Posterior circulation vascular variants and intracranial aneurysm formation: An imaging-based study with implications for risk stratification.

The cerebral blood flow is divided into an anterior circulation and a posterior circulation connected to each other in the form of a circle called Circle of Willis (CW). It is formed by the unification of the internal carotid (ICA) and vertebrobasilar systems Posteriorly, the basilar artery, formed by the left and right vertebral arteries, branches into a left and right posterior cerebral artery (PCA), forming the posterior circulation. The internal carotid system lies anteriorly and is joined to the posterior circulation by posterior communicating (PCoA) arteries. The internal carotid artery divides into anterior and middle cerebral artery. The two anterior cerebral arteries are joined to each other by an anterior communicating artery. The posterior cerebral artery before it joins the posterior communicating artery that means its proximal part is named as the pre communicating part (P1) and the distal part as the post communicating part (P2). In the adult P1 has a diameter larger than the PCoA so that the occipital lobe gets its blood supply mainly via the vertebrobasilar system whereas in the fetus the diameter of the ipsilateral precommunicating (P1) segment of PCA is less than the diameter of PCoA, so that the blood supply to [1] the occipital lobe is mainly via the internal carotid arteries. In some persons, there is a transitional configuration in which the PCoA is equal in diameter to the P1 segment of the PCA. These variations can cause complications if thrombotic material present in atherosclerotic plaques of ICA gets dislodged into PCA through a PCoA which has a larger diameter. In the present study, the configuration of posterior cerebral circulation and its clinical relevance was studied in 40 human brains in the department of anatomy at KJSMC. Adult Type PCA was found in 60% of the specimens studied, Fetal Type PCA was found in 12.5% of the specimens, Transitional Type PCA was found in 25% of the specimens and a combination of Adult and Transitional Type was found in 2.5% of the specimens.

B a c k g r o u n d: The anatomy of arteries supplying blood to the brain often varies among the population. It applies particularly to posterior cerebral circulation. The impact of its anatomy variabilities on the formation of intracranial aneurysms has not been determined yet. The aim was to find out if posterior cerebral circulation anatomy variations coexist with basilar artery aneurysms (BAAs). We retrospectively analyzed 27 patients with BAA and a group of 30 patients matched by gender and age but without BAA. In both groups together most (66.67%) of patients were female and the average age was 59.75 ± 10.91. All of the patients had Computed Tomography performed. We assessed the occurrence of BAA, basilar artery (BA) diameter, vertebral artery (VA) diameter, posterior cerebral artery (PCA) diameter, and if patients had hypoplastic VA or PCA. Results: The presence of right VA hypoplasia significantly increased the risk of BAA occurrence (48.15% vs. 16.67%; p = 0.011). The occurrence of hypoplastic VA on either side was significantly associated with the risk of BAA formation (59.26% vs. 26.67%; p = 0.013). Patients with BAA had slightly larger left PCA diameter 1cm after division (1.96 ± 0.51 vs. 1.64 ± 0.42; p = 0.014) in comparison to those without BAA. Additionally, hypoplastic right PCA occurred more often in patients with BAA (22.22% vs. 0%; p = 0.022). Conclusions: We can conclude that the anatomy of PCA and VA affects the occurrence of BAA. Hypoplastic VA, the presence of wider left PCA and hypoplastic right PCA may be factors that coexist with BAA occurrence.

Endangered Cerebral Blood Supply After Closure of Left Subclavian Artery: Postmortem and Clinical Imaging Studies

BackgroundWe aimed to evaluate if vertebrobasilar anatomic variations impact reperfusion and outcome in intra-arterial therapy (IAT) for basilar artery occlusion (BAO).MethodsConsecutive BAO patients with symptom onset <24 h treated with...

Pathogenesis, hemodynamics, and growth of intracranial aneurysms: Future directions.

While digital subtraction angiography (DSA) is traditionally used for moyamoya disease (MMD) assessment, its invasiveness and limitations necessitate alternative methods. The higher signal-to-noise ratio (SNR) and contrast-to-noise ratio of 7T MRI improve the clarity of the image and retains the details of the structures. We aimed to assess the performance of 7T MRI in identifying hemorrhagic risk features of MMD compared with 3T MRI and DSA. This cross-sectional study recruited patients with MMD who underwent both 7T and 3T MRI scans within a 24-hour window, from March 2022 to December 2023. Patients were categorized into hemorrhagic, ischemic, and asymptomatic groups based on standard MRI findings and clinical symptoms. Corresponding DSA images acquired within 90 days were also collected as a comparative benchmark. Hemorrhage risk factors including dilatation and branch extension of the anterior choroidal artery (AChA) and posterior communicating artery (PComA) were assessed and graded on time-of-flight magnetic resonance angiography (TOF-MRA) and DSA images following established protocols. The hemorrhage locations were classified into anterior and posterior circulation groups. A total of 180 patients (mean age, 43.95 ± 11.02 [SD] years; 53.9% female) were included in the study (hemorrhagic = 51, ischemic = 37, asymptomatic = 92). Notably, 42.4% of AChA and 27.7% of PComA anomalies detected on 7T TOF-MRA were absent on 3T imaging. The 7T TOF-MRA demonstrated a strong correlation with DSA in assessing the AChA stage (weighted κ = 0.891, p < 0.001) and PComA stage (weighted κ = 0.761, p < 0.001). Higher AChA (70.6% vs 21.6% vs 6.5%, p < 0.001) and PComA (51.0% vs 8.1% vs 12.0%, p < 0.001) grades were more common in patients with hemorrhagic MMD compared with ischemic and asymptomatic groups. In binary logistic regression analysis for hemorrhagic and ischemic groups, elevated stages of AChA (odds ratio [OR] 1.90, 95% CI 1.20-3.54, p = 0.042) and PComA (OR 3.89, 95% CI 1.76-8.58, p = 0.001) were associated with increased hemorrhagic risk. Furthermore, the proportion of higher AChA (62.2%, p = 0.008) and PComA (51.3%, p = 0.010) grades were more prevalent in cases involving both anterior and posterior circulations. The 7T TOF-MRA visualization of dilatation and branching extension of the AChA and PComA indicates a heightened risk of hemorrhage, suggesting that this imaging technique could serve as a valuable noninvasive tool for identifying hemorrhagic vulnerabilities in MMD. ClinicalTrials.gov, NCT05287750, Brain Diseases on 7.0T Magnetic Resonance Imaging, First Submitted January 2022. clinicaltrials.gov/study/NCT05287750. This study provides Class II evidence that 7T-TOF MRA accurately distinguishes hemorrhagic risk in patients with MMD compared with 3T-TOF MRA and DSA.

We studied the diagnostic value of computed tomographic angiography (CTA) in the posterior circulation as a noninvasive substitute for intra-arterial digital subtraction angiography (DSA). We prospectively investigated 103 patients with acute stroke in the posterior circulation. All patients underwent CTA and Doppler ultrasound, and DSA was performed in 22 patients. Vascular findings were classified in categories according to the type of lesion and the location in the vertebral, basilar, or posterior cerebral artery. In the first part of the analysis we examined the correlation between CTA and intra-arterial DSA (n=22), and in the second part that between CTA and Doppler ultrasound (n=103). Intra-arterial DSA identified 11 stenoses, 13 occlusions, and 3 hypoplasias. The correlation between DSA and CTA was best for the basilar artery (all lesions were identified with CTA). Of the 14 lesions detected in the vertebral artery by DSA 13 were also detected by CTA, but the specific type of lesion was identified in only 7 cases. The correlation between CTA and Doppler ultrasound was lower. In conclusion, CTA is thus a reliable method for detecting lesions in the posterior circulation and may replace DSA in many cases. However, particularly in the vertebral artery DSA remains the superior technique.

The brain-supplying arteries can be divided into two communicating circulatory systems: the anterior and the posterior circulation. The anterior circulation originates in both internal carotid arteries (ICA) and in part from both external carotid arteries (ECA) if a high-grade stenosis of the ipsilater-al ICA is present. The posterior circulation arises from both vertebral arteries and the unpaired basilar artery. The posterior and anterior circulation is connected via the circle of Willis, which is known to have a very heterogeneous anatomical structure. The circle of Willis is a vascular polygon with ten components: both ICAs, both posterior communicating arteries (PCoAs), the single anterior communicating artery (ACoA), the anterior cerebral arteries (ACAs), the posterior cerebral arteries (PCAs), and the basilar artery (BA). Circle of Willis is an inefficient collateral in 50% of subjects due to insufficient communication between the anterior and the posterior circulation, and between the left-sided and the right-sided circulation secondary to the hypoplasia of the PCoA and ACoA respectively.

Bow Hunter's Syndrome.

BackgroundIt is not clear whether the configuration of the posterior part of the circle of Willis (CW) depends on the proximal part of the vertebrobasilar system. Our aim is to evaluate the posterior part of CW in association with different size of vertebral arteries (VA) in healthy volunteers.Materials and methodsThe present study was based on a sample of 923 healthy volunteers who were examined from 2013 through 2018. The duplex ultrasonographic examination of the extracranial vertebral (VA) and carotid arteries was performed. VA was defined as hypoplastic (VAH) when VA diameter in the entire course was less than 2.5 mm. All the participants underwent magnetic resonance angiography (MRA) examination. All the component vessels of the circle of Willis were assessed in each individual. We classified the posterior communicating artery (PCoA) as presence PCoA, absence/hypoplastic PCoA and fetal-type posterior circle of Willis (FCW) in which the major stem of the posterior cerebral artery (PCA) arises from ipsilateral internal carotid artery (ICA). The comparison of the posterior part of CW was made in subjects with normal VA and VAH of a different degree (communicating with basilar artery (VAH-BA) and not communicating with the basilar artery (VAH-PICA)).ResultsFCW was found in 15.9% of subjects, bilaterally–in 2.3%. FCW was more frequent in individuals with VAH than in those with normal VA (accordingly, 28.8% vs. 13.5%, p<0.001. Moreover FCW was recorded in 50% of the subjects with VA—PICA in comparison with 13.5% of those with normal VA and 22.8% with VAH—BA, p<0.005. On the contrary, absence/hypoplasia of both PCoA was mostly found in the group with normal VA in comparison with VAH-BA and VAH-PICA (accordingly, 50.7%, 38.6% and 12.5%, p<0.01).ConclusionIndividuals with VAH have a different pattern of the posterior part of CW in comparison with those with normal VA. With the increasing degree of VAH, the proportion of FCW increases, while the proportion of absence/hypoplastic of both PCoA decreases.

Association Between Vascular Anatomy and Posterior Communicating Artery Aneurysms

Introduction: Rare presentation of disease processes is absolutely intriguing to the human mind. Spinal cord infarction is abundantly reported to be secondary to cardiological procedures, patients carrying multiple vascular risk factors and vertebral artery dissections. But for it to happen in a patient who is young, relatively healthy and without vascular risk factors is quite interesting. Herein, we present the case of a patient presented with bilateral upper extremity weakness, who has a hypoplastic right vertebral artery that has coincided with him being a professional gamer with exerting compression from video‐gaming posturing of “forward leaning with neck hyperextension”, resulting in cervical spinal cord infarction.Methods: Case reportResults: Vertebral artery dissection was excluded by CTA and MRA. our hypothesis was that the patient is a professional gamer and his posture of leaning forward and neck hyper‐extension had a role in inducing his spinal cord infarction given the fact of him having a hypoplastic right vertebral artery.Conclusions: Vertebral artery disease is a well‐recognized cause of ischemia in the posterior cerebral circulation. Recently, however, cervical cord infarction, albeit being extremely rare, has been increasingly reported as a complication of vertebral artery diseases such as dissection. Awareness must be raised that such condition can also happen in the young population due to compression of the vertebral arteries, especially when one is hypoplastic.

Vertebral artery hypoplasia is not currently considered an independent risk factor for stroke. Emerging evidence suggest that vertebral artery hypoplasia may contribute to posterior circulation ischemic events, especially when other risk factors coexist. In the present literature review, we present published data to discuss the relationship between a hypoplastic vertebral artery and posterior circulation cerebral ischemia. Despite difficulties and controversies in the accurate definition and prevalence estimation of vertebral artery hypoplasia, ultrasound studies reveal that the reduced blood flow observed ipsilateral to the hypoplastic vertebral artery may result in local cerebral hypoperfusion and subsequent focal neurological symptomatology. That risk of cerebral ischemia is related to the severity of the hypoplasia, suggesting that the smaller of paired arteries are more vulnerable to occlusion. Existing cohort studies further support clinical observations that hypoplastic vertebral artery enhances synergistically the vascular risk for posterior circulation ischemic events and is closely associated with both atherosclerotic and prothrombotic processes.

Background and Purpose: Hyperacute posterior circulation ischemia (PCI) is known to have poor clinical outcomes. Pretreatment ischemic lesion is an outcome predictor in patients with basilar artery occlusion. When basilar artery occlusion occurs, collateral blood flow can be reversed through hemodynamic connections between posterior communicating artery (PComA), first PCA segment, and carotid artery. We hypothesized that the presence of PComA is related to less severe ischemia and favorable outcome in the patients with hyperacute PCI. Methods: We retrospectively selected patients with acute ischemic lesion in posterior circulation who had received thrombolysis from stroke registry between June 2008 and September 2013. All patients were examined by CT angiography (CTA) before treatment. The NIHSS scale was used to assess initial stroke severity. The presence of PComA was confirmed based on axial CTA source images. The outcome of patients was defined as modified Rankin Scale score (mRS) after three months. Results: Seventy-five patients (45 male; mean age: 69 years, range; 29-91 years) were treated by multimodal thrombolytic therapy (27 intravenous only, 37 intra-arterial only, 11 intravenous and intra-arterial method). Thirty-four of 75 patients (45.3%) had bilateral PComAs and 36 of 75 patients (48%) had unilateral PComA. Initial NIHSS scale was significantly lower in patients with bilateral PComAs than patients with absent or unilateral PComA (mean NIHSS scale 12.38±9.02 vs. 18.73±9.19, p=0.004). The rate of favorable outcome (mRS 0-2) was significantly higher in patients with bilateral PComAs in comparison to patients with unilateral or absent PComA (78.6% vs. 27.3%, p&lt;0.001). Conclusions: PComA is related to initial severity of hyperacute PCI. Well-developed collateral flow is associated with less severe ischemic damage, and as a consequence, leads to more favorable outcomes. Further prospective clinical trials are required to confirm the effect of PComA on clinical outcomes of hyperacute PCI.

Deficiency of adenosine deaminase 2 (DADA2) is a rare autosomal recessive autoinflammatory vasculopathy frequently associated with early-onset central nervous system involvement. Intracranial aneurysm formation and aneurysmal subarachnoid hemorrhage (aSAH) represent uncommon manifestations and remain poorly characterized from a neuroradiological perspective. We report the case of a nine-year-old boy with genetically confirmed DADA2 presenting with aneurysmal subarachnoid hemorrhage who underwent multimodal neurovascular imaging, including digital subtraction angiography (DSA). To contextualize this finding, a structured literature review was performed to identify previously reported cases of intracranial aneurysms in patients with genetically confirmed DADA2. Clinical presentation, hemorrhagic phenotype, aneurysm location, and treatment strategies were analyzed. In addition to our case, seven published patients with genetically confirmed DADA2 and intracranial aneurysms were identified, yielding a total of eight analyzed patients. Hemorrhagic events occurred in five of the eight patients, whereas threeof the eight patients presented exclusively with ischemic manifestations. Aneurysms were predominantly multiple and located in the posterior circulation or distal vessels. Anti-TNF-α therapy was administered in seven patients, while aneurysm-directed intervention was reported in one case. These findings suggest that DADA2-associated aneurysms represent a distinct inflammatory neurovascular phenotype characterized by multiplicity and peripheral distribution. In pediatric patients presenting with unexplained aneurysmal subarachnoid hemorrhage, particularly in the context of systemic inflammatory features, DADA2 should be considered as a potential underlying etiology. Comprehensive vascular assessment with DSA may be essential for detecting small or atypically located aneurysms in this setting.