Biomedical subjects

K Ehara

Publications and source records attributed to K Ehara.

At least 19 recordsLinked to original sources

PubMed2001

Quantitative analysis of papaverine-mediated blood-brain barrier disruption in rats.

The blood-brain barrier (BBB) is a permeability barrier of interconnected brain capillary endothelial cells. Intraarterial infusion of papaverine relieves cerebral vasospasms by inhibiting smooth muscle contractions and it may simultaneously lead to a disruption of BBB permeability. To date, the mechanism underlying this phenomenon and the quantification of BBB disruption remains elusive. We first examined the changes in cerebrovascular permeability after an intracarotid infusion of papaverine (0.20%) in rats by an in situ brain perfusion technique. We then demonstrated that changes in cerebrovascular permeability depend on the concentration of papaverine. This is the first study in which the degree of BBB disruption was accurately quantified in terms of [(14)C]sucrose and it was demonstrated that papaverine has a prolonged effect on cerebrovascular permeability. This result suggests the importance of in vivo experiments for a precise evaluation of permeability for many other agents, particularly for the central nervous system.

Animals↗

PubMed2001

Surgical approaches and strategies for skull base chordomas.

OBJECT: The management of chordomas involving the skull base continues to present a number of treatment-related problems. Recently, both radical resection and charged-particle irradiation or stereotactic radiosurgery have reportedly been found effective for tumor control and for promoting a better quality of life in patients. In this article the authors analyzed the outcomes in 17 patients with skull base chordomas who were surgically treated at Kobe University Hospital between 1972 and 2000. METHODS: Preoperative radiological examinations included magnetic resonance imaging, computerized tomography, angiography, and balloon occlusion test of the internal carotid artery. Among the various surgical approaches used to remove the tumor were the frontoorbitozygomatic, transmaxillary, transcondylar, transsphenoidal, and the transbasal. Total removal was achieved in two (12%), near-total removal in three (18%), subtotal removal in nine (52%), and partial removal in three patients (18%). Since 1990, chordomas have been radically resected via various skull base approaches; the combined total or near-total removal rate has been 80% in this period. Radical removal of the tumors has not led to an increased risk. At the final follow-up review (mean 59.5 month), 75% of the patients were still alive, and 25% had died of chordoma recurrence. The overall recurrence-free survival rate was 82% at 3 years and 51% at 5 years. The 5-year recurrence-free survival rate in the five patients who underwent the operation during the past decade was 77% (mean follow up of 5.2 years). In two patients with recurrent tumors who underwent radiosurgery, no evidence of tumor regrowth was demonstrated at 3 years posttreatment. CONCLUSIONS: The authors suggest that for the treatment of skull base chordomas radical resection is a key factor for longer survival and improved quality of life. Patients with sufficiently small tumors, which show a favorable configuration and location, can be suitable candidates for stereotactic radiosurgery.

Adolescent↗

PubMed2000

Spontaneous peritumoral haemorrhage associated with sinus confluence meningioma: case report.

BACKGROUND: Torcular or sinus confluence meningioma is rare and surgically formidable. This reported sinus confluence meningioma was associated with peritumoral intracerebral hemorrhage. The surgical strategy and the mechanism of peritumoral hemorrhage are discussed. CASE DESCRIPTION: A 42-year-old woman presented with a history of headache, vomiting, and cerebellar dysfunction for 2 months. Plain computed tomography (CT) scan and magnetic resonance imaging (MRI) demonstrated a high-density mass in the torcular region involving both lateral sinuses. MR angiography demonstrated complete occlusion of the left lateral sinus and straight sinus and stenosis of the right lateral sinus. Two years after her first operation she experienced sudden headache and left upper quadrant hemianopsia. Plain CT scan and MRI showed a hyperintense tumor in the torcular region with an intracerebral hematoma in the right occipital lobe. An angiogram demonstrated occlusion of the caudal part of the superior sagittal sinus, bilateral transverse sinuses, and straight sinus. Gross total removal of the tumor was done along with the left lateral sinus through a suboccipital and a supratentorial occipital craniotomy in the first operation. The patient underwent total resection of the tumor at second operation through a bilateral occipital and suboccipital craniotomy along with resection of the dura including the confluence, the caudal part of the superior sagittal sinus, the right lateral sinus, and the straight sinus. The postoperative course was uneventful and postoperative MRI showed total removal of the tumor. CONCLUSION: Sinus confluence meningioma may present with peritumoral hemorrhage. Radical removal may be possible when the sinus confluence is completely occluded and there is good collateral drainage.

Adult↗

PubMed2000

Image-guided microsurgery with the Mehrkoordinaten Manipulator system for cerebral arteriovenous malformations.

Four patients with cerebral arteriovenous malformations (AVMs) underwent image-guided microsurgery with the Mehrkoordinaten Manipulator (MKM) system, which integrates a robotic microscope with a computer workstation. The patients were all male, from 8 to 51 years old (mean = 24), all presenting with intracerebral haemorrhage. The lesion was located in the deep sylvian fissure in one patient, the fronto-parieto-occipital area in one and the trigone in two. Stereotactic computed tomography and magnetic resource imaging of 1-mm slices were taken. The extent of AVM and the draining vein, predetermined with the MKM workstation, could be superimposed on the microscopic view, resulting in minimum scalp incision and craniotomy, as well as allowing for a stereotactic approach to deep-seated lesions. Superimposition of the contour of the lesion was also useful for resecting the lesion, although intraoperative diagnosis of the total resection required intraoperative digital subtraction angiography. In conclusion, image-guided microsurgery with the MKM system can assist minimally invasive and maximally effective microsurgery for cerebral AVMs.

Adolescent↗

PubMed1999

Transcranial Doppler findings during balloon test occlusion of the internal carotid artery.

The authors performed transcranial Doppler ultrasonography (TCD) during internal carotid artery (ICA) balloon test occlusion (BTO) and observed changes in mean flow velocity (Vm) in the middle cerebral artery (MCA), and pulsatility index (PI) while monitoring the stump pressure (Sp) of the internal carotid artery (ICA), and neurologic findings. A group of 17 patients requiring possible temporary or permanent occlusion of the ICA in the course of planned procedures first underwent BTO. A patient who either developed neurologic changes or maintained less than 60% of preocclusion Sp or Vm in the ipsilateral MCA during BTO was considered to have a positive test. Eleven patients had negative results, while in six patients, tests were positive. Mean flow velocity showed a decrease after occlusion in all cases but not to a remarkable extent in some patients. Stump pressure decreased in all negative cases after balloon inflation and than tended to increase progressively during 15 minutes of BTO. Pulsatility index tended to decrease gradually during BTO in all negative patients. However, in positive cases, PI and Sp fell steeply. Only one positive case had a neurologic symptom of severe headache. The decreased PI in the MCA reflected autoregulatory dilation of cerebral vessels to compensate for decreased absolute cerebral blood volume following ICA occlusion. Changes in PI are a good indicator for evaluating blood flow during BTO.

Blood Flow Velocity↗

PubMed1997

Experimental syringomyelia: late ultrastructural changes of spinal cord tissue and magnetic resonance imaging evaluation.

BACKGROUND: In human hydrosyringomyelia and in the late stage of experimental syringomyelia, the spinal cord tissue adjacent to the syrinx is exposed to a similar pathophysiologic condition. We investigated the ultrastructural changes in the late stages of kaolin-induced syringomyelia, and in addition, we presented magnetic resonance imaging (MRI) findings of the cervicomedullary junction and syrinx, and the nature of edema in the spinal cord of this experimental model. METHODS: Syringomyelia was induced in rabbits by intracisternal injection of kaolin. MRI was performed at 6 weeks, and 6 and 12 months following injection, and the animals were killed by transcardial perfusion of formaldehyde solution and examined by transmission electron microscopy. Evans blue was injected intravenously in six rabbits, 6 weeks and 12 months following kaolin injection and was examined by confocal laser scanning microscopy. RESULTS: MRI showed that the syrinx communicated with the fourth ventricle in most animals. Demyelination of varying degrees and slight edematous change were seen in the perisyrinx white matter. No extravasation of Evans blue was seen by confocal microscopy. Abundant astrocytic proliferation with a large number of glial filaments was seen at the margin of the syrinx and between the axons in the perisyringeal region. The perivascular space enlargement occurred in both the gray and white matter. The endothelial junctions appeared intact. Regenerating axons and remyelination by oligodendrocytes were seen occasionally. CONCLUSIONS: The MRI confirmed the communication between the fourth ventricle and the syrinx. The ultrastructural changes were almost identical to those of the early stage syrinx, but the astrocytic proliferation was more severe, and the edema was less in the late stage. The perisyrinx edema appeared to be of the interstitial type, as in hydrocephalus. Axonal degeneration and demyelination continued with abortive attempt at regeneration and remyelination in the less edematous late stage, which might be the cellular basis for the persistence or worsening of clinical symptoms and signs in the chronic stage of syringomyelia even after surgical treatment.

Animals↗

PubMed1997

[Usefulness of fronto-orbito-zygomatic approach for intraorbital tumors: report of 31 cases].

We have encountered 31 cases of intraorbital tumors at the Kobe University Hospital between 1971 and 1996. We reviewed those cases taking into account the surgical approaches used, the removability of the tumors and functional outcome. Before 1991, frontal or fronto-temporal craniotomy had been mostly used whereas the fronto-orbito-zygomatic approach or fronto-orbital approach has been used only since 1992. After introduction of these approaches, functional outcome was significantly improved. Most of the tumors have been successfully removed totally. In particular, this approach is thought to be useful for tumors located in the deep portion of the orbit and for tumors extending intracranially. In addition, removal of the anterior clinoid process and the opening of the optic canal as well as the superior orbital fissure provides a wider operative view and enables the transposition of the optic nerve safely.

Adenoma, Pleomorphic↗

PubMed1994

Cerebral blood flow of rats with water-intoxicated brain edema.

Water intoxication brain edema was produced in rats by intraperitoneal loading of excessive amounts of distilled water (DW). In 10% and 20% groups, DW in amounts of 10 or 20% of body weight was injected, respectively. Water content of brain tissue increased proportionally to the amount of injected water, as follows: 79.8% of wet weight in control, 80.5 and 82.4 in 10% and 20% DW groups, respectively. Since cerebral blood flow (CBF) values measured by laser Doppler (LD) flowmetry were found to give a good correlation with those by hydrogen clearance method in a preliminary experiment, CBF measurement were carried out using LD flowmetry thereafter. Before the injection, CBF values were around 50 ml/min/100 g. Two hours after the water loading, CBF values in 10% and 20% DW groups were 25.6 and 20.3 ml/100 g/min, respectively. CBF values under these edematous condition decreased significantly (p < 0.001 by paired t-test) in proportion to the severity of the brain edema.

Animals↗

PubMed1994

Experimental syringomyelia in the rabbit: an ultrastructural study of the spinal cord tissue.

Hydrosyringomyelia was produced experimentally by the injection of kaolin into the cisterna magna of the rabbit, and the ultrastructural changes of the spinal cord surrounding the syrinx were investigated 2, 4, and 6 weeks after injection by transmission electron microscopy. The ependyma at the ventral part of the central canal was flat and stretched, whereas, in the dorsal part, it was split, and the syrinx extended through the dorsal median plane in most animals. Extracellular edema was found in the subependymal white matter and in and around the posterior median septum. Many nerve fibers surrounding the syrinx were in varying stages of axonal degeneration. Myelin sheaths were split, thinned, and completely lost in many nerve fibers. In some fibers, the axons were totally lost, leaving the myelin sheaths as empty tubes. Astrocytic processes containing a large number of glial filaments covered the nerve fibers adjacent to the syrinx and partially replaced the edematous area. The perivascular spaces were enlarged, especially near the syrinx and in the dorsal white matter. Oligodendrocytes remained undamaged, and the remyelination by oligodendrocytic processes was seen on some denuded axons. Sometimes, this further remyelination was abortive, especially where the edema was severe. The ultrastructural changes of the neural tissue and their sequences were identical, in most respects, to those of hydrocephalus and noncommunicating syringomyelia. The oligodendrocytic remyelination with ongoing demyelination found in this model has many similarities to those in experimental hydrocephalus.

Animals↗

PubMed1993

Intraorbital arteriovenous malformation: case report.

A case of intraorbital arteriovenous malformation presenting with visual loss, exophthalmos, and chemosis of the right eye is reported. Enhanced computer tomography and magnetic resonance imaging showed extraocular muscle enlargement and vascular abnormality in the right retrobulbar space. Angiography revealed an abnormal intraorbital vascular stain with an extremely dilated right ophthalmic artery. Total removal of the intraorbital contents was performed after unsuccessful endovascular and surgical treatment of arteriovenous malformation (AVM). Histopathological examination disclosed an AVM in the retrobulbar fatty tissue with extension into the extraocular muscles and optic nerve.

Adult↗

PubMed1993

Cerebral hyperperfusion during surgical resection of high-flow arteriovenous malformations.

Cerebral hemodynamics were evaluated in 16 patients with arteriovenous malformations (AVMs) using intraoperative thermogradient or laser Doppler flowmeter. The postexcision/preexcision blood flow ratio was determined. Two of seven patients with large AVMs (> or = 4 cm) developed a postoperative hematoma. Their flow ratios were larger than 1.9. In 4 patients with large AVMs, their blood flow ratios were reduced from an initial ratio exceeding 2.0 to less than 1.5 using carotid or special flow regulation clamps. These patients did not develop any hemorrhagic complication. In 9 patients of small AVMs (< 4 cm), the ratio was significantly low and there were no hemorrhagic complications.

Adolescent↗

PubMed1993

Spinal cord edema following freezing injury in the rat: relationship between tissue water content and spinal cord blood flow.

A spinal cord edema model was developed in the rat by inflicting a freezing injury at -40 degrees C for 3 minutes. Regional spinal cord blood flow, tissue water content, and histology were examined. White matter edema had extended several segments by 8 hours after the injury. Tissue water content increased by 20.6% at 24 hours. Spinal cord blood flow in surrounding tissues decreased by more than 25% 4 hours after the injury. The progression of spinal cord edema following freezing injury appeared to be due to disruption of the blood-spinal cord barrier.

Animals↗

PubMed1992

Tyrosine protein kinase is involved in anti-IgM-mediated signaling in BAL17 B lymphoma cells.

BAL17 B lymphoma cells, representing mature B lymphocytes, were used to analyze the role of tyrosine kinase in B cell activation. Anti-IgM-induced tyrosine phosphorylation was inhibited by preincubation of cells with tyrosine kinase inhibitor herbimycin A. Enzymatic activity of lyn protein was also inhibited by this drug, accompanied by down-regulation of p53lyn and p56lyn. However, a protein kinase C-mediated event was intact in the herbimycin A-pretreated cells, suggesting that the inhibitor acts selectively on tyrosine kinase. Anti-IgM failed to stimulate herbimycin A-pretreated cells to induce increases in inositol phospholipid metabolism or increased [Ca2+]i, whereas aluminum fluoride-induced metabolism was not altered. Moreover, membrane IgM density as revealed by flow cytometry was not changed by herbimycin A. These results indicate that tyrosine kinase(s) participates in the coupling of an Ag receptor cross-linkage to phospholipase C activation through a phosphorylation event in B lymphoma cells.

Animals↗

PubMed1992

Anterior choroidal artery syndrome after surgery for internal carotid artery aneurysms.

We report five patients with anterior choroidal artery syndrome after surgery for internal carotid artery aneurysms. All patients suffered hemiparesis, and hemisensory loss and homonymous hemianopsia were identified in 2 patients. The characteristic triad of the syndrome was recognized in only 1 patient. Dominant and nondominant cerebral hemisphere signs have been reported in association with this syndrome, and 2 patients had a speech disturbance in our series. In previous reports, neurological deficits were mild and patient prognosis was good in anterior choroidal artery infarct, in spite of the fact that the artery supplied the corticobulbar and corticospinal tracts. This report suggests the possible causes of this syndrome after surgery for internal carotid aneurysms, which involve vasospasm after subarachnoid hemorrhage, mechanical obstruction, thromboembolism, and distortion of the aneurysm clip.

Adult↗

PubMed1991

Giant carotid-ophthalmic artery aneurysms: direct clipping utilizing the "trapping-evacuation" technique.

The authors have devised a "trapping-evacuation" technique to facilitate direct clipping of giant aneurysms in the paraophthalmic region of the internal carotid artery (ICA). The giant aneurysm is collapsed by first trapping the aneurysm by temporary occlusion of the cervical common carotid and external carotid arteries, along with temporary clipping of the intracranial ICA distal to the aneurysm. Thereafter, intra-aneurysmal blood is simultaneously aspirated through a catheter placed in the cervical ICA. Exposure of the proximal end of the aneurysm neck is mandatory for successful clipping. This is accomplished by extensive unroofing of the optic canal, removal of the anterior clinoid process, opening of the anterior part of the cavernous sinus, and exposure of the most proximal intradural (C2) and genu (C3) portions of the ICA. Four cases of giant aneurysms of the paraophthalmic ICA were successfully treated by this technique and the postoperative outcome was good in all cases. Preoperative magnetic resonance imaging for evaluation of the anatomical details, balloon occlusion test of the ICA, and intraoperative measurement of cortical blood flow were important to the success of the operation. Intraoperative digital subtraction angiography via the catheter placed in the cervical ICA was useful in confirming successful clipping.

Aged↗

PubMed1991

Cerebral arteriovenous malformations: factors influencing the surgical difficulty and outcome.

The outcomes of 151 patients with arteriovenous malformations (AVMs) treated either surgically or conservatively are presented. In terms of long-term survival rate and follow-up results, the patients who underwent total excision had more favorable results than did those treated conservatively. Patient age was the most important clinical factors, with the preoperative level of consciousness being the second most important. A grading system was formulated on the basis of the angiographical factors by using multiregression analysis; the size of the AVM influenced the surgical outcome twice as much as did the location and the pattern of arterial feeding. Thus, a large AVM (greater than or equal to 4 cm) was given 2 points; a small AVM (less than 4 cm) was given 0 points; a deep AVM was given 1 point; a superficial AVM was given 0 points; an AVM supplied by three of more artery systems was given 1 point; and an AVM supplied by one or two artery systems was given 0 points. AVMs were categorized into 5 grades from Grade 0 to 4 by the summation of these points. Predicted Karnofsky scale after surgery was calculated by this grading system and the following equation: predicted Karnofsky scale = 87.2 - 5.6 x Grade. Grade 0 and 1 AVMs showed high rates of total excision (Grade 0, 94%; Grade 1, 82%) and of satisfactory outcome (Grade 0, 90%; Grade 1, 82%) and were classified as "easy" lesions. Grade 2 AVMs are lesions classified as "moderate" and had a total excision rate of 76% and a satisfactory outcome rate of 71%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1991

[Blood flow, CO2 response and autoregulation in the rat spinal cord by laser-Doppler flowmetry and hydrogen clearance].

Spinal cord blood flow (SCBF) was measured simultaneously by laser Doppler flowmetry (LDF) and hydrogen clearance (HC) in the normal Wistar rats. Under normal physiological condition, SCBF values by HC was 45.0 +/- 1.7 ml/min/100 g at the level of Th-8. LDF values were well correlated (r = 0.78) to the SCBF measured by HC, where linear regression line was obtained as y = 14.2x - 1.58. Absolute SCBF values of LDF were also calculated as 43.7 +/- 1.3 mg/min/100 g using this equation. CO2 response of SCBF were 1.09 ml/min/100 g/mmHg by HC and 1.01 ml/min/100 g by LDF, respectively. Autoregulation of SCBF maintained at a range of 55 -155 mmHg of mean arterial pressure in both methods. In conclusion, LDF is a useful technique for continuous SCBF monitoring. Since absolute SCBF value in LDF has some variance, the relative value is more suitable for accurate evaluation of SCBF during time course of an experiment.

Animals↗

PubMed1990

Hydrocephalic oedema in normal-pressure hydrocephalus.

The hydrocephalic oedema in normal-pressure hydrocephalus (NPH) was evaluated by measurement of the relaxation time of protons of the water molecules of brain tissue. Patients with NPH were divided into two groups: shunt responders and shunt non-responders. In the group of shunt responders both T1 and T2 of periventricular white matter were significantly prolonged compared to those of controls, and shortened after shunting. Both T1 and T2 of white matter were significantly longer than of gray matter, while a reversed relationship was seen in normal controls. However, in the group of shunt non-responders, T1 of white matter was significantly prolonged, while T2 of the same area not. There was no change in either T1 or T2 of this region after shunting. Both T1 and T2 were almost the same in white and gray matter in shunt non-responders. It is suggested that periventricular abnormalities seen in various diseases may be distinguished on the basis of the relaxation behavior of protons of tissue water.

Body Water↗