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Susumu Miyamoto, Haruhiko Kikuchi, Jun Karasawa and Yoshihiro Kuriyama

✓ A case of spontaneous carotid artery dissection is presented. In the case described, superficial temporal artery-middle cerebral artery anastomosis was performed because of impending stroke. Surgical revascularization is indicated in a case that shows such a rapid evolution of stroke that spontaneous resolution of the dissection cannot be awaited.

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Jun Karasawa, Hajime Touho, Hideyuki Ohnishi, Susumu Miyamoto and Haruhiko Kikuchi

✓ Between January, 1986, and October, 1990, 30 children with moyamoya disease, aged from 2 to 17 years, underwent omental transplantation to either the anterior or the posterior cerebral artery territory. The mean follow-up period was 3.8 years, ranging from 1.6 to 6.4 years. Seventeen patients had symptoms of monoparesis, paraparesis, and/or urinary incontinence and were treated using unilateral or bilateral omental transplantation to the anterior cerebral artery territory. Eleven patients had visual symptoms and were treated with unilateral or bilateral omental transplantation to the posterior cerebral artery territory.

Two patients had symptoms associated with both the anterior and the posterior cerebral arteries, and were treated with dual omental transplantations. All 19 patients treated with omental transplantation to the anterior cerebral artery and 11 (84.6%) of the 13 treated with omental transplantation to the posterior cerebral artery showed improvement in their neurological state. Patients with more collateral vessels via the omentum had more rapid and complete improvement in their neurological state. Patients with severe preoperative neurological deficits associated with the posterior cerebral artery had persistence of their symptoms.

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Mauro Bergui and Gianni B. Bradac

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Jun Karasawa, Hajime Touho, Hideyuki Ohnishi, Susumu Miyamoto and Haruhiko Kikuchi

✓ Between May, 1974, and March, 1991, 104 patients with moyamoya disease, all under 16 years old at the time of first surgery, underwent superficial temporal-to-middle cerebral artery anastomosis and/or encephalomyosynangiosis. The mean follow-up period was 9.6 years (range 4.8 to 16.0 years). Hemiplegia was the most frequent symptom before the first operation. Transient ischemic attacks (TIA's) were noted in 57 patients and minor stroke with hemiplegia in 44. The most frequent type of cortical dysfunction was aphasia (21 cases). Postoperatively, the incidence of TIA's and/or completed stroke with motor weakness of the extremities was markedly decreased, but visual disturbance progressed and major or minor stroke with visual disturbance was found in two cases. In patients under the age of 3 years, a major stroke prior to surgery resulted in a poor outcome in 36% of cases. Preoperative major stroke in patients between the ages of 3 and 7 years was less frequent, and poor outcomes were seen in 17% of this group. There were no major preoperative strokes in patients with surgery after the age of 7 years, and no poor outcomes were recorded in this group. A major preoperative stroke prior to surgery had adverse impact on the ultimate patient intelligence quotient (IQ) following surgery. All patients operated on after the age of 7 years had a normal or borderline IQ at follow-up examination.

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Pitfalls in the surgical treatment of moyamoya disease

Operative techniques for refractory cases

Susumu Miyamoto, Haruhiko Kikuchi, Jun Karasawa, Izumi Nagata, Naohiro Yamazoe and Yoshinori Akiyama

✓ Eleven cases of moyamoya disease refractory to indirect non-anastomotic revascularization, including encephalomyosynangiosis in two, encephaloduroarteriosynangiosis in seven, and encephalomyoarteriosynangiosis in two, are described. The patients suffered from recurrent cerebral ischemic symptoms, and further operative intervention, including superficial temporal artery-middle cerebral artery anastomosis and intracranial omental transplantation, was performed. The choice of operative maneuver depended on the availability of scalp arteries and on the nature of the ischemic symptoms. Although indirect non-anastomotic revascularization procedures have the advantage of technical ease and most patients respond to these procedures alone, there are some patients like the 11 presented here who are not cured by such procedures. In such cases, direct anastomotic revascularization is necessary for the prevention of stroke.

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Susumu Miyamoto, Takeshi Funaki, Koji Iihara and Jun C. Takahashi

Object

The authors evaluated the efficacy of a new flow reduction strategy for giant partially thrombosed upper basilar artery (BA) aneurysms, for which proximal parent artery occlusion is not always effective.

Methods

Eight consecutive patients with severely symptomatic, partially thrombosed, giant upper BA aneurysms were treated with a tailored flow reduction strategy, or received conservative therapies. The flow reduction strategy comprised isolation of several branches from the upper BA at their origins with bypasses in addition to parent artery occlusion.

Results

The median follow-up period of all 8 patients was 15.0 months (range 4–31 months). In 6 patients treated with flow reduction, the mean decrease in residual blood lumen was −10.7 mm (95% CI −19.7 to −1.7 mm; p = 0.029) and the mean decrease in diameter of the aneurysms was −11.5 mm (95% CI −25.1 to 2.1 mm; p = 0.082). Complete or virtually complete thrombosis was achieved in all but 1 aneurysm (83%) and shrinkage was observed in 4 (67%). In those in whom complete or virtually complete thrombosis was achieved, significant shrinkage of the aneurysm was observed (mean decrease in diameter −14.8 mm; 95% CI −28.8 to −0.8 mm; p = 0.043). Improvement or stabilization of symptoms occurred in 67% of the patients who received flow reduction treatment. Both patients who received conservative treatment had unfavorable outcomes.

Conclusions

The flow reduction strategy is effective at promoting complete thrombosis of the aneurysm. This strategy can also induce shrinkage of the aneurysm if successful thrombosis is achieved. Although the neurological outcome of the treatment appears favorable considering its intractable nature, further study of the treatment is necessary to confirm its clinical efficacy and safety.

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Keisuke Yamada, Susumu Miyamoto, Izumi Nagata, Haruhiko Kikuchi, Yoshito Ikada, Hiroo Iwata and Kazuo Yamamoto

✓ A new bioabsorbable composite sheet was developed to provide a substitute for the dura mater and was evaluated histologically and biomechanically using rats and rabbits. This composite, composed of two l-lactic acid-ϵ-caprolactone (50% l-lactic acid, 50% ϵ-caprolactone) copolymer films and a poly(glycolic acid) nonwoven fabric, displayed good mechanical properties and was completely absorbed 24 weeks after implantation in the back of rats. Histological evaluation of the composite sheet was undertaken by implanting it in 31 rabbits with dural defects and examining the sites of implantation 2 weeks to 26 months later. No infection, cerebrospinal fluid leakage, evidence of convulsive disorders, significant adhesion to underlying cortex, or calcification was noticed in any cases. In addition, the regenerated duralike tissue had a high pressure-resistant strength 2 weeks after implantation. The authors conclude that this new bioabsorbable composite sheet can be successfully used as a dural substitute.

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Study of the posterior circulation in moyamoya disease

Clinical and neuroradiological evaluation

Susumu Miyamoto, Haruhiko Kikuchi, Jun Karasawa, Izumi Nagata, Toshio Ikota and Shigekazu Takeuchi

✓ Eighty-two cases of cerebrovascular moyamoya disease were studied by cerebral angiography and computerized tomography. Occlusive lesions were demonstrated not only in the anterior circulation but also in the posterior circulation, and they were associated with the development of an abnormal vascular network (moyamoya vessels). Although occlusive lesions do occur in the vertebrobasilar system, the vertebrobasilar system also acts as a source of collateral channels to the anterior circulation in this disease.

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Tomohito Hishikawa, Koji Iihara, Naoaki Yamada, Hatsue Ishibashi-Ueda and Susumu Miyamoto

Object

The aim of this study was to assess the histopathological differences between advanced atherosclerotic carotid artery (CA) plaques with signal hyperintensity on T1-weighted MR images and those without, focusing on necrotic core size and intraplaque hemorrhage (IPH).

Methods

Thirty-five patients scheduled for carotid endarterectomy underwent preoperative CA MR imaging using 3D inversion-recovery-based T1-weighted imaging (magnetization-prepared rapid acquisition gradient-echo [MPRAGE]). The signal intensity of the CA plaque on MPRAGE sequences was classified as “high” when the intensity was more than 200% that of adjacent muscle. A total of 96 axial MR images obtained in 35 patients were compared with corresponding histological sections from 36 excised specimens. The area of the necrotic core in histological sections was compared between specimens with and without high signal intensity on MPRAGE sequences. The IPH was histopathologically graded according to the size of the area positive for glycophorin A as revealed by immunohistochemical staining. The difference between plaques with and without high signal intensity was investigated with respect to the degree of IPH. The relationship of the severity of IPH to size of the necrotic core was also evaluated.

Results

The area of the necrotic core in plaques with high signal intensity on MPRAGE sequences was significantly larger than that in plaques without high signal intensity (median 51.2% [interquartile range 43.3–66.8%] vs 49.0% [33.2–57.6%], p = 0.029). Carotid artery plaques with high signal intensity had significantly more severe IPH than plaques with lower signal intensity (p < 0.0001). The severity of IPH was significantly associated with the size of the necrotic core (p < 0.0001).

Conclusions

Atherosclerotic CA plaques with high signal intensity on MPRAGE sequences had large necrotic cores with IPH in patients with high-grade stenosis; MPRAGE is useful for the evaluation of CA plaque progression.

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Study of the posterior circulation in moyamoya disease

Part 2: Visual disturbances and surgical treatment

Susumu Miyamoto, Haruhiko Kikuchi, Jun Karasawa, Izumi Nagata, Ikuo Ihara and Sen Yamagata

✓ The involvement of the posterior circulation in moyamoya disease was studied in 178 patients. Forty-three had several types of disturbance such as visual field defect, decreased visual acuity, episodes of blindness, and scintillating scotomata. Most of these symptoms were attributed to occlusive lesions in the posterior circulation. Visual disturbances were seen more often in patients with a juvenile onset than in cases of adult onset.

Superficial temporal artery (STA) to middle cerebral artery (MCA) anastomosis and encephalomyosynangiosis (EMS) improved the cerebral perfusion both in the anterior and posterior circulation by redistribution of blood. In most cases, the visual symptoms subsided or were stabilized after STA-MCA anastomosis and EMS. These surgical procedures did not, however, lead to direct revascularization in cases of ischemia in the visual cortex. In five patients with impending blindness, transplantation of the omentum to the occipital lobe led to improved vision.