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A Yagishita

Publications and source records attributed to A Yagishita.

At least 19 recordsLinked to original sources
PubMed2006

White matter abnormalities in the anterior temporal lobe suggest the side of the seizure foci in temporal lobe epilepsy.

INTRODUCTION: White matter abnormalities in the anterior temporal lobe (WAATL) are sometimes observed on magnetic resonance (MR) images of patients with temporal lobe epilepsy (TLE). Our purpose was to determine whether WAATL could indicate if the seizure foci are ipsilateral on electroencephalograms (EEG) in TLE patients. METHODS: We reviewed 112 consecutive patients with medically intractable TLE. We compared the side of seizure foci on EEG (preoperative and intraoperative) and MR images. RESULTS: Both loss of gray-white matter demarcation and increased signal intensity changes in the anterior white matter (positive WAATL) were observed in 54 of 112 patients (48.2%) with TLE. WAATL were present on the same side as the seizure foci on preoperative intracranial EEG with subdural electrodes (iEEG) and on intraoperative electrocorticography (ECG) in all the patients. In 47 patients, MR images showed WAATL and focal lesions that were possibly epileptogenic for TLE. In 2 of the 47 patients, the seizure foci on iEEG and ECG were contralateral to the focal lesion; in the remaining 45 patients, the seizure foci on surface EEG (sEEG) and ECG and the focal lesion were on the same side. In three patients, no focal lesions were seen but WAATL were present on the same side as the seizure foci on sEEG and ECG. In four patients, MR images showed focal lesions for which epileptogenicity was questionable, and WAATL on the same side as the seizure foci on EEG. CONCLUSION: WAATL are clinically useful because they indicate the side of the seizure foci.

Adolescent↗
PubMed2006

Pantothenate kinase-associated neurodegeneration with increased lentiform nuclei cerebral blood flow.

We report a case of pantothenate kinase-associated neurodegeneration with increased regional cerebral blood flow (rCBF) in bilateral lentiform nuclei on technetium Tc-99m ethyl cysteinate dimer single-photon emission CT (ECD-SPECT). A 6-year-old boy presented with opisthotonus. T2*-weighted MR images revealed areas of marked hypointensity with a hyperintense focus in bilateral globus pallidus, creating the characteristic eye-of-the-tiger appearance. ECD-SPECT showed increased rCBF in bilateral lentiform nuclei.

Brain↗
PubMed2005

New and reliable MRI diagnosis for progressive supranuclear palsy.

OBJECTIVE: To evaluate the area of the midbrain and pons on mid-sagittal MRI in patients with progressive supranuclear palsy (PSP), Parkinson disease (PD), and multiple-system atrophy of the Parkinson type (MSA-P), compare these appearances and values with those of normal control subjects, and establish diagnostic MRI criteria for the diagnosis of PSP. METHODS: The authors prospectively studied MRI of 21 patients with PSP, 23 patients with PD, 25 patients with MSA-P, and 31 age-matched normal control subjects. The areas of the midbrain tegmentum and the pons were measured on mid-sagittal MRI using the display tools of a workstation. The ratio of the area of the midbrain to the area of the pons was also evaluated in all subjects. RESULTS: The average midbrain area of the patients with PSP (56.0 mm2) was significantly smaller than that of the patients with PD (103.0 mm2) and MSA-P (97.2 mm2) and that of the age-matched control group (117.7 mm2). The values of the area of the midbrain showed no overlap between patients with PSP and patients with PD or normal control subjects. However, patients with MSA-P showed some overlap of the values of individual areas with values from patients with PSP. The ratio of the area of the midbrain to the area of pons in the patients with PSP (0.124) was significantly smaller than that in those with PD (0.208) and MSA-P (0.266) and in normal control subjects (0.237). Use of the ratio allowed differentiation between the PSP group and the MSA-P group. CONCLUSION: The area of the midbrain on mid-sagittal MRI can differentiate PSP from PD, MSA-P, and normal aging.

Aged↗
PubMed2003

Shape-resonance-enhanced vibrational effects in the angular distributions of C 1s photoelectrons from fixed-in-space CO molecules.

Angular distributions of C 1s photoelectrons from fixed-in-space CO molecules have been measured with vibrational resolution. A strong dependence of the angular distributions on the vibrational states of the residual molecular ion has been found for the first time in the region of the shape resonance. Calculations in the relaxed core Hartree-Fock approximation have reproduced the angular distributions fairly well in the general shapes of the angular distributions due to the correct description of nuclear motion as an average of the internuclear-distance-dependent dipole amplitudes.

Journal Article↗
PubMed2002

Direct probe of the shape resonance mechanism in 2sigma(g)-shell photoionization of the N2 molecule.

Angular distributions of photoelectrons from a 2sigma(g) shell of fixed-in-space N2 molecules have been measured for left- and right-elliptically polarized and for linearly polarized light at several photon energies in the region of sigma(*) shape resonance. That allowed the determination of a set of dipole matrix elements and phase shift differences characterizing the process. These data clearly show the enhancement of the fsigma(u) partial cross section in the resonance simultaneously with an abrupt increase of the corresponding phase shift by pi, which is the first experimental demonstration of the nature of the sigma(*) shape resonance in homonuclear diatomic molecules.

Journal Article↗
PubMed2001

Effect of multiple subpial transection on motor cortical excitability in cortical dysgenesis.

We report here a 12-year-old patient with unilateral cortical dysgenesis and intractable simple partial seizure in his left arm, who underwent multiple subpial transection (MST) in the right cerebral cortex including the primary motor cortex. We investigated motor cortical excitability using multimodal transcranial magnetic stimulation (TMS) before and 1 month after MST, in which surgical cortical incisions were made with strokes 5 mm apart and 4 mm deep. Preoperative TMS studies showed hyperexcitability in the affected motor cortex as abnormally prolonged muscle responses to TMS with a wide cortical motor map, which were markedly reduced following the operation. The preoperative motor evoked potentials were large and polyphasic, and consisted of early and late components. The late component was completely abolished after MST, suggesting that this component might be due to activation of the corticospinal tract neurones by long recurrent axon branches of dysplastic excitatory pyramidal neurones, which were cut by MST, or by delayed, polysynaptic intracortical conduction with marked temporal dispersion. Intracortical inhibition in the affected motor cortex was also disrupted preoperatively and improved after MST. Postoperative recruitment order of muscle responses to TMS was bilaterally symmetrical, indicating that MST did not interfere with the function of the corticospinal tract neurones. The patient showed fair motor recovery and good seizure control after the operation. These results of TMS studies demonstrated the remarkable effectiveness of MST not only on intractable seizure but also on abnormal motor cortical organization and hyperexcitability in cortical dysgenesis.

Cerebral Cortex↗
PubMed2001

Alternating paroxysmal hemiballism-hemichorea in bilateral internal carotid artery stenosis.

A 72-year-old man presented with paroxysmal and transient involuntary movements, or "limb shaking". The attacks occurred alternately from one side of the body to the other and ceased spontaneously. Surface EMG study showed synchronous grouping discharges in multiple limb muscles, being compatible with hemiballism-hemichorea. Cerebral angiography demonstrated marked stenosis of the bilateral internal carotid arteries. Bilateral carotid endarterectomy led to complete disappearance of the involuntary movements. Alternating paroxysmal hemiballismhemichorea might be a transient ischemic attack, and alternating striatal dysfunction induced by cerebral hemodynamic or microembolic ischemia probably plays a central role in the occurrence of such involuntary movements.

Aged↗
PubMed2001

[Pitfalls in MR imaging of neurological diseases].

MR imaging is useful for the diagnosis of neurological diseases but it has many pitfalls. The author presented one patient with syringobulbia of whom neurological examinations revealed lesions in the medulla. MR images showed slit-like lesions in the medulla and pontine tegmentum of which signal intensity was similar to that of cerebrospinal fluid. However, a sagittal scout image reveals syringomyelia in the upper cervical spinal cord that was important abnormal finding for the diagnosis of this case. In a case of hypertrophic cranial pachymeningitis, neurological examinations showed right lower cranial palsies and MR images showed lesions along the right temporal bone with T1- and T2 shortening. After injection of the contrast medium, abnormal contrast enhancement was observed in the medial side of the lesions. In the anterior cranial fossa, however, the anterior falx was thick and it showed low signal on T2-weighted images and abnormal contrast enhancement. These findings of the falx indicated that the patient had hypertrophic cranial pachymeningitis. It is important to see lesions which neurological examinations detect. However, all of the images must be seen, because in the distant location, the key findings for the diagnosis may be present.

Central Nervous System↗
PubMed2000

Photoelectron angular distributions from O K shell of oriented CO molecules: A critical comparison between theory and experiment

The dynamical information (ten dipole matrix elements and eight phase differences) has been deduced from the measured angular distributions of photoelectrons from O K shell of oriented CO molecules near the ionization threshold in the region of a sigma(*) shape resonance. Light polarization parallel and perpendicular to the molecular axis has been used. An important contribution of six lsigma partial waves with 0</=l</=5 to the sigma(*) shape resonance is demonstrated. A comparison with our calculations in the relaxed core Hartree-Fock approximation reveals only a qualitative agreement, therefore a more advanced theory is needed.

Journal Article↗
PubMed2000

Manifestation of many-electron correlations in photoionization of the K shell of N2

It is demonstrated theoretically in the random phase approximation (RPA) that due to the intershell many-electron correlations the sigma(*) shape resonance in the photoionization of K shells of the N2 molecule appears not only in the 1sigma(g)-->varepsilonsigma(u) channel as it was believed earlier on the basis of single particle calculations, but in both 1sigma(g)-->varepsilonsigma(u) and 1sigma(u)-->varepsilonsigma(g) channels. As a confirmation of this phenomenon we show that the experimental angular distributions of photoelectrons ejected from fixed-in-space N2 molecules can be reproduced theoretically only after taking into account many-electron correlations.

Journal Article↗
PubMed2000

Cortical dysplasia with ossification.

We present the first case of cortical dysplasia with extensive intracerebral ossification. An eight-year-old epilepsy patient with a calcified lesion was successfully treated by surgical intervention. Pathological examination revealed a number of bizarre dysplastic cells in the whole lesion, which consisted of an epileptogenic cerebral cortex and a nonepileptogenic hamartomatous lesion with adipose tissue, vascular tissue, calcification, and ossification. The patient was diagnosed as having cortical dysplasia with ossification. Our findings support the notion that cortical dysplasia has a multipotentiality of cellular differentiation, including various hamartomatous tissues. We suggest that cortical dysplasia should be considered as a potential cause for epileptogenicity of a hamartomatous lesion even when magnetic resonance imaging (MRI) fails to disclose cortical dysplasia.

Brain Diseases↗
PubMed1999

Cortical tubers without other stigmata of tuberous sclerosis: imaging and pathological findings.

There is immense variability in the clinical presentation of tuberous sclerosis and many incomplete forms (formes frustes) exist. To investigate the imaging characteristics of cortical tubers seen in tuberous sclerosis unaccompanied by other stigmata, we reviewed MRI and CT of six patients who met the criteria for a definitive diagnosis of TS, established solely by the presence of a histologically confirmed cortical tuber. Five of the patients had a solitary cortical tuber and the last had three lesions, one of which was resected and confirmed histologically. The other two lesions were included in our study. CT showed five tubers as low density, but three were not identified. No calcified or dense lesions were observed. MRI revealed peripheral components and inner cores of seven cortical tubers in five patients, with differing signal characteristics. The subcortical cores, with T1 and T2 prolongation, were separated from the overlying cortex. Abnormal inhomogeneous high signal was observed in both the cortex and subcortical white matter on proton-density weighted or FLAIR images. A radially orientated white-matter band was observed in one patient, and central depression of the expanded gyri in another. In one patient, a cortical tuber was atypical, with a thick cortex on T1-weighted images and a blurred grey/white matter junction with diffusely increased signal on T2-weighted images. Cortical tubers without other stigmata of tuberous sclerosis are shown to be distinct from focal cortical dysplasia.

Adolescent↗
PubMed1999

Interictal hyperperfusion observed in infants with cortical dysgenesis.

We investigated increases of interictal regional cerebral blood flow (rCBF) in patients with intractable epilepsy caused by cortical dysgenesis. Using single photon emission computed tomography, we measured interictal rCBF of epileptic foci in 24 patients with cortical dysgenesis who achieved Engel Class I or II outcomes at least 1 year after surgical intervention. The patients included 14 males and ten females, ranging in age from 2 months to 34 years (mean 6 years and 5 months). In the interictal period, dysplastic areas showed hyperperfusion in four patients (17%), hypoperfusion in 15 (62%), and isoperfusion patterns in five (21%). Interictal hyperperfusion was found in four infants aged 3-4 months; three with focal cortical dysplasia and one with hemimegalencephaly. Our results suggest that interictal hyperperfusion may indicate the presence of an active epileptic focus in infants with cortical dysgenesis, but not in older children or adults with the same disorder. Given the risk of misinterpreting the normal side as hypoperfused, the phenomenon of interictal hyperperfusion in the epileptogenic area should be taken into account when diagnosing pediatric epilepsy caused by cortical dysgenesis.

Adolescent↗
PubMed1998

Submicrometre-area high-energy-resolution photoelectron spectroscopy system.

A submicrometre-area photoelectron spectroscopy system that uses a multi-layer-coated Schwarzschild objective as the soft X-ray microbeam optics has been developed. The system is located at an undulator beamline (BL-16U) at the Photon Factory in the High Energy Accelerator Research Organization. By knife-edge measurement, the microbeam size was estimated to be 160 nm at the sample position using a 25-75% criterion. Photoelectron spectral measurements revealed that the Fermi edge width was 0.12 eV, which means that the instrumental resolution was 0.05 eV, after removing the natural broadening of the Fermi edge at room temperature. This system offers both high energy resolution and high spatial resolution.

Journal Article↗
PubMed1998

A compact vacuum-ultraviolet beamline for synchrotron radiation photoelectron spectroscopy combined with an ion-scattering spectrometer, SORIS.

Apparatus for high-resolution synchrotron radiation photoelectron spectroscopy combined with high-resolution medium-energy ion scattering, named 'SORIS', has been developed for simultaneous investigations of electronic states and atomic structures on surfaces. For this purpose, a compact vacuum-ultraviolet beamline of photon energy from 5 to 700 eV has been designed for the small storage ring 'Aurora' installed at Ritsumeikan University. Owing to the small electron-beam size in the storage ring, an energy resolution E/dE of >5000 can be obtained.

Journal Article↗
PubMed1998

Spectrometer for polarized soft X-ray Raman scattering.

An experimental system for polarized soft X-ray Raman scattering spectroscopy has been constructed. The soft X-ray spectrometer is based on the Rowland circle geometry with a holographic spherical grating. Three types of gratings are used to cover the energy range from 18 eV to 1200 eV. According to a ray-trace simulation, the resolution is expected to be 200 meV at 700 eV by using a 10 micro m slit width. The polarized and depolarized soft X-ray Raman scattering spectra can be measured by rotating the soft X-ray spectrometer around the axis of the incident beam. Preliminary measurements of polarized and depolarized spectra were accomplished at undulator beamline BL-2C of the Photon Factory.

Journal Article↗
PubMed1998

High-resolution spherical grating monochromator for the undulator beamline (BL-16B) at the Photon Factory.

The design and performance of a 24 m high-resolution spherical grating monochromator (H-SGM) for the undulator beamline (BL-16B) at the Photon Factory are described. With three interchangeable gratings of 400, 900 and 2000 lines mm(-1), the H-SGM is designed to cover the photon energy range 40-600 eV. With a resolving power of approximately 2000 in the photon energy range 40-530 eV, more than 10(11) photons s(-1) have been measured. The best resolutions obtained so far, at a substantially lower photon flux, are greater than 10 000 at 250 eV and 8000 at 400 eV

Journal Article↗