Since computed tomography (CT)-guided stereotactic surgery is essentially blind surgery, it always involves the risk of injuring viable brain tissue and vessels. Thus, we have developed a new endoneurosurgical system for stereotactic brain surgery. This system consists of a neuroendoscope made of a Selfoc^® long rod-shaped deflective distribution lens 1.0mm in diameter, a special ultrasonic aspirator for fragmentation and aspiration of hard blood clots, a micromanipulator and a specially designed stereotactic attachment device, so that they can be accurately inserted into the optimum position from any direction.
We have applied this stereotactic endoneurosurgical system to 30 cases of intracerebral hematoma comprising 12 putaminal, 11 thalamic, 4 subcortical, 2 brain stem, 1 cerebellar hemorrhage. The mean age was 65 years old, 79% of patients were over 60 years old, mean hematoma volume was 22ml mean rate of removal was 85%, and there was no intraoperative or postoperative hemorrhage. During removal of an intracerebral hematoma, intraoperative bleeding was prevented by the direct observation of microvessels in the wall of the hematoma cavity.
This system was developed to allow application of stereotactic techniques to endoscopic surgery. The stereotactic endoneurosurgery is considered to be less invasive, safer, and more accurate, as it can be applied to removal of intracerebral hematoma.

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We report three patients with cerebral arteriovenous malformations (AVMs) treated twice each by means of gamma knife radiosurgery: Case 1; 16 year old girl with an AVM located in the splenium of the corpus callosum, Case 2; 9 year old boy with a pontine AVM and case 3; 14 year old boy with an AVM located in the left middle temporal gyrus. In cases 1 and 2, three- or two-year angiography demonstrated small persistent residual nidi and sequential angiographic studies showed no nidus shrinkage over the two year period following these examinations. In case 3, however, three year angiographic examination disclosed a residual nidus which was located outside the previously irradiated region. At the time of reirradiation, in cases 1 and 3, more than 20Gy was delivered at the periphery because the target volumes were very small and the residual nidi were located in noncritical brain structures. In case 2, however, because of the nidus location (within the pons), we selected the same dose (16Gy) as that used in the initial treatment, although this dose was not considered to be optimal. Relatively little information is available on the doses used for reirradiation: What is the safest, optimal dose for achieving AVM obliteration? Further study of many such cases is necessary to resolve these issues.
Although follow-up angiography has not yet been performed in these patients, in cases 1 and 2, magnetic resonance (MR) angiography showed no vascular abnormalities and MR images suggested nidus obliteration 29 and 20 months, respectively, after reirradiation. The three patients have experienced neither rebleeding nor complications related to irradiation for, respectively, nine, six and six years since the initial gamma knife radiosurgery.
Based on these three cases, as well as our long-term follow-up experience with AVM patients treated by gamma knife radiosurgery, we have tentatively concluded that: 1) If the initial treatment was optimal, the patient should be followed without reirradiation as long as diminution of the nidus size is angiographically verified to be ongoing, regardless of the results of examination at three years. 2) If the initial treatment was less than optimal, the second course of gamma knife treatment should be done three years after the initial irradiation.

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Ventral paraclinoid carotid aneurysms were clipped through the contralateral pterional approach in 3 patients. In all the patients, the superior hypophyseal artery arose from the inferomedial aspect of the internal carotid artery just proximal to the aneurysm. These findings strongly support Day's view that ventral paraclinoid carotid aneurysms arise from the distal crotch of the superior hypophyseal artery. The description “superior hypophyseal artery aneurysm” is also proposed by Day instead of the terminology such as ventral carotid, infraophthalmic and infrachiasmal aneurysm and others.
In the present cases, 2 patients (Case 1, 2) had unruptured aneurysms incidentally found, while Case 3 had ruptured carotid-ophthalmic aneurysm that was managed in acute stage of subarachnoid hemorrhage. These aneurysms arose from the internal carotid artery of its inferomedial aspect opposite to the origin of the ophthalmic artery. The aneurysmal necks in the present cases were smaller than 7 mm in size, and found just posterior to the anterior wall of the sella turcica on the lateral view of the carotid angiogram. In contralateral pterional approach, dissection of aneurysms in the prechiasmatic cistern is easy and neither resection of the skull base nor retraction of the optic nerve is necessary. Even in a patient with pre-fixed chiasma (Case 2), the aneurysm was clipped without difficulty. Thus superior hypophyseal artery aneurysms with small necks are good indications for contralateral pterional approach, which is less invasive to the optic nerve.

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The usefulness of the percutaneous transluminal angioplasty (PTA) and necessity of the surgical reconstructions for the atheromatous vertebral artery (VA) stenosis at the origin and mechanical VA stenosis at the first segment are discussed.
Between March 1984 and November 1992, 82 atheromatous VA stenoses at the origin were surgically reconstructed. After surgery, minor complications such as miosis (44 cases), Horner's syndrome (1 case), hoarseness (2 cases) and postoperative local bleeding requiring reoperation (2 cases) occurred. However, no additional cerebral ischemic sign was observed, and all anastomoses were patent. Between December 1992 and August 1994, 35 atheromatous VA stenoses at the origin were reconstructed. PTA was applied for 30 lesions and 27 were successful. Among them, 4 showed restenosis and one showed occlusion. Small thalamic infarction occurred 3 hours after uneventful PTA in 1 case. Ten surgical reconstructions were performed in cases of unabled PTA (3), with restenosis (2), with widespread stenosis (3), with mechanical compression (1) and with embolus distal to the VA stenosis (1)
For 45 mechanical VA stenoses at the first segment, surgical reconstructions were performed in all cases, because PTA was ineffective.
For reconstruction of the atheromatous VA stenosis, PTA seemed to be a simple, non-invasive, and effective method. But we should watch for restenosis after PTA and embolism during and after PTA. In these cases, PTA seems to be dangerous and surgery is the treatment of choice. We should be familiar with not only PTA but also surgery to get the best results and to avoid surgical complications.

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The microsurgical anatomy of trans-choroidal fissure (CF) approach for vascular lesions in and around the interpeduncular and ambient cisterns was studied using 3 cadavers treated by arterial and venous injection of the mixture of silicon with dye and barium sulfate. The angiographical “plexal point,” which shows the entrance of the anterior choroidal artery (AChA) coming into the inferior horn (IF) of the lateral ventricle, is thought to be the key anatomical landmark in the surgery for the vascular lesions in the ambient and interpeduncular cisterns. The transcortical route into IF through the inferior temporal gyrus is better for avoiding the injury of the optic radiation around IF.
After opening CF posterior to the plexal point between the hippocampal formation (fimbria) and the choroid plexus, the posterior cerebral artery (PCA) in the ambient cistern can be seen with minimal retraction of the hippocampal formation (fimbria). When retracting the brain, great care must be taken not to injure the hippocampus, the tail of caudate nucleus, and the lateral geniculate body. Additional partial resection of the uncus permits opening the interpeduncular cistern and can give neurosurgeons a working space large enough for access to the high basilar tip aneurysm and the retrochiasmatic lesions such as parasellar tumors.
Patients with PCA aneurysm or arteriovenous malformation (AVM) in and around the ambient cisterns, as well as those with AChA AVM in the medial temporal lobe, are likely to be good surgical candidates for trans-CF approach when their PCA is running nearly as high as the “plexal point” of AChA or higher.
For patients, however, whose PCA is running far lower than this point on the lateral angiography, the subtemporal approach is likely to be better than the trans-CF approach. Clinically for a patient with the ruptured PCA aneurysm and one with the AVM in the medial temporal lobe, good surgical results were achieved with this trans-CF approach.

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We developed a high-flow carotid shunt tube, which is thin-walled and tapered to four different sizes at the internal carotid end (3.5mm, 3.0mm, 2.7mm and 2.4mm in outer diameter).In experimental measurement using artificial blood (30% glycerine solution), the flow of the shunt tube was 4.1 times the Furui shunt, 3.0 times the Sundt shunt and 1.6 times the Javid shunt in comparison to similar outer-diameter tubes. Even the smallest shunt (2.4 mm tube) gave adequate flow for one cerebral hemisphere of over 300 ml/min for a static pressure gradient of 80 mmHg across the shunt.
In clinical use of the shunt, flow measurement of the shunts is made by inserting a 3 mm probe of an electromagnetic flow meter by cutting the shunt in half. In this way, we easily achieved an online accurate determination of carotid shunt flow.
Combined application of the high-flow shunts and their continuous flow measurement might allow detection not only malfunction of the shunts but hyperperfusional states of the brain. Accordingly, knowing the actual blood flow of the shunt, hyperperfusion syndrome might be inhibited by maintaining blood pressure at a lower level during and after the operation. It was satisfactorily used in all 13 cases, 14 operations.

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Ten patients (9 men and 1 woman, ranging in age from 61 to 85 years) with severe carotid stenosis were treated with percutaneous transluminal angioplasty (PTA). The stenosis rate was 64% to 94% (mean; 86%). There were 2 patients with TIA, 3 with a minor stroke, and 2 with a major stroke. The other 3 patients were asymptomatic and single photon emission CT showed decreases in CBF at the ipsilateral cerebral hemisphere in all patients. PTA was successful in all but 1 patient. The stenosis rate was reduced to 44% (mean). Two patients had no more TIA and there was no patient whose symptoms worsened. The CBF recovered in 9 of 10 patients. There was no complication related to the procedure.
Debris was aspirated from the guiding catheter in one patient after the inflation of the PTA catheter while the internal carotid artery was occluded with a protective balloon catheter. Among 7 patients who underwent 3 months or later follow-up angiography, a severe re-stenosis was demonstrated in one and moderate re-stenosis in 2.
In conclusion, the PTA for the carotid stenosis was a safe and effective method with the use of the protective balloon to avoid distal embolism. The re-stenosis after the PTA remains a problem to be solved.

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To investigate the precise hemodynamics of subclavian steal syndrome, we measured vertebral and basilar artery flow of a monkey by means of an electromagnetic flow-meter. Acute occlusion of the unilateral subclavian artery proximal to the origin of the vertebral artery produced “subclavian steal phenomen.” Namely, reversed flow of the vertebral artery on the same side is observed and basilar flow decreased to 30% of the resting level.
Numerous operative procedures have been proposed for the correction of subclavian steal syndrome. We have successfully treated 2 patients with symptomatic subclavian artery occlusive disease by the construction of axillo-axillary artery bypass grafts. These patients have been followed for 2 years, and they have experienced favorable patency and symptomatic improvement.
Operative procedures of our 2 patients are mentioned individually. Axillo-axillary bypass graft should be the first choice of surgical method for patients with subclavian steal syndrome because of its effectiveness, absence of serious complications and ease of performance.

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A series of 26 patients with cerebellar infarction were classified into 4 groups based on clinical and CT findings. Four comatose patients of these cases with cerebellar infarction (Group III) who were successfully treated with external ventricular drainage (EVD) alone, are presented. These 4 patients, who developed vertigo, nausea or vomiting, fell into a coma in 32 to 72 hours after the onset of their symptoms and were referred to our department of neurosurgery.
Computed tomography (CT) revealed swelling of the infarcted cerebellum and acute hydrocephalus, and therefore an EVD tube was inserted in place. Continuous postoperative monitoring of intracranial pressure (ICP) demonstrated EVD had sufficient control of ICP and therefore suboccipital decompression of the cerebellum was not indicated. All 4 cases made a gradual recovery. Three patients, independently ambulatory, were discharged to their home and 1 patient, ambulatory with assistance, was discharged to a rehabilitation hospital.
The results of our cases suggest that EVD should first be performed in the cases of cerebellar infarction with cerebellar swelling or edema accompanied by hydrocephalus. Posterior fossa decompression and removal of infarcted cerebellar tissue should be indicated only in cases where ICP cannot be controlled by EVD, even if there is no immediate recovery of the patient's impaired consciousness. Reviewing the literature pertinent to our cases, we discuss the use of ventricular drainage alone in the management of cerebellar infarction with ischemic cerebellar swelling.

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Direct surgical treatment of technically difficult or inoperable vascular lesions of the brain may become possible or safer using profound hypothermia and circulatory arrest.
A 40-year-old woman suffered from a subarachnoid hemorrhage. Angiography showed a large thrombosed and broad-based aneurysm arising from P2 portion of the right posterior cerebral artery (PCA). The patient underwent a right fronto-temporal craniotomy under hypothermic circulatory arrest at 19.6°C.
After exsanguination the aneurysmal sac was opened and the thrombus was removed. The artery was reconstructed by putting 3 long clips across the broad neck, which left the PCA slightly dilated. Postoperatively, she awoke with right oculomotor nerve paresis, left hemiparesis, and left homonymous hemianopsia, which improved later. Angiography showed complete obliteration of the aneurysm.
This initial experience indicates that patients with giant and thrombosed aneurysms might benefit from a surgical approach that includes the use of deep hypothermic circulatory arrest.

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We reviewed the risk for peri-operative stroke after skull base surgery in patients with pre-existing internal carotid artery (ICA) occlusion caused by tumor involvement, aneurysm or other processes. Eight operations in 7 patients on the ipsilateral side and 3 operations on the contralateral side of ICA occlusion were carried out in such patients. Two of there patients suffered a perioperative stroke due to unexpected hypotension during or after the operation. Since this experience, we have developed a protocol to evaluate these patients, and perform prophylactic cerebral revascularization.
From the retrospective review of our cases, the patient with ICA occlusion who has the following features should be considered for revascularization. 1. Young patients who are at risk for occurrence of tumor or aneurysm on the contralateral side. 2 Elderly patients with arteriosclerotic disease or other risk factors such as hypertension or smoking, because they have less ability to dilate their blood vessels. 3 The clinical history shows ischemic symptoms, and/or there is evidence of minor stroke on MRI or CT scan. 4. Low cerebral blood flow on Xenon CT scan (Xe/CT) (under 30ml/100g/min) and/or no response, or paradoxical response after acetazolamide (Diamox) test. 5. Poor collateral channels on angiography. 6. The hemisphere is mainly supplied through collateral vessels that will be potentially sacrificed or occluded by the operation. 7. In the case of contralateral ICA occlusion to the operation side, there is a significant risk of ICA injury. 8. Biologically, the tumor is non-angiogenic or hypovascular, because a hypervascular tumor will be expected to increase the blood supply of tumor itself as well as supplied hemisphere from collateral channels.

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