Endoscope-assisted microsurgery for intracranial aneurysms

OBJECTIVE: We discuss the role of the endoscope in the microsurgical treatment of intracranial aneurysms, analyzing its benefits, risks, and disadvantages. METHODS: This was a prospective study of 55 patients with 79 aneurysms, treated between July 1998 and June 2001, for whom the endoscope was used as an adjunct in the microsurgical treatment of their lesions. Seventy-one aneurysms were located in the anterior circulation, and eight were located in the posterior circulation. Thirty-seven patients presented with subarachnoid hemorrhage. Eighteen patients had unruptured aneurysms, of whom 5 presented with mass effect, 2 presented with transient ischemic attacks, and 11 were without symptoms. In all cases, the endoscope was used in addition to microsurgical dissection and clipping (sometimes before clipping, sometimes during clipping, and always after clipping), for observation of the neck anatomic features and perforators and verification of the optimal clip position. Intraoperative angiography was performed for all patients after aneurysm clipping. RESULTS: In the majority of cases, the endoscope was very useful for the assessment of regional anatomic features. It allowed better observation of anatomic features, compared with the microscope, for 26 aneurysms; in 15 cases, pertinent anatomic information could be obtained only with the endoscope. The duration of temporary clipping of the parent artery was significantly reduced for two patients. The clip was repositioned because of a residual neck or inclusion of the parent vessel during aneurysm clipping in six cases, and the clip position was readjusted because of compression of the optic nerve in one case. One patient experienced a small aneurysm rupture that was directly related to use of the endoscope, but this was easily controlled, with no sequelae. For many patients, the combination of the neuro-endoscope and the micro-Doppler probe made intraoperative angiography redundant. CONCLUSION: "Endoscope-assisted microsurgery" is a major advance in the microsurgical treatment of intracranial aneurysms; the endoscope allows better observation of regional anatomic features because of its magnification, illumination, and ability to "look around corners."     

Simultaneous microscopic and endoscopic monitoring during surgery for internal carotid artery aneurysms

OBJECT: The authors of this study evaluated the efficacy of simultaneous microscopic and endoscopic monitoring during surgery for internal carotid artery (ICA) aneurysms. METHODS: The endoscopic technique was applied during microsurgery in 11 patients with 13 aneurysms. Nine of these lesions were located on the posterior communicating artery (PCoA), three in the paraclinoid region, and one on the anterior choroidal artery (AChA). Eight patients had unruptured aneurysms and three had ruptured aneurysms. The endoscope was introduced after first exposing the aneurysm through the microscope and was gripped firmly by an airlocked holding arm fitted with a steering system throughout the entire surgery, including dissection of the perforating arteries and application of the aneurysm clips. Regarding paraclinoid aneurysms, clips were applied through direct visualization of the ophthalmic artery and the proximal neck. In a case involving a superior hypophyseal artery aneurysm in the paraclinoid segment, a ring clip was applied without removing the bone structure around the optic canal. In all aneurysms of the PCoA and the AChA, perforating arteries behind the lesion were identified and dissected using endoscopic control. The aneurysm clip was applied in the best position in a single attempt in 10 of 11 patients. There was no surgical complication related to the endoscopic procedures. CONCLUSIONS: Simultaneous monitoring with the microscope and endoscope is extremely useful in applying clips to ICA aneurysms. This combined method allows for direct dissection of the aneurysm, perforating vessels, and the main trunk in an area not visible through the microscope's eyepiece and promises better surgical results.     

Surgical strategies for treatment of giant or large intracranial aneurysms: our experience with 139 cases.

Giant or large intracranial aneurysms are the vascular neurosurgeon's greatest challenge. At our department, we have treated one hundred and thirty nine patients with giant or large intracranial aneurysms between 1975 and 2001. These included 37 partially thrombosed giant aneurysms. 75 aneurysms were giant (> 2.5 cm) and 64 were large aneurysms (2-2.5 cm). Three-dimensional computed tomography angiograms were performed in patients besides MRI angiography and digital subtraction angiography. These were found to be very valuable in the preoperative assessment of surgical anatomy of the aneurysm with respect to the branch arteries and perforators origin besides knowing the relations to the skull base. With our experience in surgical treatment of these 139 cases, we find that the basic technique is trapping and evacuation and not just clipping of the aneurysm neck but also reconstruction of the artery bearing the aneurysm, especially with wide-necked aneurysms. Use of multiple clipping, tandem clipping or dome clipping as per the intraoperative situation, is very helpful in dealing with giant aneurysms as also is the use of different types of clips like fenestrated clip with straight clip (combination clipping), booster clip, dome clips etc. While selecting surgical strategy for partially thrombosed giant aneurysm, securing the neck is most important. If the neck is too narrow to reconstruct, aneurysmectomy with anastomosis is one of the surgical strategies. An extracranial intracranial bypass should be considered in cases where clipping or parent artery ligation is expected to be associated with compromise of cerebral circulation.     

Complete neck clipping of internal carotid-posterior communicating artery aneurysms using bayonet-shaped aneurysm clips: technical note

Neck clipping for internal carotid-posterior communicating artery (IC-PC) aneurysms using standard straight, angled, or curved clip may result in remnant aneurysm neck. We describe complete neck clipping of IC-PC aneurysms using a bayonet-shaped clip. The bayonet-shaped clip is applied perpendicular to the long axis of the internal carotid artery (ICA), and the blades of the clip are inserted between the aneurysm neck and the ICA. Using the clip applicator, the clip is gradually rotated counterclockwise or clockwise for left or right ICA aneurysm, respectively, so that the distal and shank portions of the clip blade are located at the aneurysm neck in the posterior communicating artery (Pcom) and ICA, respectively. As a result, the distal flexure of the clip blade fits the junction of the ICA and Pcom. This technique was used in four patients with ruptured ICA aneurysms and five patients with unruptured ICA aneurysms. Postoperative cerebral angiography demonstrated no residual aneurysm neck and preservation of the Pcom in all patients. This technique is useful for cases of IC-PC aneurysm involving the origin of the Pcom.     

Dissection from Fundus to Neck for Ruptured Anterior and Middle Cerebral Artery Aneurysms at the Acute Surgery

Summary  It is generally believed that a ruptured aneurysm should be dissected from its neck to its fundus or that only the neck should be dissected. This study was conducted to clarify whether, during the acute stage, intra-operative bleeding occurs at the same site as the initial rupture point when aneurysms are dissected completely without clipping.  The subjects were 170 patients with ruptured anterior or middle cerebral artery aneurysms who were surgically treated by day 7. These aneurysms were operated on through an interhemispheric or a pterional route, respectively. Most of the aneurysms were dissected from the fundus to the neck. Complete exposure of entire aneurysms without temporary clipping was performed in 118 of 170 patients (69%). Intra-operative aneurysmal rupture occurred during 16 (9%) operative procedures. There were no significant correlations between the rate of intra-operative aneurysmal rupture occurrence and the timing of the operation, pre-operative grade or location of ruptured aneurysms. Intra-operative aneurysmal rupture occurred during dissection of the aneurysm itself in 8 patients, during dissection of the artery adhering to the aneurysm in 5 and during clip application in 3. In all the patients whose aneurysms ruptured during aneurysmal dissection, the rupture was caused by injury to the aneurysm and was not directly related to complete exposure of the aneurysm.  Intra-operative bleeding did not occur at the same site as the initial rupture point even when the entire aneurysmal complex was dissected from the fundus to the neck without clipping.     

Supraorbital eyebrow minicraniotomy for anterior circulation aneurysms

BACKGROUND: We report our experience with the minimally invasive supraorbital approach to aneurysms of the ipsilateral anterior cerebral circulation. METHODS: A prospective review of all patients who underwent operations to clip aneurysms in Newcastle between 1993 and 2002. RESULTS: Fifty-six aneurysms were clipped via minicraniotomy in 47 patients. Six patients presented with acute subarachnoid hemorrhage (SAH), 40 patients were admitted for elective clipping, and 1 patient presented with an SAH, had the responsible aneurysm clipped and was readmitted later for elective clipping of a further aneurysm. Bilateral supraorbital craniotomies were performed in 3 patients. In 6 patients, multiple aneurysms were clipped via a single craniotomy. All aneurysms were well visualized with the microscope. Endoscopic assistance was not found necessary. All were successfully clipped. Two aneurysms ruptured while being clipped. There was no direct mortality from surgery. One patient died later from a separate posterior circulation aneurysm. One patient had a significant long-term deficit but remained independent, and 1 had 3 seizures over the 12 months after surgery. This represents a 4% morbidity at 1 year. CONCLUSION: Selected anterior cerebral circulation aneurysms can be clipped with low morbidity, using an ipsilateral minicraniotomy preserving the orbital rim, and without using an endoscope. The types of aneurysm selection criteria and operative equipment used are described.     

Presurgical selection of the ideal aneurysm clip by the use of a three-dimensional planning system

Aneurysm occlusion rate after clipping is higher than after endovascular treatment. However, a certain percentage of incompletely clipped aneurysms remains. Presurgical selection of the proper aneurysm clips could potentially reduce the rate of incomplete clippings caused by inadequate clip geometry. The aim of the present study was to assess whether preoperative 3D image-based simulation allows for preoperative selection of a proper aneurysm clip for complete occlusion in individual cases. Patients harboring ruptured or unruptured cerebral aneurysms prior to surgical clipping were analyzed. CT angiography images were transferred to a 3D surgical-planning station (Dextroscope®) with imported models of 58 aneurysm clips. Intracranial vessels and aneurysms were segmented and the virtual aneurysm clips were placed at the aneurysm neck. Operating surgeons had information about the selected aneurysm clip, and patients underwent clipping. Intraoperative clip selection was documented and aneurysm occlusion rate was assessed by postoperative digital subtraction angiography. Nineteen patients were available for final analysis. In all patients, the most proximal clip at the aneurysm neck was the preselected clip. All aneurysms except one were fully occluded, as assessed by catheter angiography. One aneurysm had a small neck remnant that did not require secondary surgery and was occluded 15 months after surgery. 3D image-based preselection of a proper aneurysm clip can be translated to the operating room and avoids intraoperative clip selection. The associated occlusion rate of aneurysms is high.

     

Treatment selection for ruptured aneurysm and outcomes: clipping or coil embolization

The International Subarachnoid Aneurysm Trial has shown that coil embolization achieves a better outcome for aneurysms treatable by either clipping or coil embolization. However, many ruptured aneurysms are hardly treatable by either clipping or coil embolization. Selection of either clipping or coil embolization will affect the treatment outcome for ruptured aneurysms. The relationship between patient selection and treatment outcome in a so-called "regional center hospital" in Japan must be clarified. This study included 113 patients with ruptured intracranial saccular aneurysms measuring less than 10 mm. Selection criteria for coil embolization were principally paraclinoid or posterior circulation aneurysm, Hunt and Hess grade IV or over, and patient age 75 years or older. Other aneurysms were principally treated by clipping. Aneurysms with a dome/neck ratio of less than 1.5, distorted aneurysms, Hunt and Hess grades I-III, patient age 74 years or younger, and middle cerebral artery aneurysm were actively treated by clipping. A few exceptional indications were considered in detail. Low invasiveness coil embolization is better than clipping to obtain good neurological outcome for patients with perforators difficult to dissect, aneurysms difficult to dissect due to previous open surgery, and aneurysms requiring bilateral open surgery, despite the slightly higher rebleeding rate in coil embolization. Overall outcomes were modified Rankin Scale (mRS) 0-2 in 82 of 113 patients (73%) and mRS 3-6 in 31 (27%). Appropriate selection of clipping or coil embolization can achieve acceptable treatment outcomes for ruptured aneurysm.     

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.     

Recent trends in the treatment of cerebral aneurysms: analysis of a nationwide inpatient database

OBJECT: The most appropriate treatment for cerebral aneurysms, both ruptured and unruptured, is currently under debate, and updated guidelines have yet to be defined. The authors attempted to identify trends in therapy for cerebral aneurysms in the US as well as outcomes. METHODS: The authors retrospectively reviewed data from the Nationwide Inpatient Sample hospital discharge database (Healthcare Cost and Utilization Project, Agency for Healthcare Research and Quality) for the period 1993-2003. Multiple variables were categorized and subjected to statistical analysis for International Classification of Diseases, 9th Revision, Clinical Modification codes related to subarachnoid hemorrhage (SAH), unruptured aneurysm, and clipping and endovascular treatment of cerebral aneurysm. RESULTS: During the study period, the numbers of discharges remained stable for SAH but doubled for unruptured aneurysms. Concomitantly, the number of aneurysms treated with clip placement remained stable, and the number treated by means of endovascular procedures doubled. By the study's end, the mortality rates had decreased 20% for SAH and 50% for unruptured aneurysms. Increasing age was associated with increased mortality rates, mean length of hospital stay (LOS), and mean charges (p < 0.01). Endovascular treatment was used more often in older patients (p < 0.01). Teaching status and larger hospital size were associated with higher charges and longer hospital stays (although the association was not statistically significant) and with better outcomes (p < 0.05) and lower mortality rates (p < 0.05), especially in patients who underwent aneurysm clipping (p < 0.01). Endovascular treatment was associated with significantly higher mortality rates in small hospitals (p < 0.001) and steadily increasing morbidity rates (45%). Morbidity rates, mean LOS, and mean charges were higher for aneurysm clipping (p < 0.01). CONCLUSIONS: From 1993 to 2003, endovascular techniques for aneurysm occlusion have been increasingly used, while the use of surgical clipping procedures has remained stable. Toward the end of the study period, better overall outcomes were observed in the treatment of cerebral aneurysms, both ruptured and unruptured. Large academic centers were associated with better results, particularly for surgical clip placement.     

Balloon-assisted microvascular clipping of paraclinoid aneurysms. Technical note

Paraclinoid aneurysms represent a significant surgical challenge. Multiple techniques have been developed to maximize the effectiveness and safety of excluding these aneurysms from the cerebral circulation. Endovascular balloons have been used for proximal control of parent arteries during the treatment of aneurysms. In this report the authors describe the technique of navigating an endovascular balloon across the neck of paraclinoid aneurysms in four patients to gain proximal control, improve the accuracy of clip placement, and reduce the risk of distal embolization of intraluminal thrombus. Six consecutive patients with giant or complex aneurysms of the ophthalmic or paraclinoid internal carotid artery that were not amenable to endovascular obliteration were retrospectively analyzed. In all six patients, the aneurysm was exposed and dissected for microsurgical clipping, and attempts were made to navigate a nondetachable, compliant silicone balloon across the neck of the aneurysm. If successfully placed, the balloon was inflated during clip placement. In four patients, the balloon was successfully navigated across the neck of the aneurysm and was inflated during clip application. Internal carotid artery tortuosity precluded navigation of the balloon into the intracranial circulation in two patients. All aneurysms were completely excluded from the parent vessel according to postoperative angiography studies. No complication occurred as a direct result of the endovascular portion of the procedure. Endovascular balloon stenting of complex paraclinoid aneurysms during microvascular clipping may provide an adjunctive therapy that facilitates safe and accurate clip placement.     

Large kissing aneurysms of the middle cerebral artery: a case report--classification of kissing aneurysms

We report a rare case of kissing aneurysms located at the middle cerebral artery. A 69-year-old man had a severe subarachnoid hemorrhage associated with intracerebral hematoma (Hunt and Hess grade 5, WFNS grade V). Angiography revealed two large-sized aneurysms of the middle cerebral artery, and these aneurysms were seen as contacting each other. Both aneurysms were adherent, with fibrous tissue at each dome site. Neck clipping was performed. The difficulty of neck clipping with kissing aneurysms is dependent upon the relationship between the two aneurysmal necks. We classify kissing aneurysms into two groups based on the location of the aneurysmal neck (Type 1: each aneurysmal neck is located on the same parent artery. Type 2: each aneurysmal neck is located on different parent arteries.). In Type 1, preoperative diagnosis of kissing aneurysms is difficult and premature rupture during the application of a clip occurs frequently. Therefore, careful and meticulous dissection between the aneurysms is especially required. On the other hand, with Type 2 cases, large aneurysms (> 15 mm) are seen much more frequently than in cases of Type 1. Our classification of kissing aneurysms is useful to assess the difficulty of neck clipping for these aneurysms.     

Frameless stereotaxy-assisted clipping of distal anterior cerebral artery aneurysm: technical note and case series.

OBJECTIVE: Microsurgery for the clipping of cerebral aneurysms requires a working knowledge of the anatomy of the cerebral vasculature and its relationship to landmarks on the surface of the brain and along the skull base. However, for more distally located aneurysms of the anterior cerebral artery (ACA), locating the lesion can prove frustrating and may require much more extensive interhemispheric dissection than is otherwise needed for proximal control, exposure of the aneurysm, and clip application. We report a case series of five patients in which frameless stereotaxy and CT angiographic data sets were used to minimize the extent of surgery required to clip distal ACA aneurysms. CLINICAL PRESENTATIONS: Five patients were found to have distal ACA aneurysms during the work-up of subarachnoid hemorrhage or other neurologic symptoms. The patients comprised two with subarachnoid hemorrhage, one with dizziness, one with stroke, and one with migraines and polycystic kidney disease. Each patient was found to have an aneurysm at the pericallosal/callosal marginal junction. INTERVENTION: All five patients underwent a right parasagittal craniotomy and clipping of a distal ACA aneurysm. The location of the craniotomy and subsequent interhemispheric dissection were guided by CT angiographic data sets and computer-assisted frameless stereotaxy. CONCLUSION: Frameless stereotaxy using a CT angiographic data set is a useful adjunct to routine microsurgery in the clipping of distal ACA aneurysms. Its use obviates the need for extensive interhemispheric dissection, allows the surgeon to gain proximal control and expose the aneurysm more efficiently, and should minimize complications related to unwitting aneurysm exposure.     

Considerations in the surgical treatment of superior-wall type aneurysm at the proximal (M1) segment of the middle cerebral artery

Summary Objective. To present our experience and analyze the risks of neck clipping for superior-wall type aneurysms of the proximal segment of the middle cerebral artery (M1-Sup aneurysm).Methods. Of 14 patients with M1-Sup aneurysms, 4 suffered postoperative infarctions in the territory of the lenticulostriate arteries (LSA) or fronto-orbital arteries. We re-examined our intraoperative findings and clinical records in an effort to identify possible causes.Results. The patency of the LSA was confirmed at the end of surgery in all 14 cases. We posit that temporary occlusion of the LSA by a permanent clip resulted in delayed obstruction of the LSA in 3 patients. Other possibilities we considered were relatively long temporary occlusion of the M1, slipping of the clips and twisting of the clip blades after release of the brain retractors.Conclusion. M1-Sup aneurysms are some of the most complicated aneurysms; they carry the risk of perforator injury during neck clipping. Surgical considerations to avoid perforator injury are discussed.     

Long term prognosis of symptomatic and asymptomatic cerebral aneurysms

The authors analyze the follow-up series of 58 patients with diagnosed cerebral aneurysms who were either not treated surgically or, in surgically treated cases, in which the aneurysmal neck was not clipped. The patients are divided in three groups: untreated ruptured; ruptured treated by coating, vessel ligation or aneurysmal dome clipping; and asymptomatic cases. During the follow-up period of three to ten years, there were no bleedings from asymptomatic aneurysms and only one rebleeding from symptomatic operated aneurysms. As can be expected in the group of ruptured unoperated aneurysms, the rate of rebleeding was 40.9% with a mortality rate of 31.7%. The natural history of asymptomatic aneurysms is unclear regarding the risk of bleeding, and regardless of the obtained follow-up results in our cases, we think that all diagnosed cerebral aneurysms must be treated surgically. Certainly, individual cases must be evaluated.     

Neuroendoscope-assisted minimally invasive microsurgery for clipping intracranial aneurysms.

OBJECTIVE: The aim of this study was to evaluate the efficacy of intracranial aneurysm treatment with the help of the neuroendoscope. METHODS: Eighty-eight patients were treated from February 2000 to November 2003 for intracranial aneurysms of which 89 lesions were clipped with the help of neuroendoscope, including 82 anterior circulation aneurysms (in 81 cases) and 7 posterior circulation aneurysms. The diameters of the aneurysms were between 5 and 40 mm with mean value of 12.5 mm. In the Hunt and Hess preoperative classification, 10 cases were grade 0, 37 cases were grade I, 36 cases were grade II, and 5 cases were grade III. RESULTS: Postoperative complications were observed in 7 cases (7.9%), including hemiplegia in 5 cases (1 case with combination of aphasia), pseudomembranous enteritis in 1 case and optic blur in 1 case. We did not observe any neuroendoscope-related complications and had no postoperative deaths. CONCLUSIONS: The operative efficacy in aneurysm neurosurgery can be improved by the use of the neuroendoscope, especially for minimally invasive microsurgery operation. The neurosurgeon should pay more attention to the training of the endoscope procedure and master more knowledge about endoscopic anatomy.     

A combination of wrapping and clipping using a collagen-impregnated dacron fabric (Hemashield)

BACKGROUND: We describe techniques combining wrapping and clipping using a collagen-impregnated Dacron knitted fabric (Hemashield) for accidental arterial perforations and broad-based aneurysms. The results of these techniques in seven patients are presented. METHODS: Clip-reinforced wrapping was performed to obtain hemostasis in two patients with arterial perforations and in a patient with a ruptured broad-based aneurysm in the internal carotid artery. Clipping of the broad neck of the aneurysm and wrapping with Hemashield (wrap-clipping) was performed in four patients with unruptured aneurysms (one internal carotid artery, two middle cerebral artery, one basilar artery). RESULTS: In the three patients treated with clip-reinforced wrapping, complete hemostasis was obtained just after clip application. In the patient with a ruptured broad-based aneurysm, postoperative angiography demonstrated that the dome of the aneurysm was well compressed. In the four patients treated with wrap-clipping, postoperative angiography revealed successful clipping of the broad neck of the aneurysm. CONCLUSION: In this early experience, there were no problems in the use of Hemashield for clip-reinforced wrapping or wrap-clipping.     

脑前循环动脉瘤破裂早中期的显微外科手术治疗

目的评价脑前循环动脉瘤破裂早、中期显微外科手术治疗的疗效。方法2001年1月至2004年8月对75例脑前循环动脉瘤破裂的急性自发性蛛网膜下腔出血患者应用显微神经外科技术在早期（3d之内）、中期（3～10d）进行手术治疗,以格拉斯哥术后评分量表（GOS）对患者神经功能评分。结果81个动脉瘤,显微手术夹闭77个,包裹4个。恢复良好53例;中度病残,但生活自理9例;重度病残,生活不能自理7例;植物生存3例;死亡3例。HuntⅠ～Ⅲ级的S预后评分明显优于Ⅳ、Ⅴ级患者,时间早期（3d之内）与中期（3～10d）施行手术后的GOS评分无明显差异。结论早、中期显微手术是治疗脑前循环动脉瘤破裂的理想手段。     

Intraoperative angiography evaluation of the microsurgical clipping of unruptured cerebral aneurysms

Intraoperative angiography evaluation of the clippings of cerebral aneurysms was investigated in a series of 38 consecutive patients with unruptured cerebral aneurysms to determine any favorable impact on the outcome. Unexpected findings including major arterial occlusion or residual aneurysm were identified. Specific variables such as the size and site of aneurysm were analyzed to determine the impact on clinical outcome and the incidence of clip modification. There were 11 large and 27 small aneurysms in this series. Mortality and permanent morbidity after microsurgical clipping were 0.0% and 2.6%, respectively. Unexpected angiographic findings necessitating clip repositioning consisted of residual aneurysm in two cases and distal branch occlusion or parent vessel stenosis in four. The need for clip modification was significantly higher for large than for small aneurysms (p = 0.007), and the rate of clip adjustment increased with increasing aneurysm size (p = 0.008). Intraoperative assessment prior to wound closure allows for the recognition and correction of defects and decreases the risk of postoperative complications. Intraoperative angiography may become important in the microsurgical clipping of unruptured cerebral aneurysms, especially large aneurysms.     

Simulation of clipping position for cerebral aneurysms using three-dimensional computed tomography angiography

A novel method for the simulation of the clipping position for cerebral aneurysms based on three-dimensional computed tomography (3D CT) angiography was evaluated. Rotating the regional 3D CT angiography images including the aneurysm provided the virtual intraoperative views of 36 cerebral aneurysms that were eligible for clipping through a pterional approach with a perpendicularly applied straight clip. The cut-along-trace function of the 3D CT workstation was used to simulate the clipping position. The presence or absence of aneurysm remnants was preoperatively evaluated by observing the clipping simulation image. Intraoperative endoscopy and postoperative cerebral angiography were routinely performed to confirm the completeness of obliterations. Nineteen of 21 aneurysms for which complete obliteration was preoperatively expected were confirmed to have no aneurysm remnant. Nine of 15 aneurysms which were expected to have aneurysm remnant were confirmed to persist. The clipping simulation images could correctly predict aneurysm remnant after the initial clipping with a sensitivity of 90.5% and specificity of 60%. The present simulation method can predict aneurysm remnants and improve the likelihood of complete obliteration by clipping.