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H Okudera

Publications and source records attributed to H Okudera.

At least 19 recordsLinked to original sources
PubMed2004

Ionic pair complexes with well-separated columnar stack structure based on [Pt(mnt)2]- ions showing unusual magnetic transition: syntheses, crystal structures, and magnetic properties.

Three ion pair complexes, [4-R-benzylpyridinium][bis(maleodinitriledithiolato)platinum(III)] (abbreviated as [RBzPy][Pt(mnt)(2)]; R = Cl (1), Br (2), or NO(2) (3)), have been synthesized. The cations and anions stack into well-separated columns in the solid state, and the Pt(III) ions form a 1-D zigzag chain within a [Pt(mnt)(2)](-) column through Pt...S, S...S, and Pt...S...Pt interactions. The chain is uniform in 1 and 2, while it alternates in 3. Unusual magnetic phase transitions from paramagnetism to diamagnetism were observed in these three complexes at approximately 275 K for 1, approximately 269 K for 2, and approximately 184 K for 3. These phase transitions were also found in DSC measurements for 1 and 2. The overall magnetic behaviors for 1-3 indicate the presence of antiferromagnetic exchange interactions in the high-temperature phase and spin-gapped systems in the low-temperature phase. Below 50 K, 2 exhibits weak ferromagnetism. The spontaneous moments are nearly repressed by a field of 1.0 T. The crystal structure of 2 at 173 K reveals that there are two crystallographically independent [Pt(mnt)(2)](-) entries in an asymmetric unit. These two crystallographically independent [Pt(mnt)(2)](-) entries satisfy the spin-canting condition, and the EPR spectra measured at room temperature exhibit anisotropic character. Therefore, the weak ferromagnetic behavior in the low-temperature region for 2 can be attributed to the spin-canting phenomenon.

Journal Article↗
PubMed2001

Specific characteristics and management strategies of cerebral artery aneurysms: report of eleven cases.

Owing to the deep location of the posterior cerebral artery (PCA) and its close relationship with the brainstem and surrounding vital structures, surgical treatment of aneurysms in this region is complex. This study was undertaken in an attempt to better delineate the surgical risks of PCA aneurysms. A retrospective analysis was undertaken in 11 patients with PCA aneurysm surgically treated between 1988 and 1996 at Shinshu University and its affiliated hospitals. Data regarding surgical strategy, surgical complications and outcomes were analysed. Seven aneurysms were saccular (including one mycotic) and the other four were fusiform, dissecting, thrombosed and an infundibular dilatation. The locations of the aneurysms were at the P1 segment in two patients, P1-P2 junction in two, P2 segment in six and P3 segment in one. Six saccular non-mycotic aneurysms were treated with neck clipping and the other five aneurysms were treated each with proximal occlusion of the parent artery, excision of the aneurysm or wrapping. All aneurysms were satisfactorily exposed except one large saccular aneurysm. Surgical outcomes were either good recovery or moderate disability in 10 patients, and severe disability in one patient with a large aneurysm due to temporal lobe contusion. In conclusion it is the responsibility of the surgeon dealing with rare PCA aneurysms to be aware of these specific characteristics and to appreciate which surgical technique is appropriate for each patient.

Adult↗
PubMed2001

Remission of hemifacial spasm after proximal occlusion of vertebrobasilar dissecting aneurysm with coils: case report.

Intracranial aneurysm is a rare cause of hemifacial spasm and most of the previously reported cases are treated with surgical microvascular decompression. Authors report a case of hemifacial spasm caused by a dissecting aneurysm located at the vertebrobasilar junction which improved after endovascular obliteration of the affected vertebral artery with coils. The patient was a 69-year-old man with 20 months' history of left hemifacial spasm. A vertebral angiogram showed an irregular dilatation of the right vertebral artery associated with aneurysmal dilatation at the vertebrobasilar junction. Endovascular obliteration of the abnormally dilated right vertebral artery proximal to the vertebrobasilar junction was performed. The hemifacial spasm gradually improved after the embolisation and disappeared 6 months later. Endovascular proximal obliteration of the vertebral artery may have changed the hemodynamic force inside the aneurysm and eliminated the vascular compression at the root exit zone of the facial nerve.

Aged↗
PubMed2001

Pineal cavernous angioma presenting with Parkinsonism.

Cavernous angioma of the pineal region is rare, as is brain tumour coincident with Parkinsonism. The authors describe the case of a 55 year old woman with a pineal region cavernous angioma, who subsequently developed Parkinsonism after her increased intracranial pressure was relieved. The cause of Parkinsonian syndrome is unclear, but compression of the posterior thalamus and upper mid-brain with congestion of the deep venous system may have caused vascular disturbance of the nigro-striate-pallidal system. Her symptoms gradually improved after total excision of the lesion.

Female↗
PubMed2001

Isocentric head fixation for microscopic neurosurgery.

The significance of isocentering in head fixation during micro-neurosurgery is described. The approach angle to the lesion could be changeable without adjusting the focus and placement of the operating microscope by rotating the head holder when the lesion is fixed at the isocenter of the rotatable.

Head↗
PubMed2001

Skull base techniques for multiple aneurysms in the internal carotid juxta-dural ring region.

The aneurysm located in the internal carotid juxta-dural ring region is difficult to surgically obliterate. At surgery, careful drilling of the anterior clinoid process is mandatory, especially when a laterally projecting aneurysm protrudes to or inside the anterior clinoid process.In this paper, treatment procedures using the skull base techniques with intravascular coil embolisation are described by showing a case.

Carotid Artery, Internal↗
PubMed2001

How to make a three-dimensional surgical illustration of cerebral vessels with a personal computer: technical note.

OBJECTIVE: To introduce a method of making three-dimensional (3-D) illustrations of cerebral vessels with a personal computer. METHODS: We generated the 3-D images from only two views of conventional angiograms (anteroposterior and lateral views) with a personal computer, two commercial software programs, and an image scanner. RESULTS: This method was applied to 10 consecutive cases of cerebral aneurysms. 3-D images were made in a few hours, and they contributed to assessing vascular structures of an aneurysm complex. CONCLUSION: This method is useful for discussing surgical strategies preoperatively. Our method may be used in any facility where conventional angiography, personal computers, and 3-D software are available.

Cerebral Angiography↗
PubMed2000

Computer generated microsurgical anatomy of the supraclinoid portion of the internal carotid artery.

In this article we demonstrate a computer graphics model to represent the microsurgical anatomy of the supraclinoid portion of the internal carotid artery (ICA). The source of the input data is a variety of publications showing the detailed anatomy of the area. A computer graphics model of the supraclinoid portion of the ICA and relevant structures including perforators and cranial nerves was made under full colour shading using a Z-buffer algorithm. Complicated microstructures including perforators or cranial nerves are depicted in detail, and can be rotated and viewed from any direction, and thus allows understanding of the three-dimensional relations of the area. Using our method, it may be possible to represent more complicated models of various anatomies, and this methodological tool would be useful for teaching surgical microanatomy and pathology and in pre-surgical operative planning and preparation of the surgeon, introducing a new style navigational system for open microneurosurgery.

Carotid Artery, Internal↗
PubMed2000

Strategic embolisation for successful resection of a large cerebral arteriovenous malformation.

The risks accompanied by the treatment of cerebral arteriovenous malformation (AVM) are still cumulative despite recent progress in available treatment options. Pre-operative embolisation is one such option, however, it seldom makes the surgical resection difficult. The excessive embolised nidus makes the surgical resection difficult because it cannot be compressed during the resection surgery and embolised nidus as a 'glue ball' with marginal hypervascular territory is most difficult to remove. The aim of pre-operative embolisation for successful surgical resection is to put glue into the marginal part of the nidus so as to make a cleavage between the surrounding normal tissues. Remaining feedings via the dilatated leptomeningeal anastomoses from surrounding normal cortical arteries do not interfere with the resection and can be eliminated easily by coagulating the pia matter around the nidus. Strategic planning with regard to the systemic course of treatment, including the manner of resection, is important for effective pre-operative embolisation.

Adult↗
PubMed2000

Intraoperative angiography for emergency cerebrovascular surgery using an exclusively developed radiolucent Sugita head frame and fixation.

Intraoperative angiography during emergency cerebrovascular surgery, clipping operation for acute aneurysmal subarachnoid hemorrhage, is reported. For acquisition of intraoperative angiography, an exclusively developed radiolucent version of a Sugita head frame, made of engineering plastics for angiography, and an ordinary fluoroscopic unit were installed. In a radiolucent head frame, all the parts of the ordinary metallic Sugita multipurpose head frame, fixation and its accessories were made of high-molecular polymer plastics in the same size. In emergency cerebrovascular surgery, the radiolucent Sugita frame enabled us to carry out meticulous dissection and precise retraction control as the ordinary metallic system and to perform the intraoperative angiography if needed.

Cerebral Angiography↗
PubMed1999

Endovascular treatment of basilar trunk aneurysm associated with fenestration of the basilar artery.

Basilar trunk saccular aneurysms associated with fenestration are infrequent, especially in the middle or distal portion of the basilar artery. Surgical treatment of the basilar trunk aneurysm is difficult, due to its anatomical environment and the complicated surgical exposure. A 46-year-old woman presenting with Hunt and Kosnik grade II subarachnoid hemorrhage was found to have a ruptured aneurysm arising at the proximal corner of the associated fenestration in the middle portion of the basilar artery. Because of surgical difficulties anticipated in approaching the aneurysm, it was decided to treat it with endovascular embolization utilizing the Guglielmi detachable coil; and complete occlusion of the aneurysm was obtained. The efficacy of endovascular treatment for the basilar trunk aneurysm with associated fenestration is discussed from anatomical and embryological points of view, and relevant literature is reviewed.

Basilar Artery↗
PubMed1999

Ventriculocisternal drainage via endoscopic third ventriculostomy after endovascular embolization for aneurysmal subarachnoid haemorrhage.

Coil embolization is a favoured method of treating acutely ruptured aneurysms. However, subarachnoid clots cannot be removed with endovascular treatment, which is disadvantageous from the view point of preventing vasospasm. The authors report intrathecal fibrinolytic therapy via a ventricular drainage tube instituted after endoscopic third ventriculostomy for effective prevention of vasospasm after coil embolization. Two cases of poor grade aneurysmal subarachnoid haemorrhage were treated with interlocking detachable coils. Following the acute stage embolization, endoscopic third ventriculostomy was performed and a drainage tube was inserted into a lateral ventricle or basal cistern. Intrathecal fibrinolytic therapy with Urokinase was performed via the drain tube to a spinal drain. In both cases, the subarachnoid clot disappeared rapidly without any clinical signs of vasospasm. Copyright 1999 Harcourt Publishers Ltd.

Journal Article↗
PubMed1999

Computer-generated surgical simulation of morphological changes in microstructures: concepts of "virtual retractor." Technical note.

The authors' goal was to develop a computer graphics model to simulate the displacement and morphological changes that are caused by the retraction of fine intracranial structures. The authors developed an application program to interpolate the contour of models of an artery and a retractor. The center of the displacement was determined by spatial coordinates, and the shape of the displacement of the arterial model was calculated using a cosine-based formula with representation of a brain retractor. This computer graphics model was applied to the simulation of the displacement and morphological changes that occur when retraction is performed in the optic nerve. An illustrative case is presented, in which the optic nerve was displaced by a retractor to simulate the surgery performed in a carotid cave aneurysm of the internal carotid artery. The authors have named this methodological tool a "virtual retractor." This new navigational system for open microneurosurgery would be useful in teaching surgical microanatomy and in presurgical operative planning.

Algorithms↗
PubMed1999

Computer-generated microsurgical anatomy of the basilar artery bifurcation. Technical note.

The authors' goal was to develop a computer graphics model to represent the microsurgical anatomy of the basilar artery (BA) bifurcation and surrounding structures to simulate surgery of a BA bifurcation aneurysm performed via the transsylvian approach. The source of the input data was a variety of publications that showed detailed anatomy of the area. A computer graphics model of the area near the BA bifurcation including relevant structures, such as perforating branches or cranial nerves, was depicted in detail. A BA bifurcation aneurysm was added to the computer graphics model and it was rotated to simulate the transsylvian approach. After the internal carotid artery was displaced using a virtual retractor, the aneurysm was exposed, thus providing an understanding of the three-dimensional surgical orientation of the area. Designing a standard anatomical model on the basis of data culled from a variety of publications and adding morphological changes by using a virtual retractor to displace structures that obstruct the view along a critical path at the base of the brain are useful strategies of computer manipulation for surgical simulation in open microneurosurgery. This methodological tool would be useful in teaching surgical microanatomy and in introducing a new navigational system for virtual reality. Both concept and technical details are discussed.

Basilar Artery↗
PubMed1998

Monitoring of cerebral hemodynamics using near-infrared spectroscopy during local intraarterial thrombolysis: case report.

BACKGROUND: The efficacy of continuous measuring of changes in regional cerebrovascular hemoglobin saturation during local intraarterial thrombolytic therapy for middle cerebral artery (MCA) occlusion is discussed. METHODS: To obtain real-time data on changing cerebral hemodynamics, near-infrared spectroscopy (NIRS) was used during recanalization of an occluded MCA branch. Changes in regional cerebrovascular hemoglobin saturation of the affected left frontal lobe were observed immediately after intraarterial injection of urokinase (UK). RESULTS: A steady increase in regional oxygen saturation (rSO2) was observed until recanalization was confirmed angiographically as a result of 300,000 IU of UK. CONCLUSIONS: Monitoring of cerebrovascular hemoglobin saturation by NIRS is a simple, noninvasive technique suggesting its potential for intraoperative monitoring during interventional neuroradiologic procedures.

Aged↗
PubMed1998

Computer-generated microsurgical anatomy of the paraclinoid area.

To represent multiple microstructures, including perforators, dura, and cranial nerves, and to allow understanding of the three-dimensional relations of the paraclinoid area, we made a computer graphics model. The source of the input data is a variety of publications showing the detailed anatomy of the paraclinoid area. To produce the model, we traced such data, input selected points for each structure, smoothed the lines with a spline program, and added depth using wire-framing and color alterations. The computer graphic model of the paraclinoid area showing perforators, dural ring, optic nerve, and so forth, was made using a paint method for hidden line removal. It can be rotated and viewed from any direction and thus allows understanding of the relations of the area. Using our method, it may be possible to obtain a more detailed model of various anatomies including the skull base, and such data would be useful for preoperative simulation to understand relative regional relations for a specific case and as a new navigational system for open microneurosurgery. Concepts and technical details of the method are described.

Journal Article↗