To clarify the efficacy of extracranial/intracranial arterial bypass (EC/IC bypass) surgery in treatment of patients with occlusive cerebrovascular disease, we retrospectively analyzed the clinical and hemodynamic results in the patients who underwent EC/IC bypass surgery in our institute. In the last 7 years, we have carried out EC/IC bypass surgery in 75 patients with occlusive cerebrovascular disease. In these patients, we analyzed the following points: 1) correlation between preoperative angiographic/hemodynamic status and postoperative improvements of hemodynamic status, 2) correlation between postoperative improvements of hemodynamic status and neurological function after surgery, and 3) correlation between postoperative improvements of hemodynamic status and ischemic episodes after surgery. Postoperative improvements of hemodynamic status were achieved in patients who had both spontaneously developed leptomeningeal anastomosis and decreased reactivity of cerebral blood flow to acetazolamide before surgery. Obvious improvements of neurological function were noted soon after surgery in 11 patients. All of these 11 patients showed marked improvements of hemodynamic status. After surgery, 64 patients did not have any ischemic episodes, but 8 experienced transient ischemic attacks and 3 suffered from cerebral embolic infarctions. Of these 11 patients with postoperative ischemic episodes, 10 had improvements of hemodynamic status. EC/IC bypass surgery can improve hemodynamic status in patients with obviously impaired hemodynamic reserve and has a potential to improve neurological functions impaired by hemodynamic insufficiency. However, there were no correlation between improvements of hemodynamic status and occurrence of ischemic episodes. Even in the patients with hemodynamic insufficiency, the major mechanism of ischemia may be embolic.

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Both international and Japanese cooperative studies have failed to prove the positive effects of EC-IC bypass surgery for the prevention of stroke. However, we believe STA-MCA anastomosis is effective in improving the symptoms of hemodynamic cerebral hypoperfusion. Our candidates of STA-MCA anastomosis are stroke patients with both reduced cerebral vascular reserve and clinical symptoms due to cerebral hypoperfusion. The anastomosis to the insular segment of MCA can offer more blood supply than the anastomosis to the cortical branch, and is less invasive than the high flow bypass. It is also indicated in aneurysm cases of the intracavernous internal carotid artery with good collateral circulation.

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Premature rupture of a cerebral aneurysm during operation is a serious hazard. Temporary clipping of intracranial arteries has emerged as a valuable technical adjunct in the management of intracranial aneurysms. During a 4-year and 3 month period, 89 patients (35 ICA aneurysms, 23 MCA aneurysms, and 31 ACA territory aneurysms) who underwent elective temporary occlusion under normothermia and normotension were evaluated with regard to the appearance of clinical and radiological evidence of cerebral infarction in the early postoperative period. 73 of 89 patients were consequetively monitored with SEP during operation. Median nerve SEPs were used in 29 ICA and 19 MCA aneurysm operations, while posterior tibial nerve SEPs were used in 25 ACA aneurysm operations. Temporary clipping was used once in 62 cases, twice in 18 cases, three times in 7 cases and 4 times in 2 cases. Application form of temporary clipping was proximal clipping in 47 cases and trapping in 42 cases. Temporary clipping time was as follows: ICA aneurysms; 14.0±11.8 minutes, MCA aneurysms; 12.6±7.4 minutes, ACA aneurysms; 19.3±16.4 minutes. Ischemic group representing positive neurological deficits or asymptomatic perforating artery territory infarction showed longer temporary clipping time than that of non-ischemic group. Neurological deficits occurred in 6 cases (6.7%). Permanent left hemiplegia with a right hemispheric infarction developed in a ICA aneurysm case following trapping of ICA for 60 minutes. Transient neurological deficits included one ICA aneurysm with right hemiparesis, two MCA aneurysm cases with motor aphasia and sensory aphasia, and two ACA aneurysm cases with left hemiparesis. All but one positive neurological deficits cases underwent trapping as temporary clipping for somewhat longer period. Both the Acorn A aneurysm case with transient left hemiparesis and the MCA aneurysm case with transient sensory aphasia were considered as SEP false negative cases. 15 cases (16.9%) had asymptomatic perforating artery territory infarction, which included 4 cases in putamen and 4 cases in caudate with ICA aneurysm case, one case in globus pallidus with MCA aneurysm case, and 5 cases in caudate and one case in putamen with ACA aneurysm. 12 of 15 cases with asymptomatic peforating artery territory infarction underwent trapping as temporary clipping. Perforating artery territory was demonstrated to be weak in cerebral ischemia following temporary clipping of main trunk of cerebral artery in aneurysm surgery as expected in the mechanism of cerebral infarction for major trunk occlusion such as ICA occlusion.

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Generally, neurological deficits due to the mass effect of giant aneurysm are more severe in the posterior than in the anterior circulation. Direct surgical attack on giant thrombosed vertebral aneurysm involves trapping, and aneurysmectomy is often difficult. We report three cases of surgically treated giant thrombosed vertebral aneurysm, who presented with signs of mass effect without subarachnoid hemorrhage. Two cases were managed with partial aneurysmectomy after trapping of the vertebral artery, and one case with trapping and aneurysmectomy. Surgical results were satisfactory in all cases.
Internal decompression by thrombectomy, aneurysmectomy and trapping of the vertebral artery are thought to be reasonable operations for these aneurysms. In particular, the transcondylar approach is very useful in all cases. We discuss the operative method and intraoperative management of these aneurysms.
When the aneurysm is embedded in the brain stem, only a partial aneurysmectomy should be performed. Otherwise the brain stem will be injured and serious complications will occur. To reduce permanent severe complications of this operation, we use the following procedure.
1) Pre-operative precise diagnosis by using MRI and 3D-CT is very useful to determine the relation between the aneurysm, parent artery and the location of thrombus.
2) Trans-condylar approach is necessary to widen the operative field and to confirm of the position of the contralateral and distal vertebral artery.
3) Intraoperative continuous monitoring of SEP is necessary to monitor the brain stem function during operation.
4) Miniture doppler probe and micro optic fiber are useful aids to surgery.

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Helical CT scanning is a new technique that can continuously generate a volume of data. The data thus aquired with contrast medium is reconstructed for three-dimensional CT angiography (3D-CTA), including 3D-angiographic image using the volume rendering method, 2D-MIP image using maximum intensity projection method and 3D-endoscopic image using the surface rendering method.Nineteen cervical carotid artery stenoses in II patients were studied with 3D-CTA. Nine lesions in 7 patients of these cases underwent carotid endarterectomy (CEA). These 3D-CTA findings were compared qualitatively to DSA (digital subtraction angiography) findings and endarterectomy specimens.
3D-angiographic image clearly visualizes severe stenosis and occlusion of carotid artery without calcification. Carotid artery stenosis with extensive calcification is not always demonstrated such as the stenotic change of the carotid artery. 3D-endoscopic image shows vessel lumen and the inner surface of plaque bulgings and strictures, simulating angioscope. But this image is also modified by calcification. Therefore, an MIP image is useful to detect calcification in the stenotic lesion. A superimposed image of angiographic image and MIP image or endoscopic image and MIP image is more useful.
Although this technique requires further development and clinical evaluation, 3D-CTA is very valuable for the evaluation of carotid artery stenosis.

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Fifteen patients of ruptured intracranial vertebrobasilar artery dissection (VBDA) were studied to clarify the clinical problems during treatment. Subsequent rebleeding occurred in 5 of the 15 cases (33.3%) and the mortality rate of patients with rebleeding was 40%. All subsequent rebleeding cases were VBDA of the distal to PICA type. These patients were divided into two groups consisting of a surgical treatment group (chronic stage) with 9 cases and a nonsurgical treatment group with 6 cases. Surgical procedures included proximal occlusion (PO) of the vertebral artery in 7 patients, wrapping in 1 and direct clipping in 1. Postoperative complications occurred in 3 patients by PO. Although proximal occlusion seemed to be a simple and useful method to prevent rebleeding, the occurrence of ischemic complication remains to be solved. Further study is needed to determine the best treatments, including PO for VBDA.

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The frequency of unruptured cerebral aneurysms detected by magnetic resonance angiography (MRA) was analyzed retrospectively in 341 consecutive patients with headache at Yamagata Prefecture Kahoku Hospital between January 1992 and December 1994.
There were 162 males and 179 females, aged from 11 to 87 years old (mean, 50.4 years old). None of the patients had intracranial lesion. MRA detected unruptured cerebral aneurysm in 18 patients (5.3%), 6 males and 12 females, aged from 42 to 79 years old (mean, 60.1 years old). Five patients were between 40 and 49 years old, 3 were between 50 and 59 years old, 6 were between 60 and 69 years old, and 4 were between 70 and 79 years old. None was less than 40 years old or more than 80 years old. The frequency of unruptured cerebral aneurysms was reported to be 4.7-7.1% by routine“brain dock”examinations and IA-DSA, and the meanage was over 5 years older than that of patients with headache. The frequency of unruptured cerebral aneurysms is 7.9% in the 228 patients with headache, excluding those aged less than 40 years or more than 80 years.
Patients with headache tend to be younger than those undergoing routine“brain dock”examinations, suggesting that unruptured cerebral aneurysm is more frequent in patients with headache.

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We describe a case of de novo aneurysm formed 2 years and 8 months after the initial cerebral angiogram. The patient, a 52-year-old male, suffered from subarachnoid hemorrhage on September 25, 1996. He was admitted to our department two days after onset. He has a past history of cerebral infarction and hypertension. Cerebral angiogram revealed an aneurysm at left A₁-A₂, junction that was not found on his first angiogram. We diagnosed this as a de novo aneurysm and performed an operation on September 30. The ruptured aneurysm was successfully clipped through the left pterional approach. He was discharged from our hospital with no neurological deficits. De novo aneurysms are not common findings and most are formed because of the change of hemodynamics of the circle of Willis after IC occlusion has taken place or IC ligation has been carried out.
Some authors reported the coexistence of this new aneurysm and a persistent primitive artery. In our case, there was no vascular anomaly that influenced the formation of de novo aneurysm nor a history of the operation of other aneurysms. It is very interesting that a de novo aneurysm could be formed within a very short follow-up period as in our case, in which the aneurysm was not accompanied by subarachnoid hemorrhage at the first cerebral angiogram. In this paper we discuss the nature of de novo aneurysm and compare our case with the reported cases.

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We report a case of a large aneurysm originating from a peripheral middle cerebral artery. A 27-year-old man, who was admitted for a minor head injury, had an asymptomatic peripheral aneurysm of the left middle cerebral artery. He had no history of congenital heart disease, systemic infectious disease, or severe head injury.
On intraoperative inspection the aneurysm was a fusiform type and had a smooth and thick wall, which suggested that the aneurysm was congenital in origin. The aneurysm was treated with dome clipping.
We discuss the origin and treatment of peripheral middle cerebral artery aneurysms with a review of literature and emphasize the usefulness of 3D-CT angiography.

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It is ideal for the occlusion of chief cerebral artery to perform revascularization safely by some means in the ultraacute stage. Unfortunately, when the revascularization cannot be carried out, massive cerebral edema often occurs. Massive cerebral edema often causes lethal transtentorial herniation. Three patients with extensive cerebral infarction underwent decompressive craniectomy at the moment low density area was found on the computed tomography, that is, before massive cerebral edema occurred. This avoided complications of not only lethal transtentorial herniation but also secondary neurological deficits due to cerebral edama. Early decompressive craniectomy may have positive therapeutic significance in prevention of secondary neurological deficits due to massive cerebral edema.

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It is rare to encounter subarachnoid hemorrhage (SAH) whose origin cannot be detected by cerebral angiography. Occasionally, the detection is prevented by initial disappearance of the cerebral aneurysm as soon as it has ruptured. The collapse of cerebral aneurysm might be caused by perianeurysmal hematoma and brain, the thrombosed aneurysm, early cerebral vasospasm, and unknown etiology. We encountered a ruptured aneurysm that was finally detected by cerebral angiography in the third examination. The aneurysm was partially thrombosed pathologically. We speculate on the management of SAH whose origin cannot be detected by cerebral angiography.

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