Operative techniques to the aneurysms of the anterior communicating artery are described. The steps I (S. W.) describe here have now been taught to my residents and staff and the methods of approach have been influenced by the requirements of teaching a logical method. The method may be followed safely and logically by the experienced surgeons. The right pterional approach has always been performed with only some situations of exception; (1) there is a significant intracerebral clot in the left frontal lobe, (2) there are multiple aneurysms on the left anterior circulation, and (3) there may be other complicating factors such as a previous right frontal craniotomy and others. Advantages of pterional approach from the right are; (1) mainly we are right-handed, (2) retraction of the nondominant frontal lobe is further advantage, and (3) craniotomy on the right, can be used for aneurysms with larger left A-1.
As Wilson and Spetzler said that if the patient's condition is optimal, the success of an operation depends primarily on the skill and experience of the surgeon and that an approach adopted by a master surgeon may be inappropriate for someone less experienced, there may be suitable methods, we believe, depending upon one's experience and technical standards.

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24 cases of anterior communicating artery aneurysms with superior, posterior projection (all A. Com. A. aneurysms: 107 cases) were operated for last 5 years. Four kinds of clipping methods were used for these cases.
1. Anterior clipping (18 cases).
This was most simple and basic procedures.
2. A2 spared clipping by using straight fenestrated clip (3 cases).
This procedure was indicated, when aneurysmal neck was covered by ipsilateral A2.
3. A. Com. A. plastic clipping by using L-angled fenestrated clip (1 case).
This procedure was indicated for aneurysms without aneurysmal neck such as aneurysmal formation of A. Corn. A. itself.
4. Direct posterior clipping (2 cases).
If aneurysmal neck clipping was impossible by other procedures, direct posterior clipping was indicated for aneurysms with severe posterior projection.
Neck clipping was done completely in almost all cases, and authors emphasized usefulness of fenestrated clips.

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We studied the operative approaches to anterior communicating artery aneurysms by means of reviewing preoperative angiogram and operation records. During the past 5 years, 117 patients with anterior communicating artery aneurysms were operated on in our hospital. Among these, we examined 112 cases of which preoperative angiogram and operation records were satisfactory for this study. We checked the next points on the preoperative angiograms. 1. Neck of aneurysmplanum sphenoidale distance. 2. Direction of the anterior communicating artery. It means which A₂ is anterior to the other A₂ in the lateral view of angiogram. 3. Size of aneurysm. We checked the next points on the operation records. 1. Operative approach and side of craniotomy. 2. When the pterional approach was taken, the rectal gyrus was aspirated or not.
This analysis derived these two conclusions as below.
1. We paid attention to the correlation between the neck-planum sphenoidale distance and the fact of aspiration of the rectal gyrus in the pterional approach. The result is that the higher aneurysmal neck was, the more frequently the rectal gyrus was aspirated. So, if the neck-planum sphenoidale distance is under 12mm, which includes the majority of the cases (94% of cases), we think the pterional approach is the best approach for anterior communicating artery aneurysm. However, if the neck-planum sphenoidale distance is over 13mm, retraction of the frontal lobe becomes more extensive by the pterional approach, and we consider the interhemispheric approach is superior to the pterional approach. But these cases are only 6% of all cases with anterior communicating artery aneurysms. 2. If we take the pterional approach, the next problem is the decision of the side of craniotomy. In this study, we took notice of the direction of anterior communicating artery and the size of aneurysm. For, if the right A₂ is anterior to the left A₂ in the lateral view of angiogram and the aneurysm is small, aneurysmal neck is hidden behind the right A₂ in the right pterional approach. Therefore we think that the approach from the left is better when the right A₂ is situated anterior to the left A₂ and the size of aneurysm is smaller than 6mm. These cases are 16% of all cases in this study.

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In operating on A. Corn. aneurysms by means of the pterional approach, there is no general agreement about the approach side, for many factors, such as the patient's dominant hemisphere, the A₁ dominancy, the direction of the A. Con. A. and aneurysmal fundus, the operating surgeon's handedness, and any co-existing aneurysms or intracerebral and cisternal hematoma, must be taken in consideration.
Usually in cases of lt. A₁ dominant, a more anterior position of rt. A₁ than lt. A₁, a rightward protrusion of the aneurysmal fundus and the presence of other co-existing aneurysms and intracerebral hematoma on the lt. side, the lt. pterional approach is recommended. In our hospital, however, we operated on all of the A. Com. aneurysms except the case which had other aneurysms on lt. ICA and/or MCA by means of the rt. pterional approach. We have now investigated the operation results.
We have found that the A₁ dominancy and the direction of the A. Com. aneurysm and aneurysmal fundus are not the factors that should decide the approach side. The occurrence rate of post-operative psychiatric symptoms, such as Korsakoff's syndrome, personal change, and urinary incontinence, is significantly lower in the rt. pterional approach. In the case of a pre-rupture that needs a frontal lobectomy, the rt. pterional approach is better for management than lt., and it is not so difficult to evacuate the lt. frontal hematoma due to an A. Com. aneurysmal rupture by means of the rt. pterional approach.
Therefore, in the pterional approach, we have concluded that, in all cases of A. Com. aneurysms except having other aneurysms on lt. ICA and/or MCA, it is best to operate on them from the rt. side.

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Five hundred and fifty-eight out of 586 cases of anterior communicating artery aneurysms were operated on using bifrontal craniotomy during the years from 1961 to 1982. Details of approach and technical key point for treating this type of aneurysm are discussed in this paper.
Small but enough craniotomy with four burr holes is adopted. The anterior edge of the bone flap should be cut down frontally as close to the orbital edge as possible.
Dura mater is also opened as frontally as possible to preserve the frontal bridging veins and superior sagittal sinus.
One of the defects of this approach was the loss of olfaction. However, a new technique has been developed in order to preserve bilateral olfactory nerves.
Bilateral A₁ and A₂ are exposed to prepare for temporary occlusion at the time of aneurysm rupture. We can make the operation under dry field even when the aneurysm ruptures during the operation. In order to prolong the arterial occlusion time, 500ml of 20% mannitol solution (before May 1982) or mixture of 500ml of 20% mannitol solution, 300mg of Vitamine E and 50mg of dexamethasone (after June 1982) is administrated intravenously just before putting the temporary clips. We can safely occlude the any cerebral arteries for 40 minutes by this method.
It is very important to expose the whole anerysm. To expose only the neck portion is dangerous because it is possible to overlook another aneurysm, small bulging of the vessels or a small artery hidden behind.
In acute surgery of ruptured aneurysm, removal of subarachnoid clot decides the postoperative prognosis. In this approach, we can remove the subarachnoid clot in bilateral sylvian fissure, interhemispheric fissure and around the chiasmal cistern. Continuous ventricular drainage is routinely set in acute cases during surgery as well as in the postoperative course to control the intracranial pressure.
There were 36 deaths out of 586 cases (6.1%). Surgical results of 346 cases of anterior communicating artery aneurysms operated on during the years from 1961 to 1975 are as follows; 195 excellent cases (56.4%), 64 good cases (18.5%), 41 fair cases (11.8%), 27 poor cases (7.8%) and 19 deaths (5.5%).

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The authors have devised a new attractive microsurgical approach for the surgery of anterior communicating aneurysms. It is by frontal median route and is named'unilateral interhemispheric approach'. The advantages of this approach are:
1) Less damage to the frontal lobe and the other intracranial normal structures such as the superior sagittal sinus.
2) Full identification of the aneurysm and the adjacent normal parent arteries.
3) Removal of interhemispheric hematoma which is occasionally found in acute stage but is inaccessible by subfrontal approach, thus preventing the possibility of cerebral vasospasm.
4) Preservation of the olfactory sense.
The disadvantage is, on the other hand, occasional sacrifice of a superior cerebral vein but without evident deficiency by this procedure.
This approach consists of frontal coronal scalp incision, right frontal craniotomy, separation of the right frontal lobe from the left frontal lobe in the interhemispheric fissure and access to aneurysms.
47 patients operated on by this ap% in grade III, 50% in grade IV patients but there was no death in grade I and II patients.
Postoperative mental changes were found in 19.5% of the patients and the right olfactory sense was preserved in 75.6% but the left olfactory sense was preserved in all of the 41 patients examined.

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The best treatment for intracranial aneurysm is seemingly direct surgical attack with the neck clipping. The direct neck clipping for carotid-siphon aneurysm, however, is hazardous and difficult as compared with other intracranial aneurysms because of its location adjacent to the skull base, the optic chiasma, and the cavernous sinus. The authors discuss the surgical treatment, especially the approaches to the carotid-siphon aneurysms based on our surgical experiences of 35 cases with 39 such aneurysms.
IC-oph aneurysms projecting superiorly can be treated with neck clipping through the ipsilateral pterional approach. Otherwise, IC-oph aneurysms projecting posteromedially are prefered to clipped through the space between the optic chiasma and the tuberculum sellae via the contralateral pterional approach.
Large aneurysms arising from the carotid-siphon are especially difficult for direct neck clipping except for superiorly projecting IC-oph aneurysms, which can be treated with neck clipping through the pterional approach.

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Of 113 patients with cerebral aneurysms undergoing surgery by direct approach at our hospital from May 1981 to April 1983, seven cases with carotid-ophthalmic aneurysms were examined mainly for the surgical procedures.
As regards the two cases with the Kothandaram's suprachiasmal type, there were no problems with the procedures. The five cases with the subchiasmal type underwent the surgery by the ipsilateral pterional approach. All the patients required unroofing by means of a microsurgical drill for the sake of security of the neck of the aneurysms. In three of the five cases, clipping could be performed, but not in the other two.
The problem of whether the neck of an aneurysm is easily secured or not should be discussed from various viewpoints, such as the position of the neck, size of the aneurysms and positional relationships between the aneurysms and the ophthalmic artery and/or the anterior clinoid process, etc. Even so, it is difficult to define the problem with certainty. But it is our impression that the anterior clinoid process was revealed as coming over the C₂ portion of the internal carotid artery and a small angle between C₂ and C₄ portion, that is, the strong refraction posteriorly centering the C₃ portion angiographically suggest that the operational field was unfavourable.

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Dorsally projected internal carotid aneurysms (aneurysms projecting upward on the lateral view of the carotid angiogram) are rare. We have encountered 5 such cases (3%) in our series of 150 intracranial internal carotid aneurysms in the past five years. These aneurysms were located in the portion of the internal carotid artery between the origin of the posterior communicating artery and the distal carotid bifurcation. They characteristically had a wide-based neck with thin wall. Although clipping of this type of aneurysms should be the choice of treatment, it carries a high risk of intraoperative rupture, most likely at the neck. Two of the 5 cases ruptured intraoperatively; another ruptured one month after the operation from a part of the semi-spherical aneurysm which had not been included in the clip. Two patients died because of rupture. Three representative cases are described and various technical problems including selection of an appropriate clip for this type of aneurysm and measures to be taken in case of intraoperative rupture are discussed.

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Thirty-seven consecutive patients with aneurysm of the middle cerebral artery were operated on between October, 1980 and December, 1982. All of them were operated in the neutral and slightly chin up position of the head. Thirteen of 37 patients associated with multiple aneurysm and were operated at the same time. The our standard approach is a medium-sized frontotemporal craniotomy. As a rule the sylvian fissure is split from proximally to distally after the chiasmatic and carotid cisterns are opened. The dissection proceeds more deeply to identify the trunk of the middle cerebral artery before dissection of the aneurysm, and then the neck of aneurysm is dissected safely. We emphasize that the merits of the neutral position of the head are as follows; (1) the parent artery can be dissected initially and easily, and (2) if bilateral craniotomies are necessary in cases of multiple aneurysm, they are performed easily to treat aneurysms without change of patient's position at one stage.

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The ordinary approach to bifurcation aneurysm of middle cerebral artery mainly recommended is as follows. Ipsilateral internal carotid artery was identified at first, then the stem of middle cerebral artery was followed distally to keep Ml, M₂ and neck of aneurysm. This approach is, however, not suited for aneurysm which projected rostrally or laterally from M1 and attached to dura mater. Because, premature rupture may occur before finding internal carotid artery by the retraction of middle cerebral artery. We prefer to use another method, called distal approach, for such cases. Using this approach it is easy to keep distal M1, proximal M2 and aneurysmal neck. Technically, sylvian fissure is opened about 2-3 cm long distally from aneurysm and the branches of middle cerebral artery are followed proximally to distal M1. Once the distal M1 and proximal M2 are identified, the neck of aneurysm is easily treated. The indication of this approach is decided by CAG findings. When the projection of aneurysm is laterally or inferiorly from M2 at AP view and is obviously rostrally from M1 and M2 at lateral view, it is good indication of this approach. Especially, when the top of the aneurysm is thought to attach to dura matter, it is the absolute indication. By our experiences, the lateral view findings seem to be more useful. During a 15-year period, distal approach was used in 48 of 111 cases of ruptured bifurcation aneurysm and premature rupture was seen in only one case. It is necessary neither cortical incision nor parenchymal resection for treatment of bifurcation aneurysm of middle cerebral artery.

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Microsurgery for cerebral aneurysms has been commonly practiced in recent years, and various microsurgical procedures are reported by several authors.“Distal trans-Sylvian approach (D. T. S.)”for middle cerebral (MC) and internal carotid (IC) artery aneurysms, may be taken not only in our institute but in many others. But, concerning with D. T. S. for MC-AN, that for IC-AN is not commonly accepted compaired with front-basal approach (F. B.). In this paper, authors explained the actual operative procedures of D. T. S. and attempted to clarify the advantages and the disadvantages of D. T. S. compared with F. B..
The advantages are as follows:
1) Brain retraction in this approach is less than F. B..
2) We can get all components of the parent artery, the aneurysm and the others inspite of more narrow and slitlike operative field compaired with F. B.. Especially in the cases of internal carotid artery aneurysm, this operative field corresponds to the course of supraclinoid portion of internal carotid artery.
3) Clot in the Sylvian fissure may be evacuated easily.
4) It is not necessary to extend the craniotomy to the skull base.
The disadvantages are as follows:
1) Rude operative procedures may injure Sylvian vein and the surrounding structures to cause more serious brain damage.
2) Various kinds of aneurysmal clips may be needed in this slitlike operative field.
3) Aneurysmal fundus may appear before confirming its neck and parent artery in some cases.

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Two cases of aneurysms of the peripheral site of the posterior cerebral artery are reported, and the surgical approaches performed on them are also discussed.
These patients underwent surgery by the subtemporal approach. Since the distance to the peripheral site of the posterior cerebral artery is long enough even with the subtemperal approach and the posterior site of the temporal lobe is located on the tentorium cerebelli, the temporal bone should be removed sufficiently and an operating microscope should be preliminarily prepared so that the focus can be adequately adjusted toward this side. In our two cases, however, it was necessary to sacrifice the Labbé's vein. (In one case, dysphasia appeared transitionally.) Because the posterior cerebral artery runs inside the hippocampal and the lingual gyri, it is often difficult to reach its peripheral site directly. For safety's sake also, it is more secure to pursue the peripheral site after confirming and securing the proximal part of the posterior cerebral artery with the removal of the cerebrospinal fluid. By this approach, it was necessary to remove a part of the hippocampal gyrus in the second case, but clipping could be accomplished without damaging the cranial nerves, penetrating branches from the posterior cerebral artery or the posterior choroidal arteries.

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Surgical approaches to multiple intracranial aneurysms were reported.
1) Aneurysms of the unilateral circle of Willis' plus ipsilateral MC aneurysm-through frontotemporal craniotomy, pterional approach.
2) 1) plus distal AC aneurysm-through anteriorly extended frontotemporal approach. The distal AC aneurysm approached interhemispherically.
3) 1) plus ipsilateral distal PC aneurysm-through posteriorly extended frontotemporal approach. The distal PC aneurysm approached subtemporally.
4) 1) plus contralateral IC and/or MC aneurysm-approximately 1/2 of IC and 1/3 of MC contralateral aneurysms could be clipped successfully through unilateral pterional approach.

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Four hundreds thirty nine cases of direct operations on intracranial aneurysms have been performed since April 1973 by myself.
Sylvian fissure must be opened very superficially to start with. The widest part of the Sylvian fissure should be identified and separated. Since the MC trifurcation is located in the widest portion of the Sylvian fissure, the aneurysms of the MC trifurcation could be reached smoothly by this method.
Gyrus Rectus or interhemispheric approach is better if the anterior communicating artery is located more than 1.5cm, above the frontal base. When the anterior communicating artery aneu-aneurysm is pointing downwards, A₂-Acom is to he considered in the approach. When the rysm is pointing superiorly “U” of A₁ dominancy is to be considered.
Separation of the aneurysm should be done from the neck of the aneurysm. The technique of dome coagulation has to be use sometimes.
The permanent clipping of the neck of the aneurysm should be done only after complete delination and confirmation of the aneurysm.

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Authors reported the simplified method of procedure for direct aneurysmal surgery at anterior circle of Willis.
Simplified method: On operating table, the patient's head was turned to the healthy side at an angle of 45 degrees to a horizontal line. Linear scalp incision was made as seen in Fig. 1 and temporal muscles were also incised by straight fashion. Wound was retracted by two Gelpi retractors, and two key burr holes were perforated at the site of subpterion (on the spheno-squamous suture) and the site of ca 1cm postero-superior portion from fronto-zygomatico-sphenoidal junction (the site between Linea temporalis and spheno-frontal suture). The small craniotomy was done and a ca 3cm×4cm oval-shaped skull flap was removed till the time of closure. When dura was reflected, superficial Sylvian veins were seen at the center of the operative field. Then, aneurysmal neck exposure was begun. After the aneurysmal neck clipping was completed, dura was sutured and few suspending sutures and tenting suture were done. Drain at subdural or epidural space was not set up.
Results: Thirty aneurysmal patients of chronic stage were treated by this simplified method, and most shortest operating time was 80 minutes of internal carotid artery (IC-PC) aneurysm. There were no significant troubles or complications produced by this method.

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The authors have devised a new cosmetic craniotomy in the surgery of intracranial aneurysms for the purpose of early recovery to the social activities of the patients.
The key procedures in the craniotomy are to cover the operative wound by the hair, to pre-serve the temporal branches of the facial nerve and to avoid bone defect.
The eyebrow is not shaved and the hair is shaved only up to 4 cm behind the hair line and 2cm above the zygomatic arch. For the protection of the temporal branches of the facial nerve, it is important to avoid any thermal effect on the branches by electrocautery and to retract the scalp, the galea aponeurotica, the frontal periosteum and the temporal fascia in a sheet so as to minimize the traction effect on the branches. The temporal muscle is bluntly dissected from the temporal bone and is posterolaterally retracted. A rhombic free bone flap is made and after the intracranial procedures on the aneurysm are completed, the bone flap is fixed by silk threads and bone defect is completely replaced with Bioresin. The temporal muscle is sutured at its anterior margin to soft tissues and its medial margin is fixed to the bone flap. Scalp is closed in layers.
The authors have experienced the cosmetic craniotomy on 60 cases and without any case with paralysis of the temporal branches of the facial nerve. There was no case with difficulty in mastication soon after the surgery but there were two cases with temporary difficulty in opening the mouth which was attributed to abnormal contracture of the temporal muscle.

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“Pterional” approach for aneurysmal surgery have been widely used since Yasargil's report¹⁾. Facial paresis or anterior temporal depression caused by this approach are well known as common complications from cosmetic point of view. We reported some techniques for prevention of facial paresis and temporal depression. We stressed following points: 1) Don't damage facial nerves (rami temporales or rami zygomatici) when incise the scalp or muscle. 2) Don't injure the temporal muscle too much. The temporal muscle must be attached to the bone flap. 3) The defect of the bone should be replaced by bone dust or resin.

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In this study, several surgical problems in the surgery for acute cerebral aneurysm are discussed relating to the clinical outcome. These include: sinking effect of the decompressive procedures as mannitol administration and ventricular drainage, degree of the brain retraction, and aneurysmal rupture during the operation and temporary clipping.
In particular, the effect of operative procedures on the clinical manifestation of the cerebral arterial vasospasm (VS) are discussed.
Nineteen out of 115 objective cases showed a poor clinical result. The main causes of poor prognosis are VS (12 cases), intracerebral hematoma or brain edema caused by excessive brain retraction (2 cases), re-bleeding attack from residual aneurysm (1 case), normal pressure hydrocephalus (1 case).
Fourty-nine cases (45%) showed symptomatic VS, of these fifteen retained a neurological deficit (N. D.). Twelve out of the 15 resulted in severe N.D. by VS. When the sinking effect of the decompressive procedures is not achieved, the number of case having symptomatic VS with N. D. is significant increase in the occurrence of symptomatic VS. This is true especially with cases existing N. D. Cases with aneurysm rupture and temporary clipping also show a higher incidence of symptomatic VS with N. D.
These operative problems increase the brain edema has subsided pressure of the fragile brain in the acute stage of subarachnoid hemorrhage (SAH). When VS occurred before the brain edema has subsided, decreasing cerebral circulation caused by VS resulted in excessive brain ischemia, and brain damage followed.
Clinical problems of SAH in the acute stage are not limited to VS which is only one of the important pathophysiological conditions as brain edema, increased ICP and so on. So importance of the VS should not be overestimated in the selection of operative procedures and methods, and also medical management.

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Prevention of rebleeding is thought to be the main purpose of surgery in intracranial aneu ysms. But in acute stage, the management of the subarachonoid hemorrhage is more important since it is the cause for the neurological deterioration of the patient in acute stage. Hence the method of SAH is very important in acute stage.
351 cases of direct aneurysm operation have been done. This includes 130 cases of early operations is within 24 hours of onset.
CT is essential to select the mode of management. Along with the management of the SAH, decompose of the swollen brain should also be considered. When the SAH is minimal and is conbined to the basal cisterns, direct aneurysm operation could be taken up on the usual way. When this is accompanied by hydrocephalus, ventricular tap just before craniotomy is necessary. When there is hematoma, this should be evacuated partially or completely before approaching the aneurysms. The evacuation should be done by the pterional approach. Cisternal drainage should be established for more than 2 weeks of post operative period.
When the hematoma is found in the ventricle, in the interhemispheric fissure or frontal lobe, interhemispheric approach is better.
When the patient in neurological Gr IV external decompression should be given.

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In our intracranial operation of ruptured cerebral aneurysms in acute stage, at first, continuous ventricle drainage was done in almost all cases. After then brain was slacked and operation became easier. This drainage was used postoperatively for controlling intracranial pressure. The design of craniotomy was chosen by CT findings. From our study subarachnoid clots which was shown as high density area over sixty in CT number causes symptomatic vasospasm. Bifrontal craniotomy was performed so frequently in acute stage operation to evacuate subarachnoid clots bilaterally which had high CT number over sixty. During evacuation of subarachnoid clots 10 to 100 mMol NaNO₂ was used for prevention of postoperative vasospasm. In desection of aneurysm temporary clipping of parent artery under administration of 20% mannitol or“Sendai cocktail”was used in all cases for prevention of premature rupture of aneurysm. In these two years eighty-eight cases which had ruptured aneurysms in anterior circle of Willis were operated on in acute stage within 48 hours after the onset. Operative results were followed two months after the operation. Seventy-three cases (82.9%) were able to work, in seven cases (8.0%) rehabilitation was necessary and eight cases (9.1%) were died.

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To evaluate the effect of removal of subarachnoid blood clots on the prevention of delayed ischemic deficit, 239 consecutive cases hospitalized within 24 hours after rupture of cerebral aneurysms were analyzed. They were classified in Grades 1 to 4 according to the system of Hunt and Hess.
Delayed ischemic deficit causing permanent disability and death occurred significantly less frequently in the patients who underwent radical operation in which subarachnoid blood clots were removed extensively and aggressively along the arteries in addition to clipping the aneurysms within 48 hours after the onset, than in the patients whose operations were planned to be delayed or the patients in whom aneurysms were clipped within 48 hours after the onset but subarachnoid clots were not removed radically.
In the group of radical operation, the outcome was more favorable than in the other treatment groups. If the patients 70 years old or more who consisted more than half of the patients with unfavorable outcomes had been excluded, the outcome might be much better.
Recently, the subarachnoid clots are removed by sharp flow of saline ejected through a small and fine needle during the radical operation. This technique avoids the mechanical stimuli to the vessels by a suction tube and minimizes the injury to the brain.

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Removal of blood clot in the cistern is an important procedure in the operation for acute stage of ruptured cerebral aneurysm. Possible technical complications which may occur by this procedure were described. There were hemorrhagic infarction in the frontal lobe in relation to cutting of the veins traversing the Sylvian fissure and small infarction in the basal ganglia due to mechanical injury of the perforating arteries arising from the circle of Willis.
The hemorrhagic infarction tended to occur when the traversing veins were composed only with several of small tributaries of vein and eventually were cut during opening of the Sylvian fissure. Another risk was a damage of the large vein draining from the medial frontal region and traversing the proximal part of the fissure.
Damages of the perforating arteries may occur when the hard clots at the base was forcefully tried to be removed. It was also possible that a drainage catheter inserted in the prepontine cistern through the space behind the carotid artery may occlude the perforators. Cases of small infarction on postoperative CT were presented.

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In order to prevent post-operative vasospasm, extensive hematoma removal from basal cistern has been effected during acute stage aneurysm operation. However, not all blood clot could be removed from cisterns which were remote from operation entrance, as well as from subarachnoid spaces covering the brain surface. Therefore, it is vital to wash out the blood and its brake-down products via cisternal drainage post-operatively. During past two years, we have performed 27 aneurysmal operation within four days following aneurysmal rupture. Among them, we performed post-operative cisternal drainage in 16 patients. Following removal of cisternal blood clot, cisternal drainage was performed from carotid cistern and Sylvian fissure (Group A; 4 patients). Following removal of cisternal blood clot, Liliequist's membrane was opened and clot was also removed from the intercrural cistern. If sufficient amount of CSF flowed out of the basal cistern, cisternal drainage was performed (Group B, 7 patients). If sufficient amount of CSF did not come out of the basal cistern, third ventriculostomy was effected perforating a small opening on the midline of the lamina terminalis, and then cisternal drainage was performed (Group C; 6 patients). According to the total amount of drained CSF during 6-8 days post-operatively (80-2500ml), drainage effect was divided into 3 categories; fair (more than 501ml), moderate (301-500ml) and poor (less than 300ml). In group A, 3 out of 4 patients were poor and no fair was included. However, 4 out of 7 in group B, and 3 out of 6 in group C were fair. Only one poor was included in each group B and C. The symptomatic vasospasm occurred in 37% of all 27 patients. No symptomatic vasospasm occurred in patients with mild cisternal hematoma on CT scan. In patients with moderate to marked cisternal hematoma on CT image, symptomatic vasospasm occurred in 43, 60, 100% of patients whose drainage effect was fair, moderate, poor, respectively. Thus, when hematoma in basal cistern is moderate to marked on CT image, Liliequist's membrane is opened and intercrural hematoma is removed. If sufficient amount of CSF does not flow out of the basal cistern, third ventriculostomy is effected and then cisternal drainage is performed from the carotid cistern and Sylvian fissure.

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From our experiences on 3 operative cases of ruptured intracranial aneurysm, a subarachnoid hematoma in the prepontine cistern remains long time and influences on the occurrence of late spasm of the cerebral arteries. Computed tomography did not reveal the presence of blood clot in the prepontine cistern clear, and the condition in an early stage of subarachnoid hemorrhage was not always severe in 3 cases. The continuous drainage from the lateral ventricle or the subarachnoid cistern was set after the aneurysm was obliterated by surgery. Nevertheless the late spasm of the basilar artery had developed and massive blood clot in the prepontine cistern was found at autopsy in 3 cases. The pathological study of the pons indicated the findings affected by blood circulation disturbances. The blood clot in the prepontine cistern is required to remove but it is difficult to open the prepontine cistern wide and to remove blood clot completely though supra or infratentorial surgical approach is used, therefore the irrigation by the drains in the lateral ventricle and subarachnoid cistern is tried hard to wash away blood clot in the prepontine cistern during and after the operaiton.

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Self-retaining retractors are indispensable in the modern aneurysm surgery. It is, however, well known that these spatulas sometimes deliver focal ischemic brain damage. Much attention should, therefore, be paid to control the pressure of brain spatula during retraction in order to avoid resultant focal deficit. Ninety-four patients with ruptured aneurysm were closely examined by CT scans pre and postoperatively on the presence of focal ischemic brain damage. In 77 patients out of 94 of the early series of the surgery, the duration of the retraction by a spatula was not restricted and was variable depending on the condition of the brain cortex. In 17 patients of the late series, a brain spatula was applied rep eatedly with a duration of less than 5 minutes with more than 2 minutes intervals. Pre and postoperative CT scans in both series were shown in the following table.
Positive CT scan findings indicating focal ischemic damage
Early series 14/77 cases (18. 2%)
Late series 2/17 cases (11. 8%)
There are some reports concerning the relationship between the pressure of brain retractor and the focal brain ischemia. In an experimental work using a rat brain, r-CBF under the brain retractor pressure of 30 mmHg for 30 minutes decreased to 0-40 ml/100 g/min. Another experimental study using an awake monkey demonstrated that r-CBF below 23 ml/100 g/min produced a transient focal paralysis and r-CBF below 18ml/100 g/min generated more profound neurological deficits.
The authors supposed that the decrease in r-CBF was caused not only by capillary compression, but also by stasis of the cortical arteries and their penetrating arterioles after cortical compression by a brain spatula and that our results of the surgery with an intermittent brain compression method revealed favorable outcome in the condition of the brain after aneurysm surgery.

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To estimate the causative factors of operative injury by aneurysm surgery, serum creatine phosphokinase activity of brain type was determined electrophoretically during and after operation.
The pre-operative enzyme activity was low enough (0.29±0.26mU/mL) All operated cases were divided into two groups by the peak value of the enzyme activity. One group was named “Mildly Elevated Cases” and another was “Highly Elevated Cases”. In the former group, the peak value of CPK-BB activity (1.26±0.58mU/mL, N=30) was lower than that at the time of SAH onset (2.25±1.25 mU/mL, N=14, the cases of Grade III-V).
The site of aneurysm and the difference of operative approach (pterional approach versus interhemispheric approach) were not reflected as the difference of enzyme activity.
In the cases of high pre-operative Grade and with basilar aneurysm, the peak value of CPK-BB activity was markedly high (4.92±1.65 mU/mL, N=19). Regarding the operative technique, brain retraction, brain aspiration, use of temporary clip and the removal of bilateral subarachnoid clot are the main factors which elevate the CPK-BB activity in serum.
Practically, the quantitative evaluation of operative injury is possible by determining the blood sample from 2 to 6 hours after neck-clipping of the aneurysm.

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After the early surgery for ruptured intracranial aneurysms, small infarcts developed in the head of caudate nucleus and nearby structures. In the present report, the mechanism of infarction was studied and problems of operative techniques were pointed out.
Pterional approach was employed in 90 0f 112 patients with aneurysms on the anterior circulation for neck clipping performed within 72 hours after ruptures. Seven of them developed small infarcts in the head of caudate nucleus and surrounding region, which are perfused by Heubner's artery. Five of seven cases were with anterior communicating artery aneurysm, the rest with middle cerbral artery aneurysm. Temporary clipping less than 5 minutes was employed in 3 cases. No premature rupture of hypotensive episode was noted during operations. Courses of 26 Heubner's arteries were analized in 13 cadaveric brains. Ten of 26 Heubner's arteries (38%) run anteriorly, not superiorly to A₁portions, making curved courses in the inferior surface of frontal lobes with their convexities anteriorly. Seven of 26 Heubner's arteries (27%) give rise to perforating branches near the olfactory stem in the inferior surface of frontal lobes. Retraction of frontal lobe in pterional approach can obviously cause traction and/or kinking of the origin of Heubner's artery, or compression of its perforating site, any of which leads to the circuratory impairment. Kinking or compression of Heubner's artery caused by its retraction can cause serious brain damage just after subarachnoid hemorrhage, when cerebrovascular autoregulation is lost and cerebral metabolism is impaired.
When the frontal lobe is retracted in pterional approach, Heubner's artery should be freed from surrounding structures and be handled in such a manner as not to cause its compression and/or kinking.

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In these 7 years we experienced 461 (431 cases) direct operation of cerebral aneurysms.
Except for the cases which showed vasospasm or had intracerebral hematom, the injury of various kinds of perforate arteries by direct operation were showed in 17 cases (4.2%).
The relationship of injured perforate arteries and position of aneurysms are as follows;
1) ant. choroidal artery were injured in 6 cases of 14 IC-choroidal aneurysms., (following is an.)
2) thalamoperforate aa. were injured in 4 cases of 109 IC-PC an.,
3) medial-striate aa. were injured in 1 case of 13 IC bifurcation an.,
4) medial-striate aa. were also injured in 2 cases of 136 A. com. A. an.,
5) lat. lenticulo-striate aa. were injured in 2 cases of 112 M₁-M₂ junction an., and
6) Internal peduncular aa. or ant. thalamo-perforate aa. were injured in 2 cases of 9 Basilar top an.
As to the cause of injury or closure of perforating branch (p.b.) in clipping of cerebral aneurysms, following were considered;
1) aneurysms with broad neck, 4 cases,
2) large aneurysm, 2 cases,
3) unconfirmed closure of p.b. due to premature rupture of aneurysm 3 cases,
4) simulationeous closure of b.p. in trapping of aneurysm 1 case,
5) closure of p. b. due to unsuitable clip (such as too long clip), 1 case, and
6) indirect closure of p. b. due to kinking of parent artery in clipping of aneurysms 6 cases.
Prognosis were, generally bad (fair-6, poor-2, and dead-1 ) except for 3 cases. At this points, authors must examine themselves with modesty.
And then, these complications have to be avoidable by sufficient consideration of various arrangement before operation and constant effect of technical elevation of each operators.

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Injury to perforating arteries resulting from aneurysm operations was studied using 373 cases with 428 aneurysms. All aneurysms were operated on between 1977 and 1982. Cerebral infarction due to perforator injury was evaluated by pre- and postoperative CT findings. Operation records, cerebral angiography, video and photos taken during operation were also studied. Postoplerative and one year follow ups of neurological signs were also evaluated.
In 428 aneurysms (A. co.: 127, A,: 3, IC-Ophth: 7, IC-PC: 92, IC-Ach.: 30, IC-Bif.: 14, M₁: 14, MC: 131, Basilar Bif.: 10), 46 aneursysms (11%) revealed postoperative hypodensity area on the CT due to injury of perforating arteries after the aneurysm operation. IC-Bif. and Basilar Bif. aneurysms had a higher incidence and MC aneurysms had a lower incidence of perforator injury. Concerning aneurysm size, the bigger the aneurysm, the higher the incidence of trouble with the perf orators.
Of the 46 cases showing postoperative hypodensity area, postoperative changes were negative or slight in 33%, but 65% showed moderate to severe motor palsy or consciousness disturbance. After the one year follow up, almost all cases recovered but 22%retained moderate to severe deficits.
Perforator injury was caused mainly by the temporary clipping of the parent artery in 46%of cases. Others were caused by dissection procedure (17%), occlusion due to clipping (15%), sacrifice (7%), injury during aneurysm rupture (7%) and others (8%).
To reduce perforator injury during aneurysm operations, use of a temporary clip should be avoided, sharp dissection should be employed and manipulation of the perforators should be avoided.

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33 surgical cases of aged patients exceeding 65 with ruptured cerebral aneurysm were studied in terms of operative procedures and prognosis. Of these 33 cases, 6 cases showed aggravations of clinical signs and CT findings. The pitfalls for operative procedures in aged patients are summarized in the following points.
1) Injury to the veins leads to impairment of venous return which provokes cerebral contusion, ischemic infarction or intracerebral hematoma. At the time of dissection and separation of the Sylvian fissure or interhemispheric fissure, unnecessary cutting of the veins should be avoided.
2) Pointing procedure at the time of premature rupture or use of a temporary clip lead not only brain edema due to decreased blood flow, but also impairment of the vital structures due to injury to the perforators once in a while.
3) Removal of clots with a suction tube or bipolar forceps are prone to avulsion or kinking of perforators which lead to small infarcts in the vital structures. And further, retraction with a spatula makes the brain prone to contusion or infarction in aged patients. Consequently, extensive clot removal should be avoided in aged patients.
4) Arteriosclerotic changes of the artery are so severe that the parent artery adjacent to the aneurysm easily become flexuous, stenotic or occluded by clipping procedures. Consequently, intentional incomplete clipping combined with wrapping should be done as necessary.

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Twenty of 51 cases of unruptured cerebral aneurysm experienced by the authors during the past 9 years were complicated with cerebral infarction. Clipping made on all of these 20 cases resulted in cerebral edema in 2 cases, postoperative convulsion in 5 cases and aggravated infarct symptoms due to exaggerated cerebral ischemia in 8 cases, as complicated postoperatively, as well as intracerebral hemorrhage in 6 cases. These postoperative complications led to 7 of 20 cases aggravated more or less than before operation, of these 7 cases 2 died. On the other hand, clipping was made on all of 31 cases of unruptured cerebral aneurysm detected concomitantly with other affections than cerebral infarction, which clipping, however, resulted in postoperative intracerebral hemorrhage in only one case.
Considering that infarcted brain is apt to present aggravated infarct symptoms, edema and hemorrhage according to the operative procedure and that cases complicated with cerebral infarction have comparatively advanced ages and short life expectancy, it can be thought that unruptured cerebral aneurysm complicated with cerebral infarction should be defined with caution for its operative indication.

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It is important that forceps for aneurysm clips should be used unclasping when neurosurgeons are trying to approach and to clip aneurysm neck. It is difficult to insert clip beside aneurysm neck clipping forceps since the tip of clip is fixed and surgeons can not control the width of the tip of clip.
We emphasize that necessity of some techniques of clipping by the left hand even the right-handed surgeons. In some cases such as aneurysms of the left ophthalmic artery, internal carotid artery, and some basilar artery and anterior communicating artery by the left pterional approach, it is more convenient to use for clipping by the left hand than using the right hand. In such cases we can use the right hand to separate and to move surrounding cranial nerves and perforating arteries. We should train to use both hands for clipping aneurysm necks skillfully.

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Nineteen of 20 cases with the aneurysm of the distal anterior cerebral artery underwent operations, of whom 4 cases (21%) went to death. As 2 of 4 cases were in serious conditions with the complication of intracerebral hematoma, they were outside the indication of operation. So, it can be said that the mortality is 12%(2 of 17 cases). The cause of death was the postoperative intracerebral hematoma due to the dissection of the bridging vein. We try to cut the tip of superior sagittal sinus and do retraction of both bridging vein and frontal lobe, so as not to cut the frontal lobe.

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Incidence, causes and effect on postoperative results of premature rupture during surgery were analysed in 402 consecutive cases with ruptured cerebral aneurysm, on whom the operation was carried out with operative microscope. The operation was performed within 2 weeks after the last SAH in 194 cases (Group 1) and beyond 2 weeks in 208 cases (Group 2).
Incidence of premature rupture was 34/194 (17.5%) in Group 1 and 16/208 (8%) in Group 2. Most of the rupture occurred during dissection of the aneurysmal neck and at neck clipping in both groups (28 cases in Group 1 and 15 cases in Group 2), and others during retraction of frontal lobe in Group 1 (6 cases). The rupture was relatively frequent in cases with anterior communicating and middle cerebral aneurysms in both groups and was not affected by patient's conditions and timing of surgery in Group 1. Postoperative course was not affected by occurrence of the rupture in Group 2; only one case deteriorated postoperatively due to premature rupture. Overall morbidity and mortality in Group 2 were 8/208 (4%) and 4/208 (2%), respectively. However, mortality rate due to premature rupture was high in Group 1; 6/34 (18%) with the rupture vs. 15/160 (9%) without the rupture, particularly higher in cases operated on within 3 days after SAH and classified into Grade IV and V. Postoperative morbidity and mortality were not affected by use of temporary clips in both Group 1 and Group 2.
Use of temporary clips for a short time during dissection of aneurysm and at neck clipping is effective to prevent premature rupture and improve the results.

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In our clinic, temporary clip is often applied following Dr. Suzuki's method of preoperative mannitol cover in order to prevent premature rupture and to simplify the surgical procedure. The tolerance time of temporary clipping is discussed in our experience to evaluate its safety.
1) The application of temporary clip in the direct aneurysm surgery was performed in 94 cases among 190 aneurysm cases.
2) The longest tolerance times without new deficit were 46, 32.5, 12.5, 15.7 minutes for Acom, distal AC, IC and MC aneurysms respectively.
3) There were 8 patients with postoperative new dificits. Severe infarction occurred in 2 cases of them with occlusion of 40 and 63 minutes after premature rupture. 5 patients had transient hemiparesis for about one day which were thought to be most likely caused by emboli originating from the aneurysm. In another case with cerebral infarction and incidental aneurysm, hemiparesis, which lasted for a week, occurred after temporary occlusion of 8 minutes.
4) The incidence of the cases with postoperative new deficit was 3.2% and in only 1.2% the occlusion was for less than 20 minutes.

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We have reported that the preoperative mannitol administration under normothermia and normotension was effective to protect the ischemic damage. Recently, using the “canine model of complete ischemic brain regulated with a perfusion method”, the effects of various agents, which are thought as free radical scavenger, were investigated. More favorable effects were found when the combined administration of mannitol, vit. E and dexamethasone was made as compared with single administration of the each drug. This experimental results are thought to indicate that this new combination therapy may be useful in the clinical cases.
In this study, based on 81 aneurysm cases, which received defenitive aneurysm surgery by utilizing temporary clipping and preoperative administration of combined drugs, 20% mannitol 500 ml containing vit. E 300 mg and dexamethasone 50 mg, the occlusion time, the occlusion sites of main arteries and the complication due to temporary clipping were examined. There was no case which showed the sequelae apparently due to temporary occlusion.

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The effect of mannitol on the cerebral circulation and on the circulating blood was examined in the cerebral ischemia following the vasospasm due to ruptured cerebral aneurysm. Three hundred ml of 20% mannitol solution was used by drip infusion for 30 min through this experiment, and the same volume of physiological saline solution was used for the controls. For the measurement of cerebral circulation, the mean transit time of the hemisphere was calculated by the bolus injection of 20 mCi of ^99mTcO₄^-. The mean transit time of the ischemic brain was 7.22±0.22 sec, while this was shortened to 6.55±0.25 sec after the mannitol infusion.
The influence of mannitol for hyperfunction of platelet was shown by the measurement of platelet adhesiveness. The statistically significant decrease of the platelet adhesiveness was observed after the infusion of mannitol, inspite of the slight decrease of it in case of controls using physiological saline.
RBC aggregation measured by RBC aggregometer was high in SAH patients. This increased aggregation of erythrocytes was improved after the use of mannitol. These results showed that the mannitol might contribute to the improvement of microcirculation in the ischemic brain through either the increasing effect of CBF or the correction of intravascular components.

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Intraoperative premature rupture, as well as when dissection is difficult or when adequate clipping demands a collapsed aneurysm in large or giant aneurysms, temporary arterial occlusion may become necessary. The authors performed cervical carotid clamp in the management of 16 cases of internal carotid aneurysms. The morbidity and mortality of our series are compared between the aneurysms treated with carotid clamp and those without it (20 cases). The criteria of the use of carotid clamp are as follows: 1) intractable hypertension over 200mmHg. 2) acute onset of third nerve palsy with the angiographical evidence of large daughter aneurysm. 3) giant aneurysm. 4) aneurysms situated proximal to the posterior communicating artery and difficult to trap in the intracranial portion. 5) aneurysms of which neck are larger than the diameter of internal carotid artery.
The morbidity (1/16) is not significantly different from that (5/20) of aneurysms treated without carotid clamp. However, neurological, EEG and dynamic CT scan (GBF) changes induced by the preoperative carotid compression should be carefully checked before the use of carotid clamp in the management of difficult internal carotid aneurysms.

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The purpose of this study is to clarify the decrease of the CBF values in suction with distance, close suction, or temporary proximal clipping. The CBF values were measured with electrolytic H₂ clearance methods and thermo-coupled tissue flow meter. The middle cerebral arteries of the animals were exposed with transorbital approach, and cut the small perforating arteries or the branches of the middle cerebral arteries which might not influence on cortical CBF values. The CBF values of the dogs in static, close suction, suction with distance and proximal clipping were 37.0 ml/100 g/min, 14.0, 21.5, 11.8 respectively. Those of the cats were 44.1, 28.2, 35.7, 13.2 respectively. In clinical state is, the more close suction influences on the cortical blood flow. It is desirable to suck with distance when the aneurysm ruptures.

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The authors reported two cases of aneurysmal formation as a complication in the use of temporary intracranial arterial clip.
The first case, 48 years old male, was operated on his anterior communicating artery aneurysm through the right pterional approach 40 days after its rupture. During the surgery, the aneurysm ruptured at the time of neck dissection and the right Al poriton was temporarily clipped with Scoville' clip for 15 minutes. The aneurysm was successfully obliterated, but the patient suffered postoperatively from three attacks of subarachnoid hemorrhage and the right carotid angiography 7 days after operation revealed a newly formed aneurysm at the Al portion where the temporary clip had been applied. The patient died 13 days after operation and massive subarachnoid hemorrhage from the rupture of the new Al aneurysm was demonstrated in autopsy.
The second case, 56 years old female, was operated on her right IC-PC aneurysm on the 23rd day after initial rupture, which ruptured during surgery, and the right IC was temporarily clipped at the immediate proximal portion with Heifetz No.107 clip for ten minutes. The aneurysmal neck was successfully clipped, and the right carotid angiography 35 days after operation, revealed an aneurysmal formation on the IC proximal to the clip where the temporary clip had been applied. The right internal carotid was then ligated and the patient was discharged in full activity.
The authors have been using a flexible silver probe with a slightly ballooned tip for aneurysmal neck dissection for these ten years. The diameter of the tip is approximately 1.0 mm and, when it can be passed around the neck of an aneurysm, the blades of the various aneurysm clips can also successfully be passed through the probe's tract. The tip can easily be flexed at any desired angle with fingers during surgery.

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312 cases of direct surgery for intracranial aneurysms were experienced in our service for last 5 years. It is the purpose of this paper to introduce some of our intraoperative technique which have been successfully applied for.
1) Management of premature rupture of aneurysm around the neck It has been recommended that muscle piece with Alon-Alpha adhesives should be applied to the ruptured orfice for hemostasis. However, this technique did not work well in many cases in such a time of crisis. In our successfully treated cases, temporary clips were placed on both distal and proximal side to the aneurysm as the first step. A piece of small oxycell ball were inserted into the ruptured orfice and obstructed it, then a Heifetz clip was placed on the neck including the ruptured orfice. After this clipping, temporary clips were removed. When hemostasis was confirmed, Biobond adhesive was dripped over for securing the clip in place.
2) Management of unruptured doughter aneurysms around the neck These daughter aneurysm around the neck have hazards to occur rupture at the time of the neck clipping of the parent aneurysm. Therefore, bipolar coagulation should be proceeded with weak power before the clipping. We experienced such small doughter aneurysms quite oftenly disappeared by bipolar coagulation.
3) Dissection of the posterior communicating artery In the pterional approach to the basilar head aneurysm, the posterior communicating arteries bothers operative field for manipulating the neck of aneurysm in some occasion. If preoperative angiographical studies indicate well developed open Willis circle, we may cut in the middle of the posterior communicating artery without any complication. Cutting of the artery should be done by use of small clip application. Bipolar coagulation and injuries of the perforators should carefully be avoided.
By this procedure, the operative field will be widered and it facilitate dissection of the neck and applicaiton of the clipping forceps much easier.

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Among many techniques to obliterate the aneurysm, clipping of the neck of an aneurysm is one of the most important and the best procedures in this microneurosurgical era. For unusual aneurysms, such as fusiform type, giant, serpentine, with broad or wide neck, it is necessary to use some special techniques to clip without any problem.
Recently we are employing multiple clipping methods for a special aneurysm. This technique requires two or more clips for one aneurysm. These clips are applied to the neck or the dome of the aneurysm in two ways:
1. in pararell way
2. in crossing way
In the pararell application, each clip obstructs the neck or dome only partially, but after using two or more clips the aneurysm is completely occuluded. A problem arises in the cross application that the blades of a second or third clip do not completely close due to the thickness of the blades of previously placed clip. To resolve this problem we utilize a window of a fenestrated clip. Another way to solve this problem is to shorten the blades of a clip by cutting the tip of the blades at surgery. This cutting method of blades is very convenient in the multiple clipping method and also sometimes in the clipping with only one clip.
From January 1980 till May 1983, we operated 450 cases of intracranial aneurysms using various Sugita clips. In this series, multiple clipping method were used in 33 cases without any problems such as incomplete clipping or postoperative stenosis or kinking of surrounding vessels. Every neurosurgeon can obtain an additional number of clips of different forms, angles and lengths as he likes during surgery in this multiple clipping method.

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The word“broad neck”had been used vaguely up to this time and no definition decided in aneurysm surgery. Therefore, intraoperative management of the broad neck aneurysm was not discussed in detail formerly. On this report we measured the diameter of the parent artery and the aneurysmal neck and decided on the definition of the broad neck aneurysm on the angiographic films from our consecutive 55 cases. The definition of the broad neck aneurysm is that the diameter of the aneurysmal neck is wider than the diameter of the parent artery within 1 cm proximal to the aneurysm. The results are as follows. ICPC, IC anterior choroidal artery aneurysm: The average diameter of the parent artery is 4.5mm. The average diameter of the neck is 4.0mm. The percentage of the broad neck is 23.5%.
IC-bifurcation aneurysm: The average diameter of the parent artery is 3.2mm. The average diameter of the neck is 4.3mm. The percentage of the broad neck is 75.0%.
Middle cerebral artery aneurysm: The average diameter of the parent artery is 3.3mm. The average diameter of the neck is 4.2mm. The percentage of the broad neck is 87.5%.
Acom aneurysm: The average diameter of the parent artery is 2.9mm. The average diameter of the neck is 3.0mm. The percentage of the broad neck is 25.0%.
Distal anterior cerebral artery aneurysm: The average diameter of the parent artery is 1.9mm. The average diameter of the neck is 3.4mm. The percentage of the broad neck is 75.0%.
Basilar artery aneurysm: The average diameter of the parent artery is 3.6mm. The average diameter of the neck is 5.9mm. The percentage of the broad neck is 83.3%.
There were a few discrepancy between the radiological measurement and the actual intraoperative measurement. When we operate the broad neck aneurysm, the most cautions point is not to make stenosis or kinking of the parent artery and the distal artery, but clipping of the broad neck aneurysm is not always easy. We are forming the new surgical neck to these aneurysms. The concrete method of the formation of the new surgical neck is that we pinch the aneurysmal dome at just distal to the essential neck with bipolar forceps and weak current is on intermittently at several times. After this technique we can apply the aneurysmal clip easily with safety not to make stenosis or kinking of the parent artery and the distal artery. We recommend this method.

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Use of dome coagulation technique in clipping of intracranial aneurysms. Operating microscope has made clipping of intracranial aneurysms safe and accurate. When bigger than large sized aneurysms are encountered, it is sometimes difficult to see the opposite side of the aneurysm, even after clipping the neck of the aneurysm.
Clipping was sometimes found to be incomplete on inspection after the aneurysm dome was coagulated to a smaller size. Coagulated artery shows degenerative changes histologically. Degenerative tissue is thought to be weak and is predisposed to the development of new aneurysm and subsequent rupture. Hence aneurysm neck plasty seems to be dangerous. So, after clipping, I coagulate the aneurysm dome to make it small.
When the aneurysm is clipped completely, instead of directly coagulating, the dome is ruptured, and then coagulated to a smaller size. When the aneurysm is not clipped completely, the dome is coagulated to a smaller size. Then the placement of the clip is easily verified. When it is found incomplete or include a smaller branch, proper correction is made after the shrinking the aneurysm to a confortable size.

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The “neck making technique” with bipolar coagulation in the clipping of the aneurysm is described. This technique is very useful, to make safe preparation for the neck clipping, or to obtain the “best point of clipping”.
In dissecting the aneurysm from adjacent structures, the forceps of a bipolar coagulator is attached parallel to the wall of the aneurysm and coagulation is done at this position. The coagulated wall of the aneurysm is shrunken and a small space is made between the aneurysm and the adjacent structures. Through this space, further dissection and the coagulation is performed to make the “neck” of the aneurysm.
If the reverse side of the aneurysm can be observed directly by this procedure, the “neck” can then be clipped. If it is difficult to reach, or the perforators can not be spared in clipping, the size of the aneurysm should be reduced by cutting the dome, then the “neck making” is performed to make the “best point” of clipping.

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Recently, we experienced a case of recurrence of cerebral aneurysm 6 years after surgery, in spite of muscle wrapping after neck clipping. Since, we threw doubt on the suitability of muscle piece for wrapping material, experimental study on histological change after wrapping of the intracranial arteries of 43 dogs was done.
The findings obtained are:
1) Bemsheets adhered closely to the arterial wall and made up toughly reinforcing wall by proliferation of collagen fibers in the space of retiform of cotton fibers after one month. Proliferation of the collagen fibers correlated in degree with the passage of time.
2) Muscle, fascia, and dura adhered relatively closely to the arterial wall but they were absorbed and disappeared after one to two months.
3) Lyodura unfitted on the arterial wall and was revealed necrotic change in the curved portion of it.
4) Coating with Aron alpha A was revealed unfit on the arterial wall and tended to crack with the passage of time.

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The patient, a 42-year-old male, suffered from subarachnoid hemorrhage in June 1974. A broad based saccular aneurysm on the C₂ portion which projected superolaterally was shown on the left carotid angiogram (CAG). In the 27th of June 1974, neck clipping and coating with Biobond^® of the aneurysm were performed through the left pterional approach. Postoperatively he suffered from right hemiparesis and aphasia, but these symptoms recovered in 10 days after operation. Repeated CAG was done 7 times during about 3 years postoperatively. On these examinations it was found out that rest neck coated with Biobond^® had been expanding into the saccular aneurysm gradually. In the 18th of July 1976, the reoperation was performed through the left pterional approach again. Operative findings as follows: the aneurysm and the parent artery were covered with the elastic hard“Scar”. Beneath the“Scar”, the Biobond^® film was found. The“Scar”and the Biobond^® film were sharply dissected with scissors. The Biobond^® film attached to the aneurysm is easy to dissect, while the film attached to the metal clip is difficult. The recurrent aneurysm was covered with the Biobond^® film partially, which was stripped out from the parent artery. The clip, applied at the first operation, was removed. Then the encircle type clip was used to the aneurysm. Tissue reaction, nature and adhesive power of the Biobond^® film were discussed about based on operative findings. It is pointed out that prevention of recurrence of the aneurysm is difficult by means of coating with Biobond^®. We concluded that wrapping and coating combined method must be choiced to prevent recurrence of the aneurysm.

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