Twenty-nine patients were admitted to Osaka Neurological Institute with symptoms of acute cerebral ischemia. On admission, cerebral blood flow (CBF) was evaluated by CT with inhalation of stable xenon (Xe^S), followed by cerebral angiography. The latter disclosed occlusion of the main trunk of the internal carotid artery, middle cerebral artery, or else M₂ segment. Twenty-one patients underwent superficial temporal-middle cerebral artery anastomosis on the day of admission, and the other patients with relative or definite low density area on CT scans on admission were treated conservatively. Within 6 hours of onset, the critical cerebral blood flow level, which was defined as a value to induce cortical infarction, decreased in proportion to the time between the onset and Xe^S CT-CBF study (time- and residual flow-dependent period). After this period, the critical level existed at about 19 ml/100g/min (time-independent period) within 24 hours. And the patients' prognosis had a significant positive correlation with the residual CBF.
In summary, the measurement of CBF is mandatory to select the best choice of therapy for patients with acute ischemic cerebrovascular disease.

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Percutaneous transluminal angioplasty (PTA) was performed on the stenotic lesions of subclavian and proximal vertebral arteries. Successful dilatation was achieved in 14 of 14 cases of subclavian artery stenosis and in 6 of 8 cases of proximal vertebral artery stenosis. Re-stenosis occurred one year after PTA in one case of subclavian artery stenosis, but no other complications occurred. In these 7 cases, vascular endoscopy was applied before PTA and all occlusive lesions were found to be round smooth-surfaced lumen. Therefore, we conclude that PTA is a very safe alternative method of immediate treatment for stenotic lesions of subclavian and proximal vertebral arteries.

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Even with the recent progress in microneurosurgery on intracranial aneurysms, there are still many controversial problems in dealing with intracavernous, paraclinoidal and basilar aneurysms. A series of 8 patients with these aneurysms has been treated by“a combined epi- and subdural direct approach (Dolenc's method)”in our institute since 1988.
This elegant surgical approach can be performed by the same technical procedure used in the conventional pterional approach except that the exposure of anteromedial part of the cavernous sinus (Dolenc's triangle) is mandatory. We would regard this sophisticated approach as“pterional transcavernous approach.”
Using this approach for basilar aneurysm, sufficient spaces are obtained for neck-clipping with/without temporary basilar artery occlusion and a good visualization of perforating arteries around the lesion. An illustrative case of a large basilar top aneurysm treated with“pterional transcavernous approach”is presented in this paper. These surgical advantages will be emphasized and the limits of this approach will be discussed.

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Indications for surgery of multiple and unruptured aneurysm remain controversial. This report evaluated the long-term outcome in 62 patients with multiple aneurysms who suffered from a subarachnoid hemorrhage.
Of the 62 patients, 29 were surgically treated on only the ruptured aneurysm (group A) and 33 on both ruptured and unruptured aneurysms (group B). During a 5.5-year follow-up period, four (13.8%) of the 29 patients in group A bled from unruptured aneurysm. The mean risk of hemorrhage was 2.5% per year. Two of the 4 patients died and two became disabled.
The analysis of the long-term outcome during a 4.5-year follow-up period in group B indicated that the factors of poor final outcomes were age over 66 years, systemic disease, severe vasospasms and high neurological grade (Hunt and Kosnik grade IV) on admission.
A comparative study between ruptured and unruptured aneurysms on size, location and shape of aneurysms was made angiographically and showed that aneurysms that were rod-shaped, larger than 5 mm, with bleb and anterior communicating artery aneurysm tended to rupture.
In conclusion, indications for surgical treatment of multiple and unruptured aneurysms are as follows: 1. age of less than 65 years and no severe systemic disease, 2. uneventful recovery from the initial subarachnoid hemorrhage, 3. rod-shaped aneurysm larger than 5mm with bleb, 4. aneurysm at the anterior communicating artery.

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Two cases of moyamoya disease accompanied by an aneurysm were reported. One case had an aneurysm located within the middle cerebral artery proximate to the carotid bifurcation. Another had one located within the plexal portion of the anterior choroidal artery. Moyamoya disease can be defined as progressive arterial occlusive changes due to intimal fibrous thickening. In the aneurysm within the circle of Willis, clipping can be performed to prevent subarachnoid hemorrhage, but a major concern in clipping of the aneurysm is narrowing of the parent artery. In the aneurysm within the moyamoya vessels, this aneurysm can be expected to disappear spontaneously.

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Surgical risk factors were analyzed in 53 patients with 62 asymptomatic and unruptured aneurysms found incidentally. Forty-two patients (79%) had no postoperative problem, but one (2%) died and ten (19%) developed major or minor neurological deficits.
The size of aneurysm was the most influential factor on surgical results. Of 12 patients with 13 aneurysm(s) at or larger than 15 mm in size, one (8%) died and six (50%) developed neurological deficits. One had multiple aneurysms and another had an aneurysm at the head of the basilar artery.
Of 41 patients with 49 aneurysm(s) less than 15 mm, five (12%) resulted in an unsatisfactory outcome. Three of these worsened due to general complications, such as diabetes mellitus or liver cirrhosis, and two had neurological deficits.
In the non-surgical group (17 patients), only one patient had fatal bleeding during an average follow-up period of 44 months.
Surgical treatment for the asymptomatic aneurysm must be indicated in consideration of those surgical risks and risks of aneurysm rupture.

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We have performed embolization for spontaneous carotid-cavernous fistulas (spontaneous CCF). There were 16 cases, comprising 3 males and 13 females ranging in age from 23 to 78 (mean age: 56.). They were all type D on classification by Barrow. At first, we performed embolization of external carotid artery branches using microcoil or polyvinylalcohol particles (PVA particles) or ethylene vinyl alcohol copolymer (EVAL mixture). Subsequently we performed transvenous embolization using microcoils through internal jugular vein, inferior petrous vein to cavernous sinus or through external jugular vein to superior ophthalmic vein. Fifteen of the 16 cases were completely cured clinically and angiographically. One remaines under treatment because it was too difficult to catheterize all compartments of the cavernous sinus. After embolization, conjunctival chemosis and edema of the ipsilateral eye on all patients developed but disappeared within 2 or 3 days. There were abducens palsy and facial palsy (peripheral type) in 1 patient, and cavernous sinus syndrome in 4, but all patients recovered in 1 month. There were sigmoid sinus dural AVM in 2, which were embolized by arterial approach and improved. Transvenous embolization for spontaneous CCF is the most effective and safest treatment, but temporary complications still remain.

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Two cases of ruptured cerebellar arteriovenous malformations (AVMs) and one case of ruptured thalamic AVM with a peripheral aneurysm in their main feeders of AVMs were treated by endovascular techniques. In the first case, the aneurysm was located in the midportion of the superior cerebellar artery (SCA) which fed the nidus; in the second case, the aneurysm was in the anterior inferior cerebellar artery (AICA); and in the third case, the aneurysm was in the medial posterior choroidal artery (MPCA). All aneurysms were thought to be the cause of bleeding from CT and MRI findings.
A microcatheter was inserted very carefully just proximal to the aneurysm via the transfemoral route, and after negative results of a provocation test by amytal was confirmed, the aneurysm and nidus were embolized using ethylene-vinyl-alcohol copolymer (EVAL) simultaneously. In each cases disappearance of the aneurysms and reduction of nidus size were recognized after embolization without new neurological deficits.
EVAL is a new liquid embolic agent which forms an ethylene-vinyl-alcohol copolymer upon contact with blood and is not adhesive and soft enough to resect after embolization. In cases of AVMs with the peripheral aneurysm in the feeding artery, it is ideal to embolize aneurysms and AVMs simultaneously to prevent a rupture of the aneurysm following the increase in the intraluminal arterial pressure after embolization of the pedicle of AVM. EVAL is an appropriate embolic agent in this type of cases, because it makes repeated injection, possible until the complete disappearance of an aneurysm.

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The indications for prophylactic carotid endarterectomy (CEA) in patients with asymptomatic stenosis of the extracranial internal carotid (IC) artery remain controversial. Indications in our service are as follows: a greater than 50% reduction in carotid artery diameter (hemodynamic factor) and ulceration (embolic factor); and as shown with angiography intraplaque hemorrhage or ulceration as shown with ultrasonography. Over a 15-year period (1975-1990), 44 CEAs were performed on 41 patients with asymptomatic extracranial IC stenosis. Two of the patients died, one due to intracerebral hemorrhage that was thought to be hyperperfusion syndrome and one due to myocardial infarction. None of the other patients displayed permanent neurological deficit. Therefore, the perioperative mortality and morbidity rate was 4.5%. During postoperative follow-up (4 mo-15 yr mean 5.6±4.0 yr), five patients died, one due to cerebral infarction, one due to cerebral hemorrhage and three due to cardiac diseases. Since none of the other patients died of stroke, the stroke and death rates were 2.3%/yr. In this series, the perioperative mortality and morbidity rate was slightly high, but in the recent five-year follow-up (18 CEAs) there were no strokes or deaths. The reason for the good results may have been the use of systematic check-up on cardiac function (cardiac sonography, coronary angiography) and other risk factors (hypertension, hyperlipidemia, hypercoagulability, hyperaggregability, hyperviscosity, etc.). In conclusion, if hazardous asymptomatic lesions are demonstrated, prophylactic CEA may be performed with minimal mortality and morbidity by careful pre- and postoperative managements.

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The effect of the superficial temporal artery on middle cerebral artery (STA-MCA) anastomosis is discussed and analyzed in 27 cases of occlusive internal carotid artery (ICA) lesion (4 with ICA stenosis and 23 with ICA occlusion) from the viewpoint of retinal circulation using Doppler sonography (DS) and retinal artery pressure (RAP). Preoperatively, DS findings showed the stenosis pattern in 7 cases and the reversed-flow pattern in 19 cases. After bypass, the cases of stenosis pattern showed no prominent change. On the other hand, in the 19 reversed-flow pattern cases. Two cases showed a stenotic normograde flow and 13 showed a decrease of the reversed flow, and greater improvement could be seen in the follow-up stage. Preoperatively, the mean ophthalmic pressure index (OI: the percentage of the mean RAP to the mean systemic blood pressure) of the affected side dropped to 49.5±8.0%(normal side: 65.5±11.8%). After the bypass the mean OI was increased, but it was not statistically significant. In the follow-up stage, visual disturbance could be prevented and improved in all 27 cases. STA-MCA anastomosis appeared to decrease the reversed ophthalmic artery flow, elevate the retinal artery pressure, prevent the worsening of visual acuity and furthermore, improve the decreased visual acuity. It is believed that this procedure is indicated from the effect on the retinal circulation, and STA-MCA anastomosis should be performed to prevent and improve the ischemic retinopathies caused by ischemic ICA lesion.

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Ten patients with large or deep-seated arteriovenous malformation (AVM) were treated by preoperative or intraoperative embolization and direct surgery. AVMs were removed totally or subtotally in six cases. Partial removal of nidus or feeder clipping was performed in four cases. The outcome was as follows: excellent in 3 cases, good in 2 cases, fair in 1 case in the total or subtotalremoval group and excellent in 1 case, fair in 3 cases in the partial-removal or feeder-clipping group.
One patient revealed intracerebral hemorrhage on the 7th day after preoperative embolization. One patient with partially embolized and subtotally removed AVM manifested intracerebral hemorrhage during postoperative follow-up period. Those complications suggest the importance of hemodynamic changes and increasing risk of bleeding in residual AVM after embolization or direct surgical procedures.
Strategies of combined therapy on a programmed schedule of embolization, direct surgery and/or radiosurgery for large or deep-seated AVMs should be considered. Direct surgery should be planned soon after preoperative embolization procedure and total removal of AVM is highly recommended. Staged direct surgeries become possible after embolization in some cases.

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The functional reversibility and the possibility of hemodynamic crisis were studied in 21 patients with stenoocclusive diseases in internal carotid artery or the trunk of middle cerebral artery. Those patients showed improvement or deterioration of EEGs under induced hypertension or hypotension. The induced hypertension increases the cerebral blood flow (CBF) in the dysautoregulatory area of ischemic brain. The induced hypotension decreased the CBF of patients who possess the possibility of hemodynamic crisis. Angiotensine^® or dobutamine was administered intravenously for the induced hypertension. Alfonad^® was administered intravenously for the induced hypotension. The maximum range of induced hypertension was +30mmHg, and that of induced hypotension was -10mmHg by mean blood pressure. EEGs were recorded from 21 points on the scalp according to 10/20 international method, and analyzed by interval histograms and amplitude histograms automatically. From the interval histogram, % time of each frequency band was calculated. In the present study, the change of % time and amplitude was evaluated statistically by t-test.
EEGs of 9 patients improved under induced hypertension. In those patients, the brain function was considered to improve by the increase of CBF. Seven of those patients underwent bypass surgery, and all of them improved clinically. However, 2 of the surgical patients suffered reoccurrence cerebral ischemia due to the embolic process. Two other patients were treated conservatively. One improved after spontaneous recanalization, but the other did not improve.
EEGs of 12 patients deteriorated under induced hypotension. In those patients, the brain function was considered to deteriorate subclinically due to hemodynamic crisis. Eight of those patients underwent bypass surgery, and further occurrence of cerebral ischemia have been prevented postoperatively. Four other patients were treated conservatively, and one patient suffered the reattack of cerebral ischemia. Both surgical and conservative patients have been administered aspirin.
Therefore, the EEG analysis under the blood pressure change is useful to detect the functional reversibility and the possibility of hemodynamic crisis in patients of cerebral ischemia. To select suitable candidates for bypass surgery, those functional studies are necessary.

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