前交通动脉复合体的解剖学研究

目的通过在手术显微镜下对鞍区前交通动脉复合体及各自发出的穿支动脉的解剖和测量,进一步掌握和熟悉前交通动脉复合体的结构及毗邻血管神经的走行,为手术入路提供参考。方法在30侧(15例)福尔马林固定的成人湿性头颅标本上,模拟双侧翼点入路开颅,对鞍区前交通动脉复合体及各自发出的穿支动脉进行解剖观察和测量,所得结果用SPSS 10.0软件进行统计分析。结果描述和测量了前交通动脉复合体及其各分支、穿通动脉和神经的毗邻、走行及直径、长度。ACA均由前穿支下方的ICA发出对侧大脑前动脉借前交通动脉相接。回返动脉为ACA-A1段发出的穿动脉中最粗大的血管,起源部位、行程及数量变异大。ACoA的形态与双侧A1段直径关系密切。结论间隙Ⅱ中回返动脉起点范围通常位于前交通动脉近侧3 mm及前交通动脉远侧3 mm范围内,故在前交通动脉水平远、近侧3 mm范围内临时夹闭或解剖ACA时,易造成回返动脉损伤。在A1段近侧3~5 mm、A1段中1/3段少有穿支发出,此二处可作为ACoA动脉瘤手术时临时阻断的部位,而A1段远侧、特别在ACoA水平2 mm附近几乎均有回返动脉平行伴行,在此处解剖极易损伤回返动脉。A1段发育不全与ACoA动脉瘤可能有较高的相关性。     

Anatomic variations in the circle of Willis in patients with symptomatic carotid artery stenosis assessed with multidetector row CT angiography

PURPOSE: To assess the presence of anterior and posterior collateral pathways in the circle of Willis in patients with symptomatic carotid artery stenosis (SCAS) and to compare this to patients without carotid artery stenosis. MATERIALS AND METHODS: Multislice CT angiography was performed in 91 patients and 91 control subjects. Using consensus reading, 2 observers evaluated the presence and diameter of the anterior communicating artery (AcomA), the A1 segments of the anterior cerebral arteries, the posterior communicating arteries (PcomA) and the P1 segments of the posterior cerebral arteries. Anterior or posterior pathways were assumed to be present if the diameter of continuous arterial segments was >1 mm; both A1 segments and AcomA anterior, and ipsilateral P1 segment and PcomA posterior. Comparison between patients and controls was performed using the chi(2) test. RESULTS: In the patients we found significantly more hypoplastic (<1 mm) or invisible A1 segments (16 and 14 vs. 4 and 1, respectively, p < 0.01). The AcomA was invisible in 4 patients versus 1 control. An isolated compromised anterior pathway and a combined compromised anterior and posterior pathway occurred more frequently in the patients as compared to the controls; 9 versus 1% (p < 0.01) and 26 versus 4% (p < 0.01). CONCLUSION: A compromised anterior collateral pathway, usually combined with a compromised posterior pathway, occurs more frequently in patients with SCAS as compared to controls, which suggests a relation between symptomatic carotid stenosis and an incomplete circle of Willis.     

Evaluation of cross-circulation through circle of Willis using an ultrasonic Doppler technique. Part I. Comparison between blood flow velocity by ultrasonic Doppler flowmetry and angiogram

In 24 patients with cerebrovascular disease and 6 without organic brain lesions, the increased velocity of blood flow in both the internal carotid and vertebral arteries during a contralateral carotid compression was compared with the angiographic appearance of the circle of Willis. The flow velocity was measured using ultrasonic Doppler flowmetry. It was not possible to investigate fully the relationship between the increase of velocity of blood flow in the internal carotid artery and the anatomical variations of the circle of Willis, specifically the anterior cerebral and communicating arteries. The velocity of flow in the patients with an aplastic proximal portion of the anterior cerebral artery showed no increase. There were no differences in the increase of velocity of flow in the vertebral artery in patients with hypoplastic, normal and fetal posterior communicating arteries. It is considered that although anatomical variations of the circle vessels influence the cross-circulation via the circle of Willis, peripheral vascular factors distal to the circle also play an important role in the quantity of cross-circulation through the circle.     

The arterial patterns associated with internal carotid disease and cerebral infarcts

In 20 necropsies with 15 stenosed and 17 thrombotic occluded internal carotid arteries there were 46 cerebral infarcts larger than 1 cm diameter. Using portmortem arteriographic and pathological techniques the patterns of the neck and brain artery systems were correlated with the situation and extent of the brain infarcts. Massive infarcts involving two major cerebral artery territories were associated with distal internal carotid artery occlusion and grossly ineffective cervical and circle of Willis anastomoses. Isolated middle cerebral artery territory infarcts were associated with internal carotid occlusion or stenosis and impairment of the circle of Willis anastomoses, perhaps with middle cerebral artery stenosis. The pattern of adequate size arteries determined if these infarcts were total, deep central, anterior, medium or posterior partial territory infarcts. Boundary zone infarcts were associated with internal carotid artery disease and limitation of anterior or posterior circle of Willis anastomoses. These limitations determined which boundary zones were affected. Isolated anterior cerebral artery territory infarcts were associated with bilateral internal carotid disease and an anterior cerebral artery stenosis or small caliber anterior communicating artery. Isolated posterior cerebral artery territory infarcts were associated with internal carotid disease and a direct impairment of the ipsilateral posterior cerebral artery capability.     

Bilateral internal carotid artery agenesis with artery compression of the brain parenchyma

Bilateral internal carotid artery (ICA) agenesis is an extremely rare congenital anomaly. The most common type of collateral circulation is developed through the circle of Willis via the basilar and posterior communicating arteries. Both anterior circulations are usually supplied by enlarged posterior communicating arteries (PCOMs). We present an unusual case of bilateral ICA agenesis, which is associated with dolichoectatic left PCOM and left posterior cerebral artery (PCA) compression of left basal ganglia and thalamus. These complex cerebral and vascular anomalies can be noninvasively revealed and evaluated by CT and MR.     

Pseudoaneurysm of anterior communicating artery following transsphenoidal surgery for craniopharyngioma

Fusiform dilatation and pseudoaneurysm formation in arteries of the circle of Willis has been reported as a complication following surgery for craniopharyngiomas through craniotomies. We present a case of anterior communicating artery pseudoaneurysm following transsphenoidal surgery for craniopharygioma in an adult.     

Congenital absence of the right common carotid artery,internal carotid artery and external carotid artery associated with anterior communicating artery aneurysm: a rare case

Congenital absence of the common carotid artery (CCA), internal carotid artery (ICA) and external carotid artery (ECA) is very rare. We present such a rare case in a 53-year-old woman, associated with a saccular aneurysm of anterior communicating artery (ACA) presenting with subarachnoid haemorrhage (SAH). An embryological hypothesis for the anomalies of the aortic arch is proposed. The correlation between the abnormal haemodynamic stress of the circle of Willis caused by the absence of the right ICA and the development of intracranial aneurysm is discussed.     

The anatomy of the circle of Willis as a predictive factor for intra-operative cerebral ischemia (shunt need) during carotid endarterectomy

The collateral flow to the cerebral hemisphere after carotid cross clamping during carotid endarterectomy is mainly through the circle of Willis, and the circle is incomplete in the majority of cases. A correlation between the status of the circle of Willis and the necessity of shunting was evaluated in 67 carotid endarterectomies with pre-operative four-vessel cerebral angiogram. All carotid endarterectomies were performed with selective shunting, based on the change of consciousness and motor function after carotid test clamping under regional anesthesia. Of the 55 patients with either an anterior or a posterior communicating artery, only four (7.3%) required shunting. Twelve patients had neither anterior nor posterior communicating artery, and 10 (83.3%) showed signs of cerebral ischemia necessitating shunting. Mandatory shunt was significantly higher in patients with absence of collaterals (p = 0.00). The rate of intraoperative cerebral ischemia was significantly higher in patients with poor collateral circulation defined by the anatomy of the circle of Willis.     

Microanatomy of the perforators of the anterior communicating artery complex

We describe the microanatomy of the perforating arteries arising from the anterior communicating artery complex (5 mm distal of the anterior cerebral artery, the anterior communicating artery, and 5 mm proximal of the distal anterior cerebral artery). Thirteen unfixed human brains were used in this study. The origin and number of perforators are described, as is the site of brain penetration, and results are correlated with previous studies. The hemodynamics of blood flow ib relation to the formation of an anterior communicating artery aneurysm and different surgical approaches are mentioned. The neuropsychological outcome after aneurysm clipping with regards to the pattern of blood supply from the anterior cerebral artery complex is also discussed. [Neural Res 1997; 19: 577-587]     

Cerebral aneurysms and variations in the circle of Willis

In order to obtain information about the relationship between variations in the circle of Willis and aneurysms, 44 complete circles of Willis with aneurysm were studied macroscopically. The incidence of variations was significantly higher in the aneurysm series than in the control circles without aneurysm. There was a definite correlation between asymmetric proximal segments of the anterior cerebral artery and aneurysms of the anterior communicating artery, and a tendency to correlation was found in the case of asymmetric posterior communicating arteries and aneurysms on the internal carotid artery-posterior communicating artery junction. In the light of these findings it seems likely that through hemodynamic changes variation in the circle of Willis plays some role in the development of cerebral aneurysms.     

Bihemisphere Ischemia Due to a Unilateral Lesion: A Case Report

Bihemispheric ischemic strokes secondary to unilateral vessel disease are uncommon. We present the case of a 70-year-old man with multiple acute/subacute bilateral infarcts. The patient was found to have stenosis of the left internal carotid artery secondary to herpes zoster ophthalmicus vasculopathy, with involvement of the left proximal middle and anterior cerebral arteries. Angiographic studies also revealed A1 segment aplasia of the right anterior cerebral artery (ACA), thus indicating dependence on the left-sided circulation for perfusion of the bilateral ACA vascular territory. This case illustrates how A1 segment aplasia, an anatomic variant of the circle of Willis detected by angiographic studies, can contribute to bilateral infarction in the ACA vascular territory.     

Prediction of the extent of thrombus formation in the parent artery after endovascular occlusion of a distal anterior cerebral artery aneurysm using computational fluid dynamics

Endovascular coiling of a cerebral aneurysm and coil occlusion of the parent artery have been occasionally performed to treat cerebral aneurysms; however, it is difficult to predict the accurate extent of thrombus formation in the parent artery proximal to the coiled aneurysm and the coil-occluded parent artery preoperatively, and unexpected occlusion of the arterial branches can occur by thrombus extension into or in the parent artery. The authors describe a case of a distal anterior cerebral artery (ACA) aneurysm treated by endovascular parent artery occlusion (PAO) with preoperative computational fluid dynamics (CFD) prediction of the extent of thrombus formation. A 73-year-old woman presented with subarachnoid hemorrhage and an aneurysm that was located on the right pericallosal artery distal to the paracentral artery bifurcation. Endovascular coiling of the aneurysm and the pericallosal artery was planned. In advance of the treatment, CFD was performed to predict the extent of thrombus formation with specific wall shear stress and shear rate thresholds. The hemodynamic results indicated that coiling of the aneurysm resulted in thrombus formation in the pericallosal artery up to just distal to the paracentral artery ostium; therefore, the treatment was implemented according to the CFD prediction. Postoperative digital subtraction angiography revealed that the extent of thrombus formation was consistent with the preoperative CFD prediction. This technique may prevent unexpected occlusion of arterial branches.     

Aneurysms of the anterior communicating artery and anomalies of the anterior part of the circle of Willis]

Aneurysms of the anterior communicating artery are much more frequently encountered in subjects with developmental anomalies of the anterior part of the Willis circle than in the general population. The most frequent anomaly is hypoplasia of the A1 ACa segment, duplication of the anterior communicating artery or accessory artery of the corpus callosum. In the material of the authors of 130 surgically treated cases of the aneurysm situated in the anterior communicating artery complex developmental anomalies were found in 37.7%.     

Collateral configuration of the circle of Willis: transcranial color-coded duplex ultrasonography and comparison with postmortem anatomy

BACKGROUND AND PURPOSE: The anterior communicating artery (AcoA) and posterior communicating arteries (PcoA) of the circle of Willis provide the main route for collateral blood flow in cases of carotid artery obstruction. Transcranial color-coded duplex ultrasonography (TCCD) allows real-time measurement of the collateral function of the AcoA and PcoA. The primary objective of this study was to determine the collateral artery threshold diameters for supplying collateral flow. METHODS: In 12 acute stroke patients with a median age of 75 years (51 to 91 years), the collateral integrity of the circle of Willis as assessed by TCCD and carotid compression tests was compared with their postmortem anatomy. The lengths and diameters of the collateral arteries were measured. RESULTS: TCCD demonstrated absent anterior collateral flow in 3 patients. In 1 of these patients, absence of anterior cross-flow was due to an occluded anterior cerebral artery, which was revealed at autopsy. Absent posterior collateral flow was found in 14 hemispheres. In 2 of these hemispheres, autopsy revealed a fetal configuration of the posterior cerebral artery hampering posterior collateral flow. The median (range) diameters as found at autopsy of the functional (n=19) and nonfunctional (n=16) collateral arteries of the circle of Willis were 1.1 (0.4 to 2.0) and 0.5 (0.3 to 0.7) mm, respectively (P=0.003). PcoA diameters were found to correlate negatively (rho=-0. 50, P=0.01) to the diameters of their accessory P1 segments. CONCLUSIONS: The threshold diameter allowing for cross-flow through the primary collateral arteries of the circle of Willis is between 0. 4 and 0.6 mm.     

Histochemical studies of the adrenergic innervation of canine cerebral arteries

The glyoxylic acid method was used to examine the adrenergic innervation of the major cerebral arteries of the circle of Willis in dogs. Fluorescent nerve fibers were observed in whole-mount preparations of the part of the internal carotid artery lying in the cavernosus sinus, the anterior, middle and posterior cerebral arteries, the posterior communicating artery and the basilar artery. Adrenergic nerve fibers were most abundant in the proximal portions of the anterior, middle and posterior cerebral arteries as well as in the posterior communicating artery. The distal smaller arteries were less densely innervated than larger ones. The basilar artery contained a moderate number of fluorescent fibers while the internal carotid artery lying in the cavernosus sinus had a very sparse innervation. The peak wavelengths of the excitation and emission spectra of the fluorescence were analyzed by means of a microepifluorescence spectrophotometer and were about 415 and 465 nm, respectively. These values suggest that the fluorescent fibers are adrenergic ones containing norepinephrine.     

Cerebral blood flow regulation: vascular resistance adjustments in the circle of Willis.

Continuous measurements of systemic blood pressure (BP), cerebral perfusion pressure and CBF were accomplished in the cat during transient hypertension, hypercapnia and bilateral carotid artery occlusion. From these measurements resistance values in the circle of Willis and in the cerebral arteries distal to the circle were calculated. The results indicate that the arteries of the circle of Willis and the arteries distal to the circle of Willis dilate and contract independently.     

Cerebral hemodynamics in relation to patterns of collateral flow.

BACKGROUND AND PURPOSE: We sought to investigate the relation between collateral flow via different pathways and hemodynamic parameters measured by dynamic susceptibility contrast-enhanced MRI in patients with severe carotid artery disease. METHODS: Dynamic susceptibility contrast-enhanced MRI was performed in 66 patients and 33 control subjects. Patients had severe stenosis (>70%, n=12), unilateral occlusion (n=38), or bilateral occlusion (n=16) of the internal carotid artery (ICA). Cerebripetal flow and collateral flow via the circle of Willis were investigated with MR angiography. Collateral flow via the ophthalmic artery was investigated with transcranial Doppler sonography. RESULTS: Patients with ICA stenosis had well-preserved cerebral perfusion and were in general not dependent on collateral supply. Patients with unilateral ICA occlusion had impaired cerebral perfusion. However, appearance time, peak time, and mean transit time in white matter were less increased in patients with than in patients without collateral flow via the circle of Willis (P<0.05). Furthermore, patients with collateral flow via both anterior and posterior communicating arteries had less increased regional cerebral blood volume than patients with collateral flow via the posterior communicating artery only (P<0.05). Patients with bilateral ICA occlusion had severely compromised hemodynamic status despite recruitment of collateral supply. CONCLUSIONS: In patients with unilateral ICA occlusion, the pattern of collateral supply has significant influence on hemodynamic status. Collateral flow via the anterior communicating artery is a sign of well-preserved hemodynamic status, whereas no collateral flow via the circle of Willis or flow via only the posterior communicating artery is a sign of deteriorated cerebral perfusion.     

Bilateral infarction in the territory of the anterior cerebral arteries

An elderly hypertensive man had extensive bilateral infarction in the distribution of the anterior cerebral arteries. The circle of Willis was fully formed, but occlusion of the dominant anterior cerebral artery, aggravated and perhaps caused by postlaparotomy hypotension, produced the dramatic lesions, causing akinetic mutism. This stroke pattern occurs in various settings and does not require an anomalous azygous unilateral supply to both anterior cerebral arteries.     

Prediction of stroke-prone gerbils and their cerebral circulation

We attempted to predict the severity of cerebral ischemia, prior to permanent occlusion of a common carotid artery (CCA), in the gerbil by measuring the diameter of the distal CCA before and during temporary ligation and correlated the severity of cerebral ischemia and the pattern of cerebral circulation. All gerbils with reduction of the diameter over 44% after temporary occlusion developed severe neurological signs following permanent ligation. These gerbils lacked any connection between the left and right anterior cerebral arteries (ACA) and the pericallosal arteries originated from the ACA of the occluded side. No gerbils with reduction of less than 30% developed neurological signs and those gerbils possessed a definite anastomosis between the ACAs from both sides. Six of 7 gerbils without connection between the ACAs whose pericallosal arteries originated from the ACA of the non-occluded side proved to be moderately symptomatic. It was concluded that we could reliably predict severely symptomatic and moderately symptomatic gerbils with specific cerebral circulation patterns prior to permanent occlusion of the CCA. The preselected 'stroke-prone' gerbils should be useful for the investigation of cerebral ischemia and the evaluation of pharmacological agents.     

脑梗死患者脑血管病变及侧支循环状态的研究

目的探讨脑梗死患者的责任病变血管及侧支循环主要方式。方法对110例脑梗死患者行牛津郡社区卒中项目（OCSP）分型,进行全脑数字减影血管造影（DSA）检查,判定梗死的责任血管、侧支循环是否存在及方式。结果各型患者,病变血管共137条,其中颈内动脉（ICA）54条（39．4％）、锁骨下．椎动脉（SUB—VA）42条（30．7％）、大脑中动脉（MCA）29条（21．2％）、颈总动脉（CCA）和基底动脉（BA）各4条（各2．9％）、无名动脉2条（1．5％）、大脑前动脉（ACA）和大脑后动脉（PCA）各1条（各0．7％）;责任血管ICA49条（44．5％）、MCA27条（24．5％）、SUB—VA19条（17．3％）及CCA3条（2．7％）、IA2条（1．8％）,余3支血管各1条（均占0．9％）。7例（6．4％）未发现异常。经软脑膜支吻合代偿59例,Willis环代偿49例,来自各种颅外代偿计27例,两种及以上方式联合代偿19例,罕见代偿3例,未发现代偿6例。结论脑动脉病变最多位于ICA、SUB-VA主干,其次位于MCA;前循环病变较后循环病变具有更高的梗死发生率。侧支循环代偿以Willis环最充分,软脑膜支吻合最常见;脑梗死的类型和预后受血管病变和侧支循环状态的综合影响。