Variations of perforating arteries of anterior communicating artery in cases with anterior communicating artery aneurysms: a cadaveric anatomical study.

PURPOSE: In terms of postoperative morbidity and mortality, preservation of the perforating arteries branching from the anterior communicating artery (ACoA) during clipping is particularly imperative in patients with ACoA aneurysm. In the present study, we aimed to investigate whether perforating arteries originated from ACoA were pushed away in a different location in patients with ACoA aneurysm. Furthermore, if they did so, we aimed to identify the direction in which they were dislocated and how the perforating arteries could be preserved during clipping. METHODS: Herein, we categorized 40 brains obtained from cadavers into two groups. The first (n = 26) and second (n = 14) groups included cases without and with ACoA aneurysms, respectively. After completing the preparation procedure, the brains were dissected using surgical microscope and the relevant anatomical region was examined and photographed. Finally, statistical analyses were performed on the data and the results were documented. RESULTS: In the aneurysms with posterior and superior projections, the perforators appeared to be pushed away inferiorly and were frequently noted at the anteroinferior part of the aneurysm neck. Most of the cases, where one of the A1s was larger at one side, the perforating arteries arose from the larger A1 side. CONCLUSION: The mortality and morbidity associated with damage to the perforators can be reduced by approaching the patient from the dominant A1 side and pursuing the perforators primarily at the anteroinferior part of the aneurysm neck in the aneurysms with superior and posterior projections.

Ruptured Infundibular dilatation of the posterior communicating artery.

OBJECTIVE: An infundibulum of the posterior communicating artery (PcomA) or infundibular dilatation (ID) is considered to be a benign anatomical variant. However, some evidence suggests that ID is a pre-aneurysmal state. This case series presents cases of ruptured IDs and aneurysms originating from the IDs. METHODS: Between April 2002 and June 2020, 1337 patients were treated for aneurysmal subarachnoid hemorrhage (SAH). Among them, 7 patients with ruptured PcomA IDs were identified. Rupture IDs of the PcomA were categorized into 1) direct rupture of IDs, and 2) rupture of aneurysms originating from IDs. The clinical and radiographic factors were retrospectively reviewed. RESULTS: Two patients experienced direct rupture of IDs, while the other 5 patients presented with ruptured aneurysms originating from IDs. The 2 patients with direct rupture of IDs at presentation were relatively younger (< 50 years), while the other 5 patients with ruptured aneurysms originating from IDs were over 70 and had a history of aneurysmal SAH due to other intracranial aneurysms. Ruptured IDs were treated with microsurgery or endovascular treatment. There were no complications related to the procedure for securing ruptured IDs. Five (71.4%) patients showed favorable outcomes. One patient with initial Hunt and Hess grade 4 died due to initial brain damage with cerebral vasospasm and medical complications. CONCLUSIONS: ID of the PcomA rarely causes SAH with or without aneurysm formation. Thus, patients with IDs of the PcomA should be carefully followed up for a long period, especially those with a history of aneurysmal SAH.

Clinical and morphological risk factors for the recurrence of anterior communicating artery aneurysms after clipping or coiling.

BACKGROUND: The aim of this study was to evaluate clinical and morphological factors associated with recurrence in anterior communicating artery (AcomA) aneurysms after clipping or coiling. METHODS: We retrospectively reviewed the clinical and radiologic features of consecutive 214 patients with AcomA aneurysms treated between January 2012 and December 2016 in a single tertiary institute. Univariate and multivariate analyses were performed to identify the relationship between clinical and morphological variables and recurrence. RESULTS: Of 214 patients, 166 were unruptured aneurysms and 109 were treated with coiling. Overall recurrence rate was 13% (28 out of 214 aneurysms) during mean 36.9 ± 18.4-month follow-up. Multivariate logistic regression analysis showed that size greater than 10 mm (OR = 5.651; 95% CI, 1.317-24.242; p = 0.020), smoking (OR = 3.474; 95% CI, 1.342-8.996; p = 0.010), coiling (OR = 2.98; 95% CI, 1.005-8.832; p = 0.049), and anterior direction of aneurysm (OR = 3.77; 95% CI, 1.12-12.66; p = 0.032) were significantly associated with recurrence of AcomA aneurysms after treatment. CONCLUSIONS: The results of this study demonstrated that coiling, large aneurysm, anterior direction, and smoking history may be independent risk factors for the recurrence of AcomA aneurysms. Therefore, careful follow-up should be needed especially in large AcomA aneurysms with anterior direction after coiling.

Can sectioning the posterior communicating artery be predicted with computed tomography angiography in the microsurgical clipping of basilar apex aneurysms?

BACKGROUND: Microsurgical clipping is a viable option for managing high-riding basilar apex aneurysms (BAXs) using a transsylvian approach. Cutting the posterior communicating artery (PCoA) at the perforator-free zone provides sufficient exposure of BAX, although it is not always safe. The aim was to qualitatively predict sectioning of the interfering PCoA by using preoperative computed tomographic angiography (CTA). METHODS: A virtual trajectory from the lesser sphenoid wing to the neck of the aneurysm was simulated on CTA in 19 consecutive patients operated on BAX aneurysms from 2013 to 2018. The angles on CTA resembled the typical view through the extended pterional craniotomy. Next, the ipsilateral PCoA was tracked from the internal carotid to its end at the posterior cerebral artery in the trajectory. RESULTS: The opticocarotid and carotid-oculomotor window served as the corridors for entering the interpeduncular fossa in 16 patients (84.2%) and in 3 patients (15.8%), respectively. The PCoA was intentionally cut during nine surgeries and preserved in 10 of them. The PCoA was cut more often when positioned toward the cranial base and more medially in the corridor; both the Kernel density analysis and the data points representing the position of the PCoA supported this finding (p < 0.01). The CTA-based position of either ends of the PCoA in the trajectory did not differ between cut and not-cut groups (p = 0.19-0.96). Aneurysm projection, rupture, size, PCoA diameter, length, and other distances on CTA were not related to the sectioning of PCoA (p > 0.05). CONCLUSIONS: The probability of PCoA sectioning is higher when the PCoA is positioned medially and closer to the cranial base. If the anatomical course of the PCoA is recognized beforehand, it can contraindicate surgery. Preoperative CTA-based planning facilitates the surgery of BAX aneurysms. Therefore, CTA can make microsurgical clipping planning more predictable for the neurosurgeon and safer for the patient.

Extracranial-intracranial bypass approach to cerebral revascularization: a historical perspective.

While the majority of cerebral revascularization advancements were made in the last century, it is worth noting the humble beginnings of vascular surgery throughout history to appreciate its progression and application to neurovascular pathology in the modern era. Nearly 5000 years of basic human inquiry into the vasculature and its role in neurological disease has resulted in the complex neurosurgical procedures used today to save and improve lives. This paper explores the story of the extracranial-intracranial approach to cerebral revascularization.

Quantitative measurement of the surgical freedom for anterior communicating artery complex-a comparative study between the frontotemporal pterional and supraorbital craniotomy; a laboratory study.

OBJECTIVE: To quantitatively measure surgical degree of freedom (SDF) to the anterior communicating artery (AComA) complex via removal of the orbital rim. Comparisons of SDF quadrants were made between a supraorbital and standard frontotemporal pterional craniotomy according to the surgeons' geometric microscope compass-based views. METHODS: Eleven latex-injected formalin-fixed cadaveric heads; 14 sides (eight unilateral and three bilateral) were dissected. Standard frontotemporal pterional and subsequent supraorbital craniotomy approaches were conducted in each specimen. Point "0" was allocated as a point 1 cm distal to the ipsilateral A1 and A2 junction of AComA. The tip of a 10-cm long pointer was used to locate point 0. The base of the pointer stick was maneuvered outside the craniotomy in eight compass directions, with the most peripheral points expressed as target points 1-8. The center of this octagon was attributed point C. A pyramid was established by connecting the points 0, C, and 2 neighboring target points. A frameless stereotaxic instrument was used as a three-dimensional digitizer to measure pyramid volume. Each neighboring two pyramids form a hexagonal cone and was expressed as a surgical freedom quadrant (cm3). The quadrants are depicted counterclockwise (surgeons view) as orbital-nasal, vertex-nasal, vertex-temporal, and orbital-temporal. RESULTS: Total SDF obtained via supraorbital and pterional approaches were 122.8 ± 109.66 and 159.94 ± 93.65, respectively (mean ± SD cm3; supraorbital < pterional by 30.2%). Supraorbital to pterional, in the orbital-nasal quadrant was 21.9 ± 35.5 and 13.04 ± 8.7, vertex-nasal 31.3 ± 28.5 and 16.7 ± 13.7, vertex-temporal 39.5 ± 42.14 and 60.4 ± 4.7, and orbital-temporal 30.14 ± 42.14 and 70.01 ± 42.14, respectively (mean ± SD cm3). In the vertex-nasal quadrant, the supraorbital approach provides a 47.3% increase in SDF compared to the standard frontotemporal pterional craniotomy approach. CONCLUSION: Given that the AComA complex is located more nasally and the surgeon's view is more vertex, we propose that a supraorbital craniotomy allows a more contralateral portion of the AComA complex to be visualized during dissection.

Microsurgical Treatment of Ruptured True Posterior Communicating Artery Aneurysm in the Distal Portion of the Posterior Communicating Artery.

The true posterior communicating artery (PCoA) aneurysms in the distal portion of the posterior communicating artery are rare. The authors describe a 63-year-old woman with 1 true PCoA aneurysms in the distal portion of the PCoA, which was treated surgically through modified pterional approach. No neurologic deficit was present at the postoperative period. Although endovascular intervention is more and more widely used in the treatment of aneurysms, the authors have also emphasized that true PCoA aneurysms in the distal portion of the PCoA can also be surgically treated in suitable patients.

How I do it-the eyebrow approach for anterior circle of Willis aneurysms.

BACKGROUND: The eyebrow approach is a keyhole technique that gives a wide access to the anterior circle of Willis. METHODS: A 4-cm linear incision is placed in the upper limit of the eyebrow and a small supraorbital bone flap is raised. A wide arachnoid dissection is essential to maximize the working space. One or multiple aneurysms may be treated by the same approach. CONCLUSIONS: The eyebrow approach is a safe technique for selected aneurysms of the anterior circle of Willis.

Assessment of the cortical artery using computed tomography angiography for bypass surgery in moyamoya disease.

Computed tomography angiography (CTA) is often used to assess the vascular status in moyamoya disease. The purpose of the study is to identify the characteristics of cortical arteries (M4) of moyamoya disease on CTA; the clinical significance of which is also discussed. A total of 38 hemispheric sides of 27 patients with moyamoya disease were included in this study. The number of M4 was visualized on CTA using cortical surface imaging and compared between the moyamoya disease group and the non-moyamoya disease group or the control group. Then, the clinical and radiological factors associated with the number of M4, the distribution of M4, and collateral circulation were examined. The number of M4 was lower in the moyamoya disease group than in the non-moyamoya disease group and in the control group (p < 0.05). There are few predictive clinical factors of the number of M4 except male sex. The prefrontal artery, precentral artery, central artery, and angular artery had a significantly higher prevalence in moyamoya disease (p < 0.05). The durocortical and periventricular anastomosis had a significantly higher prevalence in moyamoya disease (p < 0.05). The prevalence and distribution pattern of cortical arteries in moyamoya disease differed from that of the non-moyamoya disease group, and the distribution patterns of M4 might be influenced by collateral circulation. It is thus essential to recognize M4 to assess the recipient artery so as to ensure superficial temporal artery-middle cerebral artery bypass.

[Supraorbital keyhole craniotomy in surgery of anterior circle of willis aneurysms]. / Supraorbital'naya «keyhole¼ kraniotomiya v khirurgii anevrizm perednego otdela villizieva kruga.

The progress in surgical treatment of intracranial aneurysms is based on the introduction of modern minimally invasive techniques. Among the variety of keyhole approaches, supraorbital craniotomy is most often used in surgical treatment of anterior circle of willis aneurysms. The authors present the preliminary results of application of supraorbital keyhole craniotomy for anterior circle of willis aneurysms in 27 patients. Most of the patients had unruptured aneurysms (18 patients). Nine patients had SAH, and 4 of them were operated on in the acute period. The patients' condition was assessed as a grade 1-2 (Hunt-Hess scale) and grade 1-3 (Fisher scale). There were no intraoperative aneurysm ruptures, other serious complications, and deaths. Postoperative complications were assessed at 2 weeks and 6 months. The postoperative cosmetic outcome was assessed by patients as excellent.

[Minipterional craniotomy in surgery for anterior circle of Willis aneurysms]. / Minipterional'naya kraniotomiya v khirurgii anevrizm perednego otdela villizieva kruga.

One of the significant events in aneurysm surgery was promotion of a microneurosurgical technique by G. Yasargil. Despite its versatility, pterional craniotomy is associated with extensive osteotomy and a significant incision of the skin and temporal muscle, which may lead to the adverse cosmetic effects, risk of temporomandibular joint dysfunction, injury to the frontal branch of the facial nerve, and facial and scalp numbness. We present our experience with minipterional craniotomy in surgery for anterior circle of Willis aneurysms in 40 patients. There were no serious complications or deaths. Also, there were no intraoperative aneurysm ruptures. All patients had expected transient hypesthesia in the temporal region, which was not considered as a complication. This region was significantly smaller compared to that in classical pterional craniotomy. Patients assessed the postoperative cosmetic outcome as excellent.

Extradural temporopolar approach for parahypothalamic hypothalamic hamartoma and use of posterior communicating artery as resection margin pointer.

BACKGROUND: Hypothalamic hamartomas (HH) are malformations originating from the hypothalamus and are associated with seizures, hormonal and behavioral abnormalities. METHOD: Most patients, especially those with a typical syndrome characterized by gelastic seizures, precocious puberty, cognitive decline, and behavior problems, are diagnosed in childhood. Pedunculated and parahypothalamic types of hamartomas are attached to the floor by a narrow or wide peduncle in the absence of distortion of the overlying hypothalamus. This location is most commonly associated with a clinical presentation of precocious puberty, and surgical removal has proved curative in small case series. Enthusiastic resection of hypothalamic lesions are known to produce severe hypothalamic disturbance while under resection might mean inadequate response to surgery. CONCLUSIONS: In this article, the authors describe the use of extradural temporopolar approach to hypothalamic hamartoma as an improvisation to improve access with reduced morbidity and describe a surgical nuance of using posterior communicating artery to determine a safe but maximal resection margin.

Navigation of Stents across Communicating Arteries for Aneurysm Embolization.

INTRODUCTION: Endovascular coiling of aneurysms crossing the Circle of Willis has been described in small case series. The technical challenges in manipulating a stent across the Circle of Willis lie in negotiating difficult angles and small arteries. We present our experience with treating aneurysms by stent assistance in which the Circle of Willis was crossed to facilitate optimal stent deployment. MATERIALS AND METHODS: We retrospectively reviewed the cases in our institution from January 2009 to June 2012 in which the Circle of Willis was traversed to facilitate optimal stent deployment. We measured the diameter of the communicating arteries traversed, caliber of the target arteries in which the stent was deployed and the most acute angle negotiated ("critical angle"). We compare our results with other published series in the literature. RESULTS: Eight patients fulfilled the criteria: 5 males (45-66 years). There were three anterior and five posterior circulation aneurysms. Four of the aneurysms were ruptured. The PCOM was traversed in five cases, the ACOM in three cases. The mean diameter of the communicating artery was 1.17 mm. The mean diameter of target arteries was 1.27 mm. The "critical angle" was 72-147 degrees. In all patients, there was satisfactory obliteration of the aneurysm. There were two cases of minor SAH post procedure. CONCLUSION: Utilizing the Circle of Willis for optimal stent placement in aneurysm remodeling is technically feasible but challenging. This technique can be performed successfully in patients with acute SAH. The procedural risk must be balanced against potential complications such as SAH.

Pathophysiology and management of intracranial arterial stenosis around the circle of Willis associated with hyperthyroidism: case reports and literature review.

Cases of moyamoya disease or intracranial arterial stenosis around the circle of Willis (M/IAS) associated with hyperthyroidism have been reported. However, most of these previous reports were of the ischemic form of M/IAS and primary hyperthyroidism. To the best of our knowledge, no studies have documented therapy for M/IAS associated with hyperthyroidism. We discuss four previously unreported cases, including those involving the intracerebral hemorrhage form and thyroid-stimulating hormone (TSH) secretion from a pituitary adenoma (secondary hyperthyroidism). We analyzed data from 52 previously reported cases, including the 4 cases presented here, and discuss M/IAS associated with hyperthyroidism, treatment options, pathophysiology, the ischemic and hemorrhagic forms, secondary hyperthyroidism, and the relevant literature. Hyperthyroidism results in thyrotoxicosis and the stimulation of the superior cervical ganglion by TSH antibodies and f-T3/f-T4. Consequently, hypercoagulability and stenosis of the cerebral artery can occur. There are many reports of ischemic M/IAS associated with hyperthyroidism. A conservative approach to treatment is important in such cases; for example, antithyroid therapy should be the first choice to treat ischemic M/IAS. There have been only a limited number of reports on hemorrhagic M/IAS. We presume that hemorrhagic M/IAS tears the weakened vasculature in a manner similar to that of normal M/IAS (with no complicating hyperthyroidism). The authors also reported M/IAS associated with secondary hyperthyroidism due to pituitary thyroid secreting hormone secreting adenoma.

Filament perforation model for mouse subarachnoid hemorrhage: surgical-technical considerations.

OBJECTIVE: Mouse subarachnoid hemorrhage (SAH) models are becoming increasingly important. We aimed to report and discuss the detailed technical-surgical approach and difficulties associated with the circle of Willis perforation (cWp) model, with reference to the existing literature. METHODS: First, the cWp model was reproduced using ddY mice following scarification at 0 h, Days 1, 2, and 3 after SAH. Second, C57BL/6 mice were subjected to SAH with histological examination on Days 1, 2, and 3. Sham-operated mice were sacrificed on Day 2. Neurological performance, amount of subarachnoid blood, cerebral vasospasm (CVS), and neuronal injury were assessed. Relevant articles found in the MEDLINE database were reviewed. RESULTS: Induction of SAH was successfully reproduced. The volume of subarachnoid blood decreased with time due to resorption. Neurological performance was worse in SAH compared with sham. Signs of CVS could be confirmed on Days 2 and 3, but not Day 1. The cumulative number of microthrombi was significantly higher on Days 2 and 3, but not Day 1. Apoptotic and degenerative neurons were found in the cortex and hippocampal area. Our review of the literature revealed the cWp model to be the most frequently used. The present findings largely confirmed previously published results. However, detailed technical-surgical description and its discussion were sparse, which we provide here. CONCLUSIONS: The current study provides additional useful information characterizing the cWp model. This model may be of first choice at present, as important pathologies can be reproduced and most findings in the literature are based on it.

Effects of carotid endarterectomy or stenting on arterial diameters in the circle of Willis.

BACKGROUND: In patients with internal carotid artery (ICA) stenosis, the circle of Willis (CoW) is the primary collateral pathway. We compared luminal diameters in the CoW before and after carotid revascularization and compared the effects of carotid endarterectomy (CEA) and stenting on these diameters. METHODS: At a single center in the International Carotid Stenting Study, 139 patients with symptomatic ICA stenosis of 50% or more were randomized to stenting (n = 81) or CEA (n = 58). The diameters of all segments of the CoW were assessed on computed tomography angiography (CTA), before and 30 days after revascularization. All evaluations were performed blinded to treatment allocation and order of CTA. RESULTS: A .10-mm increase (95% confidence interval [CI], .02-.17; 7%; P = .01) in diameter after revascularization occurred in the ipsilateral precommunicating anterior cerebral artery (A1), whereas both the ipsilateral and contralateral posterior communicating arteries decreased in diameter by .12 mm (95% CI, .04-.21; 14%; P = .01) and .08 mm (95% CI, .00-.17; 10%; P = .05), respectively. The increase in diameter of the A1 was larger after stenting (.15 mm; 95% CI, .07-.24; P = .001) than after CEA (.02 mm; 95% CI, -.11 to .15; P = .79). Only in patients treated with CEA, the diameters of the contralateral A1 and ipsilateral precommunicating posterior cerebral artery were reduced after revascularization. CONCLUSIONS: Carotid revascularization improves anterior collateralization and reduces reliance on posterior collateral pathways via the CoW. Carotid stenting and endarterectomy appear to have different early effects on collateralization.

Clipping versus coiling for intracranial aneurysms.

BACKGROUND AND PURPOSE: The aim of this study was to compare results of clipping and coiling for aneurysms of the anterior circle of Willis. Previous studies have not identified a clear superiority of one method over the other. MATERIAL AND METHODS: The study group included 165 consecutive patients. The assessment took into account the risk of death, neurological status according to the scale of the GOS and mRS, the incidence of early complications and quality of life measured by own surveys and questionnaire EORTC QLQ-C30 v. 3.0. RESULTS: Mean follow-up was more than four years. Early and late results of treatment after embolization and clipping for all patients did not differ. Evaluation of patients with bleeding aneurysms demonstrated better outcomes after embolization, however statistical significance was observed only in terms of symptomatic scale score of QLQ-C30 questionnaire (p=0.02). For patients with non-bleeding aneurysms better outcomes were obtained after clipping, but statistical significance was found only in the early results: more excellent results in GOS score at discharge (p<0.03) and fewer complications during hospitalization (p=0.02). CONCLUSIONS: Results of treatment after clipping and coiling do not differ in total for all patients, but differ depending on the presence of bleeding. Patients with bleeding aneurysms achieve better outcomes after coiling, and patients with non-bleeding aneurysms achieve better outcomes after clipping.

Development of the Circle of Willis Score (COWS) to help guide decision making during acute tandem occlusion treatment: Preliminary analysis.

BACKGROUND: Acute tandem occlusions (TOs) are challenging to treat. Although acute carotid stenting of the proximal lesion is well tolerated, there are certain situations when the practitioner may be wary of acute stenting (bleeding concerns). OBJECTIVE: The purpose of this study was to retrospectively study patients with tandem occlusions who had re-occlusion of the extracranial ICA and develop a Circle of Willis Score (COWS) to help predict which patients could forego acute stenting. METHODS: This is a retrospective review of TO patients with a persistent proximal occlusion following intervention (either expected or unexpected). Pre intervention CTA and intraoperative DSA were reviewed, and each patient was assigned a score 2 (complete COW), 1a (patent A1-Acomm-A1), 1p (patent Pcomm), or 0 (incomplete COW). Findings from the DSA took precedence over the CTA. Two cohorts were created, the complete COW cohort (COWS 2) versus the incomplete COW cohort (COWS 1a,1p, or 0). Angiographic outcomes were assessed using the mTICI score (2b-3) and clinical outcomes were assessed using discharge mRS (good outcome mRS 0-3). RESULTS: Of 68 TO cases, 12 had persistent proximal occlusions. There were 5/12 (42 %) patients in the complete COW cohort, and 7/12 (58 %) in the incomplete COW cohort (5/12 with scores of 1a/1p and 2/12 with a score of 0). In the complete COW cohort, there were 2 ICA-ICA and 3 ICA-MCA occlusions. In the incomplete COW cohort, there was one ICA-ICA occlusion and 6 ICA-MCA occlusions. LKW-puncture was shorter in the complete COW cohort (208 min vs. 464 min, p = 0.16). Successful reperfusion was higher in the complete COW cohort (100 % vs. 71 %). There was a trend toward better clinical outcomes in the complete COW cohort (80 % vs 29 %, p = 0.079). CONCLUSION: The COWS is a simple score that may help predict a successful clinical outcome without proximal revascularization when concerned about performing an acute carotid stent during TO treatment. Evaluation in larger TO cohort is warranted.

Circle of Willis configuration as a determinant of intracranial dolichoectasia.

BACKGROUND: Circle of Willis (COW) variants might influence arterial caliber in the brain. We hypothesized that these variants would be associated with the prevalence of intracranial dolichoectasia (DE). METHODS: We examined COW variants and DE in a sample of stroke-free participants (n = 436) undergoing magnetic resonance angiography (MRA) as part of a population-based study. Large intracranial arterial diameters were obtained when available; if not, the artery was defined as hypoplastic or absent according to its visibility on MRA. Subscores for the anterior and the posterior circulations were created. DE was defined as arterial diameters ≥2 SD above the population mean for that artery, adjusting for intracranial volume. Generalized linear models with a Poisson distribution were used to evaluate predictors of both absent and hypoplastic vessels, and logistic regression was used to assess the odds ratio (OR) and 95% confidence interval (95% CI) of DE depending on COW variants. RESULTS: Only 44% of the sample had all 14 arteries present, 32% lacked 1 artery, 18% lacked 2 and 6% lacked 3 or more. DE of at least 1 artery was not associated with the total number of hypoplastic or absent arteries, but DE in a posterior circulation artery was weakly associated with the number of absent arteries in the posterior circulation (ß coefficient = 0.36, p = 0.06). DE of at least 1 artery was more frequent in those with 1 or more absent arteries (OR 1.27, 95% CI 1.03-1.57). Posterior circulation DE was more frequent in participants with at least 1 or more absent arteries at any location (OR 1.35, 95% CI 1.02-1.78). Participants with an incomplete posterior COW were more likely to have DE in the anterior circulation (OR 1.52, 95% CI 1.01-2.33). Having an absent left anterior cerebral artery (ACA) A1 segment was associated with right ACA DE (OR 34.1, 95% CI 3.16-368.2); an absent right ACA was associated with left ACA DE (OR 14.1, 95% CI 1.69-118.28). Absence of 1 (OR 1.9, 95% CI 1.1-3.4) or 2 (OR 3.0, 95% CI 1.4-6.6) of the 2 arteries connecting the anterior to the posterior circulation was associated with basilar artery DE. CONCLUSION: The COW is a pleomorphic structure that allows collateral flow to compensate for an insufficient or absent arterial component at the base of the skull. By presumed flow diversion, arteries might undergo outward remodeling. Whether this compensatory arterial dilatation is beneficial or not remains unknown.

Flow control in the middle cerebral artery during thrombectomy: the effect of anatomy, catheter size and tip location.

BACKGROUND: Catheter size, location and circle of Willis anatomy impact the flow conditions during interventional stroke therapy. The aim of the study was to systematically investigate the influence of these factors on flow control in the middle cerebral artery by means of a computational model based on 100 patients with stroke who received endovascular treatment. METHODS: The dimensions of the cervical and intracranial cerebral arteries of 100 patients who received endovascular mechanical thrombectomy for acute ischemic stroke were measured and a three-dimensional model of the circle of Willis was created based on these data. Flow control in the middle cerebral artery with variations in catheter size, catheter location and configurations of collateral vessels was determined using a computational model. A total of 48 scenarios were analyzed. RESULTS: Flow reversal with a distal aspiration catheter alone was not possible in the internal carotid artery and only sometimes possible in the middle cerebral artery (14 of 48 cases). The Catalyst 7 catheter was more often successful in achieving flow reversal than Catalyst 5 or 6 catheters (p<0.001). In a full circle of Willis anatomy, flow reversal was almost never possible. The absence of one or more communicating arteries significantly influenced flow direction compared with the full anatomy with all communicating arteries present (p=0.028). CONCLUSION: Choosing the biggest possible aspiration catheter and locating it in the middle cerebral artery significantly increases the chances of successful flow control. Flow through the collaterals may impair the flow, and circle of Willis anatomy should be considered during aspiration thrombectomy.