Search PubMed⌕ Search

Biomedical subjects

N Yasui

Publications and source records attributed to N Yasui.

At least 181 records · Page 10Linked to original sources
PubMed1992

Intraoperative anatomical studies in patients with aneurysms of the anterior communicating artery complex.

The intraoperative anatomical findings of the anterior communicating artery (ACoA) complex in 46 patients with anatomical variations were compared to those in an equal number of patients without variations in order to determine the visualization of the elements of the vascular complex. All patients underwent radical surgery for an ACoA aneurysm by one of three different surgical approaches: transsylvian, anterior interhemispheric, or basal interhemispheric. Visualization of the vascular elements was similar in patients with or without anatomical variations. The differences observed were dependent on the surgical approach selected and on the projection of the aneurysm. It was found that, even when the intraoperative anatomical field and the number of vascular elements visualized are different from those obtained in autopsy studies, the vascular microanatomical characteristics can be confirmed with each surgical approach to the extent necessary to ensure safe clipping of aneurysms in patients both with and without anatomical variations.

Cerebral Arteries↗
PubMed1992

Intraoperative localization of the central sulcus by cortical somatosensory evoked potentials in brain tumor. Case report.

Perplexing findings of cortical somatosensory evoked potentials (SEP's) for determining the central sulcus during a craniotomy are reported in a case of brain tumor. On stimulation of the contralateral median nerve in that patient, phase-reversal of SEP waves N1 and P2 was observed not only across the central sulcus but also across the precentral sulcus. In topographic mapping of the N1-P2 amplitude, the sulcus dividing the maximum polarity was the central sulcus; this was confirmed by the cortical stimulation-evoked motor responses. For accurate localization of the central sulcus by cortical SEP's, the distribution of potentials must be analyzed with extensive exposure of the sensorimotor cortex.

Brain Mapping↗
PubMed1992

[Ventricular puncture; is it a safe procedure?].

Four hundred and fifty patients underwent 755 ventricular punctures as a procedure for continuous ventricular drainage (CVD), or ventriculoperitoneal/ventriculoatrial shunt (shunt) between April, 1983 and March, 1990. In all patients, postoperative findings on CT scan and related clinical manifestations were studied. Of the total of 755 punctures in 100 cases (13.2%) some high density areas (HDA) (i.e. intracerebral hemorrhage) appeared on CT scans, and, of these, HDA larger than 3 cm in diameter (Type C) was seen in 12 cases (1.6%). On the other hand, some low density areas (LDA) appeared in 448 cases (59.3%), and, of these, an extensive LDA (Type C) was seen in 65 cases (8.6%). LDA on CT scan tended to improve gradually with time, and in one third of the cases it was undetectable one year after puncture. Nine percent of the LDA decreased in density, and they were regarded as areas of infarction or porencephalus. The factors considered to affect postoperative HDA were 1) old age, 2) puncture in the occipital region, 3) puncture in a previously damaged brain area, 4) repuncture using the same tract within a short interval from the previous puncture, 5) CVD. Conversely, factors that affected the LDA were 1) low age, 2) puncture in the occipital region, 3) puncture to normal, non-damaged brain, 4) puncture using a new tract. Ten out of 12 patients with large HDA (Type C) showed deterioration of consciousness level or epilepsy as an acute manifestation, and a prolonged disturbance of consciousness. Mental change and/or homonymous hemianopia were seen in all surviving patients in the chronic phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

[Renal cell carcinoma metastasizing to choroid plexus of lateral ventricle; a case report].

A rare case of renal cell carcinoma metastasizing to the choroid plexus of the lateral ventricle is reported. A 59-year-old woman was admitted to our institution on November 26, 1987 complaining of left-half headache for one month. She had a past history of right nephrectomy due to renal cell carcinoma 4 years before admission, and of right radical mastectomy due to breast cancer 10 years before admission. She had no abnormal neurological findings and laboratory results were normal. CT scan revealed a well-circumscribed, apparently homogeneously enhancing mass in the left lateral ventricle with mild ventricular dilatation. Left vertebral angiogram showed a tumor stain fed by the left posterior choroidal artery. The most likely diagnosis was thought to be metastasis of renal cell carcinoma. The patient underwent the operation for tumor removal via the posterior interhemispheric transcallosal approach 14 days after admission. A histological examination of the tumor determined the diagnosis of clear-cell type renal cell carcinoma. The operation was uneventful and the patient was discharged 20 days after operation without neurological deficit. But she had recent-memory disturbance, low activity, and gait disturbance in May 1989. CT scan revealed ventricular dilatation and tumor recurrence at the same site. She also suffered from diabetes due to the regrowth and invasion of primary tumor to the pancreas. She was discharged free of neurological defects after ventriculo-peritoneal shunt. In December 1989, she gradually deteriorated due to the regrowth of the intraventricular metastatic lesion, and now she is bedridden. Choroid plexus metastasis is quite rare, and, to our knowledge, only three cases have been described.

Carcinoma, Renal Cell↗
PubMed1992

[Clinical course in poor grade patients with ruptured intracranial aneurysms and extensive subarachnoidal clot].

Three hundred and eight cases with ruptured intracranial aneurysms and variable amounts of subarachnoidal clot were evaluated clinically with special emphasis on the natural course of poor grade patients. Clinical severity was classified according to the Glasgow Coma Scale (GCS); severe cases (score 3-8) and mild cases (score 9-15). Patients were further divided into four groups based on the preoperative clinical course, and on whether radical surgery was performed or not. Group A, severe cases without radical surgery (17 patients, mean GCS score 4.2); group B, severe cases (which had undergone) radical surgery (24 cases, mean GCS score 5.5); group C, patients considered as severe cases on admission that had improved to mild cases before radical surgery (3 patients, mean GCS score 11.7); group D, mild cases which had undergone radical surgery (254 cases, mean GCS score 14.3). CT findings after their last bleeding episode were evaluated in each group using subarachnoid hemorrhage (SAH) score from "0"-"3" according to the severity of SAH. In addition, the SAH-B (brainstem) score ("0"-"9") was also evaluated. In this score, the amount of SAH in each perimesencephalic cistern (a. prepontine or interpeduncular cistern, b. ambient cistern, c. quadrigeminal cistern) was considered with a possible score of "0"-"3" for each cistern. (No patient had a concurrent intracerebral or intraventricular hematoma causing a mass effect on CT scan). All cases in group A died except one patient that remained in a vegetative state. All of them had severe subarachnoidal clot (mean SAH score 2.9, SAH-B score 8.2). In group B, in patients with same scores (mean SAH score 2.8, mean SAH-B score 7.3), the outcome was as follows: 6 patients (33.3%) had full recovery or were capable of self-management, 6 patients (33.3%) were partially or fully dependent, and 12 patients (50%) were either in vegetative state or died. Patients in groups C and D with good outcome had significantly less amount of SAH, especially in the perimesencephalic cistern (group C--mean SAH score 2.3, mean SAH-B score 3.7, group D--mean SAH score 1.9, mean SAH-B score 3.3). It is concluded that duration and level of unconsciousness in the cases of SAH without concurrent hematoma causing mass effect, has a good correlation with the severity of SAH in the perimesencephalic cisterns.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1991

[Magnetic resonance imaging of aneurysmal subarachnoid hemorrhage].

Magnetic resonance imaging of subarachnoid hemorrhage (SAH) due to aneurysm rupture was evaluated in relation to CT findings in nine patients. Six patients were studied within 3 days and the other three patients were studied 4 to 6 days from the ictus of SAH using a 0.5 Tesla superconducting unit. In all of the patients, hematoma in the subarachnoid space and ventricles was demonstrated by the proton density-weighted spin echo sequence, which showed that bloody cerebrospinal fluid (CSF) had a higher signal intensity than brain tissue or normal CSF. Magnetic resonance imaging was more sensitive in detecting SAH and more informative as to the site of the ruptured aneurysm than CT. Despite some limitations in applying it to patients with acute SAH, magnetic resonance imaging has clear advantages in the diagnosis of SAH.

Adult↗
PubMed1991

Effects of a Ca2+ entry blocker (nilvadipine) on acute focal cerebral ischemia in rats.

The effects of nilvadipine, a Ca2+ entry blocker, on focal cerebral ischemia were investigated in rats having unilateral middle cerebral artery occlusion. All rats had 24 h ischemia, and were divided into three groups (ten rats per group). Groups 1 and 2 received 1.0 and 3.2 mg/kg nilvadipine s.c. respectively, just after the occlusion. Control rats received an equal volume of the vehicle. Control animals had a % infarct volume of 28.2 +/- 11.4%, and a left/right hemispheric volume ratio of 112 +/- 12%. Group-1 and -2 rats had % infarct volumes of 25.5 +/- 11.6% and 13.9 +/- 9.2% (p less than 0.01) respectively, and left/right hemispheric volume ratios of 111 +/- 9% and 103 +/- 7% (p less than 0.05), respectively. Thus, the drug reduced the infarct size and the brain edema in a dose-dependent manner. The significant decrease in the infarct volume was observed in the periphery of the frontoparietal cortex. This study supports the hypothesis that nilvadipine may be a potential therapeutic agent for cerebral ischemia. Neuropathological findings suggest the possible therapeutic effects of the drug in the ischemic penumbra.

Acute Disease↗
PubMed1991

Rat middle cerebral artery occlusion using an intraluminal thread technique.

A modification of the previous methods of producing cerebral ischaemia in rats (Koizumi et al., Longa et al.), using an intraluminal thread technique, is described. The middle cerebral artery is occluded by introducing a simple 3-0 nylon thread (0.20-0.249 mm in diameter) through the internal carotid artery in the neck. It has been proven that with this method reproducible focal cerebral ischaemia can be achieved which resembles human stroke. Therefore this simple and relatively non-invasive model is suitable for the pathophysiological investigation of ischaemic stroke and the testing of potential therapies.

Animals↗
PubMed1991

Multiple medullary venous malformations decreasing cerebral blood flow: case report.

A rare case of multiple medullary venous malformations in the right cerebral hemisphere is reported. The literature review yielded only one case of multiple medullary venous malformations. Computed tomography scan showed multiple calcified lesions with linear contrast enhancement representing abnormal dilated vessels and mild atrophic change of the right cerebral hemisphere. Single-photon emission computed tomography using N-isopropyl-p-(123I) iodoamphetamine demonstrated decreased cerebral blood flow in the right cerebral hemisphere.

Adult↗
PubMed1991

Comparison of the clinical results of STA-MCA anastomosis and the medical treatment in the cerebral low perfusion patients with viable brain tissue.

The long-term clinical results of STA-MCA anastomosis as well as the medical treatments were compared in cases that were confined as having a focal cerebral perfusion deficit with viable brain tissue, based on either the drug induced EEG and evoked potential test (DEE test) and/or by positron emission tomography (PET). The criteria for viable cerebral tissue was determined by the following four conditions: (1) functional reversibility could be confirmed by the DEE test; (2) a haemodynamic process could be found in the DEE test; (3) a haemodynamic compromise could be confirmed in the PET study; (4) misery perfusion could be confirmed in the PET study. From 1975 to 1989, 55 cases were confirmed as having viable brain tissue according to the DEE test and the PET study. Of the 55 cases, bypass surgery was performed on 35. Conservative treatment was given to the other 20 cases. There were 3 cases of perioperative neurological deterioration. One was permanent and the other 2 were transient. Results of the long-term follow up are as follows, Ipsilateral attack: 1 case (2.0%) received surgery, and 7 cases (35%) received conservative treatment. Re-attack in the contralateral or posterior circulation: 6 cases (17.2%) received surgery, and 1 case (5%) received conservative treatment. Seventy-seven per cent of the surgical cases improved or had no change in the final functional status, while only 55% of the conservative group either improved or showed no change. The incidence of ipsilateral cerebral ischaemia was significantly low in the surgical group. Contralateral and/or posterior circulation ischaemia tended to be high in this group, however.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Attenuated neuropathology by nilvadipine after middle cerebral artery occlusion in rats.

We investigated the effects of nilvadipine, a calcium antagonist, on cerebral ischemia in rats. Under halothane anesthesia, 30 rats had a 3-0 nylon suture introduced through the extracranial internal carotid artery to occlude the left middle cerebral artery. Nilvadipine was dissolved in polyethylene glycol 400. Immediately following occlusion, group 1 rats (n = 10) were treated subcutaneously with vehicle and group 2 and 3 rats were treated with 1.0 (n = 10) and 3.2 (n = 10) mg/kg nilvadipine, respectively. Perfusion fixation was performed 24 hours later, and the histopathologic outcomes were quantified. In group 1 infarct volume was 28.2 +/- 11.4% of the total cerebral volume; in groups 2 and 3 infarct volumes were 25.5 +/- 11.6% (NS) and 13.9 +/- 9.2% (p less than 0.05 different from group 1), respectively. Nilvadipine decreased ischemic neuronal injury in a dose-dependent manner and may be of use in the treatment of cerebral ischemia.

Animals↗
PubMed1991

[Problems of surgical treatment for multiple intracranial aneurysms].

A series of 105 patients presenting with multiple aneurysms and subarachnoid hemorrhage (SAH) were operated on for ruptured and unruptured aneurysms between 1976 and 1984. Clinical factors other than the severity of SAH affecting the outcomes included: 1) Misdiagnosis of the location of a ruptured aneurysm among multiple aneurysms resulted in poor outcomes because of multiple surgical approaches or rebleeding during the acute period. 2) Combinations of aneurysmal locations requiring multiple surgical approaches, such as interhemispheric and transsylvian, during the acute stage caused worse outcomes than with multi-stage surgeries. If an unruptured aneurysm could not be reached during the initial exposure, multi-stage surgery was safe if the ruptured aneurysm had been clipped during the acute period. 3) Complications occurring during unruptured aneurysm surgery. The patient's age, the location and size of the unruptured aneurysms were significant factors in the clinical prognosis. Surgery for unruptured aneurysm caused 1.8% morbidity in patients between 28 and 55 years, but 18.0% morbidity in patients over 56 years of age. Surgery for internal carotid artery aneurysms resulted in 14.8% overall morbidity. Surgery for middle cerebral and anterior cerebral artery aneurysms caused below 5% morbidity. Postoperative morbidity in patients with aneurysms less than 5 mm in diameter was 1.3%, and with aneurysms measuring 10 mm or more, 20%. The optimum treatment for multiple aneurysms with SAH should be based on all factors of the patient's condition, including the unruptured aneurysms.

Age Factors↗
PubMed1991

[Treatment for serious cases of ruptured intracranial aneurysms with severe subarachnoid clot].

Forty-one serious cases of ruptured intracranial aneurysms with severe subarachnoid clot were clinically analyzed, with special emphasis on the prognosis, pathophysiology, and surgical indications. All cases had thick subarachnoid clot without concurrent intracerebral hematoma and/or intraventricular hematoma causing mass signs on the CT scan. In this series, 23 cases underwent radical surgery while in the acute stage, 18 cases were treated conservatively (including 5 cases treated only by continuous ventricular drainage). The criterion for determining the degree of severity was defined as either a "semicoma" or "coma" state just prior to radical surgery for the radically-operated group, with the same designations for the conservative group at their time of admission. All patients except two in the conservatively-treated group died due to primary brain damage caused by massive subarachnoid hemorrhage. The two remaining cases died from other complications. On the other hand, the outcome for the 23 surgically-treated patients was as follows: Three (13%) fully recovered; three (13%) were capable of self-management; eight (34.8%) were partially or fully dependent. Nine (39.1%), died. In the radically-treated group, pre-operative factors that might predict clinical outcome were investigated. Those factors were the neurological grade, the brain-stem response, the response after the rapid administration of 20% Mannitol (300-900 ml), and the length of time from the last bleeding episode to the time that radical surgery was performed. It was recognized that there was no relationship between the neurological grade just prior to radical surgery and the outcomes in the serious cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[A case of adult pilocytic astrocytoma in the right temporal lobe].

A case of adult pilocytic astrocytoma in the right temporal lobe is reported here. The patient was a twenty-four year old man, who came to the neurological division of our hospital on October 6, 1987 because of repeated consciousness-loss attacks accompanied with uncinate fit. He had no neurological deficits. However, an EEG revealed spike-and-wave complexes in the right temporal region, and a CT scan showed a small cystic lesion in the right temporal lobe. A diagnosis of psychomotor seizure was made, and the administration of anticonvulsants was started. The incidence of attack then decreased, but after approximately two years of drug therapy the attacks increased again. A CT scan was again performed, and revealed that the lesion in the right temporal lobe was enlarging. Also a noticeable enhanced lesion, identified as a mural nodule was found in the post-contrast enhancement study. A brain tumor was then suspected, and he was admitted to the neurosurgical division on October 11, 1989. He had no neurological deficits on admission. An MRI showed a low intensity lesion in the T1 weighted image, and a high intensity lesion in the T2 weighted image. A cystic lesion with a marked enhanced mural nodule was also found in the base of the right temporal lobe, according to the Gd enhancement study. Perifocal edema was not recognized. Cerebral angiography showed no positive findings. Positron emission tomography (PET), using H2(15)O, revealed low perfusion at or around the lesion, and PET using [11C]-methionine revealed an accumulation of methionine at the lesion. A diagnosis of low-grade glioma was made, and a right temporal craniotomy, for the purpose of totally removing the tumor was performed on October 26, 1989.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Risks of surgical treatment for unruptured intracranial aneurysms].

The risks of surgical treatment for unruptured intracranial aneurysms, as well as the significance of evaluating cerebral blood flow (CBF), are here reported. Out of 72 patients who underwent unruptured aneurysm surgery without such complications as occlusion of the main trunk or perforating arteries, or brain contusion, and who according to CT scans, did not have new lesions related to the operations, 18 patients (25%) developed neurological deficits postoperatively. In 17 of these 18 patients, postoperative neurological deficits (frontal sign: 7, paresis: 4, and seizure: 6 cases) disappeared within 2 weeks following the operations. In the other patient, who was treated for subcortical hematoma in the left temporal lobe before aneurysm surgery, permanent speech disturbance appeared postoperatively. In the 18 patients with postoperative neurological deficits, the mean CBF value (36.2ml/100g/min) was statistically lower than that in the patients (46.2ml/100g/min) who had no postoperative neurological deficits (p less than 0.001). The rate of the patients with lower CBF values who developed postoperative neurological deficits, was statistically higher than that of patients with CBF values greater than 40ml/100g/min (p less than 0.002). In the patients with lower CBF values, common operative procedures for unruptured aneurysms such as craniotomy and mild brain retractions, may damage brain tissue. Careful perioperative management is needed for patients who undergo unruptured aneurysm surgery, because a lower CBF value may represent the degree of brain fragility.

Adult↗
PubMed1991

[Clinical study of growing up aneurysms: report of 25 cases].

Twenty-five cases of patients with growing up aneurysms are reported. Growth of the aneurysm was confirmed by repeated angiography within 1 month in 11 cases (short-term group), and for over 1 month in the other 14 cases (long-term group) following the initial angiography. Clinical history, shape and growth pattern of aneurysms, as well as hemodynamic factors that effect the growth were investigated in each group. The aneurysms were classified according to the shape into dome-type (smooth contour) and bleb-type (irregular contour). In all cases of the short-term group, the first angiography was performed because of rupture of the aneurysm. In this group, 4 cases bled again because of enlargement or the development of an aneurysmal bleb. Growth rate and the initial size of the aneurysm did not effect the potential of re-rupture. In the long-term group, 9 cases out of 14 (64.3%) had "non-ruptured aneurysm" at the time of first angiography. In the follow up, 5 cases were ruptured (two because of re-bleeding and three for the first time). In 3 out of these 5 cases, a bleb was demonstrated on initial angiography, and in another case, a bleb was demonstrated in follow-up angiography. Only one case ruptured because of the growth of the aneurysmal dome. Most of the aneurysms that rupture, in the follow-up survey, showed a larger growth rate in comparison with aneurysms that did not rupture. Many cases of this long-term group were associated with hypertension or vascular abnormalities which would effect the aneurysmal growth.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

The effect of distraction upon bone, muscle, and periosteum.

Bone lengthening was achieved on rabbit tibias by means of callus distraction (callotasis) using a dynamic external fixator. The periosteum and the muscle fascia were labeled with metal markers; changes in position of these markers during slow progressive distraction were monitored by soft radiography. During the waiting period before commencing distraction, the periosteal markers around the osteotomy site were elevated from the bone surface by newly formed external callus. There was an apparent lag period until the periosteal reaction occurred after osteotomy. Subperiosteal callus was first formed in an uncalcified state and subsequently became calcified. As distraction began, longitudinal migration of the periosteal markers was observed. It appears that the periosteum slides over the bone cortex, mitigating local stretching of the muscle around osteotomy site. The elongation of muscle occurs throughout the muscle substance and not simply at the site of osteotomy.

Animals↗