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The Association of the Direction of Dome of Anterior Communicating Artery Aneurysm with the Morphological Characteristics of A1Segmentof Anterior Cerebral Artery and the Hemorrhage Distribution Features on Computed Tomography:Neurosurgical Relevance and Ma

Author: ZhangLong
Tutor: QiSongTao
School: Southern Medical University,
Course: Surgery
Keywords: Anterior communicating artery Aneurysm Anterior cerebral artery A1segment Projection Clipping Microsurgical technique Embolization Subarachnoid hemorrhage Computed tomography Digital subtraction angiography A2plane
CLC: R739.41
Type: Master's thesis
Year: 2013
Downloads: 90
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Abstract


Backgroud and PurposeAnterior communicating artery(ACoA) aneurysm is the most frequently occurring type of ruptured intracranial aneurysms in most reported series, and accounting for30-37%of these aneurysms. ACoA aneurysm is the most complicated intracranial aneurysms of the anterior circulation due to the angioarchitecture and flow dynamics of the ACoA region, frequent anatomical variations, abundant perforators, deep interhemispheric location and adjacent to hypothalamus. Unruptured large or giant ACoA aneurysms have been reported to present with visual impairment, visual field deficits, electrolyte disturbance and endocrinology disturbance due to optic apparatus or hypothalamus compression. Intraluminal thrombus formation of unruptured large or giant ACoA aneurysms occasionally gives rise to thromboembolic events. ACoA aneurysms are more commonly associated with subarachnoid hemorrhage(SAH), and account for21-25.5%of spontaneous SAH, and usually rupture when they are small (<1.0cm) in size. The milder patients usually present with headache and mild disturbance of consciousness, but the sicker cases may be present with neurological deficit, endocrinology disturbance, coma or even die.There are two main ways to treat ACoA aneurysms:first, endovascular coiling, and second, microsurgical clipping. Because of their profound location, the microsurgical treatment of ACoA aneurysm while attempting to preserve the perforating arteries and maintain the patency of the ACoA is difficult and has a high incidence of surgery-related complications. Endovascular treatment is less invasive and has a low rate of surgery-related complications. Endovascular therapy is commonly performed for ACoA aneurysm as the advances in endovascular techniques and the development of new devices. Although most ACoA aneurysms can, at the present time, be treated with endovascular coiling, the choice of location for microsurgical clipping is still very important in many complex ACoA aneurysms, large or giant aneurysms that need to be reconstructed, aneurysms with a space-occupying hematoma, or very small aneurysms that cannot be coiled. There are two main surgical approaches for the treatment of ACoA aneurysms including the pterional approach and interhemispheric approach.Because of the complex anatomic variations in the ACoA complex, the direction of ACoA aneurysm varies greatly. The projection of ACoA aneurysm usually refers to the orientation of aneurysmal dome. The projection of dome is the major morphological characteristics when selecting the way to treat ACoA aneurysm. ACoA aneurysms projecting inferiorly are often tightly adhere to the optic apparatus or frontal base; in particular, for ruptured aneurysms, they often bleeds during initial brain retraction or dissection. Such premature rupture can cause hazardous bleeding if it occurs before complete dissection of the dominant A1segment of anterior cerebral artery(ACA). In these instances, the most important step is to control the ipsilateral A1segment, and thus, the A1-dominant side is better for the pterional approach. Though the direction of ACoA aneurysm has been depicted in many previous literatures, the criterion of projection of aneurysmal dome has been ambiguous and not been well defined. So, we classifyed ACoA aneurysms in detail according to the orientation of the aneurysmal dome on the lateral view of digital subtraction angiography(DSA).Anterior cerebral artery extends from the the medial aspect of the main stem of the internal carotid artery to the junction with the ACoA. The angle between Al segment and termination of the internal carotid artery is90°or nearly90°. This part of the ACA passes anteromedially superior to the optic nerve to the longitudinal fissure. The geometrical morphology of A1segment varies. The Al segment of the ACA demonstrates a large number of variations. The understanding of the geometrical morphology of A1segment will be of use to neurosurgeons while performing the microsurgical clipping operation and help to shape the microcatheter tip in endovascular embolization. Several studies have been performed regarding anatomic variations of the A1segment. Nevertheless, only a few studies have described the geometrical morphology of the Al segment. Although the relationship between the formation of ACoA aneurysm and the sign of dominant A1segment has been clinically observed, the specific correlation between the direction of dome of aneurysm and the geometrical morphology of A1segment has not, to our knowledge, been systematically evaluated. The observation of the morphology of A1segment by cadaveric dissection and microsurgical operation is more direct. But, the geometrical morphology of Al segment changes accordingly because of this tension in the process of dissection. The aim of the present investigation was to explore and describe the morphometry of the A1segment from the view of radiography, and improve the predictability of surgical clipping and guide the steam-shaping of microcatheter tip in endovascular embolization by analyzing the association of the formation and classification of ACoA aneurysms with the morphological features of A1segment.The initial head computed tomography (CT) is the "gold standard" for detecting spontaneous subarachnoid haemorrhage (SAH) and for evaluating its quantity and distribution. Though the relationship between the quantity and distribution of haemorrhage on the initial CT scan and the location of the ruptured aneurysm has been reported, the study of the association of the direction of dome with the hemorrhage distribution of ruprured ACoA aneurysm on CT is very little. The objective of the present study was to summarize the features of hemorrhage distribution on initial CT, and analyze the correlation of the quantity and distribution of haemorrhage of ruprured ACoA aneurysms on CT with the direction of dome, then to explore their clinical significance.Many authors have reported the endovascular techniques, the clinical efficacy and complications of endovascular treatment for ACoA aneurysms. However, there has been little discussion on these issues for diffrent directions of dome of ACoA aneurysms in systematic. Birknes and Proust et al. found that the endovascular treatment for anteriorly projecting ACoA aneurysms is easiest. However, they did not discuss the way to treat upward-pointing ACoA aneurysms versus downward-pointing aneurysms in detail. The purpose of this study is to compare the clinical efficacy, safety and embolizing time of endovascular embolization of upward-pointing ACoA aneurysms with downward-pointing aneurysms, and explore the endovascular techniques of diffrent directions of dome of ACoA aneurysms.The neurosurgical techniques, the clinical efficacy and complications of clipping for ACoA aneurysms have been reported. The pterional approach is the most common operative approach at present. The Al dominant side is the better side for the pterional approach in the treatment of downward-projecting ACoA aneurysms. However, no specific approach for upward-projecting ACoA aneurysms has been universally accepted. Such ACoA aneurysms are buried in the interhemispheric fissure, and thus, preparation of the bilateral A1segments is more feasible without inducing premature rupture. The goal of the present study was to compare the clinical efficacy, safety and operation difficulty of the pterional approach from the side of open A2plane with the approach from the side of closed A2plane, and explore the microneurosurgical techniques in the treatment of anterosuperior-pointing ACoA aneurysms. The first part of study, the correlation between the direction of dome of anterior communicating artery aneurysm and the morphological characteristics of A1segment of anterior cerebral artery.Object and MethodsThe digital subtraction angiography data of ACoA aneurysms and other cerebral vascular diseases which were randomly chosen in the same period in patients from the department of neurosurgery of the affiliated Nanfang Hospital of Southern Medical University between January,2005and January,2012were analyzed retrospectively.①According to the orientation of the aneurysmal dome, the ACoA aneurysms were divided into5types including anteroinferior-projecting type, anterosuperior-projecting type? posterosuperior-projecting type, posteroinferior-projecting type and complex-projecting type.②The morphology of Al segment was divided into four different patterns including "arc" pattern(type I a:convex shape, type Ⅰ b:concave shape),"S" pattern (type Ⅱ a:inverse lateral "s" shape, type II b:lateral "s" shape), approximate straight-line shape (typeⅢa:downward-sloping approximate straight-line shape, type III b:upward-sloping approximate straight-line shape, type III c:horizontal approximate straight-line shape) and non-development.Results①The directions of ACoA aneurysms in264patients were anterosuperior-projecting type in121cases, anteroinferior-projecting type in105, complex-projecting type in16, posteroinferior-projecting type in12and posterosuperior-projecting type in10. ②Among264ACoA aneurysms patients, the morphology of A1segment was type Ⅰ a in158sides, type I b in11, typeⅡ a in35, type Ⅱb in87, type Ⅲa in28, type Ⅲb in62, type Ⅲc in81and non-development in66. The morphology of A1segment in296patients with other cerebral vascular diseases was type Ⅰ a in195, type Ⅰ b in20, type Ⅱ a in47, type Ⅱ b in74, type Ⅲa in74, type Ⅲb in78, type Ⅲ c in65and non-development in39. The non-visualization of A1segment occurred was more frequent in the ACoA aneurysms group than in control group(x2=11.482, P<0.01).③The correlation between the direction of ACoA aneurysm and the morphology of dominant A1segment was significant(x2=285.259, P<0.01; C=0.666, F<0.01). The correlation between the direction of ACoA aneurysm and the morphology of non-dominant A1segment was not significant(%2=7.699, P>0.05).Conclusions①The common directions of ACoA aneurysms are anterosuperior-projecting type and anteroinferior-projecting type.②The Al segment of often appears as approximate straight-line, convex and lateral "s" shape.③The formation of ACoA aneurysm is relation to the variation of A1segment.④Usually, the dominant A1segment of is type Ⅰ a, type Ⅱ a or typeⅢa when the direction of dome of ACoA aneurysm is downward, and is type Ⅰ b, type Ⅱ b or typeⅢb when the direction of dome is upward, and is any type when the direction of dome is complicated.⑤There are no obvious relationship between the direction of dome of ACoA aneurysm and the geometrical morphology of the non-dominant A1segment.⑥The understanding of the relationship between the direction of dome of ACoA aneurysm and the geometrical morphology of the dominant A1segment will help to improve the predictability of microsurgical clipping and guide the steam-shaping of microcatheter tip in endovascular embolization.⑦The shaping mandrel is bent to conform to the shape of the horizontal portion of the AC A. When the long axis of dominant A1segment, as the endovascular approach, showing upward-sloping approximate straight-line shape, is consistent with the long axis of dome of anterosuperior-projecting ACoA aneurysm, the microcatheter tip is usually steam-shaped into a "C-shape". Except as aforesaid aneurysms, the microcatheter tip is usually shaped into a "S-shape" or "Z-shape" for endovascular treatment of other anterosuperior-projecting ACoA aneurysms and posterosuperior-projecting ACoA aneurysms.⑧When the dominant Al segment, as the approach, is approximate straight-line shape, the microcatheter tip is usually steam-shaped into a "C-shape" in the treatment of anteroinferior-projecting ACoA aneurysms.⑨When the dominant A1segment, as the approach, is convex shape or "S" pattern, the microcatheter tip is usually shaped into a "J-shape" in the treatment of anteroinferior-projecting ACoA aneurysms. The tip of microcatheter is also steam-shaped into a "J-shape" for endovascular treatment of posteroinferior-projecting ACoA aneurysms. The second part of study, the relationship between the direction of dome of anterior communicating artery aneurysm and the hemorrhage distribution features on computed tomographyObject and MethodsThe clinical and neuroimaging data in patients with ACoA aneurysms were analyzed retrospectively.①The features of hemorrhage distribution on head CT were summarized. The scale of hemorrhage distribution on cerebral cisterns and sulci was divided into four grades. Grade Ⅰ:Deposition of only the anterior longitudinal fissure with all vertical layers of blood less than1mm thick. Grade Ⅱ:Diffused mild SAH on cerebral cisterns and sulci(1~3mm). GradeⅢ:Diffused moderate SAH on cerebral cisterns and sulci(3~5mm). GradeⅣ:Diffused dense SAH on cerebral cisterns and sulci more than5mm thick.②The hemorrhage distribution on cerebral cisterns was symmetric when the difference of SAH between bilateral cisterns was less than2mm, and was asymmetric when the difference of SAH between bilateral cisterns was more than2mm.Results①The directions of dome of ACoA aneurysms in100patients were anterosuperior-projecting type in59cases, posterosuperior-projecting type in2, anteroinferior-projecting type in31and posteroinferior-projecting type in8.②Hemorrhage distribution on anterior longitudinal fissure was found in all patients. The distribution of hemorrhage did differ among cisterns(χ2=75.008, P<<0.01). The incidence of hemorrhage had a decreasing tendency for suprasellar cistern, sylvian fissure cistern, interpeduncular cistern, ambient cistern and quadrigeminal cistern.③The distribution of hemorrhage did differ between bilateral cisterns(x2=8.186, P>0.05).④The incidence of intracranial hematoma and cast form of the third ventricle all did differ between the upward-projecting ACoA aneurysms and the downward-projecting aneurysms [25(41.0%)cases vs.7(17.9%)cases, x2=5-801, P<0.05;11(18.0%)cases vs.1(2.6%)case, x2=4.025, P<0.05].⑤There was no relationship between the direction of dome of ACoA aneurysms and the scale of hemorrhage distribution on cerebral cisterns and sulci(Z=-0.837,P>0.05).⑥There was no relationship between the side of ACoA aneurysms and the side of hemorrhage deposition on cerebral cisterns(x2=0.744, P>0.05).Conclusions①When the scale of hemorrhage distribution on cerebral cisterns and sulci is high, the laceration of aneurysm is usually big. The incidence of rebleeding of the aneurysm is usually high too.②When the scale of hemorrhage distribution on cerebral cisterns and sulci is low, the laceration of aneurysm is usually small. The incidence of rebleeding of the aneurysm is usually low too.③When the hemorrhage distribution on cerebral cisterns is asymmetric, the dome of aneurysm usually points to lateral side.④The incidence of intracranial hematoma is high when the dome of ACoA aneurysms points upward.⑤The incidence of cast form of the third ventricle is high when the dome of ACoA aneurysms points upward or backward.⑥The understanding of the relationship between the hemorrhage distribution features on head CT and the direction of dome of ACoA aneurysms will help to improve prediction accuracy, ascertain the direction of aneurysmal dome and the laceration, and guide the selection of appropriate surgical methods. The third part of study, endovascular embolization of superiorly oriented anterior communicating artery aneurysms versus inferiorly oriented aneurysmsObject and MethodsOne hundred and fifty-two patients with ACoA aneurysms treated by coil embolization were divided into two groups of superiorly oriented aneurysms(n=91) and inferiorly oriented aneurysms(n=61).①Primary objective endpoints were Hunt-Hess grade, aneurysm size, dome-to-neck ratio, embolizing time, the degree of aneurysm occlusion, postoperative recurrence rate, complications rate and Glasgow Outcome Scale(GOS) at1and6months after treatment.②Acording to the simplified3-point Raymond scale, the imaging results were graded as complete occlusion, neck remnant without opacification of the aneurysmal sac, and residual aneurysm.③Follow-up angiograms were compared to postembolization angiograms and classified as further thrombosis, stable, or recanalization.Results①The embolizing time was longer in the superiorly oriented aneurysms than in the inferiorly oriented aneurysms(60.79min±27.34min vs.50.36min±24.47min; t=2.403, P<0.05).②The degree of aneurysm occlusion was lower in the superiorly oriented aneurysms than in the inferiorly oriented aneurysms(Z=-1.998, P<0.05).③There were no significant differences in postoperative recurrence rate, complication rate and GOS at1and6months after treatment between the superiorly oriented aneurysms and the inferiorly oriented aneurysms(P>0.05).Conclusions①The coil embolization of ACoA aneurysms is safe and effective.②The endovascular treatment of superiorly oriented aneurysms is more complicated and spents longer time than inferiorly oriented aneurysms.③The degree of aneurysm occlusion is lower in the superiorly oriented aneurysms than in the inferiorly oriented aneurysms.④In order to improve the degree of upward-pointing ACoA aneurysms occlusion, steam-shaping of microcatheter tip is very critical.⑤Before operation, the possible use of the balloon-or stent-assisted technique should be taken into account if the microcatheter is unstable during coiling. The forth part of study, microsurgical clipping of anterosuperior-pointing anterior communicating artery aneurysms by pterional approach from the side of open A2plane versus the side of closed A2planeObject and MethodsTwenty-nine patients with anterosuperior-pointing ACoA aneurysms treated by microsurgical clipping were divided into two groups of the approach from the side of open A2plane(n=14) and the approach from the side of closed A2plane(n=15).①Primary objective endpoints were Hunt-Hess grade, aneurysm size, dome-to-neck ratio, rate of displacement of the ipsilateral A2, rate of gyrus rectus aspiration, surgical-related complications rate, postoperative clipping results, incidence of cognitive function impairment and GOS at6months after treatment.②An open A2plane was defined as being present when the A2of the pterional approach side was located more posteriorly than the contralateral A2. A closed A2plane was defined as being present when the A2of the pterional approach side was located more anteriorly.Results①The incidence of gyrus rectus aspiration and displacement of the ipsilateral A2, cognitive function impairment at6months after treatment and the surgical-related complications was also significant lower in the approach from the side of open A2plane than in the approach from the side of closed A2plane[2(14.3%) cases vs.9(60.0%) cases, x2==6.428, P<0.05;2(14.3%) cases vs.8(53.3%) cases, P<0.05;1(7.1%) case vs.7(46.7%) cases, P<0.05].②There were no significant differences in postoperative clipping results and GOS at6months after treatment between two approachs(P>0.05).ConclusionsThe pterional approach from the side of open A2plane in patients with anterosuperior-pointing ACoA aneurysms allowes the aneurysmal necks to be secured safely, descreases operation difficulty and preventes surgical-related complications.

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