Among 25 patients with cerebral arteriovenous malformation (AVM), who were followed for more than two years after gamma unit radiosurgery, treatment outcomes were unsatisfactory in eight patients. The patients consisted of two cases whose AVMs were angiographically shown to have not been completely obliterated following the initial treatment and were therefore reirradiated, three who refused further angiographic examination despite only partial obliteration of the nidus having been obtained, and two cases of complete nidus obliteration with radiation-related morbidity or with angiography-related mortality. In the one remaining case, no neurodiagnostic imaging studies have thus far been performed because the patient has refused them. Factors which could have contributed to unsatisfactory treatment outcomes in these eight cases were as follows (three patients had multiple factors): 1) inappropriate patient selection criteria for this procedure (three cases), 2) poor delineation of the AVM on stereotactic angiography (one case), 3) imprecise delivery of the radiation dose due to incorrect dose planning (three cases), and 4) inadequate follow-up after radiosurgery (four cases). Successful radiosurgical treatment requires appropriate patient selection and precise delivery of the radiation dose to the target, as is well known. Furthermore, we emphasize that meticulous long-term follow-up is essential in successfully managing all radiosurgically treated AVM patients.

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Seventy-three patients with arteriovenous malformation (AVM) were treated with gamma knife. The patient's mean age was 29.9 presenting symptoms included prior hemorrhage in 60 (82%) and seizure in 6 (8%). Neurological dificits were present in 33 patients (45%). Eighty-one percent of AVMs were located in eloquent areas and the mean size was 19.6×19.8×20.2mm. AVM volume of less than 10cm3 was found in 60 patients (82%). The lesions were classified according to the Spetzler grading system: 42 (58%) wer Grade III, 10 (14%) were Grade II, and 11 (15%) were Grade VI. Prior surgery had been performed in 30 patients. Embolization procedures were performed in 7 patients. Conventional external irradiation was done in 4 patients. All patients were irradiated to the entire volume of the AVM nidus. The mean dose delivered to the AVM margin was 19.2 Gy and that delivered to the center was 36.9 Gy. Embolization was very useful in reducing some lesions larger than 3 cm in diameter.

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We started gamma knife surgery on May 28, 1991 and have treated 24 cases of AVM during nine months. Based on our experience, various therapeutic policies for AVM management have been assessed. Radiosurgical procedures were quite safe and patients could return to preoperative activities the day after treatment. However, we had two patients whose malformations ruptured during and after radiosurgery. As the ideal goal of AVM management is complete obliteration of the nidus as soon as possible, direct surgery and intravascular surgery remain excellent treatments, especially for ruptured AVMs with intracranial hematomas. For the treatment of large AVMs in functional areas, combination therapies can be performed and intravascular embolization may be considered in order to reduce the volume of the nidus. However, the risk of embolization is still appreciable for AVMs in functional areas. Compartment irradiation using independent isodose lines of 50% may be useful for such high risk AVM patients, though a two stage radiosurgical procedure may also be considered. Selective angiography and MR imaging are useful for the dose planning of these radiosurgical procedures.

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Eighty brain arteriovenous malformations (AVM's) in 76 cases (age 3-57, average 28) have been treated primarily by embolization using a newly development liquid embolization method (estrogen-alcohol combined with polivinyl acetate polymer). Super selective embolization was performed in 166 sessions. After confirmation of negative provocation test using amytal with or without lidocaine, infusion of estrogen-alcohol was followed by injection of polyvinyl acetate. The former was used to obliterate fine vascular networks inside the nidus by chemical embolization property, and latter was used to occlude the more proximal artery to fistulous connection. After the embolization, 11 lesions (13.8%) disappeared angiographically. The number of nidi that had a diameter large than 3cm was reduced from 45 (56.2%) to 7 (8.7%). As an adjunctive treatment, conventional neurosurgical resection was performed in 9 cases without difficulty. In 9 cases, the residual nidus was irradiated by conventional way (30 Gy in 3 weeks). Follow-up angiography (average 17 months after embolization) was performed in 39 cases. Six nidi embolized completely showed no revascularization. In the remaining 36 cases, 5 lesions were reduced in size (all were irradiated cases), 21 unchanged and 7 enlarged (not by recanalization but by collateralization and/or neovascularization). The mortality rate related to embolization was 1.3% (1 case) and morbidity rate was 23.5%. Annual rebleeding rate in incomplete embolized cases was 3.6%
Recently the gamma knife become available in Japan. Gamma knife surgey achieves complete obliteration of the nidus in about 80% of the cases irrespective of the site of the AVM, with a low complication rate (around 4%). But this favorable result is strictly dependent on the size of the nidus.
Keeping the above mentioned results in mind, our treatment strategy of AVM at present is as follows. Surgical removal might be considered in small cortical lesions. Embolization would be a primary treatment for the lesions larger than 3cm or 10ml, except when the acute surgical removal of hematoma is required in hemorrhagic case. After embolization, the lesion would be surgically removed or treated by gamma knife according to the risk of the tretment modalities. For the hemorrhagic lesions smaller than 3cm, embolization would be considered if the feeders were easily catheterized without significant risk. For the non-hemorrhagic lesions less than 3cm, gamma knife would be the treatment of choice.

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Successful gamma knife radiosurgery depends on the volume of nidus of cerebral arteriovenous malformations (AVMs). Because of lower possibility of obliteration of large AVMs treated by gamma knife radiosurgery, embolization therapies were carried out in 10 cases out of 50 AVMs to reduce the volume of nidus before gamma knife radiosurgery. The strategy is as follows: 1) when the volume of nidus is less than 5ml, gamma knife radiosurgery is selected as the first treatment. 2) when the volume of nidus is from 5 to 10ml, embolization is recommended in selective cases in which the procedure seems to be safely performed. 3) When the volume of nidus is over 10ml, embolization should be tried in all cases. In this strategy, it is essential to evaluate the accurate volume of nidus before gamma knife radiosurgery to decide whether embolization should be carried out or not. Angiography with painless fixation of Leksell frame was thought to be best procedure to meansure the accurate volume of nidus before gamma knife radiosurgery.

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The experiences of the first 144 cases of arteriovenous malformation (AVM) treated with the gamma knife at the University of Tokyo Hospital between June 1990, and May 1992 are described. One year after radiosurgery, complete obliteration was observed in 16 (31.4%), remarkable decrease in 7 (13.7%), and partial obliteration in 24 (47.1%) of 51 patients who underwent angiography. There seems to be a tendency for smaller AVMs to be obliterated earlier. The minimal dose at the periphery required for total obliteration was estimated to be 20Gy. Bleeding after radiosurgery was observed in 5 (3.5%) cases. The bleeding rate was higher for AVMs located close to ventricles. Nine (13.2%) of 68 patients showed neurological deterioration three to twelve months after radiosurgery. A low density area on CT was demonstrated in ten (17.5%) of 57 patients. These outcomes are compatible with previous reports and confirm the efficacy of stereotactic radiosurgery for cerebral arteriovenous malformations.

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In aortitis syndrome, cerebral revascularization is considered for patients showing cerebral or retinal ischemic symptoms. In these patients, all branches from an aortic arch are usually occluded. Cerebral perfusion pressure is choronically so low that the range of cerebral autoregulation is shifted to the left or disappears. In such a condition, surgical revascularization may cause a breakthrough or hyperperfusion syndrome including an intracerebral hematoma. These complications make a poor prognosis.
The authors monitored the lumbar spinal pressure to detect the hyperperfusion or breakthrough during the operation for a patient with aortitis syndrome. Spinal pressure raised markedly just after an opening of the vein graft from the aorta to the common carotid artery, showing the breakthrough phenomenon. The graft was partially occluded, and the systemic blood pressure was lowered. Reopening of the graft only made a mild spinal pressure elevation. Systemic blood pressure was gradually returned to a habitual level postoperatively. Postoperative course was uneventful. Spinal pressure reflects the intracranial pressure well, which is raised by an increase of cerebral blood volume caused by the breakthrough phenomenon. This method is simple and does not need trepanation. It is an useful monitoring technique not only during the revascularization for aortitis patients, but also during carotid endarterectomy.

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Three cases of rare dural arteriovenous shunts (dAVS) involving marginal sinus were presented with special reference to the site of abnormal arteriovenous (AV) shunting and treatment. Patients included two women and one man, ranging in age from 42 to 65 years. Clinical symptoms were bruit, headache with or without chemosis and diplopia. Angiography revealed abnormal AV-shunts situated in the marginal sinus neighboring the junction between the inferior petrosal sinus and jugular bulb. Arterial feeders contributed from the dural branches of external, internal carotid and vertebral arteries. Among them, the neuro-meningeal trunk of the ascending pharyngeal artery served as the main feeder, and dural branches of vertebral artery characteristically supplied the lesion through odontoid arterial arch collaterals in 2 cases. The lesion was drained by the veins either through the jugular bulb or through the inferior petrosal sinus. In all 3 cases, the cavernous sinus was visualized through reversed shunting flow, causing the symptoms mimicking cavernous dAVS. Trans-arterial embolization was performed in one case with clinical improvement. Trans-venous embolization using platinum coils was carried out for the rest of the patients with both angio-anatomical and clinical cure.
These lesions may represent a new clinical entity and could be recognized as marginal sinus dAVS instead of that involving the inferior petrosal sinus. Trans-venous embolization offers most curative means of treatment with fewest complications. Identification of exact AV shunting site and selection of appropriate embolization material are mandatory to achieve effective and safe embolization therapy.

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Between 1981 and 1990, superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis was performed on 43 patients who had steno-occlusion of the internal carotid or middle cerebral artery. All of these patients were followed for an average of 6.5 years (range, 0.5 to 10 years). A follow-up study showed that 7 of these cases had a recurrence of an attack on the contralateral side or in the posterior circulation, but not on the ipsilateral side. Two of them had re-attacks on the contralateral side of EC/IC bypass, and 5 re-attacks took place in the posterior circulation. The symptoms of re-attack ware: 3 cases of TIA (vertigo, nausea), and 4 cases of stroke. The times of re-attacks were: immediately following surgery, 1 case; within 2 weeks following surgery, 1 case; 6 months or more following surgery, 5 cases. Fifteen out of 43 cases had 16 steno-occlusive lesions other than the operative side on preoperative angiography. Six of the 7 re-attack cases had steno-occlusive lesions on the re-attack sides. Positron emission tomography (PET) was performed on 18 cases before and after STA-MCA anastomosis. Five of these cases had re-attacks; 2 were in the form of misery perfusion on the contralateral side prior to surgery, and the re-attacks following surgery occurred on the same side. Another 2 cases who had cerebellar ischemias after postoperative PET study showed increasing of OEF on the cerebellar hemisphere postoperatively compared with the preoperative PET study.
In conclusion, bypass surgery is effective in preventing recurrence of ischemic symptoms on the operated side. But in cases with steno-occlusive lesions on the non-operated side, a follow-up study such as cerebral hemodynamics and metabolism is necessary for predicting the occurrence of the ischemic attack of that area following surgery.

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The clinical features of common carotid artery occlusion and principles of its adequate treatment were assessed by analyzing the disease in 7 cases who underwent reconstructive surgery between 1980 and 1985. The occlusions were unilateral in 4 cases and bilateral in 3 cases, and the causes were arteriosclerosis in 2 cases, arteritis in 1 case and aortitis syndrome in 4 cases. The modes of onset were TIA-RIND in 4 cases and minor stroke in 3 cases. Concerning the hemodynamics, the patency of the internal carotid artery via collateral circulation was observed in 8 blood vessels out of a total of 10 occluded blood vessels, and the external carotid artery was patent in 2 cases in whom occlusion extended to the internal carotid artery. The cases of aortitis syndrome were complicated by multiple large vessel occlusions. Operations were performed according to the hemodynamics. These were 9 grafts (8 vein grafts and 1 artificial blood vessel) and 2 transpositions: subclavian-internal carotid artery bypass in 1 case, subclavian-external carotid artery bypass plus STA-MCA bypass in 2 cases, subclavian-common carotid artery bypass in 2 cases and bilateral aortaecommon carotid artery bypass in 1 case.
Patency of the bypass was obtained in all the cases. A reoperation was required in 1 case as stenosis of the vein graft occurred in 1.7 years. The therapeutic results were 'good recovery'in 4 cases and 'moderately disabled'in 3 cases, and the symptoms resulting in'moderately disabled'were caused by neurological deficits that existed preoperatively. Improvements were attained of the symptoms due to low perfusions such as amaurosis fugax and orthostatic dizziness. Selection of the operative mode for common carotid artery occlusion should be made according to the hemodynamics by collateral circulation and occlusive lesion complicated, and operative indications were found as subclavian-common carotid artery bypass in the cases of patent common carotid artery, subclavian-internal carotid artery bypass in the cases of patent internal carotid artery and subclavian-external carotid artery bypass plus STA-MCA bypass in the case of patent external carotid artery. Multiple graftings should be made by exposing the aortic arch in aortitis syndrome associated with multiple large blood vessel occlusion.

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The authors report a rare case of distal posterior cerebral artery (PCA) aneurysm in a 62-year-old woman presenting with both subarachnoid and intraventricular hemorrhages. The saccular aneurysm arose from the parieto-occipital artery of the PCA projecting laterally. With the patient placed in a prone position the aneurysm was approached by a supratentorial route through an occipital craniotomy, and successfully obliterated with a Sugita's clip. The patient's postoperative course was uneventful without neurological deficits. The literature concerning aneurysms originating from the distal portion of the PCA is reviewed in the literature and the surgical approaches to the aneurysm are also discussed.

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The major cause of complications of intracranial aneurysm surgery can be attributed to difficulties in visualizing the perforators originating from the contralateral side of aneurysm and/or parent arteries. To facilitate microsurgical treatment of intracranial aneurysm the authors applied an optic fiber scope with 45° or 90° angled fiber tip. This method was applied in three patients and demonstrated applicability for visualizing the contralateral perforators.

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