Occlusion of the important arterial branches or incomplete neck clipping may occur during internal carotid artery aneurysm surgery due to small arterial branches from the IC adhering to the aneurysm inself, or due to insufficient visualization of the aneurysmal neck by the aneurysmal dome. Therefore it is mandatory that these small arterial branches be completely dissected without causing circulatory disturbances before approaching the neck of the aneurysm. However, there is a danger of premature rupture by such dissection under normotension, which may cause life threatening bleeding especially in IC aneurysm surgery.
We have currently adopted the procedure of temporarily occluding the anterior choroidal artery, the posterior communicating artery or the internal carotid artery, or trapping the IC, or a combination of these during surgery of the IC aneurysm under the administration of a brain protective substance (Sendal cocktail 20%mannitol 10ml/kg, Vit. E 10mg/kg, Phenytoin 10mg/kg). And after complete dissection of the aneurysmal neck and absence of any vascular involvement is confirmed, ligation is performed to produce an aneurysmal neck followed by clipping.
In this paper, our operative procedures for IC aneurysms are described.

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Neck clipping has been thought to be a perfect method of aneurysm surgery, but it is not always satisfactory, as shown by the fact that enlarged or reruptured aneurysms are sometimes reported after clipping. The author has had three patients with a collective total of four aneurysms which enlarged and reruptured nine to ten years with wrapping or coating.
The causes were 1) a fractured aneurysm clip, 2) slipping out of the clip, and 3) aneurysm formation from the thin wall of the parent artery, enlarged residual small aneurysm or infundibular dilatation with wrapping.
Two of the three cases were reoperated on with good results. In the second operation severe adhesion with plastic adhesive and granulation made the operation very difficult and dangerous. Coating or wrapping added to clipping could not be performed completely nor effectively.
The need for postroperative angiography, DSA and plain skull film examination is emphasized.

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Study of the recurrence and enlargement of cerebral aneurysms (An) after direct intracranial surgery is important in order to elucidate of the pathogenesis and growth mechanism and to develop more reliable treatment.
By October 1985 a total of 459 cases of An, including three cases of recurrence, one case of enlargement and two of neogenesis had been experienced in our institution, and both analysis of these clinical cases and examination of enlargement factors for 67 infundibular dilatations (ID) from 398 carotid angiograms were made.
The findings obtained are:
1. Two male patients and four female patients averaged 43 years of age at the time of the initial operation and 53 years of age at the time of recurrence.
2. Recurrence and neogenesis were observed 6 to 13 years, averaging 9 years and 10 months, after the initial operation.
3. Multiple An were observed in three cases (3/6) (including 2, 3 and 4 unities, respectively), suggesting extensive fragility of the intracranial artery.
4. In terms of sites of An, ICAn showed the highest incidence [6 unities (6/12) ], followed by MCAn (3 unities), A comm An (2 unities), and ACAn (1 unity).
5. Recurrence detected was ascribable to re-bleeding (4 cases) and follow-up CT (1 case).
6. Use of malleable clip, muscle and the like seemed to be involved in the recurrence, suggesting inadaptability of the clip for the complicated morphology of An and unreliability of the muscle as reinforcement.
7. For four cases (4/6), hypertension was observed in the clinical course, and remarkable changes in blood pressure, i.e., increases in diastolic pressure, especially attracted attention.
8. All cases showed arteriosclerotic changes adjacent to the aneurysm neck to An preoperatively or at autopsy.
9. In four cases the patient returned to work; however one patient died and one remains in a vegetable state. The prognosis for cases of rebleeding is poor.
10. In terms of enlargement factors for ID, statistically significant correlations were observed among the form and size of ID in cerebral angiography, and hypertension, angle of bifurcation for internal carotid artery and posterior communicating artery, degree of development of the latter artery and the like, with very important influences of the hemodynamic stress.
These results suggested that fragility of the vascular wall, unbalance between repair mechanism and hemodynamic stress, and so forth seemed to be responsible for the recurrence and enlargement of An, the prevention of which would require development and selection of clips comfortable to the morphology of An, reliability of reinforcement materials, control of blood pressure, and long-term follow-up observations.

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Our surgical procedure for ruptured intracranial aneurysms is to dissect not only the neck of the aneurysm but the whole body and then perform aneurysmal neck ligation and clipping by means of temporary occlusion of the parent arteries under administration of brain protective agents (Sendai Cocktail).
From April 1978, to December 1983, 504 cases of ruptured aneurysm (multiplicity 23.8%) had been treated by intracranial direct operation in our clinic. Four-houndred seventy-three cases (thirty-one patients died during hospitalization) were followed up to check the occurrence of rebleeding after surgery. The follow-up period was one to seven years.
Four cases were diagnosed as rebleeding by clinical examination and two of them were confirmed by CT scan. In one case, in which a big ruptured anterior communicating artery aneurysm had been treated by body clipping and muscle wrapping, the same aneurysm rebled sixty-three days after the operation. Slipping out of the clip was thought to be the cause of rebleeding. In another case, where a left middle cerebral artery aneurysm had been treated by neck clipping, rebleeding occurred 138 days after the surgery. The cause could not be determined ever by repeated cerebral angiographies; however the austopsy revealed a very small ruptured right PICA aneurysm.
From this study it is concluded that where aneurysms were treated by our procedures rebleeding did not occur during the follow-up period.

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The rebleeding or regrowth of cerebral aneurysms treated with a clip may possibly occur a long time after operation. The authors have experienced four such cases. The occurrence rate was 0.64% of all clipped aneurysms (691 cases) in our institute. The location of the aneurysms were, Acom A in two cases, distal ACA in one and BA tip in one; and all of them were initially operated on the chronic SAH stage, and were treated with spring clips.
They showed good postoperative courses, but problems developed in 24-64 months (mean: 46.25 months) after the intial operations. In all cases another operation was then performed. From the findings of the second operation, we determined the causes to be as follows: 1) In two cases the clips had slipped out. At the first operation, it had not been possible to completely obliterate the necks of the aneurysms because of the need to avoid kinking the parent arteries, or to spare tightly adhering perforating arteries. The pulsative forces to the necks of the aneurysms over a long period seemed to have caused clip slipage.
2) In one case, abnormal aneurysmal dilatation was found in the neck beneath the clip, but the clip had not slipped out. The possible mechanism of the dilatation of the neck was thought to be similar to those of the two cases mentioned above.
3) In one case, a small new aneurysm was found adjacent to the clipped aneurysm. The reason for the appearance of this new aneurysm could not be determined.
Many authors have reported possible reasons for the recurrences of clipped aneurysms and some methods to prevent such recurrences.
From the facts we mentioned above, although it is a matter of course, we suggest that greater effort to isolate the neck of the aneurysm or to clip the isolated neck correctly is the best way to prevent recurrences. And if perfect neck clipping is not possible, additional, firm coating of the clipped aneurysm with appropriate materials should be performed.

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The authors have reported on 184 cases of aneurysms and have experienced rebleeding after clipping of the aneurysmal neck in seven cases. The causes of rebleeding in our series were local fragility in two (Case 1 and 3), HICH in two (Case 2 and 7), and new aneurysms in two (rt ACA in Case 5, It MCA in Case 6). The etiology was unknown in one (Case 4).
This time we are reporting two cases of rebleeding after clipping of the aneurysmal neck due to rupture of new aneurysms in other cerebral arteries.
Case 4. (45-years-old male): Rebleeding due to rupture of new aneurysm in the region of the right genu occurred 14 months after clipping of an aneurysmal neck of the right middle artery.
Case 6. (51-years-old male): Rebleeding due to rupture of a right middle cerebral artery aneurysm occurred 11 years after clipping of an aneurysmal neck in the region of the left genu.
In the former case, it seems that the changes of hemodynamic stress in addition to hypertension after occlusion of the right M1 due to vasospasm of the right middle cerebral artery were causative factors.
Similarily in the later case, a mini-aneurysm of the right middle cerebral artery which was undiscovered previously by the usual cerebral angiography, grew larger and ruptured after 11 years.

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Complete neck clipping has been a reliable and widely used treatment for ruptured cerebral aneurysms. However, six cases of reruptured clipped aneurysms have been reported in the literature. We experienced a case of reruptured clipped aneurysm which occurred after ten years of follow-up. We have collected data on seven such cases including our own.
In three of these cases silver clips had been used and in another three cases Heifetz clips had been used. These reports suggest that the type of clip may play some role in the re-growth of aneurysms.
In this report, we also discuss the usefulness of fibrin-glue-soaked oxycel for coating the reruptured clipped aneurysm when neck clipping has failed.

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In this paper, we report the long-term results of the treatment of 23 intracranial ruptured aneurysms by coating. Twenty three patients treated by coating were followed for a mean period of 11.2 years. The mean interval between the last hemorrhage and the surgery was 22.4 days. Ten aneurysms underwent total coating, nine with Biobond and one with Aron alpha. Thirteen aneurysms underwent partial coating, 11 with Biobond and two with Aron alpha. Six aneurysms were partialy reinforced by other materials, but no aneurysm was totally wrapped with these materials. Rebleeding occurred in six patients, and five patients died. The mean interval between the coating and the rebleeding was four years. All patients suffering rebleeding had been treated with Biobond, and three patients had undergone total coating of aneurysms. The rate of recurrent hemorrhage after total coating with Biobond was 33%. One patient suffering rebleeding underwent the second surgery 10.5 years after the total coating of the aneurysm. During the surgery, Biobond was not found in the lesion except at the tip of the aneurysmal sac. From these results, we conclude that the reinforcement of ruptured aneurysms with Biobond seems to be of little value, and a more reliable method must be developed for use with aneurysms in which clipping is not technically feasible.

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Intravascular surgery for basilar artery aneurysm is a remarkably recent method of therapy. A very important point in this procedure is continuous determination of the patient's neurological state through electroencephalographic monitoring using a compressed spectral array (EEG CSA) and through auditory brainstem evoked respones (ABR) and high quality intraoperative angiograms obtained with a digital subtraction unit (DSA).
Case: A 64-year-old female suffered subarachnoid hemorrhage from a basilar tip aneurysm (4×5×9mm). Her neurological state at admission was Hunt & Kosnik grade V. Conservative therapy was applied and a ventriculo-peritoneal shunt was performed. Her neurological state had improved to grade IV six months later. One year after onset intravascular surgery was indicated, as complications had arisen.
[Operative procedure]: The DSA consists of a portable C-arm fluoroscope, low-noise camera, two video monitors, an image-processing system, and a hard disk storage system. EEG CSA and ABR were useful neurophysical monitoring methods. The aneurysm was occluded with a Hieshima detachable balloon catheter through the femoral approach. The balloon also occluded the posterior cerebral artery and there was a immediate change in EEG CSA and ABR. The DSA soon verified this and the balloon was deflated and repositioned. The balloon was again inflated for 40 minutes and then detached. It again moved slightly and DSA showed the left posterior cerebral artery to be stenosed. Three months after the operation, the patient's neurological state had improved to Hunt & Kosnik grade III. It was concluded that DSA and double monitoring (EEG CSA, ABR) during intravascular surgery are useful in the treatment of basilar aneurysms.

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A postoperative iatrogenic aneurysm following repeated temporary clipping procedures at the same site is reported. Simultaneously pitfall of the angled fenestrated clip application to the intracranial internal carotid artery is mentioned. A 51-year-old female was involved in an SAH episode with severe headache. Her Hunt & Hess grade was II. Right CAG showed a right paraclinoid aneurysm, pointing in the medio-inferior direction. Surgery was carried out on March 19th, 1984. A right optic canal decompression was made. During careful retraction of the right optic nerve premature rupture occurred. After temporary clipping of the proxymal internal carotid artery with a Scoville clip, neck clipping was done with a Sugita angled fenestrated clip. The right supraclinoid portion of the internal carotid artery became stenotic in diameter by the clip. Then EC-IC bypass procedures were initiated. At this time the Sugita clip was forced out by the torque of the released brain, and massive bleeding from the Sylvian fissure and the frontal base was observed. A Scoville clip was again applied to the right internal carotid artery. Next a Heifetz encircled clip was applied, but hemorrhage could not be controlled. Unavoidably a third temporary clipping was done. Finally a Sugita angled fenestrated clip was again applied and bleeding was controlled. Just after removing the Scoville clip, a pinhole laceration at the clipped site was revealed. But the bleeding was easily controlled by compression with Gelfoam. In addition, Aron-alpha was applied to the surface of the bleeding area. For prevention of Sugita clip slipping, a small piece of lyodura was laid between the handle of the clip and sphenoid ridge with Aron-alpha coating. Then the STA-MCA bypass was completed. On the 26th day after the operation bloody cerebrospinal fluid was obtained during a ventriculoperitoneal shunting operation. Urgent right CAG showed an iatrogenic aneurysm at the pinhole laceration during operation. It was judged that due to film coating by Aron-alpha direct operation would be difficult. Selverstone clipping was carried out at the cervical internal carotid artery. Postoperative digital subtraction angiography revealed no iatrogenic aneurysm and patency of the EC-IC bypass. The patient has returned to work and shows no neurological deficit.
Conclusions are as followings: 1, It is possible that frequent and repeated temporary clippings against the main arterial trunk might induce minimal laceration of the arterial wall and cause development of an iatrogenic aneurysm postoperatively. In order to prevent occurrence of traumatic aneurysms, sufficient and careful repair is necessary, even with a very small laceration of the arterial wall. 2, Main trunk stenosis by clipping and slipping out of a clip caused torque force are pitfalls of Sugita angled fenestrated clip application. Prophylactic procedures for slipping out of the clip should be considered.

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In this paper we report on two cases of recurrent subarachnoid hemorrhage nine and ten years after the first surgery, in which complete reclipping was performed. Case 1 had a right ICPC aneurysm with a fractured Heifetz clip, and Case 2 had a left ophthalmic aneurysm with a slipped Scoville clip.
In reoperating long after the first operation, scarring makes the approach, exposure and reclipping more difficult than in the first operation or early reoperation. Plastic adhesive such as Biobond or cyanoacrylate and various materials used for wrapping make scar formation harder and more severe. Sometimes coating or wrapping added to the clipping is incomplete, ineffective and dangerous.
The need for angiography during the surgery to ensure complete clipping is emphasized.

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A ruptured aneurysm of the anterior inferior cerebellar artery (AICA) located in the internal auditory meatus is reported. A 43-year-old housewife suddenly had a severe headache with subsequent right hearing disturbance, nausea and vomiting. About sixteen hours from onset, the patient presented with clinical grade II (Hunt and Kosnik) and the aneurysm was clipped via the right suboccipital craniectomy. Three months after operation, the patient was fully alert and could walk alone except for the right hearing loss and mild right facial paresis.
Nine cases with ruptured aneurysm of the distal AICA are reviewed in the literature. All ten cases are discussed with special reference to anatomical relationship between the aneurysmal neck and the internal auditory meatus, operative procedures and postoperative seventh and eighth cranial nerves function.

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A rare case of moyamoya disease with associated with ruptured basilar-superior cerebellar junction aneurysm is reported in this paper. The operation was performed with the trans-Sylvian approach and resulted in dome clipping because of premature of the aneurysm but collateral circulation associated with moyamoya disease was well preserved and no neurological deficit was observed after surgery.
The authors stress the absolute operative indication for a ruptured basilar aneurysm with moyamoya disease and the necessity of preserving collateral circulation especially in dura-pial anastomotic vessels.

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Bilateral persistent primitive hypoglossal arteries (PPHA) associated with multiple aneurysms in a 59-year-old man are reported in this paper. Angiography of the left carotid artery revealed a PPHA on this side with a large aneurysm located at the junction of the basilar artery. This PPHA arose from the left internal carotid artery at the level of the C-2 vertebra. Right retrograde vertebral arteriography showed a PPHA and a small aneurysm at the trifurcation of the right middle cerebral artery. The necks of these aneurysms were successfully clipped. This seems to be the first case of bilateral PPHA associated with multiple aneurysms.

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In this paper we report on a case in which we at first experienced very good results after neck clipping of an aneurysm in the Middle Cerebral Artery (MCA), with sufficient bloodflow and no neurological deficit; but after 48 hours the main trunk of the MCA was scddenly blocked by the sliding of the clip.
In addition, we report some cases of slipping out of the clip. One is that of a 55 year-old man, attacked by arachnoidal hemorrhage and having 2.5cm in diameter. He had no neurological deficit and no angiospasm in CAG. Thirty-one days later we operated for clipping at Grade I of Hunt & Hess. Two days passed well and suddenly the patient lost consciousness because of obstruction of the MCA by slipping out of clip and died of brain edema.
In addition to this case we report two similar cases involving a 60 year-old man and 39 year-old man. As a result of these experiences we made a new and better clip with a hook on the blade to prevent slipping out and have obtained quite good results.

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Reactive polyurethane was investigated for use as coating material and compared with other materials which are presently employed in clinical use. Reactive polyurethane is a viscous li-quid which reacts with amine and water resulting in an elastomeric substance within a few minutes. After application to an aneurysm, which was made by venous pouch of the carotid artery in cats, the effect of this material as a coating material was examined macroscopically and microscopically. Other coating materials including Biobond, fibrin glue and Bemsheet were also examined. The fibrin glue was not found around the aneurysm three months after application and the amout of Biobond had substantially decreased six months after application. Bemsheet was found to coat the aneurysm well but was not sufficiently firm. The amount of reactive polyurethane had not decreased six months after application, and microscopic examination showed that the fibrous tissue had infiltrated into the many small holes which were made when it reacted with water on application, resulting in good adhesiveness between the wall of the aneurysm and the polyurethane. These results indicate the feasibility of reactive polyurethane as a coating material.

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In this paper, eight cases of spontaneous carotid-cavernous fistula (CCF) are presented and their treatment is discussed.
Three were treated with electrothrombosis by copper needle insertion, three were treated with irradiation and two were observed conservatively.
Angiographic examination showed that the CCF disappeared completely in all three patients who underwent electrothrombosis, but in two cases clinical complications appeared; i. e., transient oculomotor palsy and Gerstmann's syndrome due to stenosis of the internal carotid artery.
Lineac irradiation was applied to the fistula (100 rad per day, three times per week, total dose 4000 rad).
Clinical symptoms of all three patients improved, and angiographic examination showed that the fistulas were reduced in size in two cases and disappeared in the other.
Angiographically, spontaneous CCF were divided into three groups: localized, scattered and mixed type.
The scattered type was easily curable with any treatment, which is assumed to be because of the low blood flow at the fistula in this type.
Irradiation of spontaneous CCF is thought to be feasible as a first-choice treatment because it is non-invasive and effective.

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A 37-year old housewife was admitted to our clinic because of dysesthesia in the right arm which had started gradually one month before admission. Approxymately seven months prior to it, she had a bilateral vertebral aneurysmal operation (coating by Biobond and Oxycel)
Neurological examination revealed left hemihypesthesia below the C₂ level, motor weakness of the left arm and diminished deep tendon reflexes on the left.
On bilateral vertebral angiograms before and after the surgery, both aneurysms remained un-changed in size and the main branches of the vertebro-basilar arteries were well visualized.
CT scan combined with intrathecal and intraventricular injection of metrizamide revealed an enlarged intramedullary canal down to the midthoracic portion, Th₆. The intracranial cisterns were not filled with the metrizamide, except for a part of the cisterna magna.
A syringosubarachnoid shunt was made with a silastic catheter using microsurgical techniques. Unfortunately, her complaints and neurological condition did not change for the better.
In this paper, the geneses of the communicating syringomyelia in this case are discussed, with particular attention to the possibility of postoperative arachnoiditis at bilateral foramen Luschka and/or subarachnoid adhesion due to SAH. If syringomyelia is caused by the adhesion of the sub-arachnoid space at basal cistern, care should be given to the selection of surgical treatment.

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In cases of large and high flow AVM, it must be considered that with the technical difficulty of operation NPPB (normal perfusion pressure breakthrough) may occur after obliteration of the main feeders. Therefore, for a successful operation the prevention of NPPB during and or after operation is important. We have experienced a case of lt. parietal large AVM with a venous aneurysm. In order to prevent NPPB upon total extirpation of the large AVM, we used mild hypotension, about 100mmHg, with the drip infusion of trinitroglycerin (Mirisrol 1μg/kg/min) just after the induction of GOF anesthesia. This was followed by mild barbiturate therapy (Ravonal 3.5mg/kg/hr) after the main feeder was obliterated. Then total extirpation of the AVM was achieved uneventfully. These preventive procedures were contiuned for about 20 hours after the operation, and there was no occurrence of NPPB during or after operation. Drip infusion of trinitroglycerin (Mirisrol) is suitable for inducing hypotension in aged patints with ischemic heart disease.

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When a large cerebral arteriovenous malformation (AVM) is operated on, massive multi-focal bleeding, the so called normal perfusion pressure breakthrough (NPPB), represents a frightening and usually catastrophic complication. However recently we encountered a case of a large AVM which exhibited NPPB near the end of an operation and postoperative intracerebral hematoma. The patient was given an immediate second operation under barbiturate protection and induced hypotension and the patient's post operative course was uneventful. The large AVM was completely removed. This case emphasizes the usefulness of barbiturate administration and induced hypotension at the intra and postoperative management of NPPB.

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Massive cerebral swelling with multifocal bleeding rarely occurs after a technically successful removal of cerebral arteriovenous malformation (AVM). When manifested, this frightening complication is hardly manageable. The phenomenon, termed normal, perfusion pressure breakthrough by Spetzler and Wilson, is thought to be due to a rapid diversion of the blood flow from the AVM into the adjacent, chronically dilated, non-autoregulating small blood vessels. We recently experienced a case of large patieto-occipital AVM that exhibited multifocal massive bleeding immediately after an apparently successful total removal under the surgical microscope. High-dose barbiturate administration was then initiated during surgery and was maintained for 63 hours postoperatively. Controlled hyperventilation, and steroid and osmotic dehydrating therapy were also employed to control elevation of the intracranial pressure. The patient showed a good recovery and returned home without neurological deficits except for incomplete homonymous hemianopia. As already reported by others, this protocol seems effective for the management of the nightmarish, hardly controllable cerebral swelling with bleeding that may occur as a consequence of AVM removal.

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In this paper, a case of huge ruptured cerebellar AVM, which was totally removed by fractionated operations, is reported. A woman developed SAH at 18 years of age. Cerebral angiography showed a huge high-flow AVM occupying approximately the whole left cerebellar hemisphere, which received blood from the left SCA, AICA. and PICA. A round aneurysmal nodule was seen at the tectal segment of the left SCA. The patient became asymptomatic except for a marked bruit at the left occipital region, and was discharged without receiving any surgical procedure. At 19 years of age she developed dysarthria and double vision, and at 20 years left hemifacial spasm and hearing difficulty. At 25 years of age she was examined when she was two month pregnant. Positive neurological findings were left cranial nerve signs from the third to the eighth, left limb ataxia and trunkal ataxia. At the late stage of pregnancy she developed papilledema, and was placed under strict medical care. She gave birth to a healthy baby by caesarian section with no increase in neurological deficits. A CT scan demonstrated obstructive hydrocephalus, which was thought to be due to aqueductal stenosis caused by the mass effect of the AVM. After ventriculo-peritoneal shunt an operation for obliteration of the SCA aneurysm was carried out through the occipital transtentorial approach. The vascular lump was, however, not a true arterial aneurysm, but an enlarged portion of a arteriovenous shunt receiving several branches of the SCA. The vascular lump, which continued to the inside of the midbrain, was obliterated and removed. The vascular lump was considered to be the arteriovenous varix defined by Drake.
After discharge she was able to work as a housewife. However, one year after surgery she developed hemorrhage from the AVM, and was admitted again. After the acute stage of the SAH, partial removal of the AVM, especially of the lateral portion receiving blood from the left AICA, was carried out by left suboccipital craniectomy. After surgery cerebral angiography showed a remnant of the AVM supplied by the left SCA and PICA. The AVM was no longer of high flow. She was able to turn to her housework.
One and half years after the partial AVM removal she developed SAH again and was admitted with pontine and cerebellar signs. By reopening the previous suboccipital craniectomy the remnant of the AVM was totally removed. Thus the main part of the left cerebellar hemisphere, including the deep cerebellar nuclei, was lost. Postoperatively she could hardly walk by herself. At present, two years after the final surgery, she can walk with a stick without assistance, but can not yet return to her home life. Cerebral angiography and CT scan demonstrated total disappearance of the AVM. With a sacrifice of important cerebellar functions the holohemispheric cerebellar AVM was totally managed. Management of not easily accessible AVMs of the posterior fossa is discussed and a review of the literature on this subject is made.

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A case of arteriovenous malformation (AVM) of the left lateral recess of the fourth ventricle is presented in this paper.
The patient, an eight-year-old girl complaining of vomiting and vertigo, was admitted to our hospital with horizontal nystagmus and ataxic gait. Computerized tomography (CT) scans and angiograms demonstrated an AVM of the lateral recess of the fourth ventricle, which was fed predominantly by the choroidal branches of the left posterior inferior cerebellar artery, and drained by the petrosal vein. At first, the patient underwent resection of the nidus through the midline approach. Postoperative CT scans, however, demonstrated a residual nidus of AVM in the area of the left cerebellar peduncle and a probable draining vein in the left cerebellopontine angle. Therefore, a second operation was designed for the lateral approach. The residual AVM was found in the middle and inferior cerebellar peduncle being supplied by the choroidal branches of the left anterior inferior cerebellar artery and small branches of the left superior cerebellar artery at the cerebellopontine angle and in the lateral recess of the fourth ventricle. Postoperative angiograms revealed complete obliteration of the AVM, although CT scans demonstrated a small hematoma in the lateral recess of the fourth ventricle. The patient was discharged with mild hearing disturbance and dysmetria on the left side, which disappeared six months later.
Operative techniques as well as the surgical indication for the posterior fossa AVM are discussed and a review of the literature is given.

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