Surgery of a high basilar bifurcation aneurysm is one of the most difficult operations because of the location. Aneurysms which are located 1.5cm higher than the posterior crinoid process are difficult to approach by the usual pterional or subtemporal approaches. Our original transzygomatic anteriorsubtemporal approach is useful for aneurysms located up to 2cm higher than the posterior crinoid process. The patient is placed in a semiprone position with the face turned 60°contralaterally. The skin incision is started from the external auditory meatus. The zygomatic arch is reflected with the temporal muscle. The bone of the middle fossa is removed. The temporal lobe is retracted upwards after dural incision. The tentorial edge, PCA, fourth nerve and third nerve are recognized first. Then we approach the basilar artery and a highly situated aneurysm. In this report, authors explain this useful approach from an anatomical standpoint.

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Reconstructive surgery may be the second best method in a such case, in which neck clipping of aneurysm seems to be impossible or difficult and it cannot help selecting proximal clipping or trapping of the parent artery. Many kinds of reconstructive surgical procedures have been reported. STA (superficial temporal artery)-MCA (middle cerebral artery) anastomosis is the most common procedure. But, this method is not useful in all cases. It is not suitable for the purpose of the reconstruction of anterior cerebral artery. In some case, the amount of blood flow through the STA is not enough to maintain the function of the brain. For these reasons, not only STA-MCA anastomosis but also various kinds of reconstructive procedures should be used according to the needs of each cases.
In the last five years, 46 reconstructions of the parent artery have been performed prior to or secondary to the aneurysm surgery. The reason why these procedures were needed were as follows,
1) 6 patients with incidental aneurysm was estimated to have cerebral ischemia due to the occlusion of internal carotid artery or middle cerebral artery.
2) In 10 cases, the aneurysm was so big or giant, which might be difficult to be clipped. So, STA-MCA anastomosis or A₃-A₃ side to side anastomosis was made prior to clipping of aneurysm for the purpose of prolongation of parent artery occlusion time.
3) 3 cases with intracavernous giant aneurysm were applied the STA-MCA anastomosis and 18 cases who had a giant aneurysm at the ophthalmic or intracavernous portion of ICA were treated with the anastomosis between the cervical external carotid artery and the middle cerebral artery using a radial artery graft.
4) 7 cases with dissecting aneurysms of the vertebral artery were applied various kinds of reconstructive procedures.
5) In 6 cases, some troubles had occurred during surgery and some reconstruction were made for countermeasures against the occlusion of parent artery.
In this paper, our techniques and methods of reconstructive procedures with some examples were reported, and the cause of deterioration was discussed. To summarize our interpretation of results, it should be noted that in aneurysm surgery it is advisable to prepare simultaneously various kinds of reconstructive procedures as well, not only for the patients with a giant aneurysm or an unusual aneurysm like as dissecting aneurysm but also with an usual aneurysm. High flow bypass with a radial artery graft and intracranial interarterial bypass like as A₃-A₃ side to side anastomosis and M₁-M₂ anastomosis should be used widely in the future.
Last, please excuse me if I overemphasized my opinion more subjectively than was necessary. And I will be glad if this paper is any help to young neurosurgeons.

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The present study attempts to assess regional cerebral blood flow imaging under intravascular balloon occlusion testing, using single-photon emission computed tomography (SPECT) and 99m Tc-hexamethyl-propyleneamine oxime (^99mTc-HM-PAO) for the surgery of large cerebral aneurysms.
The balloon occlusion test was performed on 4 patients, two with ruptured large internal carotid aneurysms, one with an unruptured giant internal carotid aneurysm, and one with a vertebral dissecting aneurysm. During the balloon occlusion test of the internal carotid artery and the vertebral artery, ^99mTc-HM-PAO (20mCi) was injected intravenously 1 to 2 minutes before deflation of the balloon, and the stump pressure was monitored simultaneously. SPECT images were obtained using HEADTOME SET 031. The hypoperfusion area on the SPECT image was estimated into three grades: mild, moderate, and marked, in comparison with the unaffected area.
^99mTc-HM-PAO SPECT showed a marked hypoperfusion area in the ipsilateral cerebral hemisphere at 5 mmHg of stump pressure in one patient with a ruptured large internal carotid aneurysm, and a moderate hypoperfusion area in the basal ganglia even at 70 mmHg of stump pressure in another patient with a ruptured large internal carotid aneurysm. In one patient with an unruptured giant internal carotid aneurysm, ^99mTc-HM-PAO SPECT showed no hypoperfusion area at 50 mmHg of the stump pressure. In one patient with a dissecting aneurysm of the vertebral artery, ^99mTc-HM-PAO SPECT showed a mild hypoperfusion area in the left posterior inferior cerebellar arterial territory. No patient showed neurological deterioration during the balloon occlusion test.
In conclusion, preoperative ^99mTc-HM-PAO SPECT study during the balloon occlusion test might be a useful tool for planning the surgery of a large cerebral aneurysm, in which temporary clipping or permanent occlusion of major cerebral arteries is considered.

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Ten patients with internal carotid aneurysms were managed by internal carotid artery (ICA) ligation. Pre-, intra- and post-operative regional cerebral blood flow (rCBF) were measured by the heat clearance method and ¹³³Xe inhalation method.
Abrupt ICA occlusion was carried out in one case, abrupt ICA occlusion combined with EC-IC bypass was carried out in three cases, and gradual ICA occlusion combined with EC-IC bypass was carried out in six cases.
During ICA occlusion, rCBF were reduced less than 20% in six cases and more than 50% in four cases. Permanent cerebral ischemia occurred in four cases, and transient cerebral ischemia occurred in one case. In four cases with ischemic complications, reduction of CBF was more than 50%.
Measurement of CBF might be useful for the prediction of cerebral ischemia in the therapeutic ligation of the cervical ICA.

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During aneurysm surgery on 13 patients, regional cortical blood flow (CoBF) was continuously monitored with a thermal diffusion flow probe in an attempt to assess the effects of brain retraction, systemic hypotension and temporary major arterial occlusion on blood flow and outcome.
In mild brain retraction of less than 10mmHg, transient decrease in CoBF was observed. CoBF decreased to a critical level when retraction pressure exceeded 30mmHg and remained at a low value until brain retraction was completely removed.
In systemic hypotension, temporary arterial occlusion resulted in further decrease in CoBF as compared with normotension.
When the CoBF was above 30ml/100g/min, the safety period for temporary clipping applied at distal to the perforators was 15 minutes. The occlusion time should be shortened when CoBF is below 30ml/100g/min for less than 10 minutes.
Two patients revealed basal infarction, which was not detected by CoBF monitoring, in the territory of perforating branches. Occlusion time should be less than 5 or 6 minutes when a temporary clip is applied at the site proximal to the perforating branches. The intraoperative monitoring of CoBF is a useful adjunct in assessment of the safety period for temporary clipping which is applied to the major cerebral arteries.

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We studied the reversibility of the cortical function after temporary occlusion during aneurysm surgery by monitoring the direct cortical response (DCR).
DCR changes were studied in 43 aneurysm patients. There were no changes in PaO₂, PaCO₂, body temperature, and blood pressure during monitoring. The threshold was 3±1.1 mA, the latency 21.3±5.1 msec, and the amplitude 627±425 μV. Maximal depression of the amplitude occurred within 8 minutes. The DCR did not change in common carotid artery (CCA) occlusion (16 cases). In bilateral anterior cerebral artery (bil. A₁) occlusion (8 cases), middle cerebral artery (M₁) occlusion (17 cases), internal carotid artery (ICA) occlusion (1 case) and ICA + A₁+M₁ occlusion (1 case), based on the reduction rate of the amplitude and how long reduction lasted, changes in the DCR could be classified into 5 groups. Group 1 (4 cases): The amplitude of DCR restored before declamping. Group 2 (7 cases): Reduction rate of less than 70%. Group 3 (9 cases): Reduction rate of more than 70% lasting up to 20 minutes. Group 4 (5 cases): Reduction rate of more than 70% lasting more than 20 minutes. Group 5 (2 cases): DCR disappeared for more than 30 minutes (one case of bil. A₁ occlusion, one case of ICA+A₁+M₁ occlusion). When the reduction rate was less than 70%, or was more than 70% and lasted up to 20 minutes (Groups 1, 2 and 3), the amplitude of the DCR was restored completely. But, when the reduction rate greater than 70% and lasted for more than 20 minutes (Group 4), the amplitude of the DCR was not completely restored. When the DCR disappeared for more than 30 minutes, the amplitude of the DCR was never restored, and postoperative computed tomographic scan revealed low density (infarction) in the perfused area (Group 5). It is concluded that monitoring of the DCR is useful during temporary occlusion and when the reduction rate of the DCR amplitude is more than 70%, the safe critical time of ischemia is within 20 minutes.

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Intraoperative monitoring of the temporary occlusion of the middle cerebral artery was performed in four patients with giant or large aneurysms.
Several combined monitorings with somatosensory evoked potentials (SEPs), electroencephalogram (EEG) and direct cortical response (DCR) were recorded. SEPs and DCR showed more sensitive responses to ischemia than those of EEG, both in chronic and acute stages; however, the outcome of the patients corresponded with the findings of the EEG.
The particular property of each type monitoring is helpful in comprehensive management of giant or large middle cerebral aneurysms.

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Changes in the somatosensory evoked potentials (SEPs) were monitored during the application of temporary clips in 97 aneurysm procedures. SEPs in response to median nerve stimulation were used as an index of cortical function. Aneurysm locations were as follows: middle cerebral artery (MCA): 46 cases, internal carotid artery (ICA): 51 cases.
The period of temporary occlusion ranged from 2 minutes to 70 minutes, and the mean occlusion time was 20.3 minutes at the M₁ segment of MCA and 15.8 minutes at the cervical ICA.
In 8 patients with MCA aneurysms and 33 patients with ICA aneurysms, no changes in SEPs during temporary occlusion were seen. Among these 41 patients, however, there were 3 patients with postoperative motor deficits (false negative), 2 of which improved markedly within a few days.
In 14 patients (8 MCA aneurysms, 6 ICA aneurysms), temporary occlusion caused a significant prolongation in central conduction time (CCT). None of these 14 patients showed any postoperative deficits.
In 42 patients (30 MCA aneurysms, 12 ICA aneurysms), the SEP cortical component (N20) became flat during temporary vascular occlusion. In thirty nine of these 42 patients, the N20 peak reappeared immediately following recirculation and returned to the baseline recordings. None of these 39 patients showed postoperative neurological deficits. The length of disappearance of the N20 ranged from 2 to 38 minutes (mean of 12.3 minutes). Therefore, it is likely that the postoperative outcome can be expected to be favorable if the temporary clip is released within about 10 minutes after attenuation of the N20. The remaining three patients with ICA aneurysms whose SEP did not recover following recirculation showed postoperative morbidity. In these three patients, vascular occlusions were done at multiple sites (ie, ICA. MCA and ACA), and SEPs disappeared rapidly after temporary occlusion. Judging from this result, rapid disappearance of SEPs following temporary occlusion can be considered a danger signal.
In conclusion, intraoperative SEP monitoring during temporary occlusion was useful in detecting the severity of ischemia if the vascular territory of the occluded vessel includes the sensory pathways.

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A study was made on the usefulness and problematic points of temporary clipping and on premature rupture during surgery.
Direct aneurysm operation was performed on 232 of the 393 patients with ruptured intracranial aneurysms. Of these cases, a temporary clip was applied in 129 cases (56%), designated as group A in this study, but not in 103 cases (44%), designated as group B. An analysis was made on the difference between groups A and B with regard to age, preoperative computed tomography (CT) findings, site of ruptured aneurysms and Glasgow Outcome Scale six months after surgery. In addition, study was done on the rate of premature rupture by timing of surgery, by preoperative Hunt & Hess Grade, by site of ruptured aneurysms and by Glasgow Outcome Scale six months after surgery.
The proportion occupied by elderly patients more than 60 years of age was 43% in group A and 63% in group B; that is, the rate in which a temporary clip was applied was lower in elderly patients (p<0.01). As for site of ruptured aneurysms, a tendency was observed for the frequency of use of temporary clip to be high for anterior communicating artery aneurysms (p<0.01). However, no significant difference could be found between groups A and B in the preoperative CT and surgical results.
Of the 232 cases operated on, premature rupture occurred in 9 (4%) and a temporary clip was applied in all these cases of premature rupture. As for timing of surgery, a tendency was observed for premature rupture to occur during early operation performed within day 3. No significant difference could be found between premature rupture and preoperative grade. Analysis of the rate of premature rupture by site of ruptured aneurysms showed 3 (14%) out of 21 cases of internal carotid artery aneurysm, 5(8%) out of 63 cases of anterior communicating artery aneurysm, and 1(3%) out of 35 cases of middle cerebral artery aneurysm. Prognosis six months after surgery was somewhat unsatisfactory in the group with premature rupture during surgery. However, as the number of cases in this group was very small, the effect of premature rupture on prognosis could not be determined accurately. In patients in whom there is a possibility of premature rupture during surgery, it may be advisable to prevent such premature rupture by temporary clipping of the parent artery.

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Temporary occlusion of the cerebral artery is a very useful technique to prevent premature rupture of a cerebral aneurysm. The authors analysed the effect of temporary occlusion to prevent premature rupture during surgery and the results of intraoperative monitoring of cerebral blood flow (CBF) and somatosensory evoked potential (SEP). Incidence of premature rupture was 6.8% when temporary arterial occlusion was used during aneurysm dissection or clip application, but it was 14.0% without temporary occlusion. These data showed the advantages of using temporary occlusion in aneurysm surgery. However 5 of 88 cases (5.7%) suffered from neurologic sequelae attributable to temporary occlusion. In 3 of these cases, the temporary occlusion was continued for more than 20 minutes. In one case, a temporary clip was applied on an atherosclerotic artery and vascular occlusion occured postoperatively. The reduction in CBF and neurophysiological damage resulting from the arterial occlusion varies from patient to patient due to individual variations in the collateral circulation. The permissible occlusion time should be decided as related to the CBF reduction and the changes of SEP. According to the results of intraoperative monitoring of CBF and SEP, in those patient where CBF decreased more than 60% and SEP disappeared just after occlusion of the parent artery, the temporary occlusion should be stopped within 20 minutes, or less if possible.

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Temporary clipping of the major arterial trunk is a very important maneuver in controling excessive unexcepted bleeding and adequately exposing the aneurysm, and sometimes it is necessary to use it repeatedly. But we here experienced 5 cases in the past 5 years where neurological complications occurred secondarily to repeated temporary clippings. The duration of one temporary clipping time was 5 to 15 minutes, and clipping was repeated 3 to 5 times.
To confirm and explain these clinical experiences, three temporary clippings at 40 minute intervals of the MCA were performed on 20 cats using the O'Brien method. Pial arterial behavior and pathological changes of the brain were observed in ten non-treated and ten barbiturate-treated cats. In our experience, a single 20 minute clipping does not provoke any ischemic injury to the brain, and pial arterial caliber returns to the resting level within 40 minutes. But three 20 minute temporary clippings produced considerable ischemic injury and a dilated state of the pial artery in the cats with no treatment, although these changes were secondary to repeated temporary clippings in the cats with barbiturate treatment. From these experimental results, we concluded that even if the time is short, repeated temporary clippings may produce a higher incidence of ischemic brain damage, and if repeated temporary clippings are performed in aneurysmal surgery, brain protection with barbiturates should be conducted.

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We operated on 267 (87.8%) out of 304 patients with ruptured aneurysms and all of the 33 patients with unruptured aneurysms between April 1983 and December 1989. In this period patients with ruptured aneurysms were managed under lower blood pressure preoperatively, with no antifibrinolytics, and we used infrequent temporary occlusion of the parent vessels to avoid the risk of cerebral ischemia. Two hundred and seventeen patients (81.2%) were operated on in the early stage to prevent preoperative rerupture.
Intraoperative rupture occurred in 32(12.0%) of 267 ruptured aneurysms and in 1 (1.2%) of 83 unruptured aneurysms. To complete permanent neck clipping after intraoperative rupture, temporary clipping of the parent vessels was required in 13 cases (39.4%), point suction “bursting” bleeding in 8, and tentative dome or neck clipping in 6. Bleeding from the rent of the neck ceased spontaneously in 4 and Oxycel cotton was effective on 1 case. Temporary clipping was also used in 4 patients with large and giant aneurysms, 3 with fragile and blister aneurysms, and 1 with a complex fenestrated Acom aneurysms without occurrence of intraoperative rupture. Occlusion times ranged from 3.5 to 24.0 minutes. Of the 21 cases (7.0%) where temporary clipping was used, only one patient had new neurological deficits in the immediate postoperative period, but made a good recover.
To minimize the risk of cerebral ischemia, it is important to use temporary clipping in only selected cases and to avoid early placement of temporary clips. In particular, reduction of intraoperative rupture results in low frequency of temporary clip application. The tight clot and adhesion surrounding an aneurysm make dissection of an aneurysm-artery complex more difficult and lead to intraoperative rupture. In our experience of management of patients with ruptured aneurysms without antifibrinolytics, removal of the clot was easier in most cases because the clot was gelatinous and soft.

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Temporary clipping has demerits; for example, arterial injury or circulatory disturbance. It has been believed that temporary clipping should not be indicated because of these demerits. Recently, with the advancement of operating techniques, balloon method and monitoring, temporary stopping of cerebral arterial circulation can be done safely. We have used temporary clipping in 52 (16.3%) out of 320 cases of aneurysms.
The reason for temporary clipping was A: premature rupture (9), B: removal of a giant aneurysm (5), C: bypass formation (5), D: correction of incomplete clipping (12), E: reduction of multiple clipping (9), and F: manipulation of invisible or hiddened tissue (12). Duration of temporary clipping was 3-45 minutes average of 7 minutes. Cause A. B. C. were longer than D. E. F.. The number of clip was 2-4 and more in the cause A. B. C. than D. E. F.. The comment for temporary clip were 1. in the case of sclerotic artery or vasospasm, temporary clipping was contraindication. 2. many temporary clips disturbed watching the operation field and manipulation. 3. Temporary clipping should be indicated before premature rupture because uncontrollable point sucking cases led farther aneurysmal rupture or tissue damage and sometimes led to impossible state of clipping.

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Although temporary clipping is used in aneurysmal surgery, its value has not been determined. In this study, we have assessed the influence of temporary clipping upon higher brain function and a cerebral infarct occurring in the territory of the Heubner's artery in patients with ruptured anterior communicating artery aneurysms. The subjects consisted of 89 patients operated on in the acute stage through the pterional approach (ranging in age from 35 to 70 years). Temporary clipping was used only when neck clipping was hard to perform because the aneurysm adhered strongly to the surrounding tissue, or because intraoperative bleeding occurred. Temporary clipping was performed on 22 patients, but not on the remaining 67. Temporary clips were placed at the dominant or bilateral Al segments. We observed cerebral infarction in the head of caudate nucleus on CT scans obtained within 48 hours after operation. These two groups showed no significant differences in age, preoperative neurological grade, or the amount of blood clots on CT scans.
The development of the cerebral infarction significantly related to the following factors: the use of a temporary clip, intraoperative bleeding, and dissecting time (the time interval between the beginning of exposure of the internal carotid artery and the termination of aneurysmal clipping). As this dissecting time became longer, it was more difficult to perform aneurysmal clipping. If temporary clipping was used for the same period, the perforator territory infarction occurred more frequently in cases with intraoperative bleeding, longer dissecting time, or both.
Approximately 80% of the patients showed an excellent or a good outcome, regardless of the cerebral infarction in the territory of the Heubner's artery. However, higher brain functions were affected in patients with the perforator infarction. We performed neuropsychological tests such as WAIS, colored matrices test, and Benton retention test. Higher brain functions were kept intact both in 6 patients with no abnormality on CT scans and in 3 with small perforator infarctions. (<2cm). In 2 patients with large infarctions (<2cm), attention and memory were slightly impaired, although they showed normal daily activities. In 2 patients with bilateral perforator infarctions, however, memory and thinking faculties were markedly disturbed. They developed Korsakoff's syndrome and their outcome became poor. These neuropsychological impairments could be attributed to the infarction in the territory of the perforator, including the limbic system.
In order to obtain a better outcome and maintain mental functions in patients with ruptured anterior communicating artery aneurysms, perforator injury must be avoided and temporary clipping should be used with the greatest care.

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It has been suggested that plastic adhesives such as Biobond and Aron a, which are clinically used for reinforcement of cerebral aneurysms, have had problems in terms of in vivo degradation and decreased strength. We have previously reported excellent results with Bemsheets, which are composed of 100% cellulose, as a wrapping material. We have prepared various solutions of ethyl cellulose (liquid cellulose) and studied the physical properties, operative manipulability, and histological findings of each solution. The following results were obtained.
1) Cupric sulfate, ethanol, acetone, and diethyl ether solutions of cellulose showed problems in terms of toxicity, flexibility of the film, tissue-adhesive properties, viscosities, and boiling points.
2) Ethyl acetate (concentration of cellulose: 6-25%; polymerization degree: 10-100) solutions showed no histological toxicity and had favorable adhesive properties. The physical property test of the solution revealed that the pH levels of an ethyl acetate solution (cellulose concentration: 10%; polymerization degree: 100) and Biobond were 7.35 and 3.16, respectively, and that the viscosities were 1385 cp and 626 cp, respectively. The test of the physical properties of the film, based on cast coating of 254 ym in thickness, revealed that a) the liquid cellulose and Biobond, after drying, were 17.8±2.8 and 109.8±44.2 in thickness (μm), respectively, b) the formation time of the liquid cellulose and Biobond was 62 sec and 1800 sec, respectively, c) coating strength (gm) (total summation upon rupture of a film of 5cm in length and 5mm in width by tensile force; tension velocity, 100 mm/min) was 432.3±51.4 and 8.0±5.6, d) strength index (Kg/cm²) [strength/(width of coat×thickness of coat)] was 572.8±84.7 and 2.4±1.8, and e) elongation rate (%) was 14.8±3.5 and 705±188.8. Thus, the cellulose coat was markedly stronger than Biobond.
3) When the concentration of cellulose was low, the coat was thin and viscosity and strength were low. On the other hand, when the concentration of cellulose was greater than 15%, the coating flexibility diminished and its strength was also decreased. However, when the degree of polymerization was increased, strength was increased without a reduction in flexibility even at the same concentration of cellulose.
With appropriate arrangement of the degree of polymerization and concentrations of ethyl cellulose, and solvent, liquid cellulose was demonstrated to possess excellent characteristics as a coating material because of its remarkable strength, flexibility, less tendency to elongate and ability to inhibit growth of cerebral aneurysms.

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All of the arteries around the aneurysm, especially perforating arteries, should be preserved when clipping aneurysms. However, perforating arteries often arise close to the aneurysmal neck. And even when great care is taken in dissecting the perforating arteries from the wall of the aneurysm, these arteries move and attach to the sac by the pulsating movement of the cerebrospinal fluid. In these instances, there is little space for the blades of a clip and this makes neck clipping difficult. To avoid the occlusion of the arteries on aneurysmal clipping, we have tried a new technique; that is, we put oxycell cotton between the aneurysmal neck and these perforating arteries, and leave the arteries aside to preserve space for clipping.
In this paper, the surgical treatment of aneurysms using this technique is reported. There were 12 cases operated on in the acute stage, (Acom: 5, BA: 3, IC: 2, MC: 1, VA: 1). Neck clipping was performed and the perforating arteries around the aneurysm were successfully preserved by this method. Postoperative CT scanning revealed no low density area, and there were no neurological deficits in any case.
This method may be a useful technique for preserving the perforating arteries in aneurysmal surgery.

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Deviated blade fenestrated clips developed by one of us were applied very successfully in 55 cases of cerebral aneurysms. Among them, there were 36 cases of ICA aneurysms and 14 cases of A Com A aneurysms which corresponded to 33% of the aneurysms operated on.
The characteristic feature of the clip is its lateral deviation of occluding blades. Eleven different types of this clip are currently available.
In cases where the neck of a cerebral aneurysm is located obliquely in the rear of the parent artery in the operative field, this clip is particularly effective. The clip is capable of closure parallel to the parent artery axis at the aneurysm neck, so that major rupture at the neck by the edge of the blades or residue of aneurysm neck were significantly eliminated. There was actually no rupture at the neck of the aneurysms, except for one giant IC-PC aneurysm.
As a large majority of ICA aneurysms are located postero-lateral to the parent artery in the operative field, and superiorly projecting type of A Com A aneurysm is also located postero-lateral to A Com A, which is the most difficult and hazardous if it is ruptured at the neck, the clips were extremely useful in these aneurysms to provide safer and more exact occlusion of the aneurysm neck.

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In cases of difficult aneurysms the temporary occlusion of blood flow makes the operation easy; however, ischemic damage of the brain must always be considered. Temporary clipping of the parent artery is easy, but ischemic damage may be severe.
On the other hand, a tentative clip which is put on the aneurysm either partially or totally, has the following merits:
1) Preparation of the aneurysm is easy and safe.
2) There is less ischemic damage.
But there are the following demerits:
1) The part of the aneurysm on which a tentative clip is put should be prepared.
2) At the time of tentative clipping the back side of the aneurysm cannot be seen.
Temporary clipping and tentative clipping, each has its own merits and demerits.
We have to approach aneurysms on the base of sufficient knowledge.

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The prognosis of patients with subarachnoid hemorrhage due to a ruptured cerebral aneurysm is chiefly influenced by initial damage of the brain on insult, the operation and the occurrence of vasospasm.
However, the operation may play the most important part of these three factors. The authors think that the results of an operation for cerebral aneurysms will depend on the occurrence of premature rupture during the dissection of an aneurysm from the surrounding tissue.
In order to prevent premature rupture of a cerebral aneurysm and to shorten the time of temporary clipping of the parent arteries during dissection, the authors use the technique of initial clipping with good results. So, the authors explain the technique of initial clipping in our representative cases.
Finally, based our experiences, the authors state the merits of this technique and discuss its usefulness in surgery.

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Incidence, causes and effect on surgical results of intraoperative aneurysmal rupture were analyzed in 618 consecutive cases of ruptured cerebral aneurysms. Intraoperative rupture was noted in 75 cases, an incidence of 12%. Most of the ruptures occurred during dissection of the aneurysmal neck and at neck clipping. Intraoperative aneurysmal rupture was relatively frequent in cases with anterior communicating artery, middle cerebral artery and vertebro-basilar artery aneurysms. Incidence of rupture was significantly high in cases operated on within 3 days and in cases classified into grades IV. Incidence of bleeding was not affected by the use of a temporary clip in all cases except cases with an anterior communicating artery aneurysm. Postoperative morbidity and mortality rates were 18% and 12% in cases with and without intraoperative aneurysmal rupture. This difference was not statistically significant. It may be very important in preventing intraoperative rupture and obtaining meaningful recovery of patients that active and judicious use be made of temporary clips for as short a time as possible without inducing severe hypotension.

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In principle, surgery of aneurysms must be done without bleeding, so that an approach should be selected that does not touch the ruptured site of the aneurysm. This paper will report how to control and treat bleeding if it occurs during operation.
(1) Thought must be give to how and where to control bleeding if it occurs during the approach.
(2) If ruptures, it is very important to suck the blood so that the bleeding point of the aneurysm can be observed.
(3) Temporary clipping, tentative clipping and dome coagulation methods are useful.
(4) When a broad necked aneurysm ruptures at the neck, it is difficult to control the bleeding with ordinary clips because ruptured site belongs to the rest of the aneurysm. The fenestrated clip is useful for controlling such bleeding.
(5) When the aneurysm is torn away, it is sometimes possible to reconstruct the parent arteries by suturing or by coagulation of the aneurysmal orifice.
These technical points are described.

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A 74 year old male patient who suffered a sudden onset of severe headache, followed by left oculomotor paresis was studied with carotid angiography, which disclosed a saccular aneurysm on the left IC-PC portion. After a left pterional craniotomy, a saccular aneurysm with a very thin wall and a broad neck was found compressing the IIIrd cranial nerve. The left C₁ -C₂ portion of the internal carotid artery appeared to be highly sclerotic. During preparation of the waist of the aneurysm, premature bleeding occurred from the dome, which was strongly adhered to the IIIrd cranial nerve. Temporary clips applied to the C₁, A₁ and M₁ portions were hardly able to control the bleeding, since the wall of the C₁ was too tough to be occluded by temporary clips and the fetal type posterior communicating artery was patent. The bleeding point of the aneurysm was successfully controlled by a gentle compression of a cottonoid and, thereafter, the waist of the aneurysm was clipped. After complete preparation of the neck, it was successfully clipped permanently.
The problems in the treatment of this type of aneurysm were, firstly, a highly sclerotic wall of the C₁ portion of the IC artery, the characteristics of which should be estimated before applying a temporary clip. Secondly, a strong adhesion of the thin aneurysmal wall to the IIIrd cranial nerve, resulted in difficulties in the suction control of bleeding. Thirdly, the broad neck of the aneurysm caused difficulties. This kind of particularly fragile aneurysm should meticulously be treated by complete preparation of the neck as a first step.

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Surgical treatment of cerebral aneurysms is often difficult because of their tendency to rupture prematurely during operation. Such aneurysms which easily rupture are categorized into three types. One is those which have a very thin dome. Another is pseudoaneurysms which are secondarily produced around the perianeurysmal clot and have a very fragile wall. The third is so called blister-like or dorsal aneurysms which have no apparent neck and have a very thin dome. In this paper, we present a technique for clipping such aneurysms. Aneurysms which look to rupture easily are first enveloped in a piece of cotton gauze. The wrapped aneurysms are clipped thereafter. Our experience shows that thin walled aneurysms are clipped easily and safely with this technique. We recommend this technique especially in cases of blister-like aneurysms.

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Induced hypotension has commonly been used during intracranial aneurysm surgery in order to facilitate dissection and reduce the risk of intraoperative rupture. It is not known for certain, however, whether this procedure is appropriate or not. We analyzed intraoperative prognostic factors, including induced hypotension below 60 mmHg mean arterial blood pressure (MABP) using trimetaphan camsylate, in 90 patients who underwent clipping of intracranial aneurysms. The intraoperative factors were temporary clipping, low density areas and brain swelling on postoperative CT scan, and intraoperative rupture. In addition, we investigated the Hunt & Kosnik grade, CT grade, and past history of hypertension as preoperative factors, and delayed ischemic neurological deficits (DIND) as a postoperative factor. The data were evaluated using methods of multivariate statistical analysis (quantification theory 2nd family).
These factors affected the prognosis in the following order according to their relative influence strengths: preoperative factors, postoperative factor, and intraoperative factors. In all cases induced hypotension below 60 mmHg MABP had a little influence on prognosis, but in patients with a past history of hypertension or in Hunt & Kosnik grade III and IV patients, induced hypotension had an adverse effect on outcome. These patients have a high probability of developing reduced cerebral blood flow and impaired autoregulation after subarachnoid hemorrhage. Especially when extended for over 30 minutes, induced hypotension below 60 mg MABP was more harmful. It is concluded that, in order to facilitate dissection during intracranial aneurysm surgery, temporary clipping is superior to prolonged induced hypotension.

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Injury of perforating arteries resulting from aneurysmal surgery was studied in 780 aneurysmal cases, and seventeen of these (2.2%) revealed a postoperative hypodensity area on CT due to injury of the anterior choroidal artery, the recurrent artery of Heubner, the lateral lenticulostriate artery and the thalamoperforating artery. Cerebral infarction due to injury of these perforating arteries and the outcome of these patients were evaluated by per- and postoperative CT findings, operation records and cerebral angiography.
Of the 17 cases showing a postoperative hypodensity area on CT, 9 cases recovered from neurological deficits, but 8 cases retained moderate to severe neurological deficits. Patients with injury of the Heubner artery showed better outcome, but patients with injury of other perforating arteries showed poor outcome.
Injury of these perforating arteries was caused mainly by improper frontal lobe retraction, blunt dissection or clipping procedure of broad neck or large aneurysms, or temporary clipping of the parent artery. To reduce injury of these perforating arteries during aneurysmal surgery, it is important to execute careful sharp dissection and to expose the entire aneurysmal dome in order to gain precise anatomical understanding as to the perforator, parent artery and aneurysmal neck.

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The long-term result of intracranial aneurysms treated by wrapping between 1961 and 1986 was reported. Twenty-one cases were treated by wrapping only, 11 by body clipping and wrapping, and 20 by body ligation and wrapping. These 52 cases were 2.7% of all directly operated aneurysm cases during this period. Among the 42 cases followed-up, rerupture occurred in only two cases, both of which were incompletely wrapped. It was therefore concluded that entire wrapping of aneurysm or residual portion of aneurysm after body clipping or body ligation resulted in a favorable outcome.

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When patients are operated on for cerebral aneurysms, a parent artery or its branch may be inadvertently occluded by a clip or kink of the artery. Usually this operative complication results in serious neurological deficits and poor prognosis. It remains most important to carry out careful dissection of the aneurysms and related arteries with microsurgical technique. As an adjunct to the surgical technique, we examined the efficacy of intraoperative portable digital subtraction angiography (DSA) in preventing arterial occlusion during the clipping of aneurysms.
Between February, 1985 and December, 1989 we operated on 132 patients with cerebral aneurysms. Fifty-one cases (Group 1) were treated in the period before portable DSA was available. After the introduction of portable DSA, 81 cases (Group 2) underwent definite therapy for aneurysms with routine intraoperative DSA following the clipping. Four patients of Group 1 (7.8%) were found to have arterial occlusion demonstrated by postoperative angiography, including one case of anterior communicating artery aneurysm, two cases of middle cerebral artery aneurysm and one of anterior cerebral artery aneurysm. In contrast, only one of the Group 2 patients (1.2%) suffered permanent occlusion of an artery. In three cases including two anterior communicating artery aneurysms and one middle cerebral artery aneurysm, intraoperative portable DSA revealed vascular occlusion immediately after the clipping procedure. The occlusion was released by reapplying clips, and the second DSA demonstrated patent arteries.
Portable DSA was particularly useful in visualizing branches of the parent artery of the aneurysm when not all of the branches are identified in the operative field. Another advantage is that more natural blood flow can be observed without brain retraction because DSA was usually done after removal of the retractors. No complication related to the portable DSA was encountered.
It is suggested that intraoperative portable DSA is an important adjunct to the safer treatment of cerebral aneurysms. Inadvertent occlusion of the arteries following clipping can be discovered and corrected before it causes permanent neurological deficits.

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Early epilepsy is a well-documented complication after aneurysm operations, but the mechanism is not well clarified. After aneurysm clipping, CSF drainage equipped with electrodes was inserted around aneurysm in 25 cases in which 20 patients were operated on within 48 hours after onset of subarachnoid hemorrhage and 3 during the chronic stage. Two cases had unruptured aneurysms. Both scalp and depth EEGs were continuously monitored for 7 to 14 days after operation. In these 25 cases, anticonvulsant was given in only one case.
Three types of EEG abnormalities were recorded. Type A: Spike or sharp wave localized to deep recordings and not observed from scalp EEGs. The peak of spike incidence was day 1 or 2 after operation in cases of less prominent SAH on preoperative CT. In cases of massive SAH, an increase of spike incidence was observed. Type B: Sustained paroxysm localized to deep recordings. This was recorded in 7 cases from day 2 to 13. In 5 cases, prominent SAH was observed on CT. Type C: Secondary generalization of seizure discharges was observed in 2 cases with massive SAH. Epileptiform discharges started from deep recordings. Administration of VPA did not prevent occurrence of type A discharge. These results suggest that early epilepsy after aneurysm operation may originate in the infero-medial part of the frontal or temporal lobe damaged by either SAH per se or surgical manipulation. Possible mechanisms of postoperative epilepsy after aneurysm operation and indication of prophylactic administration of anticonvulsant are in this paper.

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