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Dive into the research topics where Kazuhisa Iwamoto is active.

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Featured researches published by Kazuhisa Iwamoto.


Interventional Neuroradiology | 2011

Outcomes analysis of ruptured distal anterior cerebral artery aneurysms treated by endosaccular embolization and surgical clipping.

Sachio Suzuki; Akira Kurata; Masaru Yamada; Kazuhisa Iwamoto; K. Nakahara; K. Sato; Jun Niki; M. Sasaki; Takao Kitahara; K. Fujii; S. Kan

Although endovascular surgery is now widely used to treat intracranial aneurysms, no comparative studies of clipping versus endovascular surgery to address distal ACA aneurysms at the same institution are available. We compared the results of these treatment modalities to address distal ACA aneurysms at our institution. We treated 68 patients with ruptured distal ACA aneurysms (endovascular surgery, n=13; clipping surgery, n=55). We performed a retrospective comparison of the treatment outcomes. To study the efficacy of endovascular surgery we classified all our cases into three types: type A were small-necked aneurysms, type B were wide-necked aneurysms on the parent artery, and type C were aneurysms in which the A3 portion of the ACA arose from the aneurysmal dome near the neck. Intraoperative hemorrhage occurred in 7.7% of aneurysms treated by endovascular surgery and in 34.5% treated by clipping surgery. In 7.7% of the endovascularly-treated aneurysms we noted coil migration during embolization surgery; venous infarction due to cortical vein injury occurred in 7.3% of clipped aneurysms. Of the endovascularly-treated aneurysms, 7.7% manifested post-embolization hemorrhage; 23.1% manifested coil compaction. In clipping surgery, postoperative rerupture occurred in 1.8% of the aneurysms; one patient presented with postoperative acute epidural hematoma. Clip dislocation was noted in 1.8% of aneurysms. Angiography was indicative of post-treatment vasospasm in 7.7% of aneurysms treated endovascularly and in 50.9% of the clipped aneurysms. The clinical outcome showed no significant difference between endovascular surgery and clipping surgery.


Neuroradiology | 2009

Direct-puncture approach to the extraconal portion of the superior ophthalmic vein for carotid cavernous fistulae

Akira Kurata; Sachio Suzuki; Kazuhisa Iwamoto; Tomoko Miyazaki; Madoka Inukai; Katsutoshi Abe; Jun Niki; Masaru Yamada; Kiyotaka Fujii; S. Kan

IntroductionThe transvenous approach via the superior ophthalmic vein (SOV) is an available approach for carotid cavernous fistula (CCF), especially in the event that there is no other suitable approach route to the fistula. Surgical exposure of the peripheral roots of the SOV is commonly used; however, often, the SOV is often not accessible because of anatomical problems and/or complications. In this paper, we present and discuss our original direct-puncture approach to the extraconal portion of the SOV.MethodsAn attempt on three patients with traumatic CCF failed with the transarterial approach and the conventional venous approach via the inferior petrosal sinus; therefore, the patients were treated with the direct-puncture approach to the extraconal portion of the SOV using two-dimensional digital subtraction angiography with local anesthesia.ResultsAll cases that had tortuous and partially stenotic division of the SOV were treated successfully with this approach and without complications.ConclusionThis approach will become an alternate approach, especially when the peripheral roots of the SOV are focally narrowed and tortuous, making it impossible to insert a catheter.


Journal of Neurosurgery | 2012

A new transvenous approach to the carotid-cavernous sinus via the inferior petrooccipital vein

Akira Kurata; Sachio Suzuki; Kazuhisa Iwamoto; Kuniaki Nakahara; Madoka Inukai; June Niki; Kimitoshi Satou; Masaru Yamada; Kiyotaka Fujii; Shinichi Kan; Toshiro Katsuta

OBJECT The transvenous approach via the inferior petrosal sinus (IPS) is commonly used as the most appropriate for carotid-cavernous fistula (CCF) or cavernous sinus sampling. However, sometimes the IPS is not accessible because of anatomical problems and/or complications, therefore an alternative route is needed. In this paper, the authors present and discuss the utility of a transvenous approach to the cavernous sinus via the inferior petrooccipital vein. METHODS Four patients, 3 with dural CCFs and the other with Cushing disease, in whom endovascular surgical attempts failed using a conventional venous approach via the IPS, underwent a transvenous approach to the cavernous sinus via the inferior petrooccipital vein (IPOV). One dural CCF case had only cortical venous drainage, the second CCF also mainly drained into the cortical vein with slight inflow into the superior ophthalmic vein and inferior ophthalmic vein, and the third demonstrated drainage into the superior and inferior ophthalmic veins and IPOV. RESULTS In all cases, the cavernous sinus could be accessed successfully via this route and without complications. CONCLUSIONS The transvenous approach to the cavernous sinus via the IPOV should be considered as an alternative in cases when use of the IPS is precluded by an anatomical problem and there are no other suitable venous approach routes.


International Scholarly Research Notices | 2011

Dural Arteriovenous Fistulas in the Cavernous Sinus: Clinical Research and Treatment

Akira Kurata; Sachio Suzuki; Kazuhisa Iwamoto; Kuniaki Nakahara; Makoto Sasaki; Chihiro Kijima; Madoka Inukai; Katsutoshi Abe; Jun Niki; Kimitoshi Satou; Kiyotaka Fujii; Shinichi Kan

Introduction. The purpose of this paper is to clarify the clinical course, with the dural carotid cavernous fistula (CCF), featuring a pallet of symptoms, paying special attention to radiological findings. Methods. Seventy-six consecutive patients with dural CCFs were investigated in detail, all of whom were defined by angiography. Results. The most common initial symptom was diplopia in 47 patients (62%) and the most frequently observed on arrival were type II, featuring cranial nerve palsies followed by the classical triad in 27, and then type I only with cranial nerve palsies. The time until admission with type I (mean: 6.7 W ± 6.0) was significantly shorter than that with type II (mean: 25.1 W ± 23.5). Branches from bilateral carotid arteries widely inflowing into bilateral carotid cavernous sinus were present in 30 (39%), 20 (26%) of which also demonstrated direct inflow into the intercavernous sinus. type I and II had more multiple venous drainage routes as compared with type III (classical triad only on arrival) and IV (initial development of the classical triad followed by cranial nerve palsy). Conclusion. In our series of dural CCF patients, the most common initial symptom was cranial nerve palsy, mostly featuring multiple venous drainage including cortical drainage. Such palsies should be added to the classical triad as indicative symptoms. Bilateral carotid arteries often inflow into cavernous and intercavernous sinuses, which should be taken into account in choice of therapeutic strategy.


Brain Tumor Pathology | 2004

Late-onset multiple sclerosis mimicking brain tumor: A case report

Kazuhisa Iwamoto; Hidehiro Oka; Satoshi Utsuki; Tatsuya Ozawa; Kiyotaka Fujii

Multiple sclerosis (MS) is a demyelinating disease that predominantly affects those aged in their twenties to their forties. We recently observed a case of rapidly progressive late-onset MS in an elderly patient with a large, single lesion on magnetic resonance imaging (MRI), which was difficult to distinguish from a brain tumor. This case is reported here with a review of the literature. A 69-year-old woman who presented with left hemiparesis was admitted to our institute. A tumor lesion was strongly suspected from the MRI finding of a large solitary lesion adjacent to the right lateral ventricle. Her left hemiparesis became rapidly worse, so we decided to perform stereotactic biopsy. Histopathological examination indicated that the patient had a demyelinating disease such as multiple sclerosis. Steroid pulse therapy was started after the operation and led to a marked improvement of the symptoms. With follow-up for more than 1 year after discharge, she has shown no sign of relapse. Late-onset MS should be suspected if edema or mass effect is not visualized around the lesion on MRI, bearing in mind that late-onset MS can have a progressive course in elderly patients.


Interventional Neuroradiology | 2007

Efficacy of Endovascular Surgery for Unruptured Internal Carotid Artery Aneurysms Presenting with Cranial Nerve Symptoms

Sachio Suzuki; Akira Kurata; S. Kan; Masaru Yamada; Jun Niki; I. Yuzawa; K. Sato; Kazuhisa Iwamoto; Hidehiro Oka; K. Fujii

Whether endovascular surgery is able to reduce the mass effects of unruptured aneurysms is still controversial, although some reports have suggested efficacy in cases of internal carotid artery aneurysms with cranial nerve palsy. Here we assessed outcome in a series of cases. Between April 1992 and April 2005, 18 patients with unruptured internal carotid artery aneurysms presenting with cranial nerve palsy were treated by endovascular surgery. The patients were two males and 16 females aged from 19 to 84 (mean 59.6 years). Aneurysms were located in the cavernous portion in 14, at the origin of the ophthalmic artery in one and at the origin of P-com in three. The aneurysms were all embolized using Guglielmi detachable coils, Interlocking detachable coils, Cooks detachable coils or Trufill DSC and detachable Balloons were applied to occlude the proximal parent artery. We analyzed the efficacy of endovascular surgery for such aneurysms retrospectively. The mean aneurysm size was 21.4 mm and the mean follow-up period was 57.7 months. Palsy of IInd cranial nerve was evident in three patients, of the IIIrd in eight, of the Vth and Vth in one each, and of the VIth in nine. Post embolization occlusion was complete in nine patients and neck remnant in the other seven. Regarding complications of endovascular surgery, one case (5.6%) showed TIA after embolization. Overall 11 (46%) cranial nerve symptoms showed complete resolution, eight (33%) showed some improvement, and five (21%) were unchanged. In three cases (12.5%), the symptoms worsened after treatment. The shorter the duration of symptoms was a factor predisposing to resolution of symptoms. In complete resolution cases, the timing of treatment after symptoms appeared and the time of complete resolution were in proportion. These results showed that there is no difference in reduction of mass effects between surgical clipping and endovascular surgery for unruptured internal carotid artery aneurysms. With endovascular surgery, the rapidity of treatment after symptoms is the most important factor for successful results.


Journal of NeuroInterventional Surgery | 2012

Efficacy of endovascular surgery for ruptured aneurysms with vasospasm of the parent artery

Akira Kurata; Sachio Suzuki; Kazuhisa Iwamoto; Madoka Inukai; Kuniaki Nakahara; Kimitoshi Satou; June Niki; Makoto Sasaki; Kiyotaka Fujii; Shiichi Kan; Takao Kitahara

Introduction In the presence of vasospasm it is recommended that surgical clipping for a ruptured aneurysm should be delayed until it disappears, but this may be associated with re-rupture of the aneurysm resulting in a poor outcome. The indications for endovascular coil embolization in such cases are discussed. Methods Since November 2002, endovascular coil embolization has been used in 18 consecutive patients with ruptured aneurysm with vasospasm of the parent artery ranging from 2 to 28 days (mean 9 days) after the initial subarachnoid hemorrhage. After successful obliteration of the aneurysm, a microcatheter preceded by a guidewire was introduced into the peripheral vessels with vasospasm of the A2 or M2 portions in order to release the vasospasm mechanically. Results Endovascular procedures were performed successfully in all but one of the cases (94%), resulting in complete occlusion in 14 of 17 patients and mild dilation of the vasospasm in all 17 patients without technical complications or re-rupture of the aneurysm. In the one case of failure because of a tortuous artery, surgical clipping was performed after disappearance of the vasospasm. Cerebral infarction occurred in four patients, but only one correlated with the distribution of catheterization and the neurological deficits had completely disappeared 3 months after the onset. Conclusion Catheterization of parent vessels in cases of vasospasm is safe for coiling and also mechanically releases vasospasm. Vasospasm of M2 and A2 segments can be treated with microcatheterization only.


Interventional Neuroradiology | 2006

New Development of a Dural Arteriovenous Fistula (AVF) of the Superior Sagittal Sinus after Transvenous Embolization of a Left Sigmoid Sinus Dural AVF. Case Report and Review of the Literature.

Akira Kurata; Sachio Suzuki; Kazuhisa Iwamoto; Masaru Yamada; K. Fujii; S. Kan

Transvenous occlusion of an affected sinus has become a standardized curative treatment for dural sinus arteriovenous fistula. A 57-year-old man with a left sigmoid sinus isolated dural AVF was successfully treated with tansarterial followed by transvenous embolization. Follow-up angiography one year and two months thereafter showed complete disappearance of the dural AVF. However, one year later, superior parasagittal sinus dural arteriovenous fistula had newly developed, for which the etiology and a careful point for follow-up are here discussed.


Neurological Research | 2011

Contrast stasis in large and giant internal carotid artery aneurysms as a good prognostic factor for endovascular coil embolization: retrospective study

Sachio Suzuki; Akira Kurata; Masaru Yamada; Kazuhisa Iwamoto; Kuniaki Nakahara; Jun Niki; Kimitoshi Sato; Kiyotaka Fujii; Shinichi Kan

Abstract Objective: Before treatment for large and giant aneurysms, we need some of the predictors to prognose a good result. In this retrospective study, we attempted to determine criteria such as angiographic signs to identify good candidates for effective endovascular surgery. Methods: This study involved 45 patients with large or giant aneurysms treated by endovascular embolization. For angiographic study, we delivered a bolus injection of contrast medium. All aneurysms were confirmed angiographically and the morphology was defined in detail before endovascular embolization. We divided the patients into two groups based on angiographic findings. Group A (n = 16) manifested stasis of the contrast medium in the aneurysm on venous phase. Group B (n = 29) exhibited other findings. We retrospectively evaluated the relationship between stasis of the contrast medium in the aneurysm and results of endovascular embolization. Results and Discussion: There was no significant difference between the two groups with respect to the size of the aneurysm. However, the neck/dome ratio (P = 0·04) and size of the neck (P = 0·003) were significantly different between groups A and B. The morphological outcome was better in group A than group B (P = 0·03). We demonstrate that contrast stasis is a good predictor of outcome in patients with large or giant aneurysms to consider the endovascular embolization. Hemodynamic studies on large patient populations may reveal other factors predictive of a good treatment outcome.


Stroke Research and Treatment | 2012

Altered Hemodynamics Associated with Pathogenesis of the Vertebral Artery Dissecting Aneurysms

Akira Kurata; Sachio Suzuki; Kazuhisa Iwamoto; Kuniaki Nakahara; Katsutoshi Abe; Madoka Inukai; June Niki; Makoto Sasaki; Kiyotaka Fujii; Shingo Konno; Shinichi Kan; Kazuaki Fukasaku

The etiology of the vertebral dissecting aneurysms is largely unknown, and they frequently occurs in relatively healthy young men. Objectives and Methods. A series of 57 consecutive cases defined by angiography were evaluated with regard to deviation in the course of the affected and contralateral vertebral arteries. Division was into 3 types: Type I without any deviation, Type II with mild-to-moderate deviation but not over the midline; and Type III with marked deviation over to the contralateral side beyond the midline. Results. The most frequent type of VA running was Type III for the affected and Type I nonaffected side, with this being found in all 17 patients except one. All of the Type III dissections occurred just proximal to a tortuous portion, while in cases with Type-I- and Type-II-affected sides, the majority (33 of 39) occurred near the union of the vertebral artery. In 10 of 57, a non-dominant side was affected, all except one being of Type I or II. With 12 recent patients assessed angiographically in detail for hemodynamics, eleven patients showed contrast material retrograde inflowing into the pseudolumen from the distal portion of the dissection site. Turbulent blood flow was recognized in all of these patients with retrograde inflow. Conclusions. Turbulent blood flow is one etiology of vertebral artery dissection aneurysms, with the sites in the majority of the cases being just proximal to a tortuous portion or union of vessels. In cases with dissection proximal to the tortuous course of the vertebral artery, retrograde inflow will occur more frequently than antegrade, which should be taken into account in designing therapeutic strategies.

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