Treatment of some large, deep-seated arteriovenous malformations is still a challenge to neurosurgeons. The recent development of non-invasive imaging modalities has increased the chance of finding asymptomatic AVM's, for which evaluation for treatment is more complicated than in symptomatic cases. Currently there are 3 major treatment options for AVM: microsurgical removal, radiosurgery, and intravascular embolization. It is not easy to choose the best single modality or combination of modalities for individual patients, who have different types of onset, neurological deficits, size and location, and social background. After the installation of the Gamma Knife in November 1991, we established an “AVM Treatment Board.” It comprises vascular neurosurgeons, endovascular neurosurgeons, and radio-neurosurgeons, and meetings are held twice a month. Every AVM case referred to us is presented to the board, and treatment strategy is selected after a discussion among experts who know the advantages and drawbacks of each treatment modality. We describe this board system in detail and emphasize the importance of gathering expertise in decision making.

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The efficacy of carotid endarterectomy for stroke prevention in patients with high grade symptomatic and asymptomatic carotid stenosis has been extensively studied. Large multicenter prospective randomized studies have documented the benefit of this operation for reducing the risk of stroke if the surgery can be done with acceptably low perioperative morbidity and mortality. Because these studies documented a substantial benefit from surgery, the number of patients undergoing carotid endarterectomy in the United States has increased substantially during the last five years.
However, numerous studies analyzing the database maintained by the United States Health Care Financing Authority (HCFA) indicate that the morbidity and mortality associated with carotid endarterectomy is considerably higher in general practice than was the case in the prospective randomized studies. This raises the question as to whether or not the results of the prospective randomized studies can be generally applied to patients undergoing carotid endarterectomy for stroke prevention in the United States.
This paper will briefly review the findings of two large prospective randomized studies, the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and the Asymptomatic Carotid Atherosclerosis Study (ACAS). The results of five outcomes studies based on analysis of data in the HCFA database will also be reviewed. The limitations of both prospective randomized studies and large database outcomes studies will be discussed. The use of a disease-specific, searchable, computerized database developed at the Dartmouth-Hitchcock Medical Center for patients undergoing carotid endarterectomy will be reviewed. Finally, the efforts of the Outcomes Committee of the American Association of Neurological Surgeons and Congress of Neurological Surgeons to prospectively evaluate the outcomes of patients undergoing carotid endarterectomy via an on-line surgical outcomes reporting system, will be discussed.

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We report the case of a 65 year-old woman with acute MCA embolism. Acute stage diffusion weighted MRI showed a limited high intensity area in the left MCA territory, while Tc^99mHMPAO SPECT demonstrated hypoperfused area in the entire left MCA territory. She underwent the embolectomy. After the operation, she recovered from aphasia and right hemiparesis. The highintensity area demonstrated by diffusion weighted MRI became overt infarction on T2 weighted MRI taken 1 month later. However, the hypoperfused area where diffusion MRI did not show abnomal high intensity was saved from infarction.
Diffusion weighted MRI (DWI) in acute occlusion of the major cerebral vessels.
We investigated the relation between DWI findings and regional cerebral blood flow (measured by SPECT) in 95 patients with acute stroke. In 87 cases (91.6%), DWI showed an irreversible ischemic lesion in the early stage as a high-intensity area (HIA). The extent of HIA was related to the degree of reduction in cerebral blood flow and to the time from the onset. Thirty-nine patients (out of 95 patients) with major cerebral vessel occlusion were classified into 4 types. Type 1: no HIA, 3 cases; Type 2: limited HIA in perforators area, 9 cases; Type 3: limited HIA in cortex, 11 cases; Type 4: extended HIA, 16 cases.
Reperfusion therapy may be indicated for patients classified into Type 1, 2, and 3. However, patients classified into Type 4 may not be suitable for revascularization therapy.

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We have surgically treated 36 patients with cerebral arteriovenous malformations (AVMs) since 1991, when intraoperative digital subtraction angiography (DSA) was introduced. The patients ranged in age from 6 to 67 years (mean=33.8) and had a mean grade of 3.4. Preoperative embolization was employed in 18 patients to occlude surgically inaccessible feeders and to reduce arterial blood supply to large AVMs by 50%. The embolic material was silk thread and polyvinyl alcohol particles in 9 patients, and liquid coils in 9. Intraoperative DSA using portable equipment was used in all 36 patients. Frameless stereotactic microsurgery with the Mehrkoordinaten Manipulator (MKM) system was performed in 4 patients; 2 patients had trigone AVM, one motor cortex AVM, and the other sylvian AVM. Endovascular embolization resulted in transient hemianopsia in 1 patient but no permanent deficits nor death. Three patients underwent partial resection, after which the residual nidus involving the motor cortex, the thalamus, and the basal ganglion was stereotactically irradiated. One patient died of postoperative bleeding complication, and mild neurological deficits appeared in 2 patients. Surgical mortality and morbidity were 2.8% and 5.6%. In conclusion, endovascular feeder occlusion is safe and useful as a preoperative adjuvant therapy. Intraoperative DSA is essential for the surgery of cerebral AVMs, and image-guided microsurgery allows stereotactic access to deep-seated lesions while sparing the brain.

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Vertebral artery (VA) dissecting aneurysms that involve the origin of the posterior inferior cerebellar artery (PICA-involved type) have a hemodynamically unique character. To our knowledge, discussions of the ideal surgical treatment have not involved enough patients.
We conducted a retrospective clinical study of 14 patients with PICA-involved vertebral artery (VA) dissecting aneurysm presenting subarachnoid hemorrhage. The 14 patients underwent 15 surgical procedures, including 6 proximal clippings alone, 2 aneurysm body clippings just distal to the origin of PICA, 1 proximal clipping combined with PICA clipping, and 6 trappings.
Of the 7 patients treated with methods sacrificing PICA (trapping, proximal clipping combined with PICA clipping), 4 (57.7%) developed infarction in the distribution of PICA. Of the 8 patients treated with methods sparing PICA (proximal clipping, aneurysm body clipping), 2 (25%) developed infarction. Aneurysm persisted in 4 of the 6 patients treated with proximal clipping alone. In one of the 4 patients, rebleeding occurred on the 18th postoperative day.
Proximal clipping alone may be unfavorable for the treatment of PICA-involved VA dissecting aneurysms, because thrombosis of the aneurysm is delayed due to a retrograde flow from the contralateral VA into ipsilateral PICA, carrying a risk of rebleeding. Proximal clipping with additional PICA clipping or trapping with revascularization of PICA are recommended.

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We studied angiographic changes of embolized arteriovenous malformations (AVMs) by comparing pre- and postembolization angiograms and angiograms preceding radiosurgery. This study sought factors determining the usefulness of embolization as a pretreatment to enhance the success of subsequent radiosurgery. Thirty-seven patients with cerebral AVMs treated in this manner over 4 years were studied. In these cases, AVMs were embolized with cyanoacrylate and were treated with Gamma-knife radiosurgery. The mean size of the AVM nidus was reduced by a fraction of seven following embolization.
The subsequent angiogram for planning radiosurgery showed further nidus reduction in 16 AVMs, no change in 10, and regrowth in 11. In all size-reduction cases the nidus was sufficiently packed, and 2 AVMs had thrombosed completely before radiosurgery. All the regrowing AVMs were of the diffuse type, 7 of which were associated with already-developed leptomeningeal channels, and the remaining 4 were fed by newly sprouted meningeal feeders. Five AVMs disappeared following radiosurgery, all representing size-reduction or no-change cases. Analysis of cases with regrowth showed increased risk of that event with feeder occlusion of a multi-axially supplied AVM, lack of reduction of shunt flow, or remaining meningeal feeders.
On the other hand, when embolization as pretreatment prior to radiosurgery succeeds in producing a small, compacted, plexiform nidus with slow shunt flow, it furthers the likelyhood of successful radiosurgery. Nidus embolization and occlusion of fistulous and meningeal feeders are mandatory, while proximal feeder occlusion and use of embolic materials that risk recanalization should be avoided to prevent nidus regrowth.

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To evaluate the efficacy of superficial temporal artery (STA)-proximal middle cerebral artery (MCA) anastomosis, we analyzed the long term outcome of patients treated with bypass surgery.
Over a 12-year period, 87 patients were defined by clinical and laboratory criteria as suffering from hemodynamic cerebral ischemia. All patients had one or more episodes of focal cerebral ischemia due to unilateral internal carotid or middle cerebral artery occlusion. Computerized tomography scans either were normal or showed evidence of watershed infarction. The cerebral blood flow and/or cerebrovascular reserve capacity or cerebral oxygen extraction fraction were found to be impaired in all patients. Based on these criteria, STA-proximal MCA anastomosis was performed. No patients suffered postoperative strokes, resulting in a morbidity rate of 0%. Over a mean follow-up period of 50 months, 3 patients dropped out and the follow-up rate was 96.5%. Only 1 patient died of stroke (brain stem infarction) and other causes of death were myocardial infarction, malignant neoplasm, renal failure, diabetic coma and pneumonia. No significant difference was demonstrated in survival rate between 84 patients and the age- and sex-matched control. Eight patients had another episode of cerebral ischemia. The 2-, 5- and 10-year cumulative recurrence rates were 4.8%, 8.5% and 16.4%, respectively. Only 2 patients had further ischemic events ipsilateral to the side of bypass surgery, and their symptoms were transient ischemic attacks.
In view of these findings, we conclude that STA-proximal MCA anastomosis constitutes appropriate therapy for patients with hemodynamic cerebral ischemia.

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To clarify the clinical significance of local fibrinolytic therapy for acute ischemic stroke, patients with major artery occlusion were analyzed in respect to cerebral blood flow (CBF) and somatosensory evoked potentials (SEP). In 41 patients SEP was monitored and in 18 patients CBF was measured by SPECT using HMPAO and assessed semiquantitatively: multiple regions of interest (ROIs) were placed on the section images, and R/L ratio was calculated (where R represents a mean count of the ROI in the affected hemisphere, L on the opposite side).
Reperfusion significantly reduced the development of infarction in the ROI with an R/L ratio between 0.65 and 0.85. No correlation was observed between the development of infarction and the duration of ischemia. R/L ratio correlated significantly with N19 and central conduction time. The R/L ratio in the patients with N19 negative was far below the critical value of 0.65-0.85. The rate of recanalization, the size of infarction, and the outcome of the patients with N19 positive were higher, smaller, and better than those of the patients with N19 negative. The present study shows that reperfusion achieved by fibrinolytic therapy in the acute stage can prevent ischemia in a limited blood flow value, and SEP could be a good indicator to evaluate the ischemic level.

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Thrombosed giant cerebral aneurysms are technically challenging lesions to directly obliterate even for experienced neurosurgeons. From April 1996, 5 patients with thrombosed large and giant cerebral aneurysms were surgically treated under deep hypothermic circulatory arrest (DHCA). Increased blood loss and post-operative pericardial and pleural effusion resulting from open chest procedures became significant problems in the initial experience of DHCA. Therefore, we have adopted the closed chest technique with use of a heparin-coated circuit of percutaneous cardiopulmonary support system (PCPS) in 4 recent cases with 1 anterior and 3 posterior circulation aneurysms.
Both thrombosed giant upper basilar artery (BA) and large internal carotid artery aneurysms were directly clipped without any new neurological deficit, resulting in good outcome (Glasgow Outcome Scale of MD and GR). In 2 cases with thrombosed and dolichoectatic aneurysms originating from the vertebrobasilar (VA-BA) junction and extending to the midbasilar trunk, one was trapped and the other was treated by aneurysmorrhaphy and clip reconstruction of the VA-BA trunk through the extended petrosectomy after revascularization to the BA. The last patient made a good recovery (MD), but the other has been severely disabled due to progression of brain stem infarction.
Patient outcome tended to depend on the pre-operative neurological status in our series. Preservation of all viable perforating arteries from the parent artery and aneurysmectomy for sufficient decompression were crucial to achieving a good outcome. The use of PCPS allowed us to reduce the systemic doses of heparin to one-third of the conventional dose, thus resulting in no serious hemorrhagic complications. DHCA is mandatory for direct surgery of complex and giant cerebral aneurysms, especially in the posterior circulation.

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A 78-year-old woman developed subarachnoid hemorrhage (SAH) manifesting as severe headache and vomiting. On admission, her consciousness was clear and she had no neurological deficits. Computed tomography scan revealed SAH localizing mainly in the ambient and quadrigeminal cistern. Cerebral angiogram disclosed a saccular aneurysm at the bifurcation of the left posterior cerebral artery and the posterior temporal artery, which was 10×8×6mm in size and projected superomedially. On the fourth day after admission, the left P3 aneurysm was clipped via the left occipital interhemispheric route. The postoperative course was uneventful. Four weeks later, she was discharged without any neurological deficits.
To clip without difficulty the P3 aneurysm via this route, the occipital craniotomy should be made up to the confluens Herophili and the transverse sinus caudally, and the Rosenthal basal vein should be nominated as a reasonable landmark to the ambient cistern. Occasional adhesion of the left trochlear nerve to the arachnoid membrane was encountered, so care must be taken not to injure the nerve during manipulation. Although this approach to the P3 aneurysm provides wide working space and easy orientation, it may be more beneficial to select the surgical approaches through the temporal lobe, such as the subtemporal or trans-choroidal fissure approach, in case the aneurysm is relatively large and is protruding in the posterior direction.

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An eighty-year-old man who had subarachnoid hemorrhage and large intracerebral hematoma caused by a ruptured aneurysm of the left middle cerebral artery was treated with acute dome embolization using Guglielmi detachable coil and subacute CT guided stereotactic aspiration of the hematoma. As a result of these less invasive treatments, he returned to his regular daily life without any neurological deficits or complications.

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