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Biomedical subjects

T Iwabuchi

Publications and source records attributed to T Iwabuchi.

At least 73 records · Page 4Linked to original sources
PubMed1990

Cerebral microthrombosis in symptomatic cerebral vasospasm--a quantitative histological study in autopsy cases.

A comparative investigation of the pathogenetic factor in symptomatic cerebral vasospasm was made by quantitative histological and clinical studies in four patients who died immediately of symptomatic cerebral vasospasm (Cases 1-4) and in two who died without fatal cerebral vasospasm (Cases 5 and 6). Histological examination of the brain from Cases 1 and 2 found many white and fibrin microthrombi together with ischemic and infarctic changes in the territories of spastic arteries, which corresponded to the low-density areas (LDAs) observed on computed tomographic (CT) scans and the typical neurological symptoms. In Case 3, who had suffered severe vasospasms in bilateral anterior cerebral and middle cerebral arteries, bilateral LDAs were observed on CT scans and multiple fibrin thrombi were seen diffusely throughout the brain. In Case 4, extensive bilateral LDAs (lt greater than rt) were observed on CT scans, and multiple microthrombi were seen diffusely but predominantly in the left cerebral hemisphere. Only in Case 3 the possible complication of disseminated intravascular coagulation could not be ruled out. Only negligible thrombi were observed in Cases 5 and 6, whose immediate cause of death was considered to be acute hydrocephalus and aneurysmal rerupture, respectively. Distributions of microthrombi were significantly greater in the regions clinically identified to have been ischemic or infarctic.

Aged↗
PubMed1990

Development and clinical usefulness of a new neuroendoscope system for CT-guided stereotactic brain surgery.

Since computed tomography (CT)-guided stereotactic surgery is essentially blind surgery, it always involves the risk of injuring viable brain tissue and vessels, and it is difficult to obtain a sufficient amount of biopsy specimen from cystic or necrotic lesions. Moreover, the direct observation of the lesion would provide extremely valuable information. The authors have therefore developed a new subminiature rigid endoscope and an ultrasonic aspirator for use in stereotactic surgery, as well as a new micromanipulative system to attach the equipment to the stereotactic frame so that they can be accurately inserted into the optimum position from any direction. The new neuroendoscope includes a graded refractive index glass rod only 1.0 mm in diameter (Selfoc, Nippon Sheet Glass Co., Osaka), which provides a focal depth from 1 mm to infinity, as well as an extremely bright and wide visual field with an angle of 70 degrees. Furthermore, because the outer probe and endoscopic sheath share the outer rigid metal tube 4.5 mm in outer diameter, a large internal channel of 2.1 mm in diameter allows the introduction of various microinstruments such as an ultrasonic aspirator probe, laser probe, and biopsy forceps. When a miniaturized video camera is attached, the surgical procedures can be controlled using the video monitor and photographed. The new probe for the ultrasonic aspirator has been developed in various types suitable for fragmentation and aspiration of hematomas and brain tumors, so under endoscopic control even the harder coagulants and tumors can be removed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[Subependymoma of the septum pellucidum. MRI features and its usefulness in planning surgery].

A 61-year-old female was referred because of headache and gait disturbance. A computed tomography (CT) scan revealed a midline isodense mass lesion. The limit of the tumor was equivocal even after administration of contrast medium. Magnetic resonance imaging (MRI) study, however, clearly showed the relationship between the tumor and the surrounding structures, such as the corpus callosum, the ventricular cavities. The tumor had originated from the region of the septum pellucidum and positioned just beneath the corpus callosum from the genu to the splenium with the roof of the third ventricle pushed downward. The tumor was totally extirpated via the interhemispheric paratranscallosal route. The tumor was typical subependymoma. The post-operative course was uneventful. Transient psychiatric disturbance and inability to retain recent memory were observed and the former subsided in several weeks. CT and MRI characteristics of subependymoma are summarized and the usefulness of MRI to locate tumors and to plan proper surgical approaches are emphasized.

Cerebral Ventricle Neoplasms↗
PubMed1990

[Experimental study on liquefaction of intracranial hematoma: usefulness of tissue-plasminogen activator (t-PA), a hematolytic agent, and its combination].

In stereotaxic aspiration of intracerebral hematoma and extensive removal, or cisternal drainage for subarachnoid hematoma, rapid and safe liquefaction and removal of clots are important and urgent measures to be taken. We performed a pharmacological experimental study on the efficacy, administration method, and toxicity of various hematolytic agents, especially tissue-Plasminogen Activator (t-PA). The following findings were obtained. 1) The amount, hardness, and histological findings concerning the remaining hematoma differed markedly according to which hematolytic agents were used. 2) The local effects of each hematolytic agent continued for about 4-8 hours but markedly decreased thereafter. 3) The hematolysis rate following single administration (6 hours after the blood collection) was 88.9% with t-PA + Elase (Fibrinolysin + Deoxyribonuclease), 85.4% with t-PA, 84.6% with t-PA + Urokinase, 80.2% with t-PA + Urokinase + Elase, 27.55 with Elase + Urokinase, 24.6% with Elase + Urokinase + Heparin, 17.2% with Heparin + Urokinase, 16.4% with Urokinase, 13.2% with Elase + Heparin, 12.6% with Elase, 9.3% with Heparin, and 10.1% with the control (Saline). Locally administered t-PA had remarkably greater hematolytic effects than Urokinase on the hematoma (p less than 0.001). 4) The hematolysis rate after 24 hours of repeated administration of small doses at 8-hour intervals was 100% with t-PA + Urokinase + Elase, 94.2% with t-PA, 93.8% with t-PA + Urokinase, 50.9% with Elase + Urokinase, 46.6% with Elase + Urokinase + Heparin, 33.7% with Urokinase, and 4.8% with the control.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[Postoperative MR findings in acoustic neuromas: nerve edema within the internal auditory canal].

Postoperative MR findings of eleven acoustic neuromas were analyzed. MRI's were able to clearly visualize residual tumor around the 7th and 8th cranial nerves that were left to preserve cranial nerve function, although conventional X ray CT scans often failed to detect it due to artifacts in the parapetrous area. The facial nerves preserved during operations were also visualized from their brainstem portion to the internal auditory meatus. These findings indicate that MRI is excellent in delineating soft tissue in the CP angle that would be overlooked by conventional X ray CT scan. It was also found that the nerve bundles within the internal auditory canal gained increased signal intensity on the T1 and proton weighted images after surgical interventions and that this effect extended into the most distal end of the nerve bundles and even into the intracochlear portion of the cochlear nerve. The nerve bundles with increased signal intensity were conspicuously enhanced after intravenous administration of Gd-DTPA. This indicated that the blood nerve barrier of the nerves within the internal auditory canal were disrupted due to the surgical manipulations in excising tumors. Following such surgical manipulations, nerve edema ensued, although manipulations in the cerebello-pontine angle were done carefully and protectively under a surgical microscope. The clinical significance of disruption of the blood nerve barrier and following nerve edema were discussed from the standpoint of preservation of the 7th and 8th cranial nerve functions.

Blood-Brain Barrier↗
PubMed1990

[Disproportionately large communicating fourth ventricle with bilateral exotropia: report of two cases].

Two cases of disproportionately large communicating fourth ventricle (DLCFV) accompanied by consciousness disturbance and bilateral exotropia are reported. Case #1 was a 21-year-old male who suffered from consciousness disturbance and bilateral exotropia due to malfunction of the ventriculoperitoneal shunt (VPS) which had previously been operated on twice for a left parietal arteriovenous malformation, which had caused ventricular hemorrhage several times. The last hemorrhage was massive and made ventricular casting, including the fourth ventricle. Both bilateral exotropia and the fourth ventricular dilatation were well controlled by the reconstruction of the VPS. Case #2 was a 66-year-old female, semicomatous because of massive subarachnoid hemorrhage with ventricular casting hematoma due to rupture of the right middle cerebral aneurysm. Though an improvement of the consciousness disturbance was obtained by continuous ventricular drainage (CVD), bilateral exotropia and consciousness deterioration appeared after lumboperitoneal shunt followed by the removal of the CVD. Another CVD was then carried out and some improvement was obtained again. However, the same symptoms appeared again after the VPS, followed by the removal of the CVD. The patient finally died despite a third CVD. Autopsy revealed a markedly dilated fourth ventricle and massive subarachnoid clots particularly around the foramen of Magendie and Luschka. The pathogenesis of DLCFV and bilateral exotropia are also discussed.

Adult↗
PubMed1990

[Facial nerve preservation in the region of the zygomatic arch].

In order to preserve the frontotemporal branch of the facial nerve in frontotemporal and trans-zygomatic craniotomies, electromyographic responses from the facial muscles were recorded preoperatively. Incising the frontotemporal branch of the facial nerve could be avoided by identifying the crossing point of the frontotemporal branch of the facial nerve on the superior border of the zygomatic arch. The crossing points were investigated in 20 patients and in most cases they existed between 2 cm and 6 cm from the anterior border of the external auditory canal. Another important point to preserve the facial nerve is to conserve the layer in which the facial nerve is included. Therefore, the surgical anatomy in the region of the zygomatic arch and temporal area was reviewed in detail. This knowledge is crucial for neurosurgeons to dissect precisely in this region without causing postoperative facial palsy.

Craniotomy↗
PubMed1990

[Postoperative facial and vestibular nerve palsy: experimental study of its pathophysiological mechanisms].

The 7th and 8th cranial nerves were shifted in the cerebellopontine (CP) angle of dogs by cerebellar retractions that were similar to those performed in humans with monitoring of auditory evoked brainstem responses (ABR). Postoperatively, the vestibular, facial nerves, and brainstem were histologically examined. Caudal-to-rostral shifts of the nerves could induce vestibular and/or facial nerve damages. The most vulnerable portion of the vestibular nerve was located between the vestibular ganglions and the area vestibularis-the most lateral end of the internal auditory canal. This indicated that due to traction force derived from surgical interventions, the nerves and vessels were avulsed at the fundus of the internal auditory canal. The vestibular nerve may be potentially injured more easily and frequently than the cochlear and facial nerves in retromastoid craniectomies with lateral decubitus position in humans. Direct injuries of the facial nerves in the CP angles were not observed in this study. It was elucidated that the facial nerve was usually injured in the facial canal proximal to the geniculate ganglion due to traction force derived from manipulations in the CP angle. It is likely that as facial nerve edema progresses postoperatively, the facial nerve is gradually compressed within the narrow labyrinthine portion of the facial canal. This may be the cause of delayed postoperative facial nerve palsy. The importance to recognize how not only cochlear but also vestibular and facial nerve are injured by the usual manipulations in the CP angle is stressed.

Animals↗
PubMed1990

[Recordings of evoked electromyographic responses from the extraocular muscles to monitor the oculomotor, trochlear, and abducens nerve function during skull base and orbital surgery].

The methods to record evoked electromyographic responses by micro malleable clip electrodes applied directly to the extraocular muscles are described. This electrophysiological monitoring enables surgeons to localize the ocular motor nerves accurately in the skull base of the middle, posterior fossa, and orbit. In cavernous sinus surgery, electrical stimulation over the dura elicited vigorous responses from the extraocular muscles and subsequently it was possible for the surgeon to avoid severing the ocular motor nerves. In orbital surgery, distended and thinned extraocular muscles were precisely localized and preserved anatomically and functionally. These monitoring methods may play the same role as electrical stimulation to the facial nerves in acoustic neuroma surgery.

Abducens Nerve↗
PubMed1990

[Cyst formation of meningioma: report of two cases and review of literature].

Cystic meningioma is rare and said to account for 1 to 2% of all types of meningioma. Here we report two cases of cystic meningioma. Case 1 is a 25-year-old man. He had suffered from sporadic epileptic seizure for about two years until the first CT was performed. It revealed a large cystic lesion at the right parietal region in touch with the midline structure. A nodular high density area was delineated in the contrast enhanced CT on the medial wall of the cyst. He showed no neurological abnormality at all. Case 2 is a 56-year-old female who had been complaining of memory disturbance, and an episode of sudden dizziness followed by a syncope that lasted for a few minutes. Neurological examination revealed slight right hemiparesis, right homonymous hemianopsia and left papilledema. A large cystic lesion was delineated at the temporal region in the plain CT, and no positively enhanced region could be found in the contrast enhanced CT. After surgical removal of the tumors, both cases were identified as cases of meningioma. They were diagnosed histopathologically as a fibroblastic meningioma and a meningotheliomatous meningioma respectively. The wall of the cyst consisted of the cortical surface per se in both cases. Preoperative diagnosis of such cases and the mechanism by which the cyst is formed were also discussed.

Adult↗
PubMed1990

[Selective injury of the vestibular and facial nerves following microvascular decompression procedures for hemifacial spasm: A case report].

Microvascular decompression procedures were carried out to relieve right hemifacial spasm in a 54-year-old man. His facial spasm was satisfactorily cured but he complained of severe vertigo, and slight facial palsy was also shown after the operation. Electronystagmograph disclosed spontaneous horizontal and rotatory nystagmus toward the non-operated (left) side. The postoperative caloric test showed profound dysfunction on the operated side. His hearing was well maintained postoperatively. These findings indicated, in addition to facial nerve injury, that the peripheral portion of the vestibular nerve was selectively damaged by the operative manipulations. It was shown that both the facial and vestibular nerves tended to be injured when the nerve trunk was shifted caudal-to-rostrally due to manipulations in the CP angle. It was stressed that caution should be paid to preserve not only the cochlear but also the vestibular nerve function in cerebellopontine angle manipulations.

Arteries↗
PubMed1989

Molecular cloning and expression in Escherichia coli of the Bacillus licheniformis bacitracin synthetase 2 gene.

The structural genes for the entire bacitracin synthetase 2 (component II) and for a part of the putative bacitracin synthetase 3 (component III) from Bacillus licheniformis ATCC 10716 were cloned and expressed in Escherichia coli. A cosmid library of B. licheniformis DNA was constructed. The library was screened for the ability to produce bacitracin synthetase by in situ immunoassay using anti-bacitracin synthetase antiserum. A positive clone designated B-15, which has a recombinant plasmid carrying about a 32-kilobase insert of B. licheniformis DNA, was further characterized. Analysis of crude cell extract from B-15 by polyacrylamide gel electrophoresis and Western blotting (immunoblotting) showed that the extract contains two immunoreactant proteins with high molecular weight. One band with a molecular weight of about 240,000 comigrates with bacitracin synthetase 2; the other band is a protein with a molecular weight of about 300,000. Partial purification of the gene products encoded by the recombinant plasmid by gel filtration and hydroxyapatite column chromatography revealed that one gene product catalyzes L-lysine- and L-ornithine-dependent ATP-PPi exchange reactions which are characteristic of bacitracin synthetase 2, and the other product catalyzes L-isoleucine-, L-leucine, L-valine-, and L-histidine-dependent ATP-PPi exchange activities, suggesting the activities of a part of bacitracin synthetase 3. Subcloning experiments indicated that the structural gene for bacitracin synthetase 2 is located near the middle of the insert.

Bacillus↗
PubMed1989

[Pathophysiology of cochlear nerve injury incurred through surgical manipulation in the cerebellopontine angle. Scanning electron microscopic observations].

Cochlear nerve injuries caused by surgical manipulation in the cerebellopontine (CP) angle were electrophysiologically and morphologically investigated in dogs. Operative procedures similar to those performed in the CP angle in humans were performed. Lateral-to-medial retraction of the cerebellar hemispheres applied traction force to the cochlear nerve. Brainstem auditory evoked potentials and compound action potentials from the intracranial portions of the cochlear nerves were recorded during the procedures. As a result of the traction force produced by manipulations in the CP angle, the Schwann-glial junctions of the cochlear nerve were separated in some dogs. The exit portions of the cochlear nerve fibers and the branches of the internal auditory artery from the tractus spiralis foraminosus at the fundus of the internal auditory canal. This finding may explain occasional occurrence of postoperative high frequency hearing loss among patients who undergo surgical manipulation in the CP angle. In some cases, massive hemorrhage and exudation of plasma were observed in the deep portion of the modiolus, where they compressed the cochlear nerve trunk. This is apparently one of the causes of intraoperative failure of cochlear function. In this study, no correlations between electrophysiological and morphological findings were established.

Action Potentials↗
PubMed1989

[A case of intracranial osteochondroma: its MR images].

A 15-year-old boy was referred to our department due to left abducens palsy and trigeminal neuralgia. CT scans that had been taken fourteen months before this referral failed to disclose any abnormality. CT scans taken on admission, however, demonstrated an irregular calcified lesion in the left parasellar region. This implied that some ossifying process had been progressing during these fourteen months. MR images clearly demonstrated tumor contour and it was shown that high and low intensity spots were evenly scattered within the tumor. Consequently, tumor appearances in MR images were totally different from those in CT scans. MR images were useful in investigating contour and extension of osteochondroma, but CT scans were necessary to locate calcified foci within the tumor.

Adolescent↗
PubMed1989

[Failure to preserve hearing in acoustic neuroma surgery: experiences after introduction of MRI].

This report elucidates our experiences on acoustic neuroma surgery, in which auditory function was lost postoperatively, although conservation of hearing had been intended preoperatively. Five ears from four patients (two ears: unilateral, three ears from bilateral acoustic neuromas) were operated on via standard retromastoid route, with monitoring of auditory evoked potentials. Abolition of ABR occurred when surgical manipulations were performed within the internal auditory canal. Pulling tumor tissue away from the cochlea toward the brain stem has proved to be a hazardous procedure. Recognizing the condition of tumor tissue within the internal auditory canal is prerequisite for hearing preservation. For this purpose, MRI is very useful because tumor tissue within the internal auditory canal can be clearly visualized. The preoperative criteria in selecting candidates for hearing preservation operations should be more strict because most acoustic neuromas with a diameter of more than 10mm cannot be resected without causing loss of hearing, and, even in such small tumors, the cochlear nerves are infiltrated by tumor cells. Most ABR changes during operations seem to be explicable from avulsion of the cochlear nerve fibers and/or the internal auditory artery from the fundus of the internal auditory canal-the tractus spiralis foraminosus. Postoperative recordings of ABR indicated that progression of degeneration of the cochlear nerve fibers occurred after surgery. This phenomenon may explain postoperative delayed hearing loss observed clinically.

Adolescent↗
PubMed1989

[The role of subarachnoid periarterial acidosis and platelets aggregation in symptomatic cerebral vasospasm: an experimental study].

The possible role of subarachnoid periarterial acidosis and platelets aggregation in symptomatic cerebral vasospasm after subarachnoid hemorrhage was studied in animal experiments. Canine or feline subarachnoid space was irrigated with low pH (6.49 +/- 0.06, N = 10) physiological saline or with high pH (8.0) Hartmann solutions after subarachnoid hemorrhage was induced by cisternal autologous blood injection. Angiographical changes of the basilar artery, neurological conditions, platelet functions in blood taken from the superior sagittal sinus, and histological findings particularly those concerning intraarterial blood were examined comparatively before and after the irrigation and, in relation to different irrigation fluids. No significant differences were observed in the angiographical changes of the basilar artery either before or after irrigation. Neither did different irrigation fluids have an effect on these changes. As for the neurological conditions, however, deterioration after irrigation was more frequent and evident in the group treated with physiological saline than in the group treated with Hartmann solution. Platelet function in the blood taken from the superior sagittal sinus also tended to be more activated in the group treated with physiological saline. In animals treated with physiological saline, histopathological examination of the autopsied brain revealed marked intraluminal platelets aggregation, particularly in the basilar artery and its branches where subarachnoid clots were mostly evident. An affirmative result for the preamble was obtained in this study.

Acidosis↗