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Persistent primitive trigeminal artery: volume-rendered 3D time-of-flight lateral (A) and superior (B) views showing persistent primitive trigeminal artery (blue arrow) arising from the cavernous internal carotid artery (ICA) and communicating with the basilar artery, which is hypoplastic prior to the anastomotic point (green arrow). In the lateral view (A), the anomalous artery with the ICA resembles Neptune's trident and the letter " tau " in Greek.
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Cerebral arteries may exhibit a wide range of variation from normal anatomy, which can be incidentally discovered during imaging. Knowledge of such variants is crucial to differentiate them from pathologies, to understand the etiology of certain pathologies directly related to a vascular variant, and to depict the changes in collateral circulation...
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Giant serpentine aneurysm (GSA) with rare aortic and supra-aortic vascular anomaly is technically difficult to treat. Often such patients suffer without treatment. We have treated a patient by a different approach which is not regularly followed. This case has many developmental anomalies with complicated anatomy, and it is a challenge to the treat...
Citations
... In contrast, 499 cases were used for training the CNN for automated aorta segmentation (16). The small number of training cases may be problematic since large variations in the CoW geometry have been reported (34). The limited number of training cases may also be a further explanation for the slightly worse segmentation performance of the sinuses in ICAD patients. ...
Introduction: Intracranial 4D flow MRI enables quantitative assessment of hemodynamics in patients with intracranial atherosclerotic disease (ICAD). However, quantitative assessments are still challenging due to the time-consuming vessel segmentation, especially in the presence of stenoses, which can often result in user variability. To improve the reproducibility and robustness as well as to accelerate data analysis, we developed an accurate, fully automated segmentation for stenosed intracranial vessels using deep learning.
Methods: 154 dual-VENC 4D flow MRI scans (68 ICAD patients with stenosis, 86 healthy controls) were retrospectively selected. Manual segmentations were used as ground truth for training. For automated segmentation, deep learning was performed using a 3D U-Net. 20 randomly selected cases (10 controls, 10 patients) were separated and solely used for testing. Cross-sectional areas and flow parameters were determined in the Circle of Willis (CoW) and the sinuses. Furthermore, the flow conservation error was calculated. For statistical comparisons, Dice scores (DS), Hausdorff distance (HD), average symmetrical surface distance (ASSD), Bland-Altman analyses, and interclass correlations were computed using the manual segmentations from two independent observers as reference. Finally, three stenosis cases were analyzed in more detail by comparing the 4D flow-based segmentations with segmentations from black blood vessel wall imaging (VWI).
Results: Training of the network took approximately 10 h and the average automated segmentation time was 2.2 ± 1.0 s. No significant differences in segmentation performance relative to two independent observers were observed. For the controls, mean DS was 0.85 ± 0.03 for the CoW and 0.86 ± 0.06 for the sinuses. Mean HD was 7.2 ± 1.5 mm (CoW) and 6.6 ± 3.7 mm (sinuses). Mean ASSD was 0.15 ± 0.04 mm (CoW) and 0.22 ± 0.17 mm (sinuses). For the patients, the mean DS was 0.85 ± 0.04 (CoW) and 0.82 ± 0.07 (sinuses), the HD was 8.4 ± 3.1 mm (CoW) and 5.7 ± 1.9 mm (sinuses) and the mean ASSD was 0.22 ± 0.10 mm (CoW) and 0.22 ± 0.11 mm (sinuses). Small bias and limits of agreement were observed in both cohorts for the flow parameters. The assessment of the cross-sectional lumen areas in stenosed vessels revealed very good agreement (ICC: 0.93) with the VWI segmentation but a consistent overestimation (bias ± LOA: 28.1 ± 13.9%).
Discussion: Deep learning was successfully applied for fully automated segmentation of stenosed intracranial vasculatures using 4D flow MRI data. The statistical analysis of segmentation and flow metrics demonstrated very good agreement between the CNN and manual segmentation and good performance in stenosed vessels. To further improve the performance and generalization, more ICAD segmentations as well as other intracranial vascular pathologies will be considered in the future.
... During the assessment, CTA was also reviewed to avoid pitfalls affecting perfusion interpretations, such as vascular stenosis, or vascular variants. 9 Additionally, NECT were evaluated by a single reader for signs indicative of hypoxia. 10 The findings were categorised as normal, equivocal or hypoxia. ...
... Aplasia of the A1 segment is found in 1% of people (1). Thus, both A2 segments are supplied via the available A1 segment, which covers the entire ACA territory (4 interventions in the anterior communicating artery territory or ischemic events, as it increases the risk and extent of brain ischemia in the frontal lobe (5). Two-thirds of cases have more common anatomical variants of CoW in the posterior region (4). ...
... The variation is found unilaterally in 11%-29% and bilaterally in 1%-9% (6). Studies on CoW variations are numerous and vary widely depending on age, sex, health status, side and number of vessels affected, location within the CoW, and method for data collection (4). Despite the high degree of CoW variability described and classified into 22 different types by Riggs, Lazorthes, and Krabbe-Hartkamp (2), to our knowledge, there is no research on the incidence of simultaneous A1 aplasia and ipsilateral P1 hypoplasia in the literature. ...
... The effectiveness of compensation of the CoW depends on the presence of its vessels and their size. A complete CoW has an effective intracranial collateral circulation and a greater compensatory capacity in cerebral ischemia, but variations in the CoW cause changes in hemodynamics(4). In the case of ICA occlusion and A1 hypoplasia or aplasia, collateral supply to the ACA and middle cerebral artery occurs through reverse flow in the ...
Purpose The cerebral arterial circuit provides collateral circulation to the brain and protects the brain from ischemia, by sustaining tissue perfusion in case of reduced or impaired blood flow through its branches. Although many random anatomical variations in the circle of Willis (CoW) are of minor importance, some increase the risk of ischemic events, aneurysm, and atherosclerosis, and play an important role in endovascular and surgical treatment planning. Case presentation We report a rare arterial variation of the CoW diagnosed by computed tomography angiography in a patient with ischemic stroke. We found aplasia of the A1 segment of the left anterior cerebral artery and ipsilateral hypoplasia of the P1 segment of the left posterior cerebral artery. Conclusion For neurosurgeons, neurologists, and neuroradiologists, detailed knowledge of the numerous anatomical variations in the arterial supply to the brain is crucial to make a correct diagnosis and choose the appropriate treatment. The type of CoW variation influences stroke severity and outcome, with an incomplete CoW related to more severe conditions (higher National Institutes of Health Stroke Scale scores, more severe neurological deficits, and worse neurological outcomes) and poor prognosis.
... In addition, 232 patients (232/250, 92.8%) had Category II abnormalities in the intracranial arteries, whereas 112 patients (112/136, 82.4%) had Category II abnormalities in the extracranial arteries. These findings are also inconsistent with the results of previous studies, which reported rates of abnormalities of up to 60% [23,24]. The reason for these discrepancies is as yet unclear; however, they could be related to the selection bias in this retrospective study, and differences in imaging modalities, scanning parameters, or scan range. ...
Background and Objectives: Vascular abnormalities within the anatomical coverage are frequently encountered in imaging studies. The aortic arch is often overlooked as an anatomical blind spot, especially in neck magnetic resonance (MR) angiography. This study investigated the prevalence of incidental aortic arch abnormalities. We also estimated the potential clinical significance of aortic arch abnormalities as blind spots detected on contrast-enhanced neck MR angiography. Materials and Methods: Between February 2016 and March 2023, 348 patients were identified based on contrast-enhanced neck MR angiography reports. The clinical and radiological characteristics of the patients and the presence of additional imaging studies were assessed. The aortic arch abnormalities and coexisting non-aortic arterial abnormalities were classified into two categories according to their clinical significance. We performed the χ2 test and Fisher’s exact test for group comparisons. Results: Of the 348 study patients, only 29 (8.3%) had clinically significant incidental aortic arch abnormalities. Among these 348 patients, 250 (71.8%) and 136 (39%) had intracranial and extracranial abnormalities, respectively; the clinically significant intracranial abnormalities in the two groups were 130 lesions (52.0%) and 38 lesions (27.9%), respectively. In addition, there was a significantly higher tendency of clinically significant aortic arch abnormalities (13/29, 44.8%) in the patients who had clinically significant coexisting non-aortic arterial abnormalities than in the other group (87/319, 27.3%) (p = 0.044). The patient groups with clinically significant intracranial or extracranial arterial abnormalities had higher rates of clinically significant aortic abnormalities (31.0% and 17.2%), but there was no statistical significance (p = 0.136). Conclusions: The incidence of clinically significant aortic arch abnormalities was 8.3% on neck MR angiography, with a significant association between aortic and coexisting non-aortic arterial abnormalities. The findings of this study could improve the understanding of incidental aortic arch lesions on neck MR angiography, which is of crucial clinical importance for radiologists to achieve accurate diagnoses and management.
... There are many anatomical variants of the MCA. The duplication of MCA and the accessory MCA are anomalous arteries present in individuals at 2-2.9% and 2.7%, respectively [17]. Duplication of the MCA occurs when the anomalous artery arises from the distal ICA and runs parallel to the MCA, whereas an accessory MCA occurs when the artery originates from the ACA [17]. ...
... The duplication of MCA and the accessory MCA are anomalous arteries present in individuals at 2-2.9% and 2.7%, respectively [17]. Duplication of the MCA occurs when the anomalous artery arises from the distal ICA and runs parallel to the MCA, whereas an accessory MCA occurs when the artery originates from the ACA [17]. The anomalous MCAs can be differentiated from the original MCA by either examining the bifurcation of the MCA (present in the dominant original MCA) or comparing the ICA bifurcation to the contralateral side [17]. ...
... Duplication of the MCA occurs when the anomalous artery arises from the distal ICA and runs parallel to the MCA, whereas an accessory MCA occurs when the artery originates from the ACA [17]. The anomalous MCAs can be differentiated from the original MCA by either examining the bifurcation of the MCA (present in the dominant original MCA) or comparing the ICA bifurcation to the contralateral side [17]. If the two arteries reconnect distally, it is referred to as fenestration. ...
Background:
Extensive randomized controlled clinical trials for endovascular thrombectomy in anterior circulation large vessel occlusions (internal carotid arteries and M1 segment of middle cerebral arteries) have been published over the past decade, but there have not been randomized controlled trials for distal arterial occlusions to date. Distal arterial occlusion randomized controlled trials are essential to decide on patient selection, imaging criteria, and endovascular approach to improve the outcome and reduce complications.
Summary:
The definition of distal arterial occlusion is however unclear, and we believe that a uniform nomenclature of distal arterial occlusions is essential for the design of robust randomized controlled studies. We undertook a systematic literature review and comprehensive analysis of 70 articles looking at distal arterial occlusions and previous attempts at classifying them as well as comparing their similarities and differences with a more selective look at the middle cerebral artery. Thirty-two articles were finally deemed suitable and included for this review. In this review article, we present 3 disparate classifications of distal arterial occlusions, namely, classical/anatomical, functional/imaging, and structural/calibre, and compare the similarities and differences between them.
Key messages:
We propose the adoption of functional/imaging classification to guide the identification of distal arterial occlusions with the M2 segment starting at the point of bifurcation of the middle cerebral artery trunk/M1 segment. With regards to the anterior temporal artery, we propose that it will be considered a branch of the M1 and only be considered as the M2 segment if it is a holo-temporal artery. We believe that this is a practical method of classification in the time-critical decision-making period.
... Ab-normal vessel develops from the fusion of the inferior tympanic branch of the ascending pharyngeal artery with the caroticotympanic artery. Agenesis of ICA occurs in less than 0.01% of the population, while the bilateral absence of the artery is seen in less than 10% of cases of agenesis [13,14,19]. Prevalence of hypoplasia is 0.079% [19]. ...
... Agenesis of ICA occurs in less than 0.01% of the population, while the bilateral absence of the artery is seen in less than 10% of cases of agenesis [13,14,19]. Prevalence of hypoplasia is 0.079% [19]. Other variants of the internal carotid artery include duplication, ICA fenestration, and high or low branching of the carotid artery (from T2 to C1 level). ...
... Abnormal vessel develops from the fusion of the inferior tympanic br ascending pharyngeal artery with the caroticotympanic artery. Agenesis of IC less than 0.01% of the population, while the bilateral absence of the artery is than 10% of cases of agenesis [13,14,19]. Prevalence of hypoplasia is 0.079% variants of the internal carotid artery include duplication, ICA fenestration, a low branching of the carotid artery (from T2 to C1 level). ...
Computed tomography (CT) angiography is the main method for the initial evaluation of cerebral circulation in acute stroke. A comprehensive CT examination that includes a review of the three-dimensional and maximum-intensity projection images of the main intra and extracranial arteries allows the identification of most abnormalities and normal variants. Anatomical knowledge of the presence of any normal variants, such as fenestration, duplications, and persistent fetal arteries, plays a crucial role in the diagnosis and therapeutic management of acute stroke. However, the opposite is also true. In fact, sometimes it is the clinical picture that allows weighing how relevant or not the alteration found is. Therefore, in this review, a concise representation of the clinical picture attributable to a given arterial vessel will be included.
... Circle of Willis is the most important collateral system in the brain with multiple potential anatomical variations [11][12][13]. Some of the most common variations in the circle of Willis include hypoplasia or aplasia of one or both posterior communicating arteries (PCoA) (34 to 68%), hypoplasia or aplasia of the A1 segment of anterior cerebral artery (ACA) (4 to 10%), absence or fenestration of anterior communicating artery (ACoA) (12 to 21%), persistent fetal origin of posterior cerebral artery (fPCA) (4% to 26%), and infundibular dilatation or widening of PCoA (7% to 15%) [14][15][16][17][18][19][20]. Although there are numerous studies on anatomical variations of the circle of Willis, presence of any association between anatomical variations of circle of Willis and incidence of ischemic stroke is still unclear [21][22][23][24][25][26][27]. ...
Aim: To study of Circle of Willis both morphologically and radiologically and its variations in the branching pattern of the Circle of Willis and to correlate it clinically. Introduction: The circle of Willis (CoW) is an anastomotic arterial network on the base of the brain. Its major role is to provide efficient collateral circulation to cerebral and cerebellar tissue to prevent ischemia, and subsequent transient ischemic attack or stroke. The circle of Willis (CoW) is a vascular network formed at the base of skull in the interpeduncular fossa. Its anterior part is formed by the anterior cerebral artery, from either side. Anterior communicating artery connects the right and left anterior cerebral arteries. Posteriorly, the basilar artery divides into right and left posterior cerebral arteries and each join to ipsilateral internal carotid artery through a posterior communicating artery. Anterior communicating artery and posterior communicating arteries are important component of circle of Willis, acts as collateral channel to stabilize blood flow. In the present study, anatomical variations in the circle of Willis were noted and correlated those with clinically. Methods: 50 apparently normal formalin fixed brain specimens were collected from human cadavers.
... Anatomical variants of the cerebral arteries are encountered in a regular basis as an incidental finding. [1] Fenestration means a vascular variation that begins with a common origin and then splits into two parallel luminal channels and re-joins distally. [2] Each channel has its endothelium and tunica media but may share the adventitia as well. ...
... The etiology is thought to be due to the failure of midline fusion during embryogenesis, but this is controversial, depending on the site of fenestration. [1] It differs from duplication that the latter variation also has a duplicated origin [2] [ Table 1].{Table 1} ...
... We have conducted a comparative review, seeking the reported cases so far regarding the association of ICF with nonaneurysmal anomalies or pathology [1], [8], [9], [10], [11], [12], [13], [14], [15], [16] [ Table 2].{Table 2} ...
Background: Cerebral arteries have been identified with multiple anatomical variations, including a concomitant fenestration with
aneurysms, but no association is proven. Aim: to investigate non aneurysmal disorders associated with intracranial arterial fenestration.
Methods: A thorough and detailed analysis of the available literature from 1970 to 2020 in PubMed were contemplated to identify and
address all the disorders associated with arterial fenestration with exclusion of intracranial aneurysms. Results: While segmental vulnerability
may induce invisible anatomical histological and hemodynamic changes, cadaveric studies showed that the frequency of fenestration is
up to 40% higher than the clinical reports, and the cadaveric reports also showed a higher occurrence of such fenestrations as compared
to radiological studies. The vertebrobasilar system, the most common site of fenestration. Fused vertebrae and other vascular defects of
up to 7% are previously associated with the vertebral artery fenestration. Conclusion: intracranial fenestration is a critical anatomical
variant. Thus, A comprehensive angiographical examination can enhance overall prognosis in presurgical planning in association with
other vascular abnormalities.
Keywords: Anatomy, arterial fenestration, nonaneurysmal, vascular
... Arterial fenestrations are short divisions of the vascular lumen in two vascular channels, each with its own tunica intima, media and adventitia, although a shared adventitia is possible [8]. They are relatively common incidental, asymptomatic variants in the intracranial arterial system, most frequently encountered at the level of the anterior cerebral-communicating artery complex. ...
Internal carotid artery (ICA) anatomical variations are relatively rare occurrences during diagnostic imaging procedures. Their presence can have important prognostic consequences in the evaluation of vascular neurological diseases. It is therefore important to have a good knowledge about these variations, in order to avoid unwarranted medical interventions. We present the case of a patient harboring a right ICA fenestration in the cervical segment, misdiagnosed as a dissection on computed tomography angiography, admitted in the Department of Neurology and treated accordingly. The possible pathological and embryological origins of arterial fenestrations are discussed, and a brief review of the literature related to ICA fenestrations is presented.
... A PPTA arises from the proximal cavernous part of the ICA and courses posteriorly to join the basilar artery. Recognition of a PPTA is of clinical significance due to its association with aneurysms and several vascular variants [1,4]. In addition, identification of a PPTA before performing surgery in parasellar region or endovascular procedure is crucial for operative planning. ...
... Early angiographists did not describe a specific sign for this vascular variant, however, in 1994 it was mentioned that these anatomical features give a characteristic appearance on MR sagittal images of the brain which resembles the Greek letter tau (s) [2]. In 1999 the appearance on sagittal MRI images was likened to Neptune's trident and this term is now found in many publications [3,4,8]. Unfortunately the appearance on lateral projection of the internal carotid artery and PPTA connecting it to the upper part of the basilar artery only has two prongs and therefore the term trident is misleading. ...
