The authors report their experience with direct surgery for partially thrombosed giant intracranial aneurysm (PT-GIA) showing mass effect without recent subarachnoid hemorrhage. Three cases with the lesions located in the VA-PICA, IC-Pcom and MC, respectively, are presented.
Thrombectomy, aneurysmectomy and neck-clipping are thought to be reasonable operation for these PT-GIAs. Intraoperative problems and management of PT-GIA are described.
The most common and dangerous complication is major vessel occlusion or stenosis induced by slipping of a clip. To prevent this, we have following devices. (1) The dome of the PT-GIA is opened first, and the thrombus is removed piece by piece. (2) In the neck, fine thromboendarterectomy is performed. (3) The CUSA system is very useful for thromboendarterectomy. (4) Finally, the neck is clipped safely after the PT-GIA has been converted into a pliable sac.
Such internal decompression of the PT-GIA allows us to identify the surrounding tissue and prevent damage to perforating vessels at neck-clipping.
When a PT-GIA is embedded in the brain stem, aneurysmectomy should be restricted to a partial one or the brain may be injured.
Intraoperative aneurysmal rupture, one problem that may arise, can be controlled by short temporary occlusion of the proximal main artery with the neck being clipped safely. All three patients showed satisfactory postoperative courses.

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The authors experienced two cases of miliary internal carotid aneurysms that were torn off at the neck during operative manipulation. The neck clipping could be done with difficulty partially including the wall of the parent artery. Reappearance of the aneurysm and its enlargement were observed shortly after the operation. It was considered that the reappearence was caused the clip slipping out in one case and by possible fragile tissue of the aneurysm remaning proximal to the clip in the other. Careful follow-up is needed in the case of aneurysms, especially of the IC, when the neck is torn off during the surgery.

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The patient, a 47-year-old man, suffered from severe subarachnoid hemorrhage on November 20, 1983. A broad-based saccular aneurysm (4×4mm) at the angle of the anterior communicating artery and left A-2, which projected to right superiorly, was revealed on the angiogram.
Two days later, neck clipping of the aneurysm was performed through the left pterional approach. Because of the high-positioned anterior communicating artery, the operative field was extremely restricted. The aneurysm neck wall looked very thin. Under mannitol administration and temporary clipping of the left A-1, a bayonet Sugita clip was placed at the neck. At that moment, a part of the neck might have been torn, and there was bleeding, but it stopped several minutes later.
Just after the operation, the patient showed an uneventful recovery, and, for the prevention of delayed vasospasm, ticlopidine chloride (300mg per day) was administered. Five days after the operation, the level of consciousness dropped to stuporous and CT revealed an increased high density area at the aneurysm site. Angiography showed a new aneurysm (2.5×8mm) at the anterior communicating artery just beside the clip.
On December 2, 1983, reoperation was performed through the same approach. A massive elastic hard clot in which the clip and bilateral A-1 to A-2 was embedded was removed meticulously piecemeal fashion using scissors. Under bilaterally placed A-1 temporary clips, the former clip was removed and a 45° angled fenestrated Sugita clip with a 5mm blade length was successfully applied on the neck of the aneurysm and the left A-2 was spared in the clip fenestration. Postoperative CT revealed a small frontal intracerebral hematoma, but the patient recovered to lead a useful life.
Although the minor tear at the neck wall of the aneurysm was considered to be the main cause of the pseudoaneurysm formation, administration of an antiplatelet agent also might act as an important promoting factor.

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Early rebleeding after neck clipping occurred in four among 218 patients who underwent direct surgery on an intracranial aneurysm. In three cases of internal carotid artery aneurysm, hemorrhage occurred during two to five days after the operation. A significant portion of the aneurysm remained in two cases and a small portion of the neck remained in one case on angiography after rebleeding. In a case of anterior communicating artery aneurysm, rebleeding occurred on the 21st postoperation day. On angiographyp erformed on the fourth day after neck clipping, the aneurysm was completely, obliterated. However, a new aneurysm grew in another portion of anterior communicating artery on angiography after rebleeding. The mechanism of development of the new aneurysm was presumed to be that the arterial wall was injured by tweezers during surgical manipulation of the arteries and hypertensive-hypervolemic therapy after the operation accelerated the development of the new aneurysm.
If there is doubt concerning misplacement or incomplete placement of a clip during surgery, angiography just after the operation is of great value in planning a reoperation, but it will be very difficult to predict the development of a new aneurysm and to plan for follow-up angiography before rebleeding.

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Nine cases of ruptured cerebral aneurysms with imperfect neck clipping are reported, and their clinical characteristics including problems in the initial operation are discussed. The patients included six women and three men, with a mean age of 54 years, all of whom had neck clipping as an initial treatment within three months after their most recent subarachnoid hemorrhage. Three of the patients had the aneurysms on the anterior communicating arteries and four on the carotid communicating and vertebrobasilar arteries. The aneurysms were small (12mm or less in diameter) on the angiogram in five of the nine patients. There was no case of giant aneurysm. Eight of the nine patients had rebleeding, and one showed regrowth of the aneurysm on the serial angiogram after the operation. Rebleeding occurred within 14 days in six of the eight patients. The outcome of the patients was unfavorable, with a mortality rate of 66.7%. Three of the four patients undergoing reoperation, however, showed good or fair outcomes. The reasons for imperfect clip placement at the initial operation were incomplete dissection of the aneurysmal neck in four patients, fear of kinking or occlusion of the parent vessels in three, and premature or slipped clip in two. These facts emphasize the importance of confirming perfect clip placement during surgery. If doubt exists, reoperation should be considered as early as possible within two weeks after the initial operation following immediate postoperative angiography.

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Generally, radical management of cerebral aneurysms is undertaken by clipping the neck of the aneurysm completely, but, in some cases, we have no choice but to clip it partially. We studied the rebleeding of partially clipped aneurysms during the postoperative period.
Twelve out of 390 cerebral aneurysms (3.1%) were clipped partially. The incidence by site was as follows: ICA, 2.1%; ACA, 1.5%; MCA, 6.5%; VBA 5.3%.
One aneurysm out of the 12 rebled one and a half months after the operation because of a slip of the misused temporary clip. Two patients died within two postoperative months due to complications.
In the other nine cases, the aneurysms, coated with cyanoacrylate, have not rebled during the follow up period, which has averaged seven years and 10 months.

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Aneurysms with a diameter of more than 13mm (global aneurysms) arising from the parasellar portion of the internal carotid artery (IC) present a special surgical problem.The topographical region, the size, and the thickness of the aneurysmal neck wall all pose problems in attempt to clip such aneurysms.
This report describes a technique successfully used with global aneurysm.
The aneurysms were approached by the standard pterional approach. Then, when the aneurysmal neck had been suitably prepared for application of a clip by freeing it of the surrounding tissues, temporary clips were applied at the distal and proximal parts of the aneurysm of the IC and at the posterior communicating artery.
The aneurysmal dome was then punctured with a needle and the blood aspirated with the needle in place. The aneurysmal neck was then occluded by an aneurysm clip.
The postoperative course in both cases was uneventful.
The advantages and shortcomings of the procedure are discussed.

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Internal carotid (IC) flow was monitored in 35 patients during aneurysm surgery using an electromagnetic flowmeter around the carotid artery in the neck. This was advantageous in patients with large aneurysms to reveal internal stenosis or kinking of a related artery, that was not suspected from the surgical observation. It was also useful for control of induced hypotension to prevent ischemic complications, especially for patients with severe SAH (grade III, IV). Autoregulation response, studied before craniotomy, was lost and IC flow severely decreased under mild hypotension. Systemic blood pressure did not always give indications for caution against cerebral ischemia.

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The authors have applied the microsurgical anterior interhemispheric approach (AIH, developed by Z. Ito in 1981) as a surgical approach for anterior communicating artery aneurysms (Aco-AN). AIH has several benefits: brain compression is minor, clot evacuation in the interhemispheric fissure and frontal lobes is possible without significant additional brain retraction; and approaches to the Aco-AN are possible without removal of a part of the brain tissues, such as the rectal gyrus. However, in cases of high- or posterior-positioned Aco-AN and aneurysms proximal to the knee portion in the anterior cerebral arteries (ACA), more interhemispheric dissection and brain retraction cannot be avoided in the aneurysmal operation if AIH is applied.
In these instances, the microsurgical basal interhemispheric approach (BIH) seems to be reasonable in order to make the dissection less extensive since the Aco-AN can be approached more inferiorly than in AIH. BIH was developed for anterior lesions of the third ventricle by N. Yasui, one of the authors. BIH could have the same benefits as AIH, mentioned above, and additional benefits accrue in that interhemispheric dissection is minimal in extension and distance and clot evacuation from the subchiasmatic to the prepontine cistern is possible without additional dissection or brain retraction. The purpose of this paper is to describe the practice of BIH and elucidate its characteristics compared with AI H.
The subjects were 19 patients with ruptured Aco-AN admitted to the authors' hospital from January 1985 to February 1986; BIH was applied in each case. The mean age of the subjects was 56 years. The interval from the last bleeding to the aneurysmal operation was from four hours to six days, with 15 of the patients being operated on within 24 hours. Preoperative consciousness levels showed alertness in nine, drowsiness in nine and semicoma in one. In six patients out of the 19, all the basal cisterns were packed with subarachnoid hematoma detected by CT scan. The operations were initiated under bifrontal craniotomy, applying the same methods as in AIH. In addition, a bilateral vertical craniotomy was performed at the frontal base, approximately 2cm away from the midline, and the anterior wall of the frontal sinus was removed. The first step in the interhemispheric dissection was not performed toward the knee portion of ACA compared with AIH, but to the planum sphenoidale and tuberculumn sellae directly. After aneurysmal clipping, clot evacuation from the subchiasmatic to the prepontine cistern was performed in 11 out of the 19 patients to establish the cerebrospinal fluid (CSF) pathway.
The patients were followed (mean: 6.1 months) and their outcomes were evaluated. Operative results were full recovery in 15 and self-management in four. Postoperative infection, cosmetic problems and olfactory nerve injuries were not experienced. These good outcomes could be the result of factors such as the minimal procedures employed during the operations and the easy establishment of the CSF pathway.
In conclusion, BIH is superior to AIH in cases with a high-positioned Aco-AN. But, it is stressed that both approaches should be undertaken with minimum brain retraction and sharp dissection, especially at the acute stage of subarachnoid hemorrhage.

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A successfully treated case of fusiform aneurysm arising from the Al portion of the anterior cerebral artery is reported. This 47-year-old man complained of the sudden onset of severe headache and vomiting on July 10, 1982. He was transferred to a local hospital and CT scan revealed subarachnoid hemorrhage at the basal cisterns. He was then referred to our hospital one month later. Enhancement CT scan showed a fusiform high-density area at the chiasma cistern. Left carotid angiography revealed a fusiform aneurysm of the proximal anterior cerebral artery 13×7mm in size. Elongation of the intracranial cerebral arteries and irregular deformity of the right proximal anterior cerebral artery were also found on the angiogram. He was operated on via the left pterional approach. The Al portion of the left anterior cerebral artery showed semifusiform configuration with the body behind the parent artery. There were no branches from the aneurysm itself. Sugita's angled fenestrated clip was successfully placed to form the parent artery. The postoperative course was uneventful, and the patient was discharged with mild neurological deficit one month after the operation.
Fusiform aneurysm involving the restricted segment of the anterior cerebral artery is quite rare, and only one such case has been reported. In this report, our case was described and surgical problems were discussed.

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Eight cases of the subchiasmal-global IC-ophthalmic aneurysms were operated on through the ipsilateral pterional approach, and the neck clippings of the aneurysms were performed in seven of them. Two cases resulted in insufficient clipping because of slip-out of the clip and IC stenosis, and one case resulted in trapping of the aneurysm. From these experiences, we concluded that:
(1) Routine exposure of the ICA in the neck is necessary for the preparation for rupture of the aneurysm, temporary occlusion or trapping to soften the aneurysm at neck dissection and/or at the time of clip application and also for the trapping.
(2) Preservation of the STA in the skin flap should be considered in preparation for possible EC-IC bypass surgery.
(3) Coagulation and cut of the falciform fold and/or removal of the anterior clinoid process could facilitate the mobilization of the optic nerve and could visualize the proximal aspect of the neck of the aneurysm easily.
(4) In recommendation of the fenestrated clip, the blade can be applied easily as parallel as possible to the axis of the ICA, and when the blade of the clip is too short or when the pressure of the clip is not sufficiently strong to the neck of the aneurysm, multiclipping of the fenestrated clips is effective for sufficient clipping.

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Direct clipping was performed in two cases of giant ophthalmic (30mm in diameter, subopticochiasmal global type) aneurysms in the right side who presented with visual disturbances in both eyes. Case 2 showed a second small aneurysm in the left IC-ophthalmic region. Preoperatively collateral circulation and tolerance to ischemia were studied by the Allcock and Matas tests. Both cases were operated on by right frontotemporal craniotomy. The neck carotid arteries were prepared for temporary occlusion during which time the brain function was monitored by scalp EEG. An STA-MCA anastomosis was performed before aneurysm surgery in Case 2.
The optic canal was opened and the anterior clinoid processes, which were well developed and pneumatized in both cases, were meticulously removed subdurally with an air drill. The anterior clinoid process in Case 1 continued to the middle clinoid process forming a bony canal around C3, which made the situation even more difficult. The cavernous sinus had to be opened around C3 in both cases in order to obtain space for the clip blade in the proximal neck of the aneurysm. Further dissection of the aneurysm from the surrounding structures such as the contralateral IC, optic nerve and chiasm could only proceed after the aneurysm had been decompressed by puncture, after which fenestrated clips could be applied without difficulty. Only one fenestrated and angled clip was applied in Case 1. Three fenestrated clips were needed in tandem manner in order to close the neck in Case 2. Here a fourth straight clip was necessary in order to stop continuous oozing, probably from the space between the tandem clips.
Postoperatively Case 1 returned to her normal household activities. Case 2 was blinded in her right eye and showed dense left hemiparesis, for which she is receiving rehabilitation at four months after the surgery. CT showed an infarction in the territory of the right anterior choroidal artery.
Discussions are presented about 1) choice of treatment, direct or IC occlusion with bypass surgery; 2) ischemia monitors and brain protection during temporary occlusion of the IC; 3) importance of opening the cavernous sinus in order to obtain the proximal neck of the aneurysm; 4) importance of protection of the posterior communicating, anterior choroidal and perforating arteries, especially when fenestrated and angled clips are applied.

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Direct neck clipping of cavernous internal carotid aneurysm is very difficult and hazardous. This is because of the deep location of such lesions for the pterional approach and their close anatomical relationship with the carotid artery, optic nerve and bony structures of the frontal base.
When ruptured, an aneurysm of this location can be presented as a subarachnoid hemorrhage, carotid cavernous fistula or epistaxis depending on the extent of development of the cavernous sinus and the sphenoid sinus and on the correlative pathway of the internal carotid artery.
The authors report two cases of internal carotid aneurysm located between the cavernous sinus and the branching of the ophthalmic artery. In both cases, the aneurysm was treated by aneurysmal neck clipping through the contralateral pterional approach, and after the operation, both patients were discharged in good condition. Case 1 was presented as recurrent massive epistaxis, and to the authors' knowledge, this is probably the first report of successful neck clipping of an internal carotid aneurysm ruptured into the sphenoid sinus. In Case 2, the aneurysm was discovered incidentally. It might have been presented as subarachnoid hemorrhage if it had ruptured before discovery.
The operation was started with the usual craniotomy for the pterional approach using a small skin incision, and the sylvian fissure was sufficiently dissected in order to obtain an adequate operative field. The tuberculum sellae, planum sphenoidale and anterior clinoid process were then drilled using a microsurgical drill which led to unroofing of the optic canal and opening of the bony wall of the sphenoid sinus. The internal carotid artery was then dissected in the proximal direction until the aneurysmal neck came in sight, retracting the optic nerve of the aneurysmal side laterally in a gentle manner, and the lateral wall of the sphenoid sinus was removed piece by piece as deemed necessary. For this process, the mucous membrane of the sphenoid sinus was detached from the bony wall and pushed downward with great attention not to injure it. When the neck of the aneurysm was secured, a clip was applied. After the clipping, the opened sphenoid sinus was filled with the fascia of the temporal muscle and fibrin glue.
In both cases, we could clip the aneurysm directly through the contralateral pterional approach because the aneurysm was small and projected medially. In our two cases, we believe, it would have been impossible to clip the aneurysm through the ipsilateral pterional approach. This is because the ipsilateral optic nerve and the distal internal carotid artery would have obstructed the vision of the aneurysm.
Generally, in the face of a cavernous internal carotid aneurysm, the possibility of direct neck clipping through the contralateral pterional approach should be considered. For the evaluation of this possibility, preoperative examinations such as angiography, angiotomography, CT cisternography and cavernous sinography are necessary to obtain precise anatomical knowledge concerning the aneurysm and surrounding structures.

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We applied our zygomatic approach and its subtemporal modification in three patients with unusual aneurysms arising at the P₁-P₃ segment of the posterior cerebral artery.
The first patient had a ruptured aneurysm of the Pi segment, which involved the perforating vessels to the midbrain. Successful application of the clip was achieved, sparing the perforating vessels and forming a neck clippable by bipolar electrical coagulation. In this patient, the zygomatic approach with partial removal of the orbital rim provided excellent exposure of the P₁ segment of the posterior cerebral artery.
The second patient had a ruptured fusiform aneurysm of the P₂ segment, in which the zygomatic approach allowed an exposure wide enough to reinforce by wrapping and clipping.
In the third patient with a ruptured giant aneurysm of the P₃ segment, a successful clipping with minimal elevation of the temporal lobe was achieved.
In all patients, the zygomatic approach and its subtemporal modification provided an exposure wide enough to permit safe manipulation.

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Surgery for aneurysm at a highly placed bifurcation is one of the most difficult operations. The usual approaches for basilar bifurcation aneurysms are pterional and subtemporal. However, aneurysms located 1.5 cm higher than the posterior clinoid process are difficult to approach these methods. The transzygomatic subtemporal approach makes it easier to approach the aneurysms situated up to 2cms higher than the posterior clinoid process.
The patient is placed in a semiprone position with the face turned 60° contralaterally. The skin incision is started just anterior to the external auditory meatus. The zygomatic arch is removed after reflecting the temporalis muscle. Part of the base of the middle cranial fossa is removed. After opening the dura the temporal lobe is retracted upwards. The tentorial edge, PCA, fourth nerve, and third nerve are seen followed by the basilar artery and aneurysm. The aneurysm is prepared and clipped. The authors report three cases treated by this approach

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Recent diagnostic innovations such as CT and digital subtraction angiography (DSA) have been increasing our ability to identify intracranial aneurysms safely and accurately. However, the overall results of management of aneurysmal subarachnoid hemorrhage, especially catastrophic hemorrhage, have not improved proportionately. This is because the risk factors for development of aneurysm remain unknown and traditional surgery has been planned after subarachnoid hemorrhage.
In this report the authors studied the effectiveness of intravenous DSA (IVDSA) for evaluation of the diagnosis of aneurysms before they rupture. Compared with conventional angiography, the diagnostic accuracy of DSA was 71.9% for 64 aneurysms (58 cases including 34 with rupture). Its diagnostic rate was limited by the size and location. In our clinical experience, aneurysms larger than 4mm have been directly diagnosed by DSA. However, because of the limited space-resolution of DSA, it cannot replace conventional angiography for evaluating the details of small aneurysms. It was necessary to perform repeated DSA by adapting the multiple directions of the injection in order to obtain precise imagings of vascular structures. False positive and misleading findings of aneurysms on DSA were due to the morphological complexities of arterial junctions and incorporated nodular densities with normal cerebral arteries and misregistration due to motion. Several representative cases were demonstrated.
In conclusion, a detailed knowledge of the vascular structure and factors simulating cerebral aneurysms will improve the diagnostic rates of unruptured aneurysms by means of IVDSA.

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Two routes in the pterional approach to the distal basilar artery aneurysms have been known: one is via the space between the optic nerve and the internal carotid artery (opticcarotid triangle: OCT), and the other is lateral to the ICA (retrocarotid approach: RCA). Although the approach via the OCT has several advantages of its own, it had been considered applicable to very limited cases. We successfully clipped such aneurysms via OCT in four cases out of 12 cases (33%), and the neuroradiological findings observed in these cases are analyzed and reported.
Measurements were made on the following items on the carotid angiogram of the cases operated via the OCT (OCT group) and the RCA (RCA group): the distance of ICA bifurcation from the midline (D) and the height of ICA bifurcation from the baseline between the anterior and posterior clinoid processes (H). Although these two values seemed to be higher in the OCT than in the RCA group, no significant difference was found. The product of D and H (D×H) was observed to be significantly higher in the OCT than in the RCA group. The value of D×H is considered one of the indicate of the size of the OCT and has proved to be useful in judging whether the approach via the OCT is applicable or not.
The approach via the OCT has several advantages, such as no injury to the oculomotor nerve, less retraction to the ICA and easy visualization of the P1 segment of the opposite side. The space of the OCT can be used not only for clipping itself but also as a line of sight to the deep structures as well as clips applied from other routes.

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The operative approach to a lower basilar trunk aneurysm located in so-called“no man's land”is difficult. A case of large AICA aneurysm with AVM treated by radical surgery by the suboccipital approach is reported.
The patient was a 41-year-old woman. She experienced an attack of headache, nausea, vomiting and vertigo nine days before admission. She had no other complaints upon admission, and an enhanced computed tomography (CT) scan demonstrated high-density areas in the right cerebellar hemisphere and cerebellopontine angle. A large aneurysm at the lower basilar artery and AVM at the right cerebellar hemisphere were visualized on the vertebral angiogram. The feeders were the AICA, SCA and PICA, and the drainers were the inferior vermian vein and petrosal vein. The aneurysm was located between the AICA, which was the main feeder, and the basilar artery. The aneurysm was approached subtemporal-trans-tentorially. However, the aneurysmal neck could not be dissected. But the neck was clipped by the suboccipital approach. The aneurysm and AICA were not visualized on the postoperative vertebral angiogram. However, surgical complaints noted were abducent, facial and acoustic nerve palsy.
The subtemporal transtentorial approach with the combined use of the suboccipital approach had an advantage in treating this large aneurysm located at the lower basilar artery.

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Fenestration of the basilar artery has been found in 0.6 to 6% of serial autopsy cases and vertebral angiographic cases. Therefore, an aneurysm arising at the fenestration of the basilar artery is rare. In the literature, only eight cases of aneurysms on a fenestrated basilar artery have been described. Four cases were surgically treated. The suboccipital and transoral-transclival approach were employed, because the fenestration of these cases was located at the proximal portion of the basilar artery.
A case of saccular aneurysm associated with a fenestrated basilar artery is presented. The fenestration was located at the middle third of the basilar artery. The aneurysm was at the proximal end of the fenestration, projected anteriorly and was located just posterior to the dorsum sellae. The patient was operated upon via a pterional approach. The aneurysm was identified through the spaces medial and lateral to the right oculomotor nerve. The deeper part of the neck of the aneurysm was hidden by the ipsilateral posterior clinoid process and the dome of the aneurysm. Sugita's clip (No.2) was applied to the neck of the aneurysm. Postoperatively, mild right hemiparesis and right oculomotor nerve paresis developed, but these symptoms gradually improved, and, six months later, the patient was free of neurological dificit. A postoperative angiogram revealed obliteration of the aneurysm and obstruction of left sided fenestrated basilar artery by the clip. Blood flow was maintained though the right sided fenestrated basilar artery.
Because of poor operative instrumentation, removal of the posterior clinoid process and a section of the tentorium was not undertaken. This would have provided a wider view and facilitated the operative procedure, and, with these procedures, the pterional approach was the procedure of choice in this case.

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