Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Masaki Komiyama is active.

Publication


Featured researches published by Masaki Komiyama.


Neurosurgery | 1993

Aneurysmal rupture during angiography.

Masaki Komiyama; Katsuhiko Tamura; Yasunori Nagata; Yoshihiko Fu; Hisatsugu Yagura; Toshihiro Yasui

The aim of the present study was to analyze the clinical data on rebleeding in cerebral aneurysms during angiography and to evaluate the importance of the time interval between the latest rupture and angiography. Fourteen personal cases and 202 patients reported in the literature are reviewed. Rebleeding during angiography occurred most often (78%) on Day O; 89% bled when angiography was performed within 6 hours of the latest rupture. The prognosis in such ruptures was poor, with a mortality of 79%. Intentional delay in angiography of at least 6 hours from the latest rupture is recommended if the associated hematoma is not large.


Neurosurgery | 1998

Moyamoya disease and pregnancy: case report and review of the literature.

Masaki Komiyama; Toshihiro Yasui; Shouhei Kitano; Hiroaki Sakamoto; Ken Fujitani; Shigeki Matsuo

OBJECTIVE AND IMPORTANCE Many female patients with moyamoya disease are of childbearing years, including those who were diagnosed before entering their childbearing years. However, there have been no extensive reviews of the management of pregnancy and delivery in association with moyamoya disease. The purpose of this report is to describe the case of a patient with moyamoya disease complicated by pregnancy and to review the literature on other such cases. CLINICAL PRESENTATION AND INTERVENTION We report a 23-year-old primipara with moyamoya disease who delivered uneventfully by cesarean section under spinal anesthesia at 38 weeks of gestation. In the literature, 30 cases were reported of patients who had been diagnosed with moyamoya disease before pregnancy and delivery, and 23 patients who were symptomatic and were diagnosed for the first time with moyamoya disease in association with pregnancy. CONCLUSION There is no evidence that pregnancy increases the risk of cerebrovascular accident or that bypass surgery decreases its risk. Poor prognosis of the patient or the newborn is mostly caused by cerebral hemorrhage and not by cerebral ischemia. It is important to control blood pressure and especially to avoid toxemia during pregnancy. Either cesarean section or vaginal delivery can be accomplished safely. Any anesthetic method can be used, provided special attention is given to avoiding hypocapnia, hypotension, and hypertension. Oral contraceptives should be avoided.


Surgical Neurology | 1999

Gamma knife surgery for skull base meningiomas: The effectiveness of low-dose treatment

Yoshiyasu Iwai; Kazuhiro Yamanaka; Toshihiro Yasui; Masaki Komiyama; Misao Nishikawa; Hideki Nakajima; Hiroshige Kishi

BACKGROUND The surgical removal of skull base meningiomas has a high morbidity rate, even by modern microsurgical standards. We evaluated the results of gamma knife surgery for skull base meningiomas using a relatively low radiation dose for the tumor margins. METHODS We reviewed 24 cases of skull base meningiomas during a 30-month period. The locations of the tumors were the petroclival region in 11 cases, the cavernous sinus region in 9 cases, and the cerebellopontine angle region in 4 cases. Eight patients (33%) had been operated on previously and fourteen patients (67%) had been treated by neuroimaging. The marginal doses for the tumors were 8 Gy to 15 Gy (median, 10.6 Gy). A large petroclival tumor 58 mm in diameter was treated with a staged treatment protocol with a 6-month interval between treatments. RESULTS Tumor regression was observed in 46% of the patients imaged during the follow-up period (median, 17.1 months). No patients revealed tumor growth in the follow-up period (100% tumor control rate). Eleven patients (46%) had improved clinically by the time of the follow-up examinations. Preexisting cranial nerve deficit in one patient worsened because of radiation injury. CONCLUSION Although a longer follow-up period is required, the relatively low minimum tumor radiation dose treatment for skull base meningiomas using a gamma knife seems to be an effective treatment with low morbidity.


Neuroradiology | 1998

Serial MR observation of cortical laminar necrosis caused by brain infarction

Masaki Komiyama; H. Nakajima; M. Nishikawa; T. Yasui

Abstract To examine the chronological changes characteristic of cortical laminar necrosis caused by brain infarction, 16 patients were repeatedly examined using T1-, T2-weighted spin-echo, T2*-weighted gradient echo, fluid attenuated inversion recovery (FLAIR) images, and contrast enhanced T1-weighted images at 1.0 or 1.5 T. High intensity cortical lesions were visible on the T1-weighted images from 2 weeks after ictus and became prominent at 1 to 3 months, then became less apparent, but occasionally remained at high intensity for 2 years. High intensity cortical lesions on FLAIR images became prominent from 1 month, and then became less prominent from 1 year, but occasionally remained at high intensity for 2 years. Subcortical lesions did not display high intensity on T1-weighted images at any stage. On FLAIR images, subcortical lesions initially showed slightly high intensity and then low intensity from 6 months due to encephalomalacia. Cortical lesions showed prominent contrast enhancement from 2 weeks to 3 months, but subcortical lesions were prominent from 2 weeks only up to 1 month. T2*-weighted images disclosed haemosiderin in 3 of 7 patients, but there was no correlation with cortical short T1 lesions. Cortical laminar necrosis showed characteristic chronological signal changes on T1-weighted images and FLAIR images. Cortical short T1 lesions were found not to be caused by haemorrhagic infarction.


World Neurosurgery | 2011

Determinants of Poor Outcome After Aneurysmal Subarachnoid Hemorrhage when both Clipping and Coiling Are Available: Prospective Registry of Subarachnoid Aneurysms Treatment (PRESAT) in Japan

Waro Taki; Nobuyuki Sakai; Hidenori Suzuki; Akio Hyodo; Shigeru Nemoto; Toshio Hyogo; Tomoaki Terada; K Satoh; Naoya Kuwayama; Shigeru Miyachi; Masaki Komiyama; Masayuki Ezura; Yuichi Murayama; Hiroshi Sakaida; Masayuki Maeda; H Nagai; T Kataoka; S Ishihara; Y Koguchi; S. Kobayashi; Y Enomoto; K Yamada; Shinichi Yoshimura; Yasushi Matsumoto; Masaru Hirohata; H Adachi; Y Ueno; T Kunieda; Chiaki Sakai; H Yamagami

OBJECTIVE To examine current determinants of poor outcome after aneurysmal subarachnoid hemorrhage (SAH) when ruptured aneurysms are treated with either microsurgery (clipping) or endovascular treatment (coiling) depending on each patients characteristics. METHODS Between March 2006 and February 2007, 534 patients with SAH were enrolled in the Prospective Registry of Subarachnoid Aneurysms Treatment (PRESAT) project. Patients were treated according to the preference of investigators who were experienced in performing both clipping and coiling. Factors influencing poor outcome (12-month modified Rankin Scale [mRS], 3-6) were determined using multivariate logistic regression analyses. RESULTS In this cohort, 32.4% of patients were World Federation of Neurosurgical Societies (WFNS) grade IV-V, and 28.1% had a poor outcome. Clipping was preferably performed for small aneurysms with a wide neck and for middle cerebral artery (MCA) aneurysms, whereas coiling was preferred for larger, internal carotid artery (ICA) and posterior circulation aneurysms. In addition to increasing age, admission WFNS grade IV-V, preadmission aneurysmal rerupture, vasospasm-induced cerebral infarct, pneumonia, sepsis, shunt-dependent hydrocephalus and seizure, postclipping hemorrhagic complications (odds ratio 4.8, 95% confidence interval 1.5-15.3, P < 0.01), and postcoiling ischemic complications (odds ratio 4.4, 95% confidence interval 1.3-15.2, P < 0.05) significantly caused poor outcomes, although the complications did not affect mortality. Type of treatment modality and size and location of aneurysms did not influence outcome. CONCLUSIONS Introducing an endovascular treatment option has made aneurysm characteristics less important to outcome, but procedural complications are problematic and should be reduced to improve outcome.


Neurosurgery | 1998

Bilateral Dissecting Aneurysms of the Vertebral Arteries Resulting in Subarachnoid Hemorrhage: Case Report

Toshihiro Yasui; Hiroaki Sakamoto; Hiroshige Kishi; Masaki Komiyama; Yoshiyasu Iwai; Kazuhiro Yamanaka; Misao Nishikawa

OBJECTIVE AND IMPORTANCE We present the case of a patient with bilateral dissecting aneurysms of the vertebral arteries resulting in subarachnoid hemorrhage. CLINICAL PRESENTATION A 44-year-old man suffered a sudden onset of severe occipital headache and nausea and then dysphasia caused by subarachnoid hemorrhage. A computed tomographic scan demonstrated right side dominant subarachnoid hemorrhage mainly in the posterior fossa. Angiography revealed bilateral, vertebral dissecting aneurysms. The right aneurysm was larger and had a bleb-like protrusion, which strongly suggested a causative lesion of the subarachnoid hemorrhage. Six months later, the patient was referred to our hospital for further evaluation and treatment. INTERVENTION The ruptured right aneurysm was trapped surgically through a lateral suboccipital approach. The patients postoperative course was unremarkable, and he was discharged on the 14th day after surgery. However, postoperative angiography demonstrated slight enlargement of the left nonruptured aneurysm. Four months after surgery, the patient developed brain stem ischemic symptoms. The angiography conducted at that time showed further enlargement of the left aneurysm. Five months after surgery, fatal rupture of the left aneurysm occurred. CONCLUSION These results indicate that sacrifice of the unilateral vertebral artery may result in an enlargement of the contralateral nonruptured aneurysm and may thus be dangerous in the case of a patient with bilateral dissecting aneurysms.


European Neurology | 1993

Dural arteriovenous fistula : a cause of hypoperfusion-induced intellectual impairment

Nobutsugu Hirono; Atsushi Yamadori; Masaki Komiyama

A 76-year-old, right-handed man developed posttraumatic dural arteriovenous fistula (DAVF) involving the superior sagittal sinus. He developed slow but progressive intellectual deterioration and gait disturbance after a minimal head trauma. Cerebral angiography demonstrated a DAVF of the superior sagittal sinus with sinus thrombosis supplied by branches of the bilateral external carotid arteries, and a DAVF of the right sigmoid sinus supplied by the right occipital artery. Selective embolization was carried out. He showed marked improvement on neuropsychological testing, especially on test items which are supposed to tap functions of the right cerebral hemisphere which showed an improved cerebral blood flow. We concluded that the intellectual impairment of our patient was caused by cerebral hypoperfusion, especially of the right cerebral hemisphere.


Journal of Trauma-injury Infection and Critical Care | 1998

Endovascular Treatment of Intractable Oronasal Bleeding Associated with Severe Craniofacial Injury

Masaki Komiyama; Misao Nishikawa; Masanori Kan; Tatsuhiro Shigemoto; Arito Kaji

BACKGROUND Severe craniofacial injury may cause intractable oronasal bleeding, which is refractory to conventional treatments. This study will evaluate the efficacy of endovascular treatment for such oronasal bleeding. METHODS Nine males between the ages of 19 and 62 years who had intractable oronasal bleeding resulting from severe craniofacial injuries received treatments of transarterial embolization using Gelfoam pledgets, polyvinyl alcohol particles, or platinum coils. We then reviewed their clinical and neuroradiologic characteristics retrospectively. RESULTS In all but one case, angiography demonstrated bleeding points as extravasation. These bleeding points were multiple in seven cases. Except for bleeding from ethmoidal arteries, selective embolization was successful. In all cases, intractable oronasal bleeding was controlled. Patient survival was not directly related to oronasal bleeding, but rather was strongly correlated with associated brain injuries. CONCLUSION Endovascular treatment is an acceptable treatment for intractable oronasal bleeding associated with severe craniofacial injuries when conventional treatments have failed.


Pediatric Neurosurgery | 2000

Basal Meningoencephalocele, Anomaly of Optic Disc and Panhypopituitarism in Association with Moyamoya Disease

Masaki Komiyama; Toshihiro Yasui; Hiroaki Sakamoto; Keinosuke Fujita; Toshihiko Sato; Mariko Ota; Masahiko Sugita

Basal meningoencephalocele is frequently associated with midfacial anomaly, optic disc anomaly, brain anomaly, cerebrospinal fluid rhinorrhea, chiasma syndrome, and endocrinologic disturbance. The combination of basal meningoencephalocele and moyamoya disease is extremely rare. A 29-year-old man had basal meningoencephalocele (transsphenoidal type), anomaly of the optic disc (morning glory syndrome), panhypopituitarism and moyamoya disease. The patient was treated by hormone replacement, but surgical intervention was not required. Basal meningoencephalocele and moyamoya disease are a possible combination of the diseases.


Neuroradiology | 1995

Simultaneous bleeding from multiple lenticulostriate arteries in hypertensive intracerebral haemorrhage

Masaki Komiyama; T. Yasui; K. Tamura; Yasunori Nagata; Yoshihiko Fu; Hisatsugu Yagura

Angiography within 1 h of the onset of an intracerebral haematoma in a hypertension man showed active bleeding from at least two lenticulostriate arteries. We discuss the pathophysiological significance of this finding.

Collaboration


Dive into the Masaki Komiyama's collaboration.

Top Co-Authors

Avatar

Toshihiro Yasui

Memorial Hospital of South Bend

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Yoshihiko Fu

Memorial Hospital of South Bend

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Hisatsugu Yagura

Memorial Hospital of South Bend

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Mitsuru Baba

Memorial Hospital of South Bend

View shared research outputs
Researchain Logo
Decentralizing Knowledge