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Dive into the research topics where Yasushi Iwamuro is active.

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Featured researches published by Yasushi Iwamuro.


Neurology | 2009

Near-infrared spectroscopy in carotid artery stenting predicts cerebral hyperperfusion syndrome

Shoji Matsumoto; Ichiro Nakahara; Toshio Higashi; Yasushi Iwamuro; Yoshihiko Watanabe; K. Takahashi; M. Ando; Masahiro Takezawa; Jun-ichi Kira

Objective: Cerebral hyperperfusion syndrome (CHS) following carotid artery stenting (CAS) or carotid endarterectomy (CEA) is rare but often fatal once intracranial hemorrhage has occurred. In particular, CHS occurs significantly earlier after CAS than after CEA. Thus a monitoring method for early detection of CHS is required. Near-infrared spectroscopy (NIRS) provides a noninvasive monitoring technique for assessing regional cerebral oxygen saturation (rSO2). This study evaluated the usefulness of transcranial NIRS during CAS for prediction of CHS. Methods: Periprocedural rSO2 was monitored in 64 cases of CAS (52 men, 12 women; 71 ± 6.6 years). The average degree of carotid stenosis was 76.8 ± 11.3% by North American Symptomatic Carotid Endarterectomy Trial criteria. Bifrontal rSO2 was monitored during the procedure using NIRS. Seventeen patients were symptomatic and 47 were asymptomatic. CHS was diagnosed by increased cerebral blood flow by SPECT performed on the day after treatment with deterioration of neurologic symptoms. Results: CHS was observed in two cases (3.1%). In the CHS group, post-reperfusion rSO2 values increased >24% from baseline until 3 minutes after reperfusion. In the non-CHS group, the normal upper limit (NUL) of the rSO2 change was set at 10.0% at 3 minutes after reperfusion. In the CHS group, rSO2 at 3 minutes after reperfusion was markedly higher than the NUL. In patients showing an rSO2 at 3 minutes after reperfusion increased by more than 10.0%, CHS following CAS could be predicted. Conclusion: Periprocedural increases in regional cerebral oxygen saturation measured by near- infrared spectroscopy can be an excellent predictor of cerebral hyperperfusion syndrome after carotid artery stenting.


Neurosurgery | 2010

Intraoperative stenting for brachiocephalic and carotid artery stenosis.

Ichiro Nakahara; Toshio Higashi; Yasushi Iwamuro; Yoshihiko Watanabe; Hideaki Nakagaki; Masahiro Takezawa; Daiki Murata; Mahmoud M. Taha

OBJECTIVEEndovascular stenting is an alternative treatment for brachiocephalic artery stenosis, replacing standard surgical approaches such as carotid endarterectomy. However, a percutaneous approach may be difficult because various conditions such as severe arteriosclerosis of iliac or femoral arteries and aortic disease. We report our experience with intraoperative stenting for these lesions, presenting indications, strategy, and results. METHODSSeven patients underwent intraoperative stent placement via an open cervical approach. The sites of lesions included 1 innominate artery, 1 common carotid artery, and 5 cervical carotid arteries. Stenting was performed with a sheath introducer placed through a surgically exposed common carotid artery via a small skin incision or common carotid artery exposed for simultaneously performed carotid endarterectomy. Distal protection was used in 6 patients with an endovascular protective balloon or external clamping with forceps. RESULTSSufficient dilation of stenosis was obtained in all cases. No complications such as transient ischemic attack, cerebral infarction, and hyperperfusion were encountered. Wound hematoma was not experienced despite perioperative antiplatelet therapy and heparinization during the procedure. Angiographic follow-up over 1 year showed no restenosis in 5 available patients. CONCLUSIONIntraoperative stenting may be an excellent alternative for patients in whom both direct surgical approach and standard percutaneous endovascular approach are not possible.


Cerebrovascular Diseases | 2010

Fibro-fatty volume of culprit lesions in Virtual Histology intravascular ultrasound is associated with the amount of debris during carotid artery stenting.

Shoji Matsumoto; Ichiro Nakahara; Toshio Higashi; Yasushi Iwamuro; Yoshihiko Watanabe; Masahiro Takezawa; Daiki Murata; Tadaaki Yokota; Jun-ichi Kira; Takeshi Yamada

Objectives: This study aimed to evaluate the relationship between the amount of aspirated debris during distal balloon-protected carotid artery stenting (CAS) and the pre-intervention plaque composition, as assessed by Virtual Histology™ (VH) intravascular ultrasound (IVUS). Methods: The study subjects were 25 consecutive patients (mean age, 73.0 ± 5.2 years; 20 males and 5 females) who underwent CAS under distal balloon protection. The average rate of carotid stenosis was 74.6 ± 12.9% by North American Symptomatic Carotid Endarterectomy Trial criteria. We assessed culprit plaque components by VH-IVUS before CAS. Aspirated debris was filtered, stained with HE and mounted onto glass slides. The quantity of debris was evaluated by measuring its surface area. We evaluated the relationship between the quantity of aspirated debris and VH-IVUS measurements before CAS. Results: The amount of debris during CAS was positively correlated with the total plaque volume in grayscale IVUS (Rs = 0.480, p = 0.015) and fibro-fatty volumes over the entire lesion length in VH-IVUS (Rs = 0.561, p = 0.001). Conclusions: Culprit lesions with large plaque volumes, especially larger fibro-fatty volumes, as imaged by VH-IVUS, are associated with large amounts of debris during balloon-protected CAS.


Journal of Clinical Neuroscience | 2009

Angioplasty and stent deployment in acute sinus thrombosis following endovascular treatment of dural arteriovenous fistulae

Eishu Hirata; Toshio Higashi; Yasushi Iwamuro; Yoshihiko Watanabe; Mitsushige Ando; Yoshiki Arakawa; Ichiro Nakahara

We report on the successful treatment of acute sinus thrombosis associated with endovascular treatment of intracranial dural arteriovenous fistulae (DAVF) by sinus angioplasty with stent deployment. A 76-year-old man presented with intracerebral hemorrhage, Cognard type IIa+b DAVF of the left sigmoid sinus, and type IIa DAVF of the torcular herophili. During transvenous sinus embolization, acute thrombosis of the stenotic lesion in the left transverse sinus occurred. The thrombosis caused isolated sinus and cortical venous reflux (CVR). The patient was treated by stent-supported sinus angioplasty, which led to an immediate improvement of the sinus thrombosis and associated CVR.


Journal of Neuro-oncology | 2006

Chondrosarcoma of the clivus presenting with intratumoral hemorrhage: case report.

Kei Harada; Ichiro Nakahara; Junya Hayashi; Masato Tanaka; Yasuhiko Akiyama; Yasushi Iwamuro; Motoaki Fujimoto

Intracranial hemorrhage from chondrosarcoma of the skull base is uncommon; only one case has been reported to date [1]. We describe a case of clival condrosarcoma presenting with intratumoral hemorrhage. This 23-year-old man suddenly presented with severe headache. Two hours after onset, the patient lost conscious and became comatose. Computed tomography revealed a clival tumor, intratumoral hemorrhage, subarachnoid hemorrhage, and ventricle dilatation (Figure 1). Emergency angiography showed an avascular tumor with no evidence of aneurysm or hypervascularity. External ventricular drainage was performed on the day of admission, and the patient gradually regained consciousness. A venticulo-peritoneal shunt placement was performed. Two months after onset, the patient maintained awaking but suffered mild disorientation, right abducens nerve palsy, right facial nerve palsy, right-sided deafness, swallowing disturbance, and mild tetraparesis. Surgery for tumor reduction and diagnosis was planned. Preoperative magnetic resonance (MR) images showed a clival tumor adhered to brainstem (Figure 2) and angiography showed avascular. Preoperatively, the most likely diagnosis was chordoma. Three months after onset, the tumor was resected via combined right subtemporal and presigmoid transpetrosal approach. The tumor had a grayish gelatinous component and a calcific bone-like component. Little bleeding occurred during resection. The dura, which should overlay the clivus, was indistinct, and the dura and subarachnoid membrane were disrupted, and partially defected. The tumor adhered to the basilar artery, right superior cerebellar artery, basilar perforator artery, and brainstem. To avoid injury to the brain and arteries, we did not remove the tumor in the area of strong adhesion. Upon histologic examination, a mix of cartilaginous matrix and mucous matrix was observed. Cellularity was mild, consisting of neoplastic chondrocytes showing a mild degree of nuclear pleomorphism. No mitotic figures were identified. Vascularity was poor, and there was no evidence of microscopic hematoma, necrosis, or thrombus in tumor vessels. Physaliferous cells, which are typical in chordoma, were not seen (Figure 3). Immunohistochemically, the tumor stained positively for S-100 protein and vimentin and negatively for epithelial membrane antigen (EMA) and cytokeratin. Grade I chondrosarcoma was diagnosed. The patient had an uneventful recovery with no decline of preoperative neurological deficits. The residual tumor was treated with gamma knife radiosurgery one month after the resection. MR images obtained 42 months after the radiosurgery showed no tumor regrowth. He has regained full consciousness and has mild left hemiparesis, right abducens nerve palsy, right facial palsy, and right-sided deafness. It is important to distinguish chondrosarcoma from chordoma because the prognosis of the former is better


Surgical Neurology | 2006

Endovascular embolization vs surgical clipping in treatment of cerebral aneurysms: morbidity and mortality with short-term outcome

Mahmoud M. Taha; Ichiro Nakahara; Toshio Higashi; Yasushi Iwamuro; Mitsutoshi Iwaasa; Yoshihiko Watanabe; Kenzo Tsunetoshi; Toshihiro Munemitsu


Surgical Neurology | 2006

Different modalities of treatment of intracranial mycotic aneurysms: report of 4 cases

Ichiro Nakahara; Mahmoud M. Taha; Toshio Higashi; Yasushi Iwamuro; Mitsutoshi Iwaasa; Yoshihiko Watanabe; Kenzo Tsunetoshi; Toshihiro Munemitsu


Surgical Neurology | 2006

Tentorial dural arteriovenous fistula presenting symptoms due to mass effect on the dilated draining vein: case report

Yasushi Iwamuro; Ichiro Nakahara; Toshio Higashi; Mitsutoshi Iwaasa; Yoshihiko Watanabe; Eishu Hirata; Kenzo Tsunetoshi; Mahmoud Taha


Journal of Trauma-injury Infection and Critical Care | 2005

Urgent endovascular stent-graft placement for a ruptured traumatic pseudoaneurysm of the extracranial carotid artery.

Yasuhiko Akiyama; Ichiro Nakahara; Masahito Tanaka; Yasushi Iwamuro; Junya Hayashi; Kei Harada; Motoaki Fujimoto


Neurologia Medico-chirurgica | 2005

Occlusion of the vertebral artery secondary to dissection of the subclavian artery: Case report

Yasushi Iwamuro; Ichiro Nakahara; Masato Tanaka; Toshio Higashi; Yoshihiko Watanabe; Kei Harada; Motoaki Fujimoto; Takayuki Oku

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Ichiro Nakahara

Memorial Hospital of South Bend

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Yoshihiko Watanabe

Memorial Hospital of South Bend

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Masahiro Takezawa

Memorial Hospital of South Bend

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Daiki Murata

Memorial Hospital of South Bend

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Kei Harada

Memorial Hospital of South Bend

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Kenzo Tsunetoshi

Memorial Hospital of South Bend

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Mitsutoshi Iwaasa

Memorial Hospital of South Bend

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Shoji Matsumoto

Memorial Hospital of South Bend

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