Thirteen cases of the anterior choroidal arteriovenous malformations (ACh AVMs) supplied by the anterior choroidal artery were reviewed and the problems of the surgical treatment characteristic to this lesion are reported.
Both the cerebral parenchyma and the lateral ventricle were the sites of the AVMs in seven cases (54%), which raised the characteristic problems of their surgical removal. In two cases (group A), the AVMs were predominantly located in the lateral ventricle and involved the medial wall of the temporal horn and the hippocampus. In five cases (group B), the large AVMs were situated in the deep cerebral hemisphere or the corpus callosum, and also were extending into the lateral ventricle. Residual AVMs were found in five cases after the first operation. In two cases of group A, the residual AVMs which were supplied by the cisternal segment of the anterior choroidal artery and situated in the medial wall of the temporal horn and the hippocampus were recognized. In three cases of group B, intraventricular residual AVMs fed by the anterior choroidal artery were identified.
It should be emphasized that the ACh AVMs often occupy portions of both the cerebral parenchyma and the lateral ventricle. Therefore, it is important to open the ventricular wall from the cerebral parenchymal side or from the inside the lateral ventricle and to carry out careful inspection in order to eliminate the risk of incomplete removal of the AVMs.

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We present a case in which bilateral aneurysm developed from junctional dilatations of the posterior communicating arteries. A follow-up study of this case strongly suggests that a junctional dilatation can develop into a true aneurysm. After reviewing nine cases in the literature, the authors conclude that junctional dilatations, especially in young women with a history of aneurysmal rupture, should be carefully followed by angiography.

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We performed a comparative study in the utilization of aneurysm clips, using Sugita and Yasargil clips.
Preoperative selection of the proper clips for aneurysm surgery is very important. The presence of knowledgeable neurosurgeons familiar with the various clips and their uses is also necessary in clip selection during an operation, in order to avoid rebleeding after the clipping operation.
We analysed 108 cases (134 ans). we can summarize our findings as to the techniques of clip selection as follows:
Sugita clips are most useful for aneurysms of the internal carotid artery, and for posterior circulation aneurysms.
Yasargil's mini-size clips are most useful for smaller-sized aneurysms; Yasargil's slightly curved clips are also useful for aneurysms of the anterior communicating artery.

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The authors presented two patients of giant aneurysm who had taken unexpected eventful coures during their treatment.
Case 1; 47 y. o. female with chronic renal failure. Her chief complaint was bitemporal hemianopia and a giant aneurysm was found in the C₂ portion of right internal carotid artery. Cross flow was good. Craniotomy was intolerable to her because of renal failure. Gradual ligation of IC was done by Selverstone clamp. She developed progressive left hemiparesis and Urokinase and low molecular dextran solution was given and started hyperbaric oxygen treatment. In the evening three times of SAH occured and she became coma and dead next day. Case 2; 61 y. o. male; past history of SAH 15 years ago who was admitted for ruptured giant aneurysm. The giant aneurysm was exposed by interhemispheric approach. About 70% of dome was yellowish hard and left A₁ entered into the dome where left A₂ emerged from, therefore clipping was given up. It was coated with Biobond and Bemsheet. A new bleb was protruded from the dome a year later and reexposure was done, however it was so hard that clipping was impossible. It was coated in the same way.
Discussion; In the Case 1 the cause of hemiparesis could be extension of thrombus. UK and low molecular dextran treatment might dissolve the clot and SAH occured subsequently. If we could use a detachable balloon and obliterate the aneurysm, SAH should be avoided. In the Case 2 if we had done either copper wire electrothrombosis as well as coating or creation of new anterior communicating artery using temporary clip, new bleb might be avoided. Each treatment has high risk for thrombosis of anterior cerebral artery or brain damage by too longer temporary clipping.

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In this paper, the authers report six cases of recurrence of SAH due to the rupture of newly developed or enlarged aneurysms which were not recognized during the previous aneurysmal operations.
Development of aneurysms from the dilatation at the origin of the posterior communicating artery was found in two patients, in whom carotid ligation had been performed previously for treatment of contralateral internal carotid aneurysms.
In three cases, newly developed aneurysms were revealed at the middle cerebral artery 6-10 years after operation for a contralateral middle cerebral artery aneurysm. In one of these cases the persistent primitive trigeminal artery was revealed by angiography; in the others small bulgings were found at the middle cerebral artery during the first aneurysmal operation.
Enlargement of a small unruptured aneurysm originally less than 2mm in diameter at the anterior communicating artery was found in one case, which had not been recognized during a previous operation for a ruptured middle cerebral artery aneurysm.
Hypertension was noted in all cases but one. Existance of a per-aneurysmal lesion or changes in the arterial wall due to hypertension, arteriosclerosis, etc., or hemodynamic stress caused by anomalies in the circle of Willis or previous carotid ligation seem to be responsible for the enlargement of existing aneurysms and the development of new ones. Our observations suggest that a preaneurysmal lesion of the cerebral artery may develop into an aneurysm and rupture, and hence control of hypertension or follow-up angiography is recommended for patients with preaneurysmal lesions or small aneurysms.

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We have experienced direct neck clipping surgery for cerebral aneurysms in 854 cases during the 15-year period from 1971 to 1985. In this series of aneurysmal surgery, postoperative complications of rebleeding and new growth of an aneurysm at the site of the clipped aneurysm were seen in two cases.
[Case I] A 37-year-old man was admitted to our service complaining of severe headache. An aneurysm was revealed at the junction of the left internal carotid artery and the ophthalmic artery by four vessel angiography. The left common carotid artery was ligated because it was assumed preoperatively that neck clipping would be difficult. One month after surgery, the patient again complained of severe headache. Right carotid angiography revealed an aneurysm at the junction of the right internal carotid artery and the posterior communicating artery which had never appeared in previous angiography. Neck clipping was successfully performed on this newly developed aneurysm. Four years after the last neck clipping, cerebral angiography failed demonstrate any further aneurysmal growth. This was a very noteworthy clinical case, because a new aneurysm developed in a short period, probably within one month. The increased hemodynamic stress was considered to be the pathogenesis of a newly developed aneurysm after contralateral ligation of the common carotid artery.
[Case II] A 38-year-old man was admitted to our service 14 days after the onset of subarachnoid hemorrhage. A ruptured left middle cerebral artery aneurysm and a non-ruptured right anterior cerebral artery aneurysm were revealed by radiological examinations. Neck clipping was successfully performed on both aneurysms and the postoperative angiogram demonstrated the disappearance of the aneurysm. The patients postoperative course was uneventful. Thirteen months after the neck clipping, however, he was readmitted to our hospital with subarachnoid hemorrhage. A newly developed aneurysm was noted just under the clip at the right anterior cerebral artery. Neck clipping was perfomed on this new aneurysm. The postoperative course was uneventful and he was discharged with no neurological deficit.
Hemodynamic stress at the site of an aneurysm and injury of the arterial wall by on inadequate clip were considered to be the major cause of the aneurysmal formation.

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In this paper, a case of ruptured newly-developed right internal carotid posterior communicating artery bifurcation aneurysm, which occurred 11 years after contralateral common carotid artery ligation for a ruptured left side aneurysm, is reported.
Common carotid artery ligation for the left internal carotid posterior communicating artery bifurcation aneurysm seemed to be effective to some extent from the following view points: rebleeding from the ipsilateral aneurysm was prevented and a decrease in size of that aneurysm was obtained.
The new aneurysm might have developed due to the long-term hemodynamic stress exerted on the pre-existing fragility of the arterial wall. Such stress may have resulted from increased blood volume in the ipsilateral internal carotid artery after the contralateral common carotid artery ligation.

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A rare case of mycotic (Aspergillus) aneurysms which were newly formed near the clip after surgery for an aneursysm of the middle cerebral artery is reported in this paper.
A 47-year-old man was admitted to our hospital after suddenly developing severe headache and vomiting. A computed tomography (CT) scan revealed a moderate amount of subarachnoid blood in the right Sylvian fissure. Four-vessel angiography demonstrated a saccular aneurysm of the trifurcation of the right middle cerebral artery. The neck of the aneurysm was successfuly clipped without the use of induced hypotension. There was no obvious bleeding during the operation and no other aneurysm was present. The postoperative course was smooth and uneventful. A cerebral angiography which was done on the 10th day after operation revealed the complete disappearance of the aneurysm. Twelve days after operation the patient complained of headache and 17 days after operation fever occurred. Headache and fever continued, but no meningeal irritation signs were detected. However, a Lumbar tap revealed cerebrospinal fluid with marked pleocytosis. No bacteria was found. Thirty-one days after operation the patient deteriorated suddenly, and next day became comatose with decerebrate posture. A CT scan revealed a right parietotemporal hematoma with ventricular hemorrhage and midline shift to the left side. A repeat cerebral angiography demonstrated two newly formed aneurysms near the clip. The hematoma was evacuated and the aneurysms were excised after clipping. These aneurysms originated from the arterial wall which was touched by the clip previously applied on the middle cerebral artery aneurysm. The vessels were fragile and control of bleeding was very difficult. The patient died five days after the second operation. Microscopic examination showed that the aneurysms were mycotic in nature; the numerous hyphae were identified as Aspergillus.
Mycotic aneurysms of fungal origin are very rare. Only 17 cases have been reported in the literature. Four of these 17 cases developed aneurysms after neurosurgical procedure. Our case is the first that followed clipping of an aneurysm. From analysis of the reported cases. The authors suggest that 1) in five cases which developed aneurysms after neurosugical procedure, damage of the arterial wall during the operation played a very important role in development of fungal aneurysms, 2) in patients who develop fungal meningitis after neurosurgical procedure, cerebral angiography is neccessary in order to detect aneurysms, 3) direct surgical treatment in the acute stage should be avoid because manipulation of the inflamed friable wall may result in its gragmentation, and the necessity to occlude the parent artery. 4) prognosis of fungal aneurysms is very poor: there is no report of survival.

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Neck clipping in the acute stage of the basilar-tip aneurysm is one of the most difficult operations in aneurysm surgery, since the aneurysm itself is deep-seated and successful management after an occurrence of premature rupture is not easy. Therefore, a sufficient exposure of the operative field with lesser brain retraction is needed, particularly for a patient with impaired consciousness judged as grade 3 (or 4) (Hunt & Hess classification) at the time of operation. The so-called orbito-zygomatic approach representing detachment of the zygomatic arch for a distance of 3 to 3.5cm and removal of 3 to 3.5cm of the lateral orbital roof seems to be an excellent method in terms of successful exposure with lesser brain retraction, since the surgeon can see into the interpeduncular cistern obliquely from below.
A case reported here is that of a 52 year-old female who was admitted at emergency eight hours after an occurrence of sudden headache, vomiting and confusion. Neurological signs at admission showed moderately impaired consciousness (20, 3-3-3 Japanese Coma Scale), the right oculomotor paresis and nuchal rigidity. CT scan showed the presence of severe subarachnoid hemorrhage in the basal cisterns and angiogram revealed the presence of antero-laterally (to the right) positioned basilar-tip aneurysm, the rupture of which caused the right oculomotor paresis.
A direct operation was performed on the following day, since her consciousness had improved up to 3 (3-3-9 formula). Orbito-zygomatic approach from the left side (the opposite side from the aneurysm dome) was applied in order to avoid undesirable exposure of the aneurysm fundus during the approach to the aneurysm neck from the right side, and to avoid excessive retraction of the brain. The aneurysm neck was successfully clipped. The postoperative course was uneventful.
The orbito-zygomatic approach seems to be very useful for direct operation on a basilar-tip aneurysm in the acute stage, particularly when the aneurysm is located at a high position.

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A 47-year old man suffering from aphasia and mild rt hemiparesis was disclosed to have lt front-parietal subcortical hematoma in CT and cerebral arteriovenous malformation (AVM) angiographically which was placed in sensory-motor area fed by three cortical branches of lt middle cerebral artery. Lt front-parietal craniotomy was performed under general anesthesia. The main feeder and one other feeder were exposed under surgical microscope. After the minor feeder was temporarily clipped to reduce the flow of AVM, the main feeder was cannulated by a 22 gauge Tephlon catheter and isobutyl-2-cyanoacrylate (IBCA) was injected through the catheter. During the injection of IBCA, the operative field was observed carefully under surgical microscope and injection was stopped immediately when IBCA filled the fine venous portion of the AVM. The AVM was obliterated immediately and no blood flow was observed when the temporary clip on the minor feeder was released. Since angiography in the operating room revealed the disappearance of the AVM, the main feeder was coagulated and sacrificed, then the operation was completed. The postoperative neurological course was good and CT showed no drawbacks, such as remarkable cerebral swelling, in the use of this procedure. Postoperative angiography revealed complete obliteration of the AVM and preservation of the normal vascular network.
Although advances in microsurgical techniques have made possible the complete, surgical resection of AVMs in the speech and sensory-motor regions without disabilities, some risks and difficulties still remain. Since embolization with IBCA can permanently obliterate AVMs without surgical removal, invasion toward the surrounding brain could be less than a surgical excision. Recently the technique of interventional radiology has been applied to embolization of AVMs, but occasionally percutaneous navigation of the balloon catheter to a feeding artery near the nidus may be impossible, especially with low flow AVMs. In such cases, exposure of the feeding artery under craniotomy is useful to prevent accidental embolization of normal vascular channels. Partial embolization is a major problem in this method. In the present case, complete embolization of AVM was performed successfully by temporary occlusion of the minor feeder to reduce the blood flow of the AVM; however, this procedure may not be available where some feeders cannot be exposed in the same operating field. In such cases, stepwise embolization may be considered. Providing on adequate amount of embolization materials and monitoring during embolization to prevent stray embolization are problems to be resolved.

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Two patients with deep-seated arteriovenous malformation (AVM) were treated by intraoperative liquid embolizations due to repeated hemorrhagic episodes. In the first case, with AVM in the head of the caudate nucleus, a frontotemporal craniotomy was performed. After the microsurgical dissection of the feeders, several anterior perforating arteries originating in the anterior cerebral artery (A₁ portion) and middle cerebral artery (M₁ portion), one of the feeders was canulated with a small-caliber polyethylene catheter, 0.6mm in outer diameter and 0.3mm in inner diameter. A small amount of isobutyl 2-cyanoacrylate (IBCA) was injected through the catheter. This procedure was repeated twice. In addition, a second intraoperative embolization was carried out because of incomplete obliteration. Although the right hemiparesis was slightly deteriorated, the AVM almost completely disappeared after the second operation. In the second case, with an AVM which involved almost the entire thalamus, a subtemporal craniotomy was done. Feeding vessels which originated in the posterior communicating artery and the posterior cerebral artery (PCA) were carefully dissected, and one of them was prepared for canulation with a small catheter. When a small amount of IBCA was injected, the proximal PCA and the internal carotid artery were temporarily occluded. The procedure was performed twice. One month later another intraoperative embolization was carried out. After the second operation the size of the AVM was decreased to 30%. However, left hemiparesis and visual disturbance were noted, although they gradually improved. No hemorrhagic episode has been experienced for two years and eight months in each case after embolization.

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We performed intravascular surgery on an extracranial AVM.
Case 1: A 45-year-old female complained of a pulsatile tumor behind the left ear and of cosmetic problems, finding it hazardous to use a comb. Superselective angiography performed through the left occipital artery revealed a nidus (4×5cm) and drainers. Soon after, embolization with PVA (polyvinyl alcohol foam) was carried out and postoperative angiography showed the tumor to have disappeared. Three months later, a small tumor on the surface of the skin was resected. Pathohistological findings showed it to be a glomus tumor.
Case 2: A 20-year-old male had suffered from a facial tumor since he was two years old. He had undergone coagulated ligation of the left common carotid artery and right peripheral facial artery.
There was improvement of the tumor after this procedure, but it became enlarged about two years before admission to our hospital. A left VAG showed the muscle branch of the left vertebral artery communicating with the branch of the left external carotid artery, these vessels being the main suppliers of the tumor. Embolization (IBCA) was performed by direct puncture of the feeding arteries. A high quality angiography machine, the portable DSA (Diasonics) was used. The AVM has shown improvement but we intend to carry out further embolization.
Embolization is now crucial in therapeutic angiography, and knowledge of its beneficial effects can help in the selection of appropriate cases. Skill, technique and excellent angiographical instruments are required. Embolization can in itself be a treatment or part of an over-all plan of therapy. One patient obtained a complete cure, while the other requires further embolization. It is our opinion that intravascular surgery is the first choice for treatment of extracranial AVM.

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Arteriovenous malformations of the choroid plexus are uncommon causes of intraventricular hemorrhage. Only 27 cases have been reported recently of this hemorrhagic form AVM. The authors experienced two cases of AVM of the choroid plexus and each of them were successfully removed by transventricular approach. We describe these two cases and present some characteristics of this disease, with a review of the literature.
Both cases were adult male patients who experienced sudden onset of headache, vomiting and decrease of their consciousness. CT scan showed massive intraventricular hemorrhage predominantly on lateral ventricules without intracerebral hematoma. Angiography revealed AVM located on the choroid plexus which were fed by the branch of the anterior or posterior choroidal arteries and drained into the great vein of Galen and the vein of Resenthal. Each of them was totally removed by transventricular approach. Pathohistological findings showed typical forms of AVM located on the choroid plexus.
As a cause of intraventricular hemorrhage in adults, the AVM of the choroid plexus is significant. Of all the cerebral AVMs, so called deep-seated AVMs are the most difficult to remove. But AVM of the choroid plexus are located on the plexus so surgical extripation is easier. It is very difficult to clarify AVM of the choroid plexus and other deep-seated AVMs preoperatively. However the following findings will support the diagnosis of the AVMs of the choroid plexus; 1: CT scan shows pure intraventricular hemorrhage without brain parencymal destruction. 2 : The blood supply is regulated of the branch of choroid arteries.

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Ten patients with arteriovenous malformations (AVMs) predominantly involving the lateral ventricle were operated upon. Computed tomography demonstrated intraventricular hemorrhage in eight patients, intracerebral hemorrhage large enough to warrant evacuation in two patients, and hydrocephalus in one patient who was admitted to the hospital because of generalized seizure. Cerebral angiography demonstrated an AVM in eight patients, but did not visualize the lesion in two patients. One patient suffered a recurrent intraventricular hemorrhage when the AVM was demonstrated, although repeated angiography had failed to disclose a vascular lesion at his first intraventricular hemorrhage 14 months before. Four AVMs were located in the head of the caudate nucleus; three were resected through frontal transcortical transventricular approach and one was resected through anterior transcallosal approach. Two of the former and the latter had excellent results. Two AVMs located in the temporal horn and trigon in the dominant hemisphere were excised through middle temporal gyrus approach with excellent results. Four AVMs of the dorsal surface of the thalamus were resected through posterior transcallosal approach; two had excellent results, and one had good result. We emphasize that the brain incision should be as small as possible when entering the lateral ventricle. Although various approaches have been proposed for lesions of the lateral ventricle, we recommend transcallosal approach for AVMs of the lateral ventricle. The position of the patient is very important; when the lateral ventricle is entered to excise on AVM, whether anterior or posterior transcallosal approach is used, the side of the lesion should be positioned slightly downward, so that the gravidity of the brain will aid in retracting the brain.

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It is difficult to decide, whether to choose operative or conservative treatment for areterio-venous malformation (AVM) of the basal ganglia caused by SAH.
Moreover it is a very serious problem with children who have no neurological deficit.
In this paper, we report the case of a six year-old boy with an AVM of the lt. lentriculostriate artery. The main feeders were lt. ant. choroid. a., thalamic a. lt. lenticulo-striat. a., post. choroid. a.. Drainage veins were spheno-pariet. v., and int. cerebr. v..
We chose the operative treatment, as we judged that, because of his youth, he would recover through rehabilitation.
We cut Ft. lenticulo-striat. a. and ant. choroid. a. as feeding artery. After the operation he had hemiplegia and motor aphasia but soon his neurological deficits improved.
After nine months he could stand on the rt. foot and raise the rt. hand straight up.
We suggest that in the case of a child, man should even operate on the AVM of lent-strait. a. area and could make him completely recover.

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In this paper, the authors report three cases of aneurysms newly formed near one that had been clipped and discuss the mechanism of their formation.
Case 1. A 48-year-old male was operated on for an AComA aneurysm 40 days after it had ruptured. At the time of the neck dissection, the aneurysm ruptured and a temporary clip was placed at the right Al portion for 15 minutes. The aneurysm was successfully obliterated, but the patient suffered from subarachnoid hemorrhage four days after surgery and following two attacks. A right CAG showed a newly formed anuerysm at the Al portion where the temporary clip had been placed. He died 13 days after operation. Massive subarachnoid hemorrhage from the new A₁ aneurysm was found in autopsy and aspergillus hyphae were recognized in the arterial wall of the A₁ portion by the microscopic examination.
Case 2. A 56-year-old female was operated on for a right IC-PC aneurysm on the 23th day after initial subarachnoid hemorrhage. During operation, the aneurysm ruptured and the right ICA was temporarily clipped at the immediately proximal portion for ten minutes. The neck was successfully obliterated. Postoperative right CAG, which was performed 35 days after operation, showed a new aneurysm at the place where the temporary clip had been applied. The right ICA was ligated and she was discharged without neurological deficits.
Case 3. A 38-year-old man was successfully operated on for an aneurysm at the bifurcation of the left MCA on the fifth day after a second subarachnoid hemorrhage. But, left CAG on the eighth day after operation showed a newly formed aneurysm proximal to the clipped aneurysm. On the 12th postoperative day, he suddenly fell into coma and a left CAG at that time showed that the new aneurysm enlarged in size. He died on the 19th day after operation. An autopsy was not performed.

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In this paper, we report a case of multiple aneurysms associated with dural arteriovenous malformation and occlusion of cerebral arteries.
A 53-years-old man was transfered to our hospital for detail examination of a subarachnoid hemorrhage (SAH). An angiogram showed three aneurysms on the left frontopolar artery accompanied by occlusion of the left callosomarginal artery, of the left middle cerebral artery and dural arteriovenous malformations between the ethmoid artery and the olfactory vein.
On Nov. 5, 1981, 14 days after the episode of SAH, a bifrontal craniotomy was performed for removal of the arteriovenous malformation and clipping of aneurysm necks. The third aneurysm was so small and broad-based that we decided to encase it with a piece of muscle and adhesive Alon α A^®.
Follow up angiography revealed a remarkable increase in the size of the encased aneurysm. On the day following angiography, the patient died of massive bleeding from the aneurysm.
Based on the histopathological examination of this case, we recommend that an aneurysm coexisting with a arteriovenous malformation and occlusion of the main artery be treated by clipping or ligation applied adequately to the aneurysm neck.

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Arterial bleeding during surgical removal of the solid cerebellar hemangioblastoma is reported to be difficult to control. Based on our operative experiences with two large and solid cerebellar hemangioblastomas, some useful strategies for such tumor removal will be proposed. Case 1. male 35 yrs.
The operation was performed by the right suboccipital approach with the patient in the left lateral decubitus position. The tumor was located within the right cerebellar hemisphere and had a large draining vein on the surface of the right hemisphere. The right anterior inferior cerebellar artery entered into the ventral portion of the tumor. Therefore, it was not possible to control this feeding artery until the tumor volume was considerably decreased. The tumor was dissected from the surrounding cerebellar parenchyma, and a Sugita's ultra-long clip was applied to the dissected solid portion of the tumor. Furthermore it was ligated with a silk thread so as to completely cut off the blood flow into the tumor. The tumor was resected piecemeal and the tumor volume was significantly reduced. The feeding vessel was finally clipped and the tumor was totally removed. Case 2. female 67 yrs.
The tumor, situated within the cerebellar vermis, protruded into the fourth ventricle and resulted in obstructive hydrocephalus. The operation was approached by the midline suboccipital craniectomy and C₁ laminectomy with the patient in a prone position. One of the feeding vessels, posterior inferior cerebellar artery, was clipped temporally. Although an attempt was made to remove the tumor in a destructive manner using CUSA, uncontrollable bleeding was encountered during the procedure. Therefore, the tumor was incised piece by piece using the monopolar electric coagulating loop. Finally, feeding artery and draining vein were clipped together. The tumor occupying the dorsal part of the fourth ventricle was removed en bloc. Conclusion: Various clips for aneurysm and monopolar electric coagulating loop are very useful for the resection of solid cerebellar hemangioblastoma. These techniques are expected to be useful for other hemorrhagic, large, and solid tumors or some AVMs.

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Four cases of cerebral arteriovenous malformations of the medial occipital lobe were successfully removed 1) with the patients in a prone position and 2) with microsurgical techniques. In this paper, the authors describe the details on positioning the patient on the operating table, keeping the head just above the heart level and rotating the table laterally when needed, and the microsurgical approach through an unilateral occipital craniotomy to those deep-seated AVMs with their unique vascular supply and drainage in the posterior end of the longitudinal cerebral fissure.

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Operating on an arterio-venous malformation (AVM) deep in the occipital lobe is difficult with some approaches because the main feeder consists of branches of the posterior cerebral artery. Particular care must be given to the approach route and the position of the spatula to protect the visual center. Thus, the deep-seated AVM is difficult to excise. For this condition we prefer the interhemispheric approach in a prone position. We have performed surgical resection on 12 cases of AVM, the main feeder of which was the posterior cerebral artery; the feeders involved seven calcarine arteries, four parieto-occipital arteries, four temporo-occipital arteries and one anterio-inferior temporal artery. All of the patients returned to routine life, except for visual field defects. Eight of the patients had had visual field defect preoperatively, consisting of two homonymous hemianopia, four upper quadrantic hemianopia, two lower quadrantic hemianopia. Postoperatively, these symptoms improved in two patients and were unchanged in three. In three patients, these symptoms were aggravated or new symptoms appeared. To minimize these symptoms, much care is required in determining the positional relations among feeder, nidus and drainer and the hemodynamics. This involves the full use of serial angiography and cinema angiography, careful determination of the neccessary extent of the craniotomy, and care in the use of the spatula, particularly when treating the feeders.

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In this paper, a case is reported in which a deep-seated arteriovenous malformation (AVM) was successfully removed from the frontal baso-medial region. AVM's located on the medial aspect of the cerebral hemisphere represent 4-15% of the total AVM's reported in the literature. These AVM's require special attention because of their obscure location, the close proximity to the critical area and the difficulties encountered in their resection.
A 41-year-old man was admitted because of a sudden onset of headache and vomiting. He was in a stuporous state with stiffness of the neck and left hemiparesis. A plain CT scan revealed right frontal hemorrhage and a clot was also seen in the ventricles. A right carotid angiogram showed an AVM, which involved the right rectal gyrus and subcallosal area, extending to the anterior hypothalamus. The AVM was supplied by branches arising from the right anterior cerebral artery (A₁ and A₂ segments), with drainage into the basal vein of Rosenthal.
The patient made a good recovery with bilateral ventricular drainages. A right frontal craniotomy was done two weeks after admission. The AVM was exposed through the interhemispheric parafalx approach and excised using micro'surgical technique without any new neurological deficits excepting a transient diabetes insipidus. A postoperative digital subtraction angiogram showed no residual AVM. The patient then developed, evidence of a communicating hydrocephalus and a ventriculo-peritoneal shunt was performed. Although recent memory was impaired, he exhibited gradual improvement and was able to return to work.

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A-34-year-old male, suffering from a sudden onset of severe headache and being unconscious, was admitted in our hospital Jan. 9. 1983. CT and CAG showed intraventricular hematoma and a large arteriovenous malformation involving the length of the corpus callosum in the midline.There were two nidi at the genu corporis callosi and one at the splenium; and the origin of bleeding seemed to be the most anterior nidus. We planned two staged operations for this vascular malformation.
After regaining consciousness, the patient underwent a bifrontal craniotomy followed by extirpation of both nidi at the genu corporis callosi. He made an uneventful postoperative recovery.
The second operation was performed four months later. The patient underwent a right occipital craniotomy with complete resection of nidus at the splenium and occlusion of the draining vein from AVM of the middle portion of the corpus callosum, using serial carotid angiography during operation. His postoperative course was uneventful and he was discharged neurologically intact. A carotid angiogram, performed six months later, revealed complete disapperance of the vascular malformation.

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A case of arteriovenous malformation in the left occipital lobe with purely left external carotid contribution is reported in this paper. The patient was a 60-year-old male, who complained of right hand sensory disturbance and headache. CT scan revealed a heterogenous low-density area in the left occipital lobe. Intravenous DSA and conventional carotid angiography showed the arteriovenous malformation, which had only feeders from the left middle meningeal and occipital artery.
These findings were confirmed surgically. This case is not only rare, but also interesting in terms of the pathogenesis of the arteriovenous malformation.

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In this paper, a case of successful treatment of arteriovenous malformation (AVM) in the right cerebral hemisphere by direct excision during infancy is presented, along with more than five years of follow-up observation.
A 6-day-old male child suffering from left hemiconvulsion due to a cerebral hemorrhage was admitted to our hospital. In this case, there were no complications during pregnancy or delivery, head circumpherence was normal, and there were no findings of congestive heart failure, retinal hemorrhage, jaundice or hemorrhagic diathesis. The only pertinent finding was a cranial bruit. After admission, a CT scan demonstrated a subcortical hemorrhage with no midline shift and a subsequent enhanced CT scan showed a round mass in the right frontal lobe. A cerebral angiography confirmed this diagnosis by revealing a large high-flow arteriovenous shunt, called an arteriovenous fistula (AVF). This AVF was located on the surface of the right frontal lobe, and was fed principally by the azygos pericallosal artery and drained into the superior sagittal sinus. The patient was treated by conservative therapy and recovered without any further seizures.
Three years later the patient returned to the hospital in a semicomatous state with left exophthlmus following generalized clonic convulsion.
A cerebral angiography showed that the AVF was moderately enlarged compared with the angiography performed three years earlier.
An operation was performed, and three aneurysmal malformations were obliterated and totally excised without interrupting the intrinsic supply of the corpus callosum or both hemispheres. In spite of the marked hemodynamic changes resulting from the surgical undertaking, the child has not suffered from either edema or hemorrhagic infarction.
As a result of the operation, the exophthlmus and the cranial bruit disappeared. Now, at the age of five and a half, the child shows steady physical developement with only slight retardation.

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