Skull base approaches allow direct, short, and multidirectional access to the aneurysms located near the base of the skull with minimal retraction of the brain and the vessels.
We describe surgical experience of skull base approaches performed in 48 patients with cerebral aneurysms. They consisted of 7 males and 41 females, and ranged in age from 20 to 77 years old with the average of 55. They included 31 aneurysms of the paraclinoid internal carotid artery, 4 of the anterior communicating artery, 9 of the distal basilar artery, and 4 of the vertebral-posterior inferior cerebellar artery.
Intradural or extradural unroofing of the optic canal and removal of the anterior clinoid process were accomplished in addition to the fronto-temporal craniotomy in surgery of aneurysms of the paraclinoid internal carotid artery. When the aneurysm was large or giant, the aneurysm was collapsed to successfully obliterate the aneurysmal neck by combined use of the trapping-evacuation technique. The rim and roof of the orbit were removed as deeply as possible, resulting in very short and direct access to the aneurysms of the anterior communicating artery without significant brain retraction.
For cases with distal basilar artery aneurysm, the fronto-orbito-zygomatic was applied. When the aneurysm was situated in a low position, the posterior clinoid process, dorsum sellae, or the upper part of the clivus were removed to expose the aneurysm and the proximal segment of the basilar artery. In case of the aneurysm located at the union of the vertebral artery or the vertebral-posterior inferior cerebellar artery bifurcation, the transcondylar approach was used to fully expose the aneurysms and the proximal and distal segment of the vertebral arteries.
Application of the skull base approaches in aneurysmal surgery resulted in an acceptable morbidity and mortality.
In conclusion, skull base approaches were safe and useful to treat some patients with cerebral aneurysm, which were considered to be difficult to reach by conventional approaches. Various approaches of skull base surgery provided the maximally effective surgery in treating patients with cerebral aneurysm with minimal invasion.

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Ten cases of vertebrobasilar trunk aneurysms around the vertebrobasilar junction (VBJ) were operated on by two routes of skull base approach: the middle fossa anterior transpetrosal approach (ATP), or the suboccipital transcondylar approach (STC). In aneurysms located higher than the internal auditory canal (IAC) on lateral angiograms, such as in AICA aneurysms, ATP offered excellent results. In aneurysms lower than the IAC, excellent results were obtainable by STC. For aneurysms on the same level as the IAC, the surgical approach was most difficult and its selection depended on the aneurysm direction and size. In aneurysms with posterior projection, preservation of pontine perforators originating from the VBJ was most important, but difficult in unilateral craniotomy for large aneurysms. An intravascular balloon was useful for temporary occlusion of the proximal vertebral arteries. The combination of skull base surgery and the intravascular technique may offer safer access to those aneurysms.

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The prognosis for most untreated posterior circulation giant aneurysms seems to be extremely poor. Direct clipping of large and/or complex aneurysms located on the upper basilar artery, however, continues to be a challenging problem for neurosurgeons. Because of the lack of working space, placement of a temporary clip on the proximal basilar artery, safe dissection of perforators around the aneurysmal neck and proper placement of a definitive clip on it are technically difficult.
We employed the transcavernous approach combined with orbitozygomatic osteotomy for enhanced upward visualization for direct clipping of large and giant upper basilar artery aneurysms. This approach provides an extradural wide operative field by elevating the dura propria of the temporal tip from the inner cavernous membrane and extradural temporal lobe retraction without the risk of compromising the anterior temporal venous drainage.
The distal ring is dissected circumferentially around the internal carotid artery free from the dural attachment for medial retractability. The posterior clinoid process and the upper lateral part of the clivus are drilled out to realize enough exposure of the proximal basilar trunk to place a temporary clip. These surgical techniques appear useful for direct clipping of giant and complex basilar artery aneurysms with the aid of profound hypothermia in selected patients.

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Cerebral aneurysm in the anterior cirulation has been treated with standard approaches, such as the pterional approach and interhemispheric approach.
These approaches have provided sufficient surgical results in cases with aneurysms of usual location and of small to moderate size. However, we have experienced some difficulties in cases with unusual location and large size.
For these difficult and complicated cases, we employed skull base approaches, including Dolenc's extra-and intradural approach (DEIA), orbitozygomatic transsylvian approach (OZTSA) and basal interhemispheric approach (BIHA).
With these skull base approaches, we treated 28 cases of anterior circulation aneurysm; 5 cases of high positioned, posteriorly projected AcomA aneurysm; 7 of proximal ICA aneurysm: and 16 of multiple, bilateral aneurysm.
Complications related to the approaches included two visual impairments caused by insufficient unroofing of the optic canal, and one CSF leakage that was resolved with treatment.
Skull base approaches, if used selectively, can provide good exposure of high positioned aneurysms and large or giant aneurysms without brain retraction, which may cause brain damage.

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The validity of carotid endarterectomy (CEA) has been demonstrated in the treatment of carotid stenosis, and has become an important operation. However, compared to the West, there is a tendency in Japan to perform angioplasty readily in carotid stenosis. To carry out CEA more safely, we presently carefully plan the operation and the management of CEA before and after surgery for 1) patients with high-position stenosis, 2) elderly patients, and 3) patients with coronary artery stenosis.
In 238 patients, 259 CEAs were carried out in our department from January 1975 to October 1995. The male to female ratio was 194: 44, with an average age of 62.1 years. Postoperative mortality and morbidity were 1.5% and 3.1%, respectively. The strategies for CEAs in high-position carotid stenosis were a) nasal intubation, b) sufficient rotation of the neck to the contralateral side and c) dissection under the posterior part of the digastric muscle. After those procedures, the carotid artery could be secured at the C1 level.
In patients over 70 years of age (n=41), mortality and morbidity were 2.4% and 7.3%, respectively. These ratios were worse than those in the patients under 70, but not significant. Because pneumonia was induced easily by lower cranial nerve palsy in patients over 70 years of age, especially in the group of minor completed strokes, careful selection of patients and frequent posture change are necessary.
Coronary artery angiography was performed in patients undergoing CEA (n=51). Coronary artery stenosis was evaluated with the Gensini scoring system (GS). In 13 patients with a history of ischemic heart disease, GS was higher than the GS in 38 patients without a history of ischemic heart disease (34.5 vs 5.7. p<0.01). However, it is necessary to note that the. GS in 14 of the 38 patients (36.8%) without a history of ischemic heart disease was more than 6 points.
In these 51 patients, percutaneous transluminal coronary angioplasty was carried out in 8 patients before CEA, and combined CEA and coronary artery bypass grafting was carried out in 2 patients. No patient demonstrated an ischemic heart attack in this group during or after surgery.
In conclusion, if the above strategy and management are done, CEA can be carried out safely even for difficult cases.

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We report 2 cases of cerebral aneurysm associated with symptomatic and angiographical cerebral vasospasm that were operated upon. The first case was hospitalized at 8 days after initial subarachnoid hemorrhage (SAH). Computed tomography (CT) revealed a low density area in the parietal lobe. A preoperative cerebral blood flow (CBF) study demonstrated low flow area corresponding to the low density area on CT.
The second case was hospitalized at 5 days after initial SAH. CT revealed no abnormal findings, although the patient showed slight hemiparesis and a deterioration of consciousness level. A preoperative CBF study demonstrated a low flow area with poor reactivity to acetazolamide (AZ) loading that correporided to angiographic vasospasm.
The surgery in these cases was performed at the 9 days and 6 days after SAH, respectively. The global CBF in the first case increased after surgery and intra-arterial injection of papaverine. The second case resulted in huge cerebral infarction corresponding to the low flow area with poor reactivity to AZ loading following surgery, and was refractory to intra-arterial injection of papaverine.
We discuss the usefulness of CBF studies, including those with AZ loading, to determine the surgical indication.

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For giant or large aneurysms on and around the basilar artery bifurcation, the (Cranio) orbito-zygomatic osteotomy is quite helpful for approach in multiple directions. Preservation of the bridging vein coming off the temporal lobe tip is preferable; for this purpose as well as for ample working space, the author often cuts the basal polar portion of the temporal lobe.
For usual sized aneurysms around the high placed basilar bifurcation, the arch of the zygomatic bone is removed, but orbitotomy is not needed except for the lateral rim. If the lateral superior portion of the orbit disturbs the trajectory to the basilar tip, the cavernous carotid or the anterior communicating artery aneurysm, this portion of the orbital bone is removed at those stages of the operation. Removal of the supraorbital bar, including the nasal bone, is also helpful for approaching the anterior communicating artery aneurysm interhemispherically.
Preservation of the olfactory nerves and the frontal sagittal bridging veins are constantly achieved through the basal interfalcine approach. The craniotomy for the basal interfalcine approach involves the frontal sinus. The outer table is incorporated to the craniotomy, but the inner table is discarded, the mucous membranes are removed, and the fronto-nasal duct is closed.

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We outline a simple and safe method for clipping of small, broad-based and thin-walled aneurysms. Premature rupture during the clipping procedure and slip-out of the applied clip are frustrating when encountered during surgical treatment of these aneurysms. Clipping of such aneurysms with a wrapping technique with a piece of oxcel is a safe and effective method to prevent premature rupture and slip-out of the clip. We report our experiences with operative results of 22 patients treated with this technique.
With regards to GORE-TEX^® wrap clip technique, GORE-TEX^® sheets can be made with readily available encircling aneurysm clips. The two blades of a conventional angled aneurysm clip are bridged with a folded piece of GORE-TEX^® sheet. After the whole circumference of an artery is covered with this thin encircling clip, the artery is firmly wrapped. By selecting the appropriate clip from various types of commercially available clips, fragile, small and broad based aneurysms can be securely wrapped with the parent artery.
In cases where there is injury or perforation during the operative procedure, the usual thin wrapping-clip technique will be adopted. Three cases were treated with this technique.
We will also highlight other previously reported techniques.

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Although great progress has been made in the surgical management of cerebral aneurysms, successful treatment of giant thrombosed aneurysms is still difficult. Parent artery occlusion therapy has been accepted as an alternative treatment for these aneurysms. However, several problems have been reported in terms of the occlusion therapy.
We have experienced 13 patients with giant thrombosed aneurysms: 3 at the cavernous portion of the internal carotid artery (ICA), 3 at the middle cerebral artery (MCA), 3 at the vertebral artery (VA), 3 at the basilar artery (BA) and 1 at the superior cerebellar artery (SCA). Nine cases were treated surgically (parent artery occlusion for 3 ICA aneurysms, neck clipping for 2 MCA aneurysms, and aneurysmectomy in 2 aneurysms) and 4 cases conservatively. While postoperative results were fairly good in cases with ICA and MCA aneurysms, aneurysms in the posterior fossa were difficult to manage surgically.
We constructed a hydraulic vascular model for the vertebro-basilar system with a giant aneurysm from silicon and glass tubes with lengths and diameters similar to those of an average adult. When unilateral VA was occluded proximal to the PICA, reversed flow from the other VA to the PICA was observed, which decreased the intraaneurysmal stagnation. Partial occlusion of the proximal VA might be preferable so as to have a residual flow value equal to that of PICA. When unilateral VA was occluded distal to the PICA, stagnation was observed in aneurysms whose neck was more than 7 mm (2.8 tubular diameter) away from the VA union.
Stagnation in the basilar head aneurysm depended on the occlusion site and the tangential flow at the aneurysmal neck. The longest half-time was observed when the BA was occluded distal to the exit of the SCA and the flow was less than 20 ml/min. In cases where the diameters of Pcoms differed greatly, intraaneurysmal thrombosis might be enhanced by placing a bypass to the PCA on the side of the smaller Pcom.

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The outcome of giant intracranial aneurysms is still unfavorable, even though neurosurgical technique has advanced recently. We report 2 patients with giant aneurysm of the internal carotid artery (ICA) who were treated by trapping and high flow bypass, using saphenous vein, and made successful recoveries.
Case I: A 58-year-old woman presented with a progressing visual disturbance on the left side. Preoperative MRI and angiograms demonstrated a giant aneurysm arising from the left ICA. She became drowsy and had right hemiparesis on balloon occlusion test. She underwent a saphenous vein graft with trapping, because of premature rupture. Postoperatively, she had mild expressive aphasia and right hemiparesis, but she recovered well with physical therapy and returned to social life as a housewife.
Case 2: A 46-year-old woman presented with a progressing visual disturbance on both sides. Preoperative MRI and angiograms revealed a giant thrombosed aneurysm of the left ICA. She was asymptomatic, but hemispheric cerebral blood flow on the left side was reduced on balloon occlusion test. She underwent a saphenous vein graft, trapping and evacuation of intraaneurysmal blood, because the left ICA was markedly arteriosclerotic. Postoperatively, her visual disturbance improved conspicuously and she returned to social life completely.
Needless to say, the ideal treatment of cerebral aneurysm is a neck clipping, but high flow bypass with trapping could be indicated, when the neck cannot be clipped for various reasons in patients with giant intracranial aneurysm.

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