Posterior Communicating Artery Research Articles

Combined lie's type D and type A agenesis of the left internal carotid artery diagnosed by magnetic resonance angiography.

To report an unusual case of combined Lie's types A and D of internal carotid artery (ICA) agenesis, diagnosed by magnetic resonance angiography (MRA). A 60-year-old woman with dizziness underwent cranial magnetic resonance imaging (MRI) and MRA of the intracranial region for the evaluation of brain and vascular lesions. The magnetic resonance machine was a 3.0-T scanner. MRI showed no abnormalities, except for multiple small white matter lesions. MRA showed that the left ICA was absent, except for the supraclinoid segment, and an anastomotic vessel was present between the paraclinoid segments of the bilateral ICAs, indicating Lie's type D ICA agenesis. The left posterior communicating artery (PCoA) was also present. Thus, there were also features of type A ICA agenesis. The anastomotic vessels between the bilateral ICAs and ipsilateral PCoA were relatively small in caliber. Lie's type D ICA agenesis usually does not communicate with the anterior and posterior circulations. We encountered a case of combined type D and type A ICA agenesis. To our knowledge, no similar case has been reported in the English literature. This is the second case of type D ICA agenesis with patent ipsilateral PCoA. We speculate that in case of type A ICA agenesis, when the development of the PCoA is insufficient to support collateral blood flow, an anastomotic vessel between bilateral ICAs may develop.

Chronic basilar artery occlusion: a retrospective monocentric study.

Acute basilar artery occlusion is a life-threatening medical emergency with a highly elevated mortality rate when left untreated. Little is known about symptoms and clinical progression of chronic occlusions. The aim of this study was to systematically analyze the clinical presentation of patients with chronic basilar artery occlusion (CBAO). Monocentric retrospective analysis of adult patients with CBAO was treated between 2015 and 2023 in the Department of Neurology, Klinikum Kassel. Inclusion criteria were basilar artery occlusion without brainstem infarction as well as patients with a basilar artery occlusion in whom revascularization could not be achieved and a follow-up period of at least 3months. A total of 15 patients were found. In five patients basilar artery occlusion was diagnosed as an incidental finding, four patients had neurological symptoms but no proven brainstem infarction (3 × transient ischemic attack, 1 × isolated posterior artery infarct) and six patients presented with acute basilar artery occlusion and a follow-up > 3months. The most common site of occlusion was midbasilar (80%, n = 12), isolated (n = 7) or in combination with other locations (n = 5). In all cases collateralization could be demonstrated by the posterior communicatingarteries. The most common vascular risk factors (VRF) were hypertension (100%) and hypercholesterolemia (67%). Patients with CBAO may present with only mild symptoms or may even be asymptomatic. This condition may be survived for a long time. The high percentage of vascular risk factors and further cerebral vessel occlusions suggest arteriosclerosis as the major causing factor of CBAO.

A Case of Posterior Communicating Artery Aneurysm Combined With an Atypical Origin of the Ipsilateral Ophthalmic Artery

Objective: Anatomy of the ophthalmic artery (OA) is of great practical importance in surgery for anterior circulation aneurysms. In most cases, the OA arises from the supraclinoid segment of the internal carotid artery (ICA) and enters the orbit through the optic canal inferolaterally to the optic nerve. The OA arising from the anterior cerebral artery (ACA) and entering the optic canal above the optic nerve is extremely rare.Clinical case: We report a case of a 29-year-old female patient admitted to Scientific Research Institute – Ochapovsky Regional Clinical Hospital No. 1 (Krasnodar, Russian Federation) with a ruptured true aneurysm of the left posterior communicating artery (PCoA) and an abnormal origin of the OA from the ACA. The disease manifested itself as ischemic stroke in the basal ganglia on the left causing diagnostic difficulties during initial hospitalization. Cerebral angiography confirmed a PCoA aneurysm and origin of the OA from the ipsilateral ACA. During surgery the neck of the aneurysm was clipped, and the aneurysm dome was opened to control the extent of clipping and remove thrombotic masses. During their removal, hemorrhage appeared from the posterior pole of the aneurysm. During the exploration it was found that the aneurysm was a dilated PCoA connecting the right ICA with the right posterior cerebral artery (PCA). A thrombosed anterior thalamoperforating artery emerged from the superior surface of the dome, and its junction with the precommunicating segment of the right PCA was detected in the region of the posterior pole of the aneurysm. The second clip was placed at the communication site between the aneurysm and the right PCA. The patient was discharged in satisfactory condition with a stable neurological status.Conclusions: The combination of abnormal anatomy of arteries at the base of the brain and cerebral aneurysms increases the risk of tactical errors and perioperative complications. Each such case requires a careful comparison of the clinical, imaging, and intraoperative findings. In the presented case of the patient with the ruptured rare PCoA aneurysm, the disease manifested atypically due to the partial thrombosis of the aneurysm and hemorrhage into the aneurysmal wall. The imaging findings revealed lacunar stroke in the thalamoperforating artery basin and an ICA aneurysm with no signs of subarachnoid hemorrhage. During the surgery the aneurysm was initially regarded as typical saccular. The opening of the dome and removal of all thrombotic masses made it possible to determine the eccentric fusiform nature of the aneurysm, perform its radical exclusion, and prevent fatal hemorrhage in the postoperative period.

Flow-diverter stents in intracranial aneurysm treatment: impact on covered cerebral artery branches.

Flow diverter stents (FDSs) have attracted interest for intracranial aneurysm (IA) treatment; however, occlusion of side branches and related complications have been reported. This study aimed to investigate the effects of FDSs in IA management when different branches of intracranial arteries are covered. A cross-sectional study was conducted using PUBMED, Embase, Web of Science, and Cochrane databases to include randomized or nonrandomized comparative-designed studies from January 2000 to August 2022 which reported outcomes of occlusion/narrowing of branches after IA treatment using FDSs. The PRISMA guidelines were used for our report. A random-effects meta-analysis was conducted to pool the outcomes, which included incidence rates of occlusion/narrowing of FDS-covered branches, branch occlusion-related symptoms, obliteration of IAs, and ideal clinical outcomes (modified Rankin Scale score ≤2). The authors identified 57 studies involving 3789 patients with IA managed by FDSs covering different branches. During the median imaging follow-up at 12 months, the IA obliteration rate was satisfactory (>70%) when covering the ophthalmic artery (OA), posterior communicating artery (PComA), anterior choroidal artery (AChoA) or anterior cerebral artery (ACA), but not the middle cerebral artery-M2 segment (MCA-M2; 69.5%; 95% CI: 60.8-77.5%) and posterior inferior cerebellar artery (PICA; 59.1%, 13/22). The overall ideal clinical outcome was observed in 97.4% of patients (95% CI: 95.5-98.9%). Higher rates of occlusion/narrowing of branches were identified when FDSs covered the ACA (66.6%; 95% CI: 45.1-85.3%), PComA (44.3%; 95% CI: 34.2-54.6%), or MCA-M2 (39.2%; 95% CI: 24.5-54.7%); the risks were lower when covering the OA (11.8%; 95% CI: 8.8-15.1%), PICA (6.8%; 95% CI: 1.5-14.5%), and AchoA (0.5%; 95% CI: 0.0-2.9%). The risk of branch occlusion-related complications was low (incidence rate <5%) for each of the six evaluated branches. Acceptable outcomes were identified following treatment of IAs when FDSs were placed across each of the six studied cerebral arteries. Treatment decisions regarding FDS placement across branch arteries should be made with the risk of complications from branch occlusion in mind.

Evaluating the Impact of Domain Boundaries on Hemodynamics in Intracranial Aneurysms within the Circle of Willis

Hemodynamic simulations are increasingly used to study vascular diseases such as Intracranial Aneurysms (IA) and to further develop treatment options. However, due to limited data, certain aspects must rely on heuristics, especially at the simulation’s distal ends. In the literature, Murray’s Law is often used to model the outflow split based on vessel cross-section area; however, this poses challenges for the communicating arteries in the Circle of Willis (CoW). In this study, we contribute by assessing the impact of Murray’s Law in patient-specific geometries featuring IA at the posterior communication. We simulate different domain extensions representing common modelling choices and establish Full CoW simulations as a baseline to evaluate the effect of these modelling assumptions on hemodynamic indicators, focusing on IA growth and rupture-related factors such as the Wall Shear Stress (WSS) and Oscillatory Shear Index (OSI). Our findings reveal qualitative alterations in hemodynamics when not modeling posterior communication. Comparisons between computing the anterior circulation and computing the whole Circle of Willis reveal that quantitative changes in WSS may reach up to 80%, highlighting the significance of modelling choices in assessing IA risks and treatment strategies.

Oclusão percutânea da comunicação interatrial do tipo seio venoso com stent coberto: a importância dos métodos de imagem para impressão de modelos tridimensionais e a melhor tomada de decisão clínica

A superior sinus venosus atrial septal defect is usually accompanied by an anomalous venous connection to a right superior or middle pulmonary vein or veins, draining directly into the superior vena cava or even into the cavoatrial junction. This is a case report of a 62-year-old female patient, diagnosed with a sinus venosus atrial septal defect, with overload of the right chambers, for whom a percutaneous occlusion procedure was planned, using a previous cardiovascular tomography and, sequentially, a three-dimensional anatomical study, with the publicly available software 3D Slicer. In addition, a resin model was printed for inspection and simulation of a stent implantation. The patient was treated percutaneously with a 60-mm covered Chetham-Platinum stent, with total occlusion of the defect, absence of residual shunts, and draining flow from the right superior pulmonary vein to the left atrium, through a posterior communication between the atria, a sine qua non prerequisite to perform this type of procedure. Planning of the percutaneous occlusion procedure of the sinus venosus atrial septal defect involves careful evaluation of imaging tests. The printing of virtual or physical models, derived from computed tomography angiography of the heart, is essential for a detailed study of the defect and associated anatomical structures, minimizing the occurrence of complications.

The Presence of Communicating Arteries in the Circle of Willis Is Associated with Higher Rate of Functional Recovery after Anterior Circulation Ischemic Stroke.

Acute ischemic stroke (AIS) is the world's second leading cause of mortality. An established method for treating stroke patients in acute settings is endovascular therapy (EVT). However, the correlation of the successful endovascular treatment of AIS with the presence of communicating arteries in the circle of Willis needs to be proven. Our study examined clinical and radiological data of 158 consecutive patients treated with mechanical thrombectomy (MT) at our comprehensive stroke center. We analyzed their CT angiograms and digital subtraction angiography (DSA) to assess anatomical variants of Willis' circle and formed two groups-collateral-negative and collateral-positive group. The first group included patients with aplasia of both anterior (ACoA) and posterior communicating Artery (PCoA). The second group included patients that have at least one communicating artery (either anterior or posterior). We evaluated their reperfusion outcomes and functional recovery three months later. Our results showed that patients with communicating arteries had smaller areas of infarction on post-interventional CT and higher rates of functional recovery (Modified Rankin Score). The ACoA had a higher impact on early and late outcomes, confirmed by lower control CT scores and more favorable functional recovery. Therefore, anatomic variants of Willis' circle should be considered as a significant prognostic factor in AIS.

Hemodynamic differences of posterior communicating artery aneurysms between adult and fetal types of posterior cerebral artery.

The recanalization of posterior communicating artery (PCoA) aneurysms after endovascular treatment has been analyzed by various factors. However, the differences between adult and fetal types of posterior cerebral artery (PCA) have not been fully investigated. The main aim of this study was to investigate hemodynamic differences of PCoA aneurysms between adult and fetal types using computational fluid dynamics (CFD). Fifty-five PCoA aneurysms were evaluated by 3D CT angiography and divided into unruptured aneurysms with adult-type or fetal-type PCAs (19 cases, UA group; 9 cases, UF group) and ruptured aneurysms with adult-type or fetal-type PCAs (17 cases, RA group; 10 cases, RF group). These native aneurysms were analyzed by CFD regarding morphological and hemodynamic characteristics. To evaluate simulated endovascular treatment of aneurysms, CFD was performed using porous media modeling. Morphologically, the RA group had significantly smaller parent artery diameter (2.91 mm vs. 3.49 mm, p=0.005) and higher size ratio (2.54 vs. 1.78, p=0.023) than the RF group. CFD revealed that the UA group had significantly lower oscillatory shear index (OSI) (0.0032 vs. 0.0078, p=0.004) than the UF group and that the RA group had lower WSS (3.09 vs. 11.10, p=0.001) and higher OSI (0.014 vs. 0.006, p=0.031) than the RF group, while the RF group presented significantly higher intra-aneurysmal flow velocity (0.19 m/s vs. 0.061 m/s, p=0.002) than the RA group. Porous media modeling of simulated treatment revealed higher residual flow volume in the fetal-type groups. These results suggested that PCoA aneurysms with fetal-type PCAs had different morphological features and hemodynamic characteristics compared with those with adult-type PCAs, leading to high risks of recanalization.

Numerical study of hemodynamic changes in the Circle of Willis after stenosis of the internal carotid artery

Background and objectivesIn clinical practice a large number of patients with ischemic stroke have internal carotid artery (ICA) stenosis accompanied by Circle of Willis (CoW) stenosis. In the presence of carotid artery stenosis, CoW atherosclerosis may cause cerebral blood flow decompensation and may promote the development of ischemic stroke. The reason for the concomitant stenosis at both sites is unknown. This study investigated the hemodynamic effects of ICA stenosis on the CoW. MethodsWe developed a three-dimensional/zero-dimensional (3D/0D) closed-loop geometric multiscale model of the cerebral artery to quantify the hemodynamic indicators, including time-averaged wall shear stress (TAWSS) and oscillatory shear index (OSI). Mild (<50 %), moderate (50–69 %) and severe (>69 %) ICA stenoses were established based on 3D models of cerebral arteries in two volunteers. Geometric multiscale computing models were numerically evaluated to obtain local hemodynamic changes in the CoW in order to assess the risk of stenosis in the CoW. ResultsModel calculations showed that for all 3D models the A1 segment of the anterior cerebral artery (ACA) or the posterior communicating artery (PCA) within the CoW exhibited a hemodynamic environment with high OSI (>0.2) and low TAWSS (<1 Pa) when the ICA had a moderate stenosis. While in the case of mild and severe stenosis in ICA, there is no such phenomenon. The proportion of the surface area possessing high OSI and low TAWSS in the A1 segment of the ACA or in the PCA was mostly greater than 60 %, which might potentially cause the formation and development of atherosclerosis in CoW and finally lead to CoW stenosis. ConclusionsTherefore, although moderate carotid artery stenosis may not cause ischemic stroke, it may cause hemodynamic changes in the CoW, which in turn may promote CoW stenosis and cause CoW decompensation. In clinical treatment attention should be paid not only to stenosis of the carotid arteries but also to changes in the hemodynamic environment within the CoW, in order to prevent the adverse effects of CoW stenosis.

Medial-type persistent trigeminal artery and ipsilateral posterior communicating artery supplying bilateral posterior cerebral arteries combined with an aberrant right subclavian artery and bicarotid trunk.

To describe a case of a medial-type persistent trigeminal artery (PTA) associated with multiple arterial variations. A 34-year-old woman with multiple sclerosis underwent cranial magnetic resonance (MR) angiography from the aortic arch to the neck region and intracranial region for the evaluation of an unruptured cerebral aneurysm that was previously detected on MR imaging. The MR machine was a 3-T scanner. There was an aberrant right subclavian artery and bicarotid trunk, medial-type left PTA and ipsilateral posterior communicating artery (PCoA) supplying bilateral posterior cerebral arteries (PCAs). The unruptured aneurysm was located at the paraclinoid segment of the left internal carotid artery and was treated successfully by coil embolization via a transfemoral approach. Only 10% of PTAs are classified as the medial type. The association with extremely large ipsilateral PCoA, which supplies the bilateral PCAs, has not been previously reported. Aberrant right subclavian arteries are common and are frequently associated with a bicarotid trunk. Before catheterization of the cerebral arteries, the aortic arch and its branches must be evaluated by MR angiography or computed tomography angiography to prevent catheterization failure via the right transradial approach.

Hypoplastic arteries of the cerebral arterial ring in the blind spot of computed tomography angiography.

Some variations of the cerebral arterial circle (CAC) are associated with an increased risk for the development of various pathological conditions. This paper aimed to determine the prevalence of hypoplastic arteries of CAC and to emphasize the limited possibility of their visualization by computed tomography angiography (CTA). The research was performed on 400 adult cadavers by macro- and microdissection of the cerebral arteries. Each case was photographed and the diameter of the arteries was measured digitally, by analyzing photographs of the bases of the brain in the ImageJ program. The largest prevalence of artery diameter <1mm (<0.6mm) in CAC had the posterior communicating artery (PCoA). PCoA on the left side was hypoplastic in 44.9% (11.4%) of cases, while the same artery on the right side was hypoplastic in 44.3% (6.6%) of cases. The posterior cerebral artery was hypoplastic on the left side in 3% (0.6%) and on the right side in 4.2% (0.6%) of cases. The anterior cerebral artery had a hypoplastic caliber only on the right side in 2.4% (0.6%) of the cases, while the internal carotid arteries did not have a diameter <1mm in any case. The anterior communicating artery showed the greatest variability in morphology. Studies on CTA describe the occurrence of aplasia in a statistically significantly higher percentage, and the occurrence of hypoplastic arteries in a statistically significantly lower percentage compared to studies on cadavers. Due to significant differences between cadaveric and radiological studies, it is necessary to analyze their results regarding arterial hypoplasia and aplasia separately. A diameter of less than 1 mm has been suggested as a criterion for arterial hypoplasia.

The effect of distal aspiration catheter position on collateral flow in mechanical thrombectomy - an in vitro study.

Endovascular mechanical thrombectomy for ischaemic stroke is one of the most effective treatments. Despite the devices and techniques that have been developed, thrombi are not always successfully retrieved. The incidence of futile reperfusion after successful clot retrieval also remains a major concern. We hypothesise that simply placing an aspiration catheter in the system compromises collateral flow which may have an impact on functional outcomes. An in vitro study was conducted using a physical pulsatile flow model designed in glass to mimic the anterior cerebral circulation with middle cerebral artery M1 segment occlusion. A 5Fr aspiration catheter was positioned at the supra-clinoid internal carotid (SC-ICA), carotid terminus (T-ICA) and M1. For each catheter position, the flow rate through the model's anterior cerebral (ACA) and posterior communicating (PCOM) arteries was measured (no aspiration applied). Our results showed significant mean percentage flow reductions in the ACA and PCOM with the catheter positioned at the SC-ICA (PCOM 59.14% ± 0.93, ACA 59.52% ± 0.82, p < 0.001), T-ICA (PCOM 81.54% ± 0.55, ACA 85.65% ± 1.54) and M1 (PCOM 75.79% ± 0.98, ACA 84.20% ± 0.43) (Mann-Whitney U Test, p < 0.001). These results indicate a significant reduction in collateral flow following the insertion of a wide bore catheter in an in vitro model. In a clinical setting, this could have an impact on patient outcome, particularly in prolonged procedures and those requiring several passes to achieve recanalisation.

Circle of Willis integrity in acute middle cerebral artery occlusion: does the posterior communicating artery matter?

BackgroundCollateral circulation is an important determinant of outcome in people with acute ischemic stroke due to large vessel occlusion (LVO).ObjectiveTo explore the impact of the circle of Willis (CW) anatomical...

Clinical, 3D Morphological, and Hemodynamic Risk Factors for Instability of Unruptured Intracranial Aneurysms.

Neurosurgeons can manage unruptured intracranial aneurysms (UIAs). However, the stability of UIAs under follow-up remains uncertain. This study aimed to examine the risk factors associated with the instability (rupture or growth) of UIAs during follow-up. We obtained information on patients with UIA who underwent ≥ 6months of the time of flight-magnetic resonance angiography (TOF-MRA) imaging follow-up in two centers. Computer-assisted semi-automated measurement (CASAM) techniques were used for recording morphological parameters and determining the growth of these aneurysms. We also recorded hemodynamic parameters at the beginning of the follow-up. The univariate and multivariate Cox regression analyses were performed to calculate hazard ratios with corresponding 95% confidence intervals for the clinical, morphological, and hemodynamic risk factors for aneurysm instability. A total of 304aneurysms from 263patients (80.4%) were included for analysis. The annual aneurysm growth rate was 4.7%. Significant predictive factors for aneurysm instability in the multivariate analysis were as follows: poorly controlled hypertension (hazard ratio (HR), 2.97 (95% CI, 1.27-6.98), P = 0.012); aneurysms located on posterior circulation (HR, 7.81 (95% CI, 2.28-26.73), P = 0.001), posterior communication artery (HR, 3.01 (95% CI, 1.07-8.46), P = 0.036), and cavernous carotid artery (HR, 3.78 (95% CI, 1.18-12.17), P = 0.026); and size ratio ≥ 0.87 (HR, 2.54 (95% CI, 1.14-5.68), P = 0.023). The management of UIAs should focus on the control of hypertension during the follow-up. Aneurysms on the posterior communicating artery, posterior circulation, and cavernous carotid arteries require intensive surveillance or timely treatment.

Flow Diverter Performance in Aneurysms Arising From the Posterior Communicating Artery: A Systematic Review and Meta-Analysis.

Flow diverters (FDs) have demonstrated a safe and effective profile. However, the use of FDs for posterior communicating artery (PComA) aneurysms remains controversial. To evaluate the safety and effectiveness of FDs for PComA aneurysms using a systematic review and meta-analysis of the literature. We performed a systematic search from inception until June 2022 for flow diversion in PComA aneurysms. Primary effectiveness was the rate of complete aneurysm occlusion defined by Raymond-Roy class 1. Primary safety outcomes were treatment-related ischemic/hemorrhagic (composite) events causing morbidity and mortality. Secondary safety was PComA patency at follow-up. Random-effects meta-analyses were used to calculate proportions, and statistical heterogeneity was assessed. A total of 13 studies with 397 patients harboring 403 aneurysms were included. Mean age was 48 years, and the mean aneurysm size was 5.3 mm. Most aneurysms were unruptured (65%). Complete occlusion at final follow-up was 73% (CI 66%-79%), and adjunctive coils were used in 10% of aneurysms. Retreatment rate was 2% (CI 0%-9%). The primary safety composite outcome was 4% (CI 3%-7%), and mortality was 1%. PComA patency at final follow-up was 76% (CI 57%-89%). Subgroup analysis, patients with fetal PComAs had a lower complete occlusion rate (42% fetal PComA vs 77%, psubgroupdifference = <.01). The performance of FDs in PComA aneurysms is comparable with outcomes found in other subtypes of supraclinoid aneurysms. Effectiveness was acceptable and safety favorable. However, effectiveness was suboptimal in patients with fetal-type PComAs; alternative treatments should be considered in these cases.

The Application of Multiple Magnetic Resonance Scanning Techniques in Evaluating the Stability of Intracranial Aneurysms.

To evaluate the stability of unruptured intracranial aneurysm (UIA) with high-resolution magnetic resonance imaging of the vessel wall (HR-VWI). A total of 92 UIA patients were enrolled. After MRA, HR-VWI imaging, the reconstruction of volume rendering (VR) and maximum intensity projection (MIP) were performed to observe the location and size of aneurysms, AR value (ratio of aneurysm height to aneurysmal diameter), SR value (ratio of maximum tumor depth to proximal parent artery diameter), and signal intensity were measured. There were 7 aneurysms with UIA located in the anterior cerebral artery, 31 aneurysms with UIA in the middle cerebral artery, 1 aneurysm with UIA in the posterior cerebral artery, 18 aneurysms with UIA in the anterior communication, 5 aneurysms with UIA in the posterior communication, 34 aneurysms with UIA in the intracranial segment of the internal carotid artery and 3 aneurysms with UIA in the vertebral artery. Among them, 8 patients had more than two multiple aneurysms. The lesion size was 2-38mm (6.3 ± 5.09). There are 46 aneurysms with wall enhancement: the maximum SR value was 7.03 and the minimum 1.2, and the maximum AR value was 7.5 and the minimum 1.0. Fifty-five aneurysms showed no enhancement of the tumor wall. The maximum SR value was 4.55 and the minimum 0.58, and the maximum AR value was 4.0 and the minimum 0.6, respectively. Patients were divided into a stable group and an unstable group according to the aneurysm wall. The enhancement rate, SR value, and AR value in the stable aneurysm group were significantly lower than those in the unstable aneurysm group (P < 0.05). MRA and HR-VWI can objectively reflect the stability of aneurysms by judging the morphology, SR value, and signal enhancement of UIA, and can provide a certain basis for diagnosis and treatment, which has become routine examination.

Fenestrated P1 segment of posterior cerebral artery, partly duplicated posterior communicating artery.

Anatomic variations at the junction of primitive internal carotid and basilar arteries are exceedingly rare. We aimed at reporting such rare variants involving the posterior communicating artery (PComA) and the P1 segment of posterior cerebral artery (PCA). The circle of Willis was dissected in an adult cadaver after removal of the cranial vault and cerebral hemispheres. The basilar end was rotated axially to the right. The P1 segment of the right PCA was fenestrated and occupied the interpeduncular fossa. The right PComA passed over the oculomotor nerve to join the anterior arm of the P1 fenestration. On the opposite side, the PComA coursed supero-medially to the oculomotor nerve and it had a partly duplicated posterior end, with two arms, medial, larger, and lateral, thinner, inserting successively into the left PCA. Extremely rare anatomic variations of the circle of Willis should not be ignored when endovascular or microneurosurgical specific approaches are intended.

A rare variant of accessory posterior cerebral artery.

The posterior cerebral artery (PCA) leaves from the distal end of the basilar artery (BA) and is joined to the internal carotid artery (ICA) by the posterior communicating artery (PComA). The archived computed tomography angiogram of a 67 y.o. male patient was studied anatomically. Anatomically normal PCAs left the BA. Both anterior choroidal arteries were found but the right one was hyperplastic. As the latter distributed parieto-occipital and calcarine branches, it was regarded as an accessory PCA. It was laterally to the normal one, inferior to the vein of Rosenthal. The terms "accessory PCA" and "hyperplastic anterior choroidal artery" describe the same morphology. Rare anatomical variants could benefit from a homogenous terminology.

Extremely long posterior cerebral artery P1 segment.

Excluding aplasia and hypoplasia of the P1 segment of the posterior cerebral artery (PCA), anatomical variations in the PCA are rare. To our best knowledge, there are few reports of an extremely long P1 segment of the PCA. Herein, we report a rare case of an extremely long P1 segment of the PCA, which was diagnosed by 1.5-T magnetic resonance angiography (MRA). A 96-year-old woman was transferred by ambulance to our hospital with impaired consciousness. Her symptom improved, and magnetic resonance imaging showed no significant findings. MRA revealed an extremely long P1 segment of the left PCA. The length of the P1 segment of the left PCA was 27.3mm. The left posterior communicating artery (PCoA) was 20.9mm, which is not considered long. The left anterior choroidal artery branched from the internal carotid artery distal to the PCoA branching position. Basilar artery fenestration was also incidentally identified. Careful imaging assessment was important for identifying the extremely long P1 segment of the PCA in the present case. This rare anatomical variation can also be confirmed by 1.5-T MRA.

Abstract Number ‐ 220: Internal Carotid Artery Hypoplasia of Unique Anatomical Variance

Introduction Hypoplasia of the internal carotid artery (ICA) is incomplete development of the ICA with the presence of empty carotid canal. Despite anecdotal data reporting less than a 0.01% of developmental anomalies of ICA, the true incidence remains unknown. Many cases are asymptomatic and thus escape diagnostic detection or appropriate intervention. In 1968, Lie and Hage described collateral circulation in ICA developmental anomalies through the Circle of Willis, persistent embryonic vessels, or skull base arteries/anastomosis or rete mirabile. While collateral systems exist, subsequent cerebrovascular insufficiency and vascular malformations may occur as a result. To our knowledge, there is an incomplete body of literature surrounding the implications of ICA hypoplasia of varying anatomy. Methods We present a case report of left ICA hypoplasia and a comprehensive literature review. Results A 70‐year‐old woman with hypertension, nicotine dependence, and chronic obstructive pulmonary disease (COPD) presented with COPD exacerbation and disorientation. Computed tomography (CT) head angiography showing left cervical/petrous ICA aplasia with presence of a small carotid canal. The left external carotid and vertebral artery originate at the aortic arch. Majority of the blood supply to the left anterior cerebral artery (ACA) and middle cerebral artery (MCA) is suppliedby the right anterior communicating artery (AComA), posterior communicating artery (PComA). There is also a small left supraclinoid and carotid terminus that reconstitute predominantly by right A1 segment and PComA (Figure 1). Conclusions Although ICA hypoplasia may be an incidental finding, accurate and promptrecognition is essential for the consideration of endovascular implications, screening for vascular malformations, understanding cerebral vascular flow, managing cerebrovascular risk, and avoiding misinterpretation of clinical and imaging patterns.