenous malformations in and around the visual pathway.

OBJECTIVE: To evaluate of the role of magnetic resonance (MR) tractography on the optic radiation with a 3-T MR unit in the surgery of cerebral arteriovenous malformation (AVM) in and around the visual pathway. METHODS: Of the 322 patients with cerebral AVMs admitted to our clinic between 1978 and 2005, a study of MR tractography was made on 29 patients. Ten of those patients had AVMs in and around the visual pathway and were included in this study. There were two men and eight women ranging in age from 15 to 64 years (mean age, 34.5 +/- 14.8 yr). All of the patients underwent 3-T tractography of optic radiation (OR) and neuro-ophthalmologic evaluation. Four of the 10 patients underwent surgical resection of the AVM. A postoperative 3-T MR study and a neuro-ophthalmologic evaluation was performed 1 month after surgery in most patients. RESULTS: The preoperative patients for whom tractography demonstrated a continuous bundle of OR from the medial temporal region to the primary visual cortex had minimal or no visual field loss, whereas the patients for whom the tractography did not show a continuous bundle of OR had significant visual loss. The patients for whom tractography in the postoperative study demonstrated a bundle of OR experienced no postoperative deterioration of the visual field loss, whereas the patients for whom tractography did not demonstrate a bundle of OR exhibited significant visual field loss. CONCLUSION: This technique is thought to be useful in confirming the integrity of and localizing deviated tract and in evaluating the surgical risk, especially for nonhemorrhagic AVMs in and around the visual pathways, taking some limitations of this method into consideration.

Adolescent↗
PubMed2006

"Target bypass": a method for preoperative targeting of a recipient artery in superficial temporal artery-to-middle cerebral artery anastomoses.

OBJECTIVE: To introduce a method for preoperative targeting of a proper recipient artery in superficial temporal artery-to-middle cerebral artery anastomosis. METHODS: Six operations for superficial temporal artery-to-middle cerebral artery anastomosis in four patients with moyamoya disease or moyamoya-like disease and two operations in two patients with atherosclerotic cerebrovascular occlusive disease accompanied by coronary artery stenosis were performed using our method. Before surgery, a 3-Tesla magnetic resonance imaging study was performed with axial T1-weighted three-dimensional magnetization-prepared rapid acquisition gradient-echo sequences and three-dimensional time-of-flight magnetic resonance angiography. Data on quantitative regional cerebral blood flow were obtained by iodine-123-labeled N-isopropyl-iodoamphetamine single-photon emission computed tomography or positron emission computed tomography. The magnetic resonance angiography and regional cerebral blood flow data sets were registered with the magnetization-prepared rapid acquisition gradient-echo data set by means of the coregistration function of the SPM2 software. We examined the arteries located on or near the cortex where the regional cerebral blood flow had significantly decreased and used the coregistered data set and MRIcro software to select the cortical artery with the largest diameter as the target recipient artery. At the surgery, the data sets were applied to the neuronavigation system and the actual site of the target was confirmed in the operation before scalp incision. The superficial temporal artery was anastomosed with the target through a small craniotomy. RESULTS: Successful bypass surgery to the target was confirmed in all cases. CONCLUSION: The "target bypass" method might be effective for cases with moyamoya disease or for cases requiring surgery through a small craniotomy.

Adult↗
PubMed2005

Whole brain magnetization transfer histogram analysis of pediatric acute lymphoblastic leukemia patients receiving intrathecal methotrexate therapy.

BACKGROUND AND PURPOSE: The purpose of this prospective study was to evaluate the hypothesis that magnetization transfer ratio (MTR) histogram analysis of the whole brain could detect early and subtle brain changes nonapparent on conventional magnetic resonance imaging (MRI) in children with acute lymphoblastic leukemia (ALL) receiving methotrexate (MTX) therapy. MATERIALS AND METHODS: Subjects in this prospective study comprised 10 children with ALL (mean age, 6 years; range, 0-16 years). In addition to conventional MRI, magnetization transfer images were obtained before and after intrathecal and intravenous MTX therapy. MTR values were calculated and plotted as a histogram, and peak height and location were calculated. Differences in peak height and location between pre- and post-MTX therapy scans were statistically analyzed. Conventional MRI was evaluated for abnormal signal area in white matter. RESULTS: MTR peak height was significantly lower on post-MTX therapy scans than on pre-MTX therapy scans (p = 0.002). No significant differences in peak location were identified between pre- and post-chemotherapy imaging. No abnormal signals were noted in white matter on either pre- or post-MTX therapy conventional MRI. CONCLUSIONS: This study demonstrates that MTR histogram analysis allows better detection of early and subtle brain changes in ALL patients who receive MTX therapy than conventional MRI.

Adolescent↗
PubMed2005

Age-related signal intensity changes in the corpus callosum: assessment with three orthogonal FLAIR images.

The presence of age-related hyperintensities of the corpus callosum has not been thoroughly evaluated. Fifty-two patients of 50 years of age or older (mean, 71 years; range, 50-87 years) were included in this study. Fluid-attenuated inversion recovery images were obtained in three orthogonal planes. Periventricular hyperintensities (PVHs) and deep white matter hyperintensities (DWMHs) were graded according to Fazekas' rating scale. Correlations between the presence of hyperintensities in the corpus callosum and age, and the grade of PVH and DWMH were statistically analyzed. PVH was categorized as grade 0 (n=4), grade 1 (n=28), grade 2 (n=10), or grade 3 (n=10). DWMH was categorized as grade 0 (n=4), grade 1 (n=25), grade 2 (n=8), or grade 3 (n=15). Hyperintensity was considered present in the corpus callosum in 31 of the 52 patients (60%). In these 31 patients, PVH was categorized as grade 1 (n=16), grade 2 (n=7), or grade 3 (n=8), while DWMH was categorized as grade 0 (n=1), grade 1 (n=10), grade 2 (n=7), or grade 3 (n=13). The presence of callosal hyperintensities was significantly correlated with age (p=0.001), and with PVH (p=0.04) and DWMH grades (p=0.004). Hyperintensities may be present in the corpus callosum with aging, and are correlated with PVH and DWMH.

Age Factors↗
PubMed2005

The pituitary gland: changes on MR images during the 1st year after delivery.

PURPOSE: To longitudinally and prospectively investigate changes in the volume and signal intensity on T1-weighted magnetic resonance (MR) images of the pituitary gland up to 1 year after delivery and evaluate whether termination of lactation has an effect on these parameters. MATERIALS AND METHODS: All participants provided informed consent for participation in the study, which was approved by the institutional review board. Thirteen volunteers (mean age, 28 years; age range, 26-32 years) underwent MR imaging 2 and 4 weeks after delivery and then at intervals of 0.5-2.0 months until 1 year after delivery. Eight participants terminated lactation during the study period. Sagittal and coronal T1-weighted images were obtained. Signal intensities of the anterior and posterior lobes of the pituitary were calculated relative to that of the pons. The volume of the pituitary was also calculated. Two-tailed paired Student t tests and separate simple linear regression analyses were used to test for statistically significant differences. RESULTS: The mean pituitary volume was 544 mm3 at 2 weeks, 523 mm3 at 4 months, 512 mm3 at 8 months, and 511 mm3 at 12 months after delivery, with significant differences between 2 weeks and 4 months (P = .002) and between 4 and 8 months (P = .003) after delivery. The mean ratio of the signal intensity of the anterior lobe of the pituitary to the signal intensity of the pons was 1.11 at 2 weeks, 1.07 at 4 months, 1.03 at 8 months, and 1.00 at 12 months after delivery, with significant differences between 2 weeks and 4 months (P = .004) and between 4 and 8 months (P = .0001) after delivery. Termination of lactation had no statistically significant effect on pituitary volume or the ratio of the signal intensity of the anterior or posterior lobe of the pituitary to the signal intensity of the pons. CONCLUSION: The volume of the pituitary gland decreases up to 8 months after delivery, and the T1-weighted signal intensity of the anterior lobe of the pituitary decreases; termination of lactation has no statistically significant effect on these parameters.

Adult↗
PubMed2005

Asymptomatic microbleeds in moyamoya disease: T2*-weighted gradient-echo magnetic resonance imaging study.

OBJECT: The aim of this study was to investigate the incidence of asymptomatic microbleeds (MBs) in patients with moyamoya disease (MMD) by using a 3-tesla magnetic resonance (MR) imaging unit. METHODS: Data on 63 patients hospitalized with MMD between 1999 and 2004 were retrospectively examined to determine the incidence of asymptomatic MBs. Gradient-echo T2*-weighted MR imaging studies obtained using 3- and 1.5-tesla units were available in 25 patients. These patients consisted of five men and 20 women, ranging in age from 17 to 66 years (mean age 41 +/- 14 years). Ischemic MMD was diagnosed in 18 patients, and hemorrhagic MMD in seven. The incidence of MBs was also evaluated using the same 3-tesla MR imaging unit in 34 healthy volunteers including seven men and 27 women, ranging in age from 18 to 71 years (mean age 33 +/- 12 years). Using the 3-tesla MR unit, asymptomatic MBs were demonstrated in 11 patients (44%); they were detected in seven patients (28%) by using the 1.5-tesla unit. In the 3-tesla MR studies in healthy individuals, MBs were found in two patients (5.8%). Based on 3-tesla MR studies, the incidence of MBs was significantly higher in patients with MMD compared with that in healthy individuals. Asymptomatic MBs were demonstrated in eight (44%) of 18 patients with ischemic MMD and three (43%) of seven patients with hemorrhagic MMD. CONCLUSIONS: Microbleeds are significantly more common in patients with MMD than in healthy individuals regardless of the disease type. The evaluation of MBs with T2*-weighted 3-tesla MR imaging might contribute to the treatment of MMD.

Adolescent↗
PubMed2005

[Distribution of ischemic leukoaraiosis in MRI: a difference from white matter lesions in CADASIL].

Previously, the distribution of white matter lesions in CADASIL has been reported to be distinct from those in patients with ischemic leukoaraiosis and Binswanger's disease. In earlier European studies, diagnostic significance of white matter lesions in the temporopolar region (Tp), medial frontopolar region (Fp) and external capsule (EC) was stressed in diagnosing CADASIL. More recently, however, high sensitivity and specificity of Tp lesions have been demonstrated. In Japan, prevalence of CADASIL is lower, and those of ischemic leukoaraiosis and Binswanger's disease, likely related to small artery disease, are much higher than in Caucasian countries. Therefore, we examined the frequencies of CADASIL-associated lesions in 17 non-demented patients with ischemic leukoaraiosis and 20 patients with Binswanger's disease. The Binswanger's disease group showed a significantly lower scores for Hasegawa Dementia Rating Scale Revised (HDSR) and a higher prevalence of hypertension, compared to the ischemic leukoaraiosis group. There was only 1 patient with Tp lesions in each group, while Fp lesions were found in 12 % and 50% in the ischemic leukoaraiosis group and Binswanger's disease group, respectively, and EC lesions in 59% and 80%. These results indicated that Tp lesions were useful diagnostic marker in diagnosing CADASIL, whereas Fp and EC lesions were non-specifically observed.

Brain Ischemia↗
PubMed2005

Different signal intensities between intra- and extracranial components in jugular foramen meningioma: an enigma.

BACKGROUND AND PURPOSE: The purpose of this study was to evaluate retrospectively differences in MR signal intensity and contrast enhancement between intra- and extracranial components of jugular foramen meningioma (JFM). METHODS: MR studies of eight patients who underwent surgery for histologically confirmed JFM were reviewed retrospectively. Signal intensity differences between intra- and extracranial components of all eight JFMs on axial T1-, T2-, and postcontrast T1-weighted images were evaluated visually. In six of the eight JFMs, quantitative signal intensity evaluations were also performed by using relative signal intensity ratios of the intra- and extracranial components of JFM to CNS tissue at the same level. Paired t tests were used to evaluate differences in relative signal intensity ratios in each JFM between intra- and extracranial components. RESULTS: Both visual and quantitative signal intensity evaluations revealed that signal intensities of the intracranial component of JFM were significantly higher than those of the extracranial component on T1-, T2-, and postcontrast T1-weighted images. Results of relative signal intensity ratios were 0.89 +/- 0.04 versus 0.77 +/- 0.02 on T1-weighted images (P = .002); 1.66 +/- 0.28 versus 0.88 +/- 0.14 on T2-weighted images (P = .003); and 2.16 +/- 0.29 versus 1.77 +/- 0.26 on postcontrast T1-weighted images (P = .01). CONCLUSION: Intra- and extracranial components of JFM display different signal intensity and enhancement patterns. These differences may be related to histologic composition, and in particular, collagen content.

Adult↗
PubMed2005

[Japanese CADASIL case with limited dementia who had the Notch 3 R141C mutation].

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a rare hereditary disease characterized by recurrent transient ischemic attacks (TIA) and strokes, and vascular dementia caused by point mutations of the Notch 3 gene. Here, we report a Japanese CADASIL case who displayed limited dementia and had the Notch 3 R141C mutation. The relationship between pathogenesis and the mutation site in Notch 3 is discussed based on the case presented here.

CADASIL↗