Biomedical subjects

Y Miyasaka

Publications and source records attributed to Y Miyasaka.

At least 37 records · Page 2Linked to original sources

PubMed2000

Vascular structure of arteriovenous malformations.

Cerebral arteriovenous malformations (AVMs) are classified angiographically into two types: the arteriovenous fistula (AVF) type and the plexiform type. However, the differences in vascular structure of these two types have not been clarified. The purpose of the present study is to elucidate the vascular structure of plexiform AVMs and to discuss the clinical significance of this classification of AVMs. Specimens of AVMs resected in 8 cases and identified by cerebral angiography as plexiform AVMs were examined. Immediately after their removal, microdissection of the terminal arterial feeder, the nidus, and the venous drainer was performed under a microscope. A histological examination of each element was then conducted. Microdissection of a portion of the vascular mass that formed the nidus made it possible to separate individual vessels of the mass from each other. Many of these individual vessels connected with the feeder on one side, while the other side anastomosed with the drainer, thus exhibiting the morphology of an AVF. From our examination of the AVMs in the present study, we inferred that the plexiform type is fundamentally a conglomeration of AVFs. It is therefore suggested that the vascular structure of this type of AVM is not fundamentally different from that of the AVF type.

Adult↗

PubMed2000

Dural arteriovenous malformations associated with cerebral aneurysms.

Only limited information is available concerning dural arteriovenous malformations (AVMs) found in association with cerebral aneurysms. The present report focuses on six such cases, concentrating attention on clinical characteristics and significance. Of a total of 46 dural AVMs encountered over a given period, six (13%) were linked with cerebral aneurysms. Particularly strong associations were noted for dural AVMs in the anterior cranial fossa (three of four cases) and convexity (all of three cases). With dural AVMs in the anterior cranial fossa, subarachnoid haemorrhage is common, so that where this is encountered the possibility of a complicating aneurysm should be considered in order to select an appropriate treatment.

Adolescent↗

PubMed2000

The effect of encephalo-myo-synangiosis on abnormal collateral vessels in childhood moyamoya disease.

Child patients with Moyamoya disease initially present with ischemic symptoms. However, the long-term risk of intracranial hemorrhage for childhood Moyamoya disease is unknown. Hemodynamic overload to the fragile collateral vessels has been considered to cause hemorrhage. We reviewed angiograms to evaluate the effect of encephalo-myo-synangiosis (EMS) on abnormally dilated collateral vessels in 13 child patients with Moyamoya disease. EMS was performed on 24 sides in 13 patients ranging from 5 to 14 years of age. Post-operative angiography (6-88 months after surgery) revealed good revascularizations through EMS (larger than one-third of the middle cerebral artery (MCA) distribution) in 18 sides (75%) and smaller revascularizations in 6 sides (25%). In cases with a good revascularization through EMS, reduction of the abnormal collateral vessels was observed not only in the basal Moyamoya vessels (94% of sides) but also in the medullary arteries derived from the choroidal arteries (62% of sides), which are considered to cause intraventricular hemorrhages in adult patients. It is suggested that EMS may reduce the hemodynamic load on dilated collateral vessels and, subsequently, the long-term risk of intracranial hemorrhage in childhood Moyamoya disease.

Adolescent↗

PubMed2000

Long-term observation after transjugular intrahepatic portosystemic stent-shunt in two patients with hepatocellular carcinoma.

Two patients with hepatocellular carcinoma (HCC) were treated with transjugular intrahepatic portosystemic stent-shunt (TIPS) and followed for 22 and 58 months thereafter. HCC was well controlled by transcatheter arterial chemoembolization. Hepatic failure or metastasis, especially in the lung, was not observed in the long-term observation. TIPS seems to be useful even in patients with HCC, provided HCC is controlled.

Aged↗

PubMed1999

Time-related changes in full-length hepatitis C virus sequences and hepatitis activity.

The activity of hepatitis varies in chronic hepatitis C virus (HCV) infection. Some patients show persistently normal serum alanine aminotransferase (ALT) values, whereas the others show high-ALT values and progress to liver cirrhosis or hepatocellular carcinoma. However, virological mechanisms causing hepatitis have not fully been elucidated. We analyzed serial changes in full-length HCV sequences in 10 patients with various profiles of hepatitis activity. In the nonstructural 5A (NS5A) and NS5B, the rate of amino acid changes, as well as the proportion of nonsilent ones, was low in patients with normal ALT values compared with those with abnormal ALT (for the rate of amino acid changes, 0 x 10(-3) vs 3.19 x 10(-3) changes/site/year (P = 0.037) in NS5A and 0 x 10(-3) vs 1.22 x 10(-3) changes/site/year (P = 0.023) for NS5B, for the proportion of nonsilent changes, 4 vs 22% (P = 0.017) in NS5A and 0 vs 16% (P = 0. 039) in NS5B). Also, the flare-up of hepatitis coincided with higher nucleotide/amino acid substitution rates in NS5B. In conclusion, the genomic structures of the NS5A and NS5B regions may correlate with hepatitis activity in chronic hepatitis C.

Adult↗

PubMed1999

A case of pseudosarcoma associated with type 3 squamous cell carcinoma of the esophagus: report of a case.

A case of a primary esophageal pseudosarcoma associated with an independent type 3 tumor is described herein. A 60-year-old male presented with dysphagia and chest discomfort. A clinical evaluation revealed a type 3 tumor in the middle of the esophagus, which was diagnosed after a biopsy to be squamous cell carcinoma (SCC). A subsequent gross examination of the subtotally removed esophagus revealed a polypoid tumor adjacent to the type 3 tumor. Histologically, the polypoid mass was composed of SCC and mesenchymal components without a transitional zone. The tumor was thus classified as a pseudosarcoma of the esophagus, and was unique in that this appeared to have developed independently from the SCC.

Carcinoma, Squamous Cell↗

PubMed1999

The factors influencing haematoma volume due to arteriovenous malformations.

Haemorrhage due to cerebral arteriovenous malformations (AVMs) varies from massive, requiring urgent operations, to clinically silent. The present study was designated to identify factors influencing haematoma size, and the pathophysiological mechanisms of massive haemorrhage were studied. 55 patients with intracerebral haematomas due to supratentorial AVMs were included in this study. Angiographic and clinical findings were retrospectively evaluated in relation to haematoma size. Statistical analysis demonstrated that small size and the presence of only one draining vein were high risk factors for massive haemorrhage. The haematoma volume in small AVMs (30 +/- 4 cm3) was significantly larger than in other AVMs (7 +/- 3 cm3) (p = 0.0005). AVMs with only one draining vein were associated with massive haematoma volume as compared to AVMs with two or more draining veins (30 +/- 4 versus 11 +/- 3 cm3, p = 0.0023). Our previous study demonstrated that feeding artery pressure (FAP) was significantly higher in AVMs with haemorrhage than in those without, as was draining vein pressure (DVP), and FAP and DVP were inversely related to the number of draining veins and the size of the AVMs. Thus, in small AVMs and AVMs with only one draining vein, local increase in DVP may thus contribute to massive haemorrhage.

Arteriovenous Malformations↗

PubMed1999

The significance of hypothermic acid-base management induced before ischemia in a rat model of transient middle cerebral artery occlusion.

We investigated the effects of acid-base management during pre- and intra-ischemic hypothermia on regional cerebral blood flow (rCBF) and infarct volume using a transient focal cerebral ischemia model. Normal temperature was maintained in a group of 7 anesthetized rats, and hypothermia (30 degrees C) was maintained in two other groups of 7 anesthetized rats, in which alpha-stat (PaCO2 measured at 37 degrees C was maintained at 36 mmHg) and pH-stat (PaCO2 corrected for body temperature was maintained at 36 mmHg) conditions, respectively, were established. rCBF was monitored by laser-Doppler flowmetry in the ischemic penumbra. The middle cerebral artery (MCA) was occluded for 2 h and then reperfused. Infarct volume was measured after 24 h and expressed as a percentage of hemisphere volume. Pre-ischemic hypothermia reduced rCBF in the alpha-stat group and the pH-stat group to 52 +/- 2% and 86 +/- 7%, respectively (p < 0.01). After MCA occlusion, rCBF dropped in the control group, alpha-stat group, and pH-stat group to 57 +/- 11%, 31 +/- 9%, 27 +/- 10%, respectively. Infarct volume in the alpha-stat group, and pH-stat group was significantly smaller (10 +/- 1% and 7 +/- 2%) than in the control group (42 +/- 7%, p < 0.01), but no differences were found between the hypothermic groups. Differences in acid-base management in the present study did not affect infarct volume, but pre-ischemic rCBF in the alpha-stat group was significantly lower than in the pH-stat group. The steeper fall in rCBF after MCA occlusion in the pH-stat group suggested that the autoregulatory response of the collateral pathways may have been reduced in this group.

Acid-Base Equilibrium↗

PubMed1999

Spontaneous carotid cavernous fistulas with special reference to the influence of estradiol decrease.

The etiology of the dural arteriovenous fistula (AVF) involving the cavernous sinus is still unknown. However, it is of interest that this condition usually occurs in post-menopausal women. The purpose of the present study was therefore to clarify the relationship between sex hormone blood levels and the occurrence of dural AVFs in the cavernous sinus. Serum sex hormone levels and factors associated with atherosclerosis were examined in 26 consecutive patients with dural AVF involving the cavernous sinus presenting at our institute during the last eight years and compared with those of a post-menopause control group. Of the present patient series, 21 (81%) were women. All except five had passed menopause. Five (24%) of the women patients presented with symptoms consistent with cessation of menstruation, namely, a blood level of estradiol significantly lower than the control value. Hypertension was recognized in 10 (71%) of 14 females who had experienced menopause 10 or more years previously and in all male patients. A sudden abnormal decrease of blood estradiol levels in female patients demonstrating symptoms consistent with menopause may thus be an important precipitating factor in the occurrence of dural AVFs involving the cavernous sinus. Hypertension, in older female and male patients, with or without longstanding low blood estradiol levels, may cause atherosclerosis of the feeding vessels in the dura mater, resulting in the opening of a normal AV shunt to provide collateral circulation.

Aged↗

PubMed1999

Efficacy of endoscopic clipping for bleeding gastroduodenal ulcer: comparison with topical ethanol injection.

OBJECTIVE: Although endoscopic clipping is used widely for the treatment of bleeding gastroduodenal ulcers, clinical trials on its efficacy are scarce. The aim of this study is to assess the efficacy and safety of endoscopic clipping for hemostasis from bleeding gastroduodenal ulcers. METHODS: The present study was designed as a retrospective study using historical controls. One hundred consecutive patients with bleeding gastroduodenal ulcers were treated by endoscopic clipping. The preceding 91 consecutive patients treated by endoscopic pure ethanol injection were regarded as controls. Forty-nine of the clipping group and 41 of the ethanol group had lesions at sites difficult to perform endoscopic manipulation. Hemostatic rates, rebleeding rates, amounts of blood transfusion, and durations of hospital stay were analyzed. RESULTS: The hemostatic rate was 96% in both clipping and ethanol groups, whereas the rebleeding rate was lower (15% vs 29%, p = 0.023) in the former than the latter. In technically difficult cases, the hemostatic rate was comparable (96 vs 90%). CONCLUSION: In patients with bleeding gastroduodenal ulcers, endoscopic clipping may be a choice of therapy because of a low rebleeding rate compared with pure ethanol injection.

Ethanol↗

PubMed1999

Tissue response of a small saccular aneurysm after incomplete occlusion with a Guglielmi detachable coil.

A 49-year-old woman had a small saccular aneurysm that was incompletely occluded with a Guglielmi detachable coil (GDC). She died from rupture of another aneurysm 42 days after the treatment. Autopsy for the embolized aneurysm revealed no neoendothelium at the aneurysmal neck, but an organized thrombus was observed limited to the periphery of the aneurysmal lumen. Although isolation of the aneurysm was not apparent, loose embolization with this method may help to reinforce the aneurysmal wall.

Aneurysm, Ruptured↗

PubMed1999

Laparoscopic treatment of cholecystocolonic fistula: report of a case preoperatively diagnosed by barium enema.

The authors present a case of cholecystocolonic fistula with no specific symptoms, such as severe diarrhea or pneumobilia, preoperatively diagnosed and treated by the laparoscopic approach. A preoperative barium enema demonstrated a cholecystocolonic fistula. The fistula was divided by the laparoscopic stapling technique. Important features in the management of this case are (1) preoperative diagnosis of the fistula by barium enema carried out for screening colorectal cancer, (2) dissection of the gallbladder from its bed before division of the fistula, and (3) use of the laparoscopic stapling technique to divide the fistula while preventing fecal soilage.

Barium Sulfate↗

PubMed1998

Ischemic stricture of the small intestine associated with acute pancreatitis.

A 37-yr-old man underwent an open drainage operation for severe acute pancreatitis and received respiratory ventilation support for 4 mo because of respiratory failure based on disseminated intravascular coagulation (DIC) and septic shock. Under intensive care, he sometimes had bloody diarrhea for about 6 wk. Colonoscopic findings suggested that the bleeding had derived from the small intestine. The patient then gradually recovered from acute pancreatitis and was discharged from the hospital. Thereafter, he suffered relapses of ileus and his symptoms progressively worsened. The patient underwent a second operation about 2 yr after the onset of acute pancreatitis. At celiotomy, multiple stenoses of the distal ileum measuring about 60 cm in length were found and the segment was resected. The resected specimen demonstrated six separate circumferential strictures and shallow ulcerations. Histologically, multiple ulcerations were restricted to the mucosa and were accompanied by marked submucosal edema and fibrosis. The mucosa between the ulcers revealed chronic regenerative changes: intimal thickening of small mesenteric arteries causing luminal narrowing and organized thrombosis in small mesenteric veins. Therefore, these were considered to be a series of segmental ischemic lesions. Note that delayed ischemic stricture of the small intestine may occur as a chronic complication of acute pancreatitis.

Acute Disease↗

PubMed1998

The value of long-term clinical follow-up for cases of spontaneous carotid cavernous fistula.

To clarify the value of clinical long-term follow-up with radiological examination, ranging from 12 to 63 months (average: 35 months), 18 consecutive patients suffering from spontaneous carotid cavernous fistula (CCF), were studied prospectively. Five aged patients without aggressive symptoms were treated conservatively, and the other 13 underwent transarterial embolization. The radiological follow-up was primarily by magnetic resonance angiography (MRA), performed from 2 to 6 times (average: 4.1 times) during the follow-up period. In three cases, CCFs persisted, but the other fifteen (83%) demonstrated complete cure as defined by long-term follow-up MRA. The three patients with persistent CCFs were comparatively young, less than 60 years old, had no atherosclerotic factors and demonstrated multiple venous drainage routes with cortical venous drainage on angiography. In two of them, the symptoms completely disappeared, and the other had only mild chemosis. However, surprisingly, in two, MRA revealed residual CCF with drainage into only cortical veins through the sphenoparietal sinus, this radiological finding being well known to signify danger. During the follow-up period, central retinal vein thrombosis occurred in two cases. The common point in these cases was that the superior ophthalmic vein was the only venous drainage route. This is also a point requiring care. We therefore emphasize the importance of careful long-term radiological follow-up for spontaneous CCF patients even when their symptoms improve or disappear. MRA is particularly suitable for this purpose and applicable in the out-patient clinic because of its non-invasive nature.

Adult↗

PubMed1998

The significance of retrograde thrombosis following removal of arteriovenous malformations in elderly patients.

BACKGROUND: Retrograde thrombosis of former feeding arteries should be considered as a distinct postoperative complication following surgery for arteriovenous malformation (AVM). Regardless of the presence of AVMs, the cerebral arteries undergo atherosclerotic changes with advancing age. In the present study, three cases in elderly patients who developed retrograde thrombosis are reported, and the effect of the patient's age on this complication is discussed. CLINICAL MATERIALS AND METHODS: The present study group consisted of 158 patients who underwent AVM resection and postoperative angiographic studies. Five patients were 65 years of age or older (elderly group) at the time of operation, 108 were between 20 and 64 years of age (adult group), and 45 were less than 20 years of age (young group). The incidence of retrograde thrombosis in the elderly group was compared with that of the other two groups. RESULTS: We found that surgery in the elderly group was accompanied by a significantly higher incidence of retrograde thrombosis (60%) than in the adult group (4%), or the young group (0%). CONCLUSIONS: The present study suggests that this complication should be considered as a serious possibility following removal of an AVM, especially in elderly patients.

Adult↗

PubMed1998

Preoperative superselective embolization of skull-base meningiomas: indications and limitations.

We evaluated the clinical significance of preoperative superselective embolization for skull-base meningiomas. The subjects consisted of 20 patients with skull-base meningiomas, and were classified into a preoperative embolized group and a non-embolized group. The volume of blood transfused during the operation, the length of the operative procedure and the neurological outcome were compared between the two groups. The results showed that, in tumors smaller than 6 cm, the blood lost during the operation was significantly less in the embolized group. In tumors larger than 6 cm, there was not difference in blood lost, perhaps because larger meningiomas tend to have tiny blood vessels that are unsuitable for preoperative embolization. There was no difference in the length of the operation between the two groups. The embolized group tended to show a better clinical outcome than the non-embolized group.

Adult↗

PubMed1998

A canine model of intracranial arteriovenous shunt with acute cerebral venous hypertension.

Increased pressure of draining veins in intracranial arteriovenous fistula is considered an important cause of clinical symptoms. To investigate hemodynamic changes in intracranial arteriovenous fistula with cerebral venous hypertension, we developed a new canine model of this condition. A lingual artery-superior sagittal sinus (SSS) shunt was constructed using a section of the femoral artery as an interposed graft; immediately after which, monitoring of SSS pressure (SSSP) and regional cerebral blood flow (rCBF) was started. The baseline SSSP was 4.1 +/- 3.7 mmHg. After shunt opening, it increased slightly but not significantly. When the SSS was occluded with a clip with the shunt closed, SSSP rose to 20.3 +/- 9.0 mmHg (p < 0.01). Finally, on shunt opening, with the SSS caudal (downstream) to it occluded, the SSSP increased to 59.5 +/- 22.9 mmHg (p < 0.01, multiple analysis of variance, contrast). The frontal lobe rCBF decreased as the cerebral perfusion pressure (CPP) (mean blood pressure minus SSSP) fell. However, cerebral vascular resistance decreased significantly and proportionately to the reduced CPP (r = 0.66, p < 0.0001). In conclusion, when an intracranial arteriovenous shunt was present, venous outflow obstruction was shown to be necessary for cerebral venous hypertension to occur. In acute venous hypertension, decreases in rCBF occurred, but the autoregulatory vasodilating response was also active.

Animals↗

PubMed1998

Pial arteriovenous malformation with massive perinidal edema.

It is generally considered that perinidal edema in an arteriovenous malformation (AVM) is caused by a concomitant intracerebral hematoma. We report a rare case of AVM with perinidal massive edema which was possibly not due to hemorrhage, and discuss the pathophysiological mechanisms of such edema development. A 60-year-old woman presented with a sudden onset severe headache. Computed tomography (CT) scans obtained two hours after the onset showed an AVM-like lesion with a small hematoma in the right parieto-occipital lobe, and unexpectedly early development of massive edema adjacent to the hematoma. Angiograms demonstrated a medium-sized AVM, and severe stenosis in the draining vein which suggested the presence of venous hypertension at prestenotic sites. Repeated CT scans and magnetic resonance (MR) images in the chronic period after the hemorrhage demonstrated persistence of the perinidal edema with mass effect. Removal of the lesion was achieved 2 months after the onset. MR images 3 months after the operation showed marked reduction of perinidal edema. The time course of the perinidal edema suggests that its development was unrelated to the hemorrhage. The findings indicate that increased venous pressure secondary to severe stenosis of the draining vein may possibly contribute to the development of perinidal edema.

Arteriovenous Malformations↗