We investigated cerebral blood flow (CBF) and metabolism in patients with hemodynamic ischemia by positron emission tomography (PET) and thermal diffusion flow meter. We also studied neuropsychological functions to evaluate the effects of surgical revascuralization.
Bypass surgery of the superficial temporal artery to the proximal middle cerebral artery was performed on 26 patients satisfying the following categories: 1) stenosis or occlusive lesion in main cerebral arteries; 2) no marked focus of infarction on CT or MRI. PET was performed before and 1 month after the operation, and CBF, the cerebral metabolic rate of oxygen (CMRO₂) and oxygen extraction fraction (OEF) were analyzed. Cerebrovascular reserve capacity (CVRC) was also calculated after acetazolamide challenge. CBF during the operation was continuously measured with a thermal diffusion flow meter. CO₂ response of CBF was analyzed before and after anastomosis. Neuropsychological functions were evaluated by Hasegawa dementia scale revised (HDS-R), minimental state examination (MMSE) and Wechsler adult intelligence scale revised (WAIS-R).
Before the operation, increase in OEF accorded with the decrease in CBF, and a significant relationship between both CBF and CVRC, and OEF and CVRC was found. A decrease in CVRC was noted prior to a decrease in CBF and elevation of OEF. CVRC caused by acetazolamide might reflect CO₂ reactivity. Significant improvement of CBF and CVRC, and normalization of OEF were observed after the operation. Also, significant improvement of neuropsychological function was observed by HDS-R and WAIS-R. Disturbance in neuropsychological function might reflect elevation of OEF.

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Recently it has been proved that carotid endarterectomy (CEA) is effective for the prevention of major stroke for the patients with symptomatic severe carotid stenotic lesion. However, the efficacy of extracranial-intracranial arterial bypass (EC-IC bypass surgery) for the patients with cerebrovascular occlusive lesion is still controversial. Several cooperative trials to clarify the surgical efficacy of stroke prevention and improvement of brain function had been unsuccessfully attempted. Despite this situation, a considerable number of neurosurgeons still believe bypass surgery should play some role in the treatment of cerebral ischemia.
In this paper, we review the pathophysiology of cerebral ischemia, and discuss how to surgically treat it.

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We describe a case involving a partially thrombosed large vertebral artery (VA)-posterior inferior cerebellar artery (PICA) aneurysm presenting with hemifacial spasm. The intraoperative findings revealed the cause of the hemifacial spasm was compression of the root exit zone of the facial nerve by the anterior inferior cerebellar artery, which was displaced by the aneurysm. Clipping of the aneurysm neck and decompression of the facial nerve were successfully performed by neuroendoscopy-assisted microneurosurgery.

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For the clipping of aneurysmal neck with preservation of main branches or perforators of cerebral arteries, we have used endoscope-assisted technique for 51 aneurysms over the last five years.
Aneurysms clipped with the assistance of endoscope include 8 involving the internal carotid-ophthalmic artery, 26 involving the internal carotid-posterior communicating artery (IC-PC) and 11 involving the basilar artery. Thirty-two aneurysms (63.1%) were non-ruptured among them. Four types of rigid endoscope (Olympus and GAAB: angle; diameter, 0; 4mm, 30; 2, 7mm, 70; 4mm, and 110; 4mm, respectively) were applied to observe the arterial branches or perforators before, during, and after neck clipping. Some aneurysms were clipped under the microscope following endoscopic observation, and some were clipped under the microscope during the observation by endoscope, whose head was seated near the aneurysms.
Some branches and many perforators that were not identified preoperatively by angiography and intraoperatively by microscope could be preserved under the endoscopic observation. No patients angiographically tested had incomplete clipping. Most patients had an uneventful course, but 1 with IC-PC aneurysm revealed temporary oculomotor palsy. There were initially several problems to be solved: 1) the poorer resolution of picture obtained by endoscope compared with that by microscope; 2) the disturbance of operative handling by using endoscope system; 3) inability of synchronized view between endoscope and microscope. These have been mostly solved. The rigid-type endoscope gives better resolution, electromagnetic-powered point setter makes both hands free from handling of endoscope and a new microscope that has an overlay system has been produced by a company (Olympus, ME 8000).
These safer and more satisfactory results indicate that endoscope assisted technique could be applicable not only for the intraventricular surgery as we have discussed but for the clipping of aneurysms.

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Complete clipping is sometimes difficult in cases with large internal carotid artery (IC) aneurysms adjacent to the distal dural ring even if various approaches are applied. To ensure safe and sure aneurysmal microsurgery, we have been using endoscopes with various angled tips, thus helping to observe the aneurysmal neck and branches from the IC in the blind spot by a surgical microscope. We used endoscopes in the surgery of 12 cases with IC aneurysms adjacent to the distal dural ring out of 85 surgical cases experienced in our institute three recent years.
Eleven had unrupted aneurysms, including 1 case with a giant aneurysm and 1 with a ruptured giant IC aneuysm. Because preoperative angiogram, 3-d MRI and 3-d CT suggested difficulties in clipping, thus we prepared an endoscope system. All patients but two underwent surgery with the Dolenc Approach. After endoscopic as well as microscopic detail observation and preparation, a clip was applied with the aid of cerebral blood flow monitoring and Doppler sonography. We used an endoscope after the clip was applied to confirm if branches from the IC artery were preserved and the clip obliterated the aneurysmal neck completely. It was difficult to monitor every checkpoint simultaneously while applying a clip with an endoscope only during aneurysmal surgery. There was not adequate room for inserting an endoscope whose caliber was 4 mm or larger. The rigid endoscope with 1.9 mm caliber was useful and safe for use in the operative field but the monitor image was not large enough.
Based on these results, we believe that a small caliber rigid endoscope is useful in observing blind corners of a surgical microscope and confirming safe and complete aneurysmal clipping, especially for the posterior projecting IC aneurysms adjacent to the distal dural ring, which are tough to prepare the aneurysmal neck for complete clipping. Improvement of the endoscope image, superimpose system with microscopic image and a safe but convenient fixation of the endoscope system will be needed.

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To define the current status of the multimodality treatment for large and critically located arteriovenous malformations (AVMs), we have made a retrospective review of 54 patients with Spetzler-Martin Grades IV and V AVMs. The size of the nidus is larger than 3 cm in diameter in all cases.
Initially, all but 1 were treated by nidus embolization with the aim of size reduction. Only 1 patient had complete nidus occlusion by embolization alone. In 52 patients, the obliteration rate of nidus volume averaged 60% after embolization. Ten patients underwent complete surgical resection of AVMs following embolization with no postoperative neurological deterioration. Thirty-one patients underwent stereotactic radiosurgery following embolization. At the time of this analysis, 30 patients underwent follow-up angiography 2-3 years after radiosurgery. The results of radiosurgery correlated well with the preradiosurgical AVM volume. Of 16 patients with small residual AVMs (<10 cm3, a mean volume of 4.7 cm3), 9 (56%) had complete obliteration, and 6 (38%) had near-total or subtotal obliteration by 3 years after radiosurgery. In contrast, of 14 patients with large residual AVMs (?10 cm3, a mean volume of 17.9 cm3), only 2 (14%) had complete obliteration, and 8 (57%) had near-total or subtotal obliteration. Repeat radiosurgery was performed for the patients with remaining AVMs at 3-year follow-up review.
This study indicates that a certain number of large and critically located AVMs can be safely treated by either microsurgery or radiosurgery following a significant volume reduction by nidus embolization. The present data also suggest the need and possible role of repeat radiosurgery in improving complete obliteration rate of large difficult AVMs, since many of those AVMs have significantly responded to initial radiosurgery.

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Emergency carotid endarterectomy (CEA) was performed in 10 patients with proximal internal carotid artery occlusion associated with profound neurological deficits. All patients visited our clinic within 5 hours from the onset, and flow of the IC was restored 4.9 hours after the onset on average. Of the 10 patients, the outcome was excellent in 3, good in 4, severe disability in 2, and 1 died. For these patients, prevention of distal embolism after CEA is most important.
According to the intraoperative findings, namely, whether or not back-flow from the distal IC was demonstrated by arteriotomy of the IC distal to the occlusion, and whether or not clotting existed in the distal IC, the 10 patients were divided into 3 groups.
Group A (3 cases): Back-flow from the distal IC was demonstrated and clotting of the distal IC was not demonstrated.
Group B (2 cases): Both back-flow from the distal IC and clotting of the distal IC were demonstrated.
Group C (5 cases): Back-flow from the distal IC was not demonstrated because of packed clotting in the distal IC.
In group A, restoration of the flow will be established without distal embolism by not only CEA but also fibrinolysis followed by percutaneous transluminal angioplasty (PTA). For group B and group C, clotting of the distal IC shoud be removed by forceps or aspiration through the distal tube of the internal shunt during CEA to prevent the distal embolism. At present, it is best to use CEA for patients with proximal IC occlusion to prevent the distal embolism, because it is impossible to know whether or not clotting exsists in the distal IC.

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We sought to determine the conditions allowing wrapping and when wrapping would be the best choice. We examined the actual use of wrapping in whole aneurysms (ANs) treated surgically. The total number of whole aneurysms was 833 ANs (718 cases) over a period of 22 years ('75/9~'97/8). Wrapping was applied for ANs in 193 cases (23%). Sixty ANs were treated with wrapping only. The reasons why we selected wrapping were as follows: 1) small neck (n=24), 2) infundibular dilation (n=17), 3) blister AN (n=5), 4) broad neck (n=5), 5) bubble like AN (n=3), 6) perforator from AN dome (n=2), 7) infraclinoid (n=2), 8) dissection AN (n=2)
We present typical angiograms including operative findings of these cases. We emphasize that conservative treatment is preferable to surgical treatment in some cases of cerebral aneurysm.

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Spontaneous arterial dissection in the anterior circulation is extremely uncommon. The natural course of this phenomenon is far from being understood, and the treatment is controversial. In this study, we report a case of anterior cerebral artery dissection presenting recurrent transient ischemic attack.
A 37-year-old male suffered from right hemiparesis and aphasia. On admission, CT scans revealed no lesion. However, in the left carotid angiography, an irregularity of the wall was observed at the left A2 proximal portion. The symptoms disappeared after about 4 hours. Under conservative treatment, the symptoms appeared intermittently. Since the progress of the dissection of the left callosomarginal artery was observed in the cerebral angiography, we performed an emergency operation. We performed side-to-side anastomoses on the left obstructed pericallosal artery and the left callosomarginal artery whose dissection had progressed to the other side. Furthermore, we ligated the left A2 proximal portion, which had expanded with a dark red color. The postoperative course was uneventful. Ischemic attack was not observed.
We believe that an arterial progressive dissection with ischemic symptoms requires surgical treatment.

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Six patients with aneurysms arising from the anterior wall of the internal carotid artery were reviewed to investigate clinical and radiographic characteristics and operative findings. The role of 3D-CT angiography (3D-CTA) was also analyzed in 3 recent patients to determine clinical usefulness in the diagnosis and surgical management of this lesion. They were all females ranging in age from 25 to 62 years with a mean age of 47.5. Five patients presented with subarachnoid hemorrhage and the remaining had an unruptured aneurysm in association with another ruptured aneurysm. The aneurysms arose from the right carotid artery in 5 patients and from the left in 1 patient. The 3 recent patients underwent 3D-CTA immediately after they were transferred to our hospital following aneurysm rupture.
At surgery 2 of 4 saccular aneurysms, which adhered to and were buried in the frontal lobe, were dissected subpially. Two patients had a blister type of the aneurysms with a wide neck, and the remaining 4 patients had a saccular type of the aneurysms with a narrow and distinct neck. A small, blister-like aneurysm in 1 patient was wrapped with thin sheets of cottonoid together with the parent artery, followed by clip placement. In the remaining 5 patients a variety of angled clips were placed in parallel to the parent artery. The 3D images generated by 3D-CTA were of great value in assessing the exact site of the aneurysms, their growth projection, the shape and the size of the fundus, and their anatomical relationships to the adjacent arteries and other landmarks such as the anterior clinoid process and the optic canals. They were also a great help in surgical planning and simulation for aneurysm dissection and neck clipping.

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