Surgical approach to a large basilar artery bifurcation and upper basilar trunk aneurysm: Case report

The authors report a double aneurysm of the basilar artery located at the basilar artery bifurcation and upper basilar artery trunk between the posterior cerebral artery and the superior cerebellar artery. Clinical presentation, neuroradiological findings, surgical approach, and the operative technique are described and discussed.     

基底动脉分叉部动脉瘤夹闭的手术体会

目的分析两种不同的手术入路行夹闭基底动脉分叉部动脉瘤,探讨该手术入路方式、规范和改进手术操作等措施,提高手术成功率和改善患者预后。方法回顾性分析10例基底动脉分叉部动脉瘤在显微镜下经两种不同手术入路夹闭治疗的临床资料。结果 10例患者术后存活9例,1例患者术前患合并多种并发疾病,全身状况差,术后1个月因多器官功能衰竭死亡。结论根据基底动脉分叉部动脉瘤的形态、位置采用不同的手术入路进行规范夹闭术操作,能提高手术成功率,改善患者预后。     

Anatomical variations of the common carotid artery bifurcation

BACKGROUND: The correlation of the common carotid artery (CCA) bifurcation and its surrounding structures is poorly described. The aim of this study was to describe the anatomy of the CCA bifurcation relative to its surrounding structures. METHOD: We dissected a total of 67 carotid specimens from 36 embalmed cadavers. CCA bifurcation occurred at the superior border of thyroid cartilage in 39% and at the body of hyoid bone in 40% of specimens. RESULTS: The superior thyroid artery arose more commonly from the CCA (52.3%) than the external carotid artery (46.2%). The vagus nerve was posterior to the carotid bifurcation in 40 (60%), posterior-lateral in 24 (36%), posterior-medial in 2 (3%) and anterior-lateral in 1 specimen (1.5%). The hypoglossal nerve was closer to the CCA bifurcation when the CCA bifurcated at the level of the hyoid bone than when it bifurcated at the superior border of the thyroid cartilage (P < 0.05). The correlation of the common facial vein and the carotid artery was highly variable. CONCLUSION: The presence of a high CCA bifurcation should caution surgeons that the hypoglossal nerve lies in closer proximity and is more vulnerable. Preoperatively documenting the level of the CCA bifurcation may be helpful in identifying those patients at increased risk of iatrogenic injury.     

Hemodynamic method to predict whether hunterian ligation of the basilar artery will lead to thrombosis of basilar bifurcation aneurysms

In some cases, basilar artery aneurysms cannot be repaired surgically and the basilar artery is occluded near the neck of the aneurysm to stop flow into the aneurysm. After the operation, the aneurysm can fill only by flow through the posterior communicating arteries (PCoAs). Hemodynamically if the flow were the same in both PCoAs and there were no phase lag in the pressures, there would be no pressure gradient for flow to go across the neck of the aneurysm and therefore the aneurysm would thrombose. We have assumed that the diameter of the artery is roughly proportional to the flow that goes through it chronically. We measured the diameters of the PCoAs in 25 patients who had hunterian ligation of the basilar artery. We also measured the maximal width, height, and depth of the aneurysms on angiograms obtained before and after operation. Eleven aneurysms thrombosed completely and had a diameter ratio of greater than 0.6; 10 aneurysms thrombosed partially and had a diameter ratio of 0.46 approximately 1.0; 4 aneurysms did not change and had a diameter ratio of less than 0.45. The ratio of the sizes of the PCoAs pre- and postoperatively was comparable in most cases, so we believe that it is possible to predict reasonably accurately from this simple measurement whether the aneurysm is likely to thrombose if the basilar artery is ligated.     

Extended lateral transsylvian approach for basilar bifurcation aneurysms

The surgical management of aneurysms of the basilar apex is one of the most challenging areas in neurosurgery. Successful treatment of this subgroup of aneurysms is dependent on the mastery of technical nuances that have been pioneered and advanced over the past 4 decades. Although both the traditional transsylvian and subtemporal approaches have distinct advantages, each is associated with significant limitations. In this article, the senior author shares his insights into a hybrid approach: the extended lateral transsylvian approach. This approach combines the assets of the two traditional approaches while eliminating their liabilities.     

Intentional body clipping of wide-necked basilar artery bifurcation aneurysms

OBJECT: Neck clipping or coil embolization cannot always achieve complete neck obstruction in wide-necked basilar artery (BA) bifurcation aneurysms. Clipping of the aneurysm body, leaving a small aneurysm rest, is one clipping method used for this kind of aneurysm to maintain the patency of the posterior cerebral arteries and perforating vessels. However, the long-term efficacy of intentional body clipping has not been well investigated. The authors reviewed their experience with intentional body clipping of wide-necked BA bifurcation aneurysms to determine suitable clipping techniques and the long-term efficacy of the procedure. METHODS: Complete neck occlusion was abandoned and body clipping intentionally performed in 17 patients with BA bifurcation aneurysms; wrapping of the aneurysm rest was made in seven cases. There were 10 ruptured aneurysms (58.8%), and the size of the aneurysm was larger than 10 mm in 11 patients (64.7%). The width between the clip blades and the base of the aneurysm neck was 1 mm in 11 cases, 2 mm in four, and 3 mm in two. Favorable outcome (Glasgow Outcome Scale [GOS] Score 4 or 5) was obtained in 13 cases (76.5%) and unfavorable outcome (GOS Scores 1-3) in four cases (23.5%). Major causes of unfavorable outcome included injury to perforating arteries and major vessel occlusion following surgical manipulation, in addition to the primary damage caused by subarachnoid hemorrhage. Subarachnoid hemorrhage did not occur during a mean follow-up period of 7.4+/-5.6 years (range 0.7-18.1 years) after treatment. CONCLUSIONS: Intentional body clipping of wide-necked BA aneurysms proved to be effective to prevent subarachnoid hemorrhage, although injury to perforating arteries remains problematic. The choice of complete neck clipping or body clipping should be established early during the microsurgical procedure to reduce the risk of injury to perforating vessels.     

Zygomaticotemporal approach to the basis cranii and basilar artery

When using the zygomaticotemporal approach, one removes the whole of the zygomatic bone with its attachment to the masseter muscle, allowing a lower and more anterior approach to the interpeduncular cistern along the inferomedial surface of the temporal lobe. Minimal brain retraction is required to give an excellent view of the bifurcation of the basilar artery and of the suprasellar region.     

Direct embolectomy of the basilar artery bifurcation. Case report.

The case is presented of a 27-year-old man who developed a basilar artery bifurcation embolus encompassing Hilal microcoil as a complication following therapeutic embolization. An immediate direct surgical approach to the basilar artery bifurcation enabled the microcoil and associated thrombus to be removed and flow to be restored in the basilar artery and its distal branches. Postoperatively, the patient made a good recovery and on discharge was neurologically normal with the exception of a right third nerve palsy. This case suggests that in selected patients a direct surgical approach to the top of the basilar artery may be possible for treatment of emboli.     

Computer-generated microsurgical anatomy of the basilar artery bifurcation. Technical note.

The authors' goal was to develop a computer graphics model to represent the microsurgical anatomy of the basilar artery (BA) bifurcation and surrounding structures to simulate surgery of a BA bifurcation aneurysm performed via the transsylvian approach. The source of the input data was a variety of publications that showed detailed anatomy of the area. A computer graphics model of the area near the BA bifurcation including relevant structures, such as perforating branches or cranial nerves, was depicted in detail. A BA bifurcation aneurysm was added to the computer graphics model and it was rotated to simulate the transsylvian approach. After the internal carotid artery was displaced using a virtual retractor, the aneurysm was exposed, thus providing an understanding of the three-dimensional surgical orientation of the area. Designing a standard anatomical model on the basis of data culled from a variety of publications and adding morphological changes by using a virtual retractor to displace structures that obstruct the view along a critical path at the base of the brain are useful strategies of computer manipulation for surgical simulation in open microneurosurgery. This methodological tool would be useful in teaching surgical microanatomy and in introducing a new navigational system for virtual reality. Both concept and technical details are discussed.     

Endosaccular occlusion of basilar artery bifurcation aneurysms using electrically detachable coils

Summary Thirteen patients with basilar artery bifurcation aneurysms, treated by electrothrombosis using electrically detachable coils, are presented. Nine of them presented after hemorrhage, two with mass effect, and two were found coincidentally with other ruptured aneurysms. Selection for endovascular therapy was based on the following criteria: 1) poor clinical condition (Hunt and Hess III-V); 2) high surgical risk; 3) age and poor medical condition; 4) morphological features (small necked aneurysms). With endovascular Guglielmi detachable coils aneurysm occlusion ranging from 70–100% was achieved in all cases. All five small necked and two large broad necked aneurysms were totally occluded. Two large aneurysms had a 95% occlusion and two other large aneurysms were 90% occluded. In another patient with a large broad based aneurysm only an 80% occlusion was achieved, because of tortuosity of the vertebrobasilar system. Our last patient, who presented as grade V clinically, was partially treated with a 70% aneurysmal occlusion. The clinical results were excellent in 10 and good in 2. The only poor outcome was seen in the grade V patient. There was no morbidity or mortality related to therapy. The only complication was an asymptomatic dissecting aneurysm at the origin of the vertebral artery. Angiographic follow up time ranged from 6 to 20 months with a mean of 9 months. Four patients were treated too recently to have their angiographic follow up at 6 months. Two patients were lost to follow up. Clinical follow up ranged from 1 to 17 months with a mean of 8.9 months. The analysis of our cases clearly shows that aneurysms, which were densely packed with coils, especially if small necked, were less likely to be reperfused and showed a longlasting stable result. Large broad based aneurysms were more likely to be reopened by blood flow after the first procedure, especially if loosely filled with coils, and needed up to 3 interventions to achieve a satisfying result, whereas later in the series a high percentage rate of occlusion was seen after the first procedure. We consider now also a less than 100% occlusion acceptable, because most of the aneurysms will rupture at the dome, which was occluded in all our cases. We conclude, that this new endovascular method is a viable alternative in the treatment of posterior circulation aneurysms with a high surgical risk, in old patients and those in poor clinical and medical condition.     

Perforating branches of the basilar bifurcation

The perforating branches of the upper basilar artery and of the first (P1) segment of the posterior cerebral artery were studied in 50 fixed brains obtained from human cadavers. No vertical branches arose from the basilar bifurcation. The upper basilar artery gave rise to horizontal branches, which were studied with reference to their angle of origin. Perforating arteries arising from P1 segments were found in all specimens. Rare branches were found to come from the inferior and anterior surfaces of P1 segments. The anatomical patterns of these branches are discussed in the light of previous reports. Preoperative knowledge of some anatomical aspects (the position of the basilar apex, the angle between the right P1 and left P1 segments, and relationships to the dorsum sellae and the mammillary bodies) can help in the selection of a neurosurgical approach and may improve the operative results in the surgical treatment of basilar apex aneurysms.     

Modifications to the orbitozygomatic approach. Technical note

The orbitozygomatic craniotomy is one of the workhorse approaches of skull base surgery, providing wide, multidirectional access to the anterior and middle cranial fossae as well as the basilar apex. Complete removal of the orbitozygomatic bar increases the angles of exposure, decreases the working depth of the surgical field, and minimizes brain retraction. In many cases, however, only a portion of the exposure provided by the full orbitozygomatic approach is needed. Tailoring the extent of the bone resection to the specific lesion being treated can help lower approach-related morbidity while maintaining its advantages. The authors describe the technical details of the supraorbital and subtemporal modified orbitozygomatic approaches and discuss the surgical indications for their use. Modifications to the orbitozygomatic approach are an example of the ongoing adaptation of skull base procedures to general neurosurgical practice.     

Angiographic and clinical results in 316 coil-treated basilar artery bifurcation aneurysms

OBJECT: The aim of this study was to analyze the effect of the endovascular treatment of basilar artery (BA) bifurcation aneurysms and to compare the results with those published by other neuroendovascular teams. METHODS: The authors performed a retrospective analysis of 316 aneurysms of the BA bifurcation that had been treated using endovascular coil occlusion between November 6, 1992, and February 12, 2005. After the initial embolization procedure, a 90 to 100% occlusion rate was achieved in 86% of the aneurysms. No complication was evident in 80% of the lesions, although periprocedural aneurysm rupture (3.2%) and thromboembolic events (12.3%) were the most frequent complications. Clinical outcome according to the Glasgow Outcome Scale (GOS) was a score of 5 or 4 in 77%, 3 in 11%, 2 in 5%, and 1 in 7% of patients. Initial follow-up angiography studies were obtained in 56% of patients at a mean of 19 months posttreatment and demonstrated a 90 to 100% occlusion rate in 70%. No recurrence was seen on 65% of the aneurysms. Coil compaction was evident on 24% of the follow-up angiograms. A second treatment was performed on 48 aneurysms (15%) a mean of 27 months after the first therapeutic session and resulted in 90 to 100% occlusion in 83% of the lesions. Complications were encountered in 19% of the aneurysms. Rupture did not occur during any of the procedures. Clinical outcome was rated as GOS Score 5 or 4 in 83% of the patients and Grade 3 in 17%. During a cumulative clinical follow up of 821 years in 237 patients, 182 patients (81%) were independent (GOS Score 5 or 4), 33 (14%) were dependent (GOS Score 3), eight (3%) were in a vegetative state, and two (1%) had died. Clinical outcome was significantly worse after previous aneurysm rupture and following procedural complications. CONCLUSIONS: These results are within the range of published data for coil treatment of BA tip aneurysms and confirm both the safety and efficacy of this endovascular treatment method.     

Subtemporal suboccipital transpetrosal transsigmoidal approach to aneurysm of the basilar artery fenestration

The aneurysm arising from the lower third of a basilar artery fenestration is a rare event. The traditional suboccipital or subtentorial transtentorial or transoral approach to this vascular malformation can be problematic. We report the case of a 52-year-old woman who suffered a Grade 4 subarachnoid hemorrhage from an aneurysm located at a fenestration of the proximal third of the basilar artery. This aneurysm was successfully clipped through a left subtemporal suboccipital translabyrinthine transsigmoidal approach. In the aneurysms of the proximal third of the basilar artery the transpetrosal approach with its variants (translabyrinthine and transsigmoidal) related to patient's clinical condition can be useful with undoubted advantages.     

Transpetrosal approach for aneurysms of the lower basilar artery

Extradural subtemporal access to the petrosal ridge and a resection of the anterior pyramidal bone produced direct observation of the lower basilar artery, with minimum retraction of the temporal lobe and preservation of the temporal bridging veins. Two patients with lower basilar trunk aneurysms facing toward the brain stem, were operated on by the "transpetrosal approach," with successful clipping of the aneurysms. Auditory function was preserved in one case. This approach decreases the possibility of retraction damage to the temporal lobe, brain stem, or cranial nerves, and may be helpful for surgery of aneurysms arising around the vertebrobasilar junction or at the origin of the anterior inferior cerebellar artery.     

Zygomatic temporopolar approach for basilar artery aneurysms

For surgery of upper basilar artery aneurysms, we have modified the temporopolar approach proposed by Sano by detaching the zygomatic arch to obtain a wide, shallow operating field. This approach seems to be suitable for anteriorly protruding, high-positioned, or large aneurysms of the upper basilar artery. We have used this zygomatic temporopolar approach in 4 patients with such aneurysms and obtained satisfactory results. In this paper, we detail the operative procedure and emphasize certain technical points to minimize temporal lobe retraction and to prevent oculomotor and facial nerve injuries.     

Plical resection in pre-temporal approach for basilar bifurcation aneurysms: preliminary surgical experience and cadaveric study

Summary   Object. Although a pre-temporal approach (PA) can provide a wide space for preservation of thalamoperforating atrteries in direct surgery for basilar bifurcation aneurysms (BBAs), it cannot always secure adequate proximal control. The authors described the advantages of plical resection added to PA for BBAs. Methods. Between October 1998 and April 2000, eight consecutive patients with BBAs were treated in the neurosurgical department of Kurashiki Central Hospital. Among them, five patients received direct clipping using this method. There were four females and one male, ages ranging from 61 to 77 (mean 70.8 years). Mean aneurysmal size and distance between the in"terclinoidal line and the aneurysmal neck was 4.5 and 9.5 mm, respectively. The operative procedures consisted of the following components; 1) fronto-temporal craniotomy with translocation of orbito-zygomatico-malar bone for PA, 2) preservation of lateral branches of the superficial sylvian veins, 3) resection of plica dural folds to increase the operative field up to the oculomotor nerve (OMN). Results. Complete clipping was achieved without thalamic infarction or temporal contusion in all patients. Three of the five patients suffered from transient right OMN palsy which recovered within two months after surgery. Conclusion. Plical resection in the pre-temporal approach might be beneficial in the surgical treatment of BBAs when proximal control seems difficult. Correspondence: Ken-ichiro Kikuta, Department of Neurosurgery, Kyoto University Graduate School of Medicine, 54 Kawahara-cho Shogoin Sakyoku, Kyoto 606-8507, Japan.