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Previous studies have reported various anatomical differences in the cerebral artery between healthy subjects and patients with posterior circulation cerebral infarction. In particular, basilar artery angulation has been associated with posterior circulation cerebral infarction. We compared anatomical variations and the degree of anterior and lateral vertebrobasilar artery angulation and deviation to compare the incidence of cerebral infarction of healthy subjects and patients with posterior circulation cerebral infarction. We compared basilar artery anatomy using brain magnetic resonance angiography in 97 patients who underwent brain magnetic resonance angiography during health checkups at our hospital and in 92 patients diagnosed with posterior circulation cerebral infarction between 2012 and 2022. Anatomical variations, including fetal-type posterior cerebral artery, hypoplastic P1 segment, vertebrobasilar dolichoectasia, and dominant vertebral artery, as well as the degree of anterior and lateral deviation and angulation, were evaluated. Correlations between these variations and the occurrence of cerebral infarction were analyzed. The prevalence of hypoplastic P1 was significantly differences in patients with posterior circulation cerebral infarction (odds ratio: 5.655). Furthermore, patients with posterior circulation cerebral infarction exhibited more acute anterior and lateral angulation, as well as lateral deviation. Hypoplastic P1 and more acute anterior or lateral angulation of the vertebrobasilar artery are associated with increased frequency of cerebral infarction., Competing Interests: The authors have no funding and conflicts of interest to disclose., (Copyright © 2024 the Author(s). Published by Wolters Kluwer Health, Inc.)

The vertebral artery originates from the subclavian artery and is divided into four segments (V1-V4). In its intracranial segment (V4), the two vertebral arteries join to form the basilar artery, an unpaired medium-sized artery. However, apart from this typical description, several anatomical variations may occur in the human body. Although in some cases such variations may be asymptomatic, they may be also associated with several pathological conditions, neurological complications, surgical complications, and increased risk of developing vascular diseases. Therefore, it is crucial to obtain sufficient information on the anatomy and variants of both arteries to prevent such complications and ensure the safe completion of surgical and radiological treatments. For this reason, we reviewed studies published up to January 2022 concerning the reported variations of the vertebral artery and basilar artery regarding their origin, course, length, and diameter. We believe that the thorough presentation of these variations would help surgeons worldwide during their daily clinical and surgical practice., (Copyright © 2022 Elsevier Masson SAS. All rights reserved.)

Background: Atherosclerotic plaques are often present in regions of arteries with complicated flow patterns. Vascular morphology plays important role in hemodynamics. In this study, we investigated the relationship between the geometry of the vertebrobasilar artery system and presence of basilar artery (BA) plaque., Methods: We enrolled 290 patients with posterior circulation ischemic stroke. We distinguished four configurations of the vertebrobasilar artery: Walking, Tuning Fork, Lambda, and No Confluence. Patients were divided into multi-bending (≥ 3 bends) and oligo-bending (< 3 bends) VA groups. The diameter of the vertebral artery (VA) and the number of bends in the intracranial VA segment were assessed using three-dimensional time-of-flight magnetic resonance angiography. High-resolution magnetic resonance imaging was used to evaluate BA plaques. Logistic regression models were used to determine the relationship between the geometry type and BA plaque prevalence., Results: After adjusting for sex, age, body mass index ≥ 28, hypertension, and diabetes mellitus, the Walking, Lambda, and No Confluence geometries were associated with the presence of BA plaque (all p < 0.05). Patients with multi-bending VAs in both the Walking (20/28, 71.43% vs. 6/21, 28.57%, p = 0.003) and Lambda group (19/47, 40.43% vs. 21/97, 21.65%, p = 0.018) had more plaques compared to patients with oligo-bending VAs in these groups. In the Lambda group, the difference in diameter of bilateral VAs was larger in patients with BA plaques than that in patients without BA plaques (1.4 mm [IQR: 0.9-1.6 mm] vs. 0.9 mm [IQR: 0.6-1.3 mm], p < 0.001)., Conclusions: The Walking, Lambda, and No Confluence geometry, ≥ 3 bends in the VAs, and a large diameter difference between bilateral VAs are associated with the presence of BA plaque.

Background: Anterior inferior cerebellar artery (AICA) can present with a myriad of variations. However, the previous studies of AICA anatomy were based on small-scale cadaveric investigation. In this study, we performed an angiographic study of AICA in 500 Chinese with Han nationality based on digital subtraction angiography (DSA)., Methods: Patients admitted to our institution between 2015 and 2018 who had underwent DSA were potential candidates for this retrospective evaluation. The exclusion criteria were: a) patients with vascular diseases of the posterior circulation; b) ischemic diseases or moyamoya disease of the anterior circulation., Results: Five hundred patients were identified. The patients ranged in age from 6 to 75 years. Two hundred thirty-seven (62.9%, 237 of 377) patients had bilateral AICAs at the same level, and 140 (37.1%, 140 of 377) had bilateral AICAs at different levels. The developing states of AICA were grade 0 in 31 (3.5%, 31 of 896), grade 1 in 373 (41.6%, 373 of 896), grade 2 in 313 (34.9%, 313 of 896), and grade 3 in 179 (20.0%, 179 of 896) hemispheres. Two hundred twenty-one (22.1%, 221 of 1000) presented with AICA-PICA common trunks. Thirty-one (3.1%, 31 of 1000) hemispheres showed no obvious AICA angiographically. AICA arose as a single trunk in 865 (86.5%, 865 of 1000) hemispheres, and as duplicate trunks in 104 (10.4%, 10 of 1000) hemispheres. Triplicate or more trunks were not seen. AICA originating from the basilar artery fenestration accounted for 4% (20 of 500) of the cases., Conclusions: This is the first attempt using DSA data to perform a large-scale investigation of AICA variations. The ever-growing need of endovascular intervention calls for more suitable anatomical explanation of the vascular structures., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: The aim of this study was to determine the anatomical localisation and morphometry of vertebrobasilar junction (VBJ) by computed tomography (CT) images which may be helpful in planning the correct procedure before surgery such as endoscopic transsphenoidal transclival approach to the retroclival space., Materials and Methods: Vertebrobasilar junction level was determined on axial, coronal reformat and sagittal reformat images. Clivus length, the distances of the VBJ to the upper and lower end of the clivus and to the bottom of the sphenoid sinus were measured. In addition, the position and distance of the VBJ relative to the midline were measured. The vertebral artery dominance was determined and the position of VBJ relative to the midline was evaluated., Results: When compared by gender, 1, a, b and c values were significantly longer in males than in females (p < 0.05). The location of the bottom of the sphenoid sinus was higher than the VBJ level in 263 (98.1%) cases, equal to the VBJ level in 1 (0.4%) case, and lower than the VBJ level in 4 (1.5%) cases. There was no statistically significant difference between the distances to the midline when the VBJs with right and left localisation were compared (p > 0.05). A statistically significant relationship was found between vertebral artery predominance and localisation of VBJ relative to the midline (p < 0.001)., Conclusions: Careful perusal of CT images and the described VBJ morphometrics can help in accurate procedure planning to avoid basilar artery injury.

Background: A clival plate and screw fitted to the craniovertebral junction (CVJ) were developed in our previous studies. However, the anatomy of intracranial structures related to clival screw placement has not been studied., Objective: To measure the intracranial anatomic parameters delineating the basilar plexus and vertebrobasilar artery (VBA) course and to determine the relationship between brainstem and clivus for safer screw placement., Methods: Morphometric analysis of the VBA was conducted on 95 patients (48 men, 47 women) by CT angiography (CTA) and of the basilar plexus and brainstem on 80 patients (44 men, 36 women) by magnetic resonance imaging (MRI) The narrowest distance between the VBA and the intracranial clivus and the distance between the VBA and the median line of the skull were measured on the axial plane at different parts. The relative positions of point I (intersection of vertebral artery and basilar artery) and the pharyngeal tubercle were analyzed. The distance between the clivus and the brainstem was measured at different levels., Results: As the VBA ascended the distances to the intracranial clivus and the midline decreased. In 83.3% cases, point I was above the pharyngeal tubercle, and in only 9.5% cases was it located on the vertical line drawn from pharyngeal tubercle. The smallest safe space between the intracranial clivus and the brainstem was 7.46 mm at the lower part., Conclusion: Appropriate screw size at the lower clivus and the pharyngeal tubercle may help avoiding inadvertent injury to the brainstem and the VBA. Preoperative CTA and MRI of the CVJ are suggested to guide the surgeon in this regard., (Copyright © 2019. Published by Elsevier Inc.)

Aim: To provide measurements of the posterior cerebral circulation using a non-invasive imaging modality., Material and Methods: One-hundred and twenty patients aged from 12 to 76 years were analyzed using computed tomography (CT) angiography. Measurements of vertebral arteries (VA), basilar artery, posterior cerebral arteries (PCA) and posterior communicating arteries were obtained. Basilar artery appearance and curvature were also noted. Differences between sides, genders and age groups were evaluated., Results: Mean diameter of left VA was 2.36±0.81 mm, and mean diameter of right VA was 2.14 ± 0.79 mm. Mean length of basilar artery was 34.07 ± 5.53 mm in males, and 30.79 ± 4.18 mm in females. There was a significant difference in basilar artery length between genders: males had a longer basilar artery (p < 0.01). There was significant difference in basilar artery diameters between patients younger and older than 60 years: older patients had a statistically larger diameter, 3.17 ± 0.76 mm, than the 2.87 ± 0.57 mm in younger patients (p < 0.05). The basilar artery was straight in 36.7%, convex to the right in 47.5% and convex to the left in 14.2% of the patients. Mean diameter of the left P1 was 1.80 ± 0.58 mm, and of the right 1.87 ± 0.54 mm. There was no statistically significant difference between the diameters of the left and right P1 segments of the PCA and also between genders (p > 0.05)., Conclusion: Modern non-invasive imaging modalities can provide precise and useful information for vessels analysis. This information may be useful for planning and performing neuro-interventional procedures as well as posterior cranial fossa surgeries.

The objective of the present work was to study syntopy of the artery of labyrinth using block-preparations of the posterior cranial fossa, variants of its branching-off from the vertebro-basiliar basin (VBB), and peculiar features of its anatomical structure. A total of 12 block-preparations of the posterior cranial fossa were available for the investigation. They were preliminarily stained with red latex and fixed in a three-point system. These procedures were followed by retrosigmoid craniotomy, opening of dura mater in the supero-lateral part of the cerebellomedulllary cistern, traction of the cerebellum, and blunt separation of the basiliar artery (BA). Variants of branching of the antero-inferior cerebellar artery (AICA) and branching of the artery of labyrinth from AICA were studied. It was shown that the artery of labyrinth branches off from the antero-inferior cerebellar artery in 100% of the cases. The latter artery formed a loop in 14% of the cases (3 ears). The average diameter of the labyrinth artery was 0.32 mm and its mean area 0.06 sq.cm. The artery of labyrinth branched off from the posterior para-stem segment of the antero-inferior cerebellar artery in 42.6% of the cases (9 ears), and from the anterior para-stem segment of AICA in 14.2% of the cases (3 ears). Within the conventional «rhombus», the artery of labyrinth was straight in 76.2% of the cases (16 ears) and arc-shaped in 23.8% (4 ears).

Aim: To examine a possible relationship between the variable vascular geometry of vertebrobasilar joint angle and basilar bifurcation angle as well as the diameters of these blood vessels., Methods: The study included 60 adult patients, of both sexes, who were divided into two groups. One group (30) consisted of patients without aneurysm of vertebrobasilar tree, and another group (30) of patients with aneurysm. The patients were examined using Magnetic Resonance Imaging (MRI) and Computed Tomography Angiography (CTA) of head and neck., Results: In the group without aneurysm of vertebrobasilar tree, in 14 (46.6%) patients diameters of the right and the left vertebral artery were approximately the same. The average value of the angle of junctions of vertebral arteries was 65.43°, and the average angle of basilar bifurcation was around 94.53°. In the group with aneurysm of vertebrobasilar tree, in 12 (40%) patients diameters of the right and the left vertebral artery were also approximately the same. The average angle of junction of vertebral arteries was 68.46º, and the average angle of basilar bifurcation was 121.93º., Conclusion: Anatomic variations of the vertebrobasilar joint angle and basilar bifurcation angle, as well as the diameters of these blood vessels, are some of the factors in the increase of the incidence of aneurysm in this anatomic area.

The lower cranial nerves receive their arterial supply from an intricate network of tributaries derived from the external carotid, internal carotid, and vertebrobasilar territories. A contemporary, comprehensive literature review of the vascular supply of the lower cranial nerves was performed. The vascular supply to the trigeminal, facial, vestibulocochlear, glossopharyngeal, vagus, spinal accessory, and hypoglossal nerves are illustrated with a special emphasis on clinical issues. Frequently the external carotid, internal carotid, and vertebrobasilar territories all contribute to the vascular supply of an individual cranial nerve along its course. Understanding of the vasculature of the lower cranial nerves is of great relevance for skull base surgery., (Copyright © 2013 Wiley Periodicals, Inc.)

Introduction: The morphological anatomy of the posterior circulation is very complex and variable. Aims of this research were to document the morphological anatomy of the posterior circulation along with variations in the Bosnian population, in patients with or without aneurysm. Measurements of the outer diameters of the vertebral artery, basilar artery and posterior cerebral artery were taken. The second aim was to determine the possible relationship between diameters of the area with subsequent aneurysm formation., Material and Methods: The study involved 60 consecutive patients, adults of both sexes, treated in the UKC Tuzla. The patients were divided into two groups. One group consisted of the patients without aneurysm of basilar artery, and the other group of patients with aneurysm. All the 60 patients were treated by means of MRI angiography., Results: The mean diameter of the vertebral artery was 2.43 mm; 3.61 mm on the right and 2.83 mm; 3.94 mm on the left. The diameter of the basilar artery varied from 3.8 mm; 3.43 mm. The diameter of the posterior cerebral arteries 2.5 mm; 2.52 mm on the right and 2.46 mm; 2.62 mm on the left., Conclusions: We have documented the various morphometry variations as well as the differences of the anatomy in this area in Bosnian population as compared to the medicine literature.

Purpose: To determine the normal anatomical features and variations of the vertebrobasilar circulation and its branches in patients who underwent multidetector computed tomography (CT) or magnetic resonance (MR) angiographies of the brain., Methods: 135 patients (male, 83 and female, 52; mean age, 50.1 years) who underwent CT (n = 71) or MR (n = 64) angiographies of the vertebrobasilar vasculature for various reasons were analyzed retrospectively. The right and left distal vertebral arteries (VAs), posterior inferior cerebellar arteries (PICAs), anterior inferior cerebellar arteries (AICAs), superior cerebellar arteries (SCAs), posterior cerebral arteries (PCAs), and posterior communicating arteries (PCoAs) were analyzed individually., Results: In 24.4% of the cases (33/135) right PICA, in 19.3% of the cases (26/135) left PICA, in 17.8% of the cases (24/135) right AICA, and in 18.5% of the cases (25/135) left AICA were absent. In cases without PICA or AICA, there was a statistically significant, moderately or well-developed AICA or PICA on the same side, respectively (P < 0.001). The most common variation was isolated absence of right PICA and was seen in 17.8% of the cases., Conclusions: The anatomic features of the branches of the vertebrobasilar circulation may be different from well-known normal anatomy. CT and MR angiographies allow a precise and detailed evaluation of vertebrobasilar circulation.

Purpose: Previous studies suggest that cerebral artery diameter and position differ with both gender and ethnicity, making diagnosis of vertebrobasilar dolichoectasia (VBD) difficult. Thus, the current study investigated the morphology and potential gender differences of the vertebral (VA) and basilar arteries (BA) in the Chinese population. The data collected also enabled some criteria to be suggested for the diagnosis of VBD by MRI., Methods: A total of 200 healthy participants who underwent magnetic resonance imaging (MRI) were enrolled. The diameters of the BA and VA were measured using high resolution MRI and the height of the basilar artery bifurcation and the position of the basilar artery were also analyzed. The 95 % confident intervals (CI) of vessel diameter were calculated., Results: The diameters of each artery measured, significantly differed with gender (p < 0.01). The 95 % CI of the BA were 2.2-4.2 mm and 2.0-4.0 mm for males and females, respectively. The 95 % CI of the VA were 1.7-3.7 mm and 1.5-3.5 mm for males, and 1.4-3.4 mm and 1.1-3.1 mm for females for the left and right side, respectively. No significant gender difference was found in height of the BA bifurcation or the position of the BA., Conclusions: There are significant gender differences in the diameter of both the VA and BA, indicating that gender needs to be considered in the diagnosis of VBD. These results also provide much needed quantitative data for the diagnosis of VBD in Chinese people.

Objects: Carotid-vertebrobasilar anastomoses-the trigeminal, otic, hypoglossal, and proatlantal intersegmental arteries-serve as transitory channels between primitive internal carotid arteries and bilateral longitudinal neural arterial plexus, which is the precursor of future basilar artery, when the human embryo reaches about 4-mm length., Material and Methods: Normal and/or abnormal morphofunctional aspects of the prenatal and postnatal forms of the trigeminal artery are described according to personal and literature data. Many arteries of similar origin and course are also noted in the differential diagnosis of the trigeminal artery., Conclusions: The persistent primitive trigeminal artery, as the most commonly carotid-vertebrobasilar anastomosis, has a reported incidence of 0.03-2.2% in the literature. There is female sex predilection, and it may be discovered in patients of any age, on either side, and in association with many vascular variants. Although the significance of persistent primitive trigeminal artery regarding the development of an aneurysm or association with another pathological condition may not be clear, its (ab)normal morphology is the inspiration for anatomists, especially for neurosurgeons, before planning diagnostic and therapeutic procedures.

Object: The authors conducted a study to elucidate the relationship between the flow patterns and the formation of aneurysms at the bifurcation of the basilar artery (BA)., Methods: Six isolated, transparent vertebrobasilar arterial systems were prepared from humans postmortem, and flow patterns and velocity distributions were studied in detail using flow visualization and cinemicrographic techniques., Results: The authors found that if the diameters of 2 vertebral arteries (VAs) were nearly equal and they formed a symmetrical inverted Y-shaped junction with the BA, the BA flow was also symmetrical. The fluid elements that flowed into the BA from 2 VAs traveled almost parallel to the vessel wall of the BA without mixing with each other, and then they flowed out through ipsilateral superior cerebellar and posterior cerebral arteries. In contrast to this, if the diameters of 2 VAs were very different or the BA was badly bent, the BA flow was disturbed as a result of the formation of swirling and secondary flows. The approaching velocity profile at the BA's terminal bifurcation was flattened if the inverted Y-junction was symmetrical, and it was sharpened if the junction was asymmetrical. Thus, in the latter case, fluid elements impinged on the vessel wall around the flow divider of the bifurcation with much larger velocities and, hence, larger kinetic energy, compared with the case of a symmetrical inverted Y-junction, exerting high fluid pressures, wall shear stresses, and wall tensions on the vessel wall there., Conclusions: The symmetrical structure of the inverted Y-junction in a normal vertebrobasilar arterial system provides a flattened approaching velocity profile at the terminal bifurcation of the BA, lowering the hemodynamic stresses (pressure, tension, and shear stress) exerted on the wall of the bifurcation. This may account for the relatively low incidence of aneurysm formation at this site.

The close relationships between the cranial nerves and the arterial vessels in the posterior cranial fossa are one of the predisposing factors for artery-nerve compression. The aim of this study was to examine the relationships of the vertebral and basilar arteries to some skull and dural structures and the nerves in the posterior cranial fossa. For this purpose, the skull bases and brains of 70 cadavers were studied. The topographic relationships of the vertebral and basilar arteries to the cranial nerves in the posterior cranial fossa were studied and the distances between the arteries and some osseous formations were measured. The most significant variations in arterial position were registered in the lower half of the basilar artery. Direct contact with an artery was established for the hypoglossal canal, jugular tubercle, and jugular foramen. The results reveal additional information about the relationships of the nerves and arteries to the skull and dural formations in the posterior cranial fossa. New quantitative information is given to illustrate them. The conditions for possible artery-nerve compression due to arterial dislocation are discussed and two groups (lines) of compression points are suggested. The medial line comprises of the brain stem points, usually the nerve root entry/exit zone. The lateral line includes the skull eminences, on which the nerves lie, or skull and dural foramina through which they exit the cranial cavity., ((c) 2008 Wiley-Liss, Inc.)

Aim: The aim of our study was to demonstrate some possible variations in the vertebrobasilar system (VBS) in the Turkish population and to compare our results with the literature., Materials and Methods: The VBS samples were taken from 109 fresh forensic autopsies and one anatomic cadaver. The widths of the vertebral artery (VA), the basilar artery (BA) and their branches were measured; dominancy and hypoplastic arteries, as well as the types of variations and their locations, were determined., Results: Hypoplastic VA was observed at rates of 20.2% on the right, 14.4% on the left and 4.8% bilaterally. The vertebrobasilar junction was found to be either at the level of bulbopontine sulcus (20%), below the sulcus (67%) or above the sulcus (12%). BA variations were observed as duplications of the proximal (0.9%) and distal segments (1.8%). Anterior spinal artery (ASA) originated as a single trunk in 12.5% of the cases. ASA arose from a transverse anastomosis connecting VAs in 6.3% of the cases. Furthermore, 15.6% of ASAs were double. The observed variations in the superior cerebellar artery were early bifurcation (7.2% on the right, 12.7% on the left), fenestration (4.5% on the right, 7.2% on the left), duplication (14.5% on the right, 12.7% on the left) and origin as a common trunk (6.3% on the right, 10% on the left)., Conclusion: Our results show that a high percentage of variations can be seen even in a small number of cases. We believe that our data are clinically important because, for example, variations are a factor which increases the incidence of aneurism and thrombus. We also think our results will contribute to the demography of our country and to clinical medicine.

Background: Detailed knowledge of the pattern of origin of the anterior spinal artery is critical as surgical and endovascular procedures involving the area of the ventral medulla and the vertebrobasilar junction are commonplace. We conducted a detailed microanatomical study to elucidate the site and pattern of origin of this critically important artery., Method: Nine adult cadaveric heads (18 sides) were examined after injection of colored silicon. In every specimen, the site of origin of the rami of the anterior spinal artery, their course, branching pattern and anastomoses, external diameters, and the distance from neighbor critical vessels were recorded. The dissections were performed with the aid of both the surgical microscope and a 0 degree endoscope., Findings: The pattern and site of origin of the anterior spinal artery show great variability. Also the distance of the origin of the two rami (right and left) forming the anterior spinal artery from the vertex of the vertebrobasilar junction and from the origin of the posterior inferior cerebellar artery is highly variable., Conclusions: Knowledge of the different pattern of origin and course of the proximal portion of the anterior spinal artery is critically important when planning and executing endovascular and surgical procedures involving the distal vertebral artery, the vertebrobasilar junction and the ventral medulla. On the basis of our and other authors' findings, we propose an overall classification of the pattern of origin and distribution of the proximal anterior spinal artery, which has clinical repercussions.

Context: The microsurgical anatomy of the posterior circulation is very complex and variable. Surgical approaches to this area are considered risky due to the presence of the various important blood vessels and neural structures., Aims: To document the microsurgical anatomy of the posterior circulation along with variations in the Indian population., Materials and Methods: The authors studied 25 cadaveric brain specimens. Microsurgical dissection was carried out from the vertebral arteries to the basilar artery and its branches, the basilar artery bifurcation, posterior cerebral artery and its various branches. Measurements of the outer diameters of the vertebral artery, basilar artery and posterior cerebral artery and their lengths were taken., Results: The mean diameter of the vertebral artery was 3.4 mm on the left and 2.9 mm on the right. The diameter of the basilar artery varied from 3-7 mm (mean of 4.3 mm). The length varied from 24-35 mm (mean of 24.9 mm). The basilar artery gave off paramedian and circumferential perforating arteries. The origin of the anterior inferior cerebellar artery (AICA) varied from 0-21 mm (mean 10.0 mm) from the vertebrobasilar junction. The diameter of the AICA varied from being hypoplastic i.e.,, Conclusions: The authors have documented the various anomalies as well as the differences of the anatomy in this area in the Indian population as compared to the Western literature.

Development of nitric oxide synthase (NOS)-and vasoactive intestinal polypeptide (VIP)-immunoreactive (-IR) nerves supplying the basilar and vertebral arteries (BA and VA) was investigated in White Wistar rats, using double immunohistochemistry. NOS-IR and VIP-IR nerves via the anterior circulation (AC), which mostly expressed NO(+)/VIP(+), extended to the BA during the second postnatal week, and usually reached as far as the rostral two third of the BA on PND 20. NOS-IR nerves were completely lack in the cBA and the VA on PND10, and often absent from these arterial regions even at PND 20. Nevertheless, a small number of VIP(+)/NOS(-) nerves were localized in the walls from the caudal BA (cBA) to the VA on PND 5. On PND 20, they frequently met with the descending NOS-IR and VIP-IR nerves via the AC around the lower portion of the middle BA. Fiber bundles containing NOS(+)/VIP(+) axons were first visualized on the caudal VA at PND 30 and observed frequently at PND 80, with a distinct increase in number of NOS-IR and VIP-IR nerves supplying the cBA and the VA. Thus, NOS-IR nerves coming from the VA develop through its own characteristic sequence that lags markedly behind the time of appearance for VIP-IR nerves from the same vascular route and for NOS-IR and VIP-IR nerves via the AC.

Background: The authors present a patient who experienced late (5-year follow-up) morphological progression of a dissecting aneurysm of the distal basilar artery after treatment with a combined microsurgical and neuroendovascular Hunterian strategy. In addition to postulating about the possible reasons underlying the evolution of this lesion, the role of stenting is discussed., Case Description: The patient was 37 years old when she suffered a subarachnoid hemorrhage from spontaneous basilar artery dissection. At the time of the hemorrhage, minimal aneurysmal enlargement was noted angiographically, and she was therefore treated nonoperatively. On reimaging 5 months later, massive enlargement of the aneurysm was noted. The patient was treated with staged bilateral vertebral artery sacrifice using a combination of microsurgical and neuroendovascular techniques. The dominant vertebral artery was clip-ligated distal to the posteroinferior cerebellar artery, whereas the contralateral vertebral artery was coil-occluded cervically 1 week later., Conclusions: Despite the patient remaining asymptomatic, follow-up angiography 5 years after the initial hemorrhage revealed further enlargement of the aneurysm as well as a newly discovered inferiorly projecting daughter sac measuring 5 mm in diameter. Clearly, certain aneurysms exist for which indirect approaches involving hemodynamic attenuation fail to prevent progression. With greater refinements in stent technology, such lesions may be more effectively treated.

Introduction: The foramen of Vicq d'Azyr, is a triangular-shaped area located rostral to the ventral median fissure of the medulla oblongata. Its importance relies on the fact that it is penetrated by small vessels from the vertebrobasilar axis that nourish vital pontine nuclei and tracts. We described the microvascular anatomy of the perforating vessels of the foramen of Vicq d'Azyr (FVA)., Materials and Methods: The vertebrobasilar junction arteries and the perforating arteries of the foramen of Vicq d'Azyr were examined using a surgical microscope in 21 formalin-fixed brain stems., Results: The total number of perforating branches found was 286 in the 21 brains, an average of 13.6 perforators per brain, range 7 to 22. They arose as distal branches of 73 main trunks, average of 3.5 per brain, range 2 to 5, originating mainly from the basilar artery in 41 (56.1 %); the left ventral spinal artery in 12 (16.4 %), and the left vertebral artery in 8 (11 %). The average outer diameters of the left and right vertebral arteries were 3.2 mm and 2.9 mm, 4.1 mm for the basilar artery, and 0.6 mm for the right and left ventral spinal arteries. The branching pattern and interesting anatomic variations of the main vessels of the vertebro-basilar junction are also described., Discussion: The vascular anatomy of the infratentorial compartment is highly variable. These variations should be kept in mind to avoid pitfalls during vascular or tumor surgery. In contrast, the entering locations of perforating vessels remain constant, referring to these zones as key areas when planning or doing surgical procedures in this region.

The course of the posterior inferior cerebellar artery (PICA) was analyzed with reference to its origin and relationships with the medullary and cerebellar surfaces and the adjacent cranial nerves in 40 brains after the injection with acrylic resins of the vertebrobasilar system. In 42.5% of instances, the PICA originated from the lateral medullary segment of the vertebral artery (VA), in 32.5% from its premedullary segment, in 22.5% from the basilar artery (BA), and in 2.5% it was absent. With reference to the level of origin, three patterns of course for the lateral medullary segment of the PICA can be outlined. (1) When it arises from the lateral medullary segment of the VA, it passes below the hypoglossal nerve, and the lateral medullary segment may form a loop with an anterosuperior convexity towards the pontomedullary sulcus (41%), or it may follow a rectilinear course (41%). It passes at the level of the accessory nerve. The tonsillomedullary (TM) segment shows a caudal loop and the telovelotonsillary (TVT) has a cranial loop. (2) When the PICA arises from the BA, it passes above the hypoglossal nerve. The lateral medullary segment forms a loop with lateral convexity (78%) and passes above or through the glossopharyngeal nerve, frequently showing a recurrent course among the roots of the IX, X, or XI cranial nerve. The TM and the TVT segments do not have loops. (3) When the PICA arises from the premedullary segment of the VA, it passes above, below, or through the rootlets of the hypoglossal nerve. In the lateral medullary segment, it follows a rectilinear course (54%) and passes the plane formed by the IX, X, and XI cranial nerves at an intermediate level with respect to the other two patterns. The TM and the TVT segments show caudal and cranial loops. The different origins and courses of the PICA derive from the selection of different branches of the primitive vertebrobasilar plexus during the development of the cerebellum. The existence of an embryologic correlation between the course of the PICA and its level of origin may be useful in the evaluation of its angiographic anatomy.

We modified surface anatomy scanning (SAS) MRI to reveal the surface appearance of the vertebrobasilar artery in the cistern. Two-cm-thick heavily T2-weighted coronal imaging using the fast spin-echo sequence with gray-scale reversal in post-processing was best for our purposes. Basi-parallel anatomical scanning (BPAS) MRI could clearly demonstrate fusiform aneurysm and its disappearance at the acutely occluded segment of the dissected vertebral artery. This simple MRI scanning technique can provide useful information on vertebrobasilar vascular lesions especially in patients with arterial dissection.

Magnetic resonance phase-contrast volume flow rate (VFR) measurement with limited resolution in small vessels is subject to two major sources of error: a) partial volume artifacts, causing systematic overestimation of the VFR, and b) errors related to the selection of vessel pixels [region of interest (ROI)], causing large inter-observer and intra-observer variability. Additionally, limited resolution results in Gibbs-ringing around vessels, which adversely affects VFR determination. In this paper, a semi-automatic model-based method is presented that effectively eliminates errors due to both partial volume effect and Gibbs-ringing and also minimizes errors from variability in the ROI selection. The model assumes a parabolic flow profile and cylindrical vessel geometry, incorporates inflow effects, and takes into account the point-spread function of the acquisition. The method automatically estimates maximum velocity, vessel radius, and VFR. The method is validated in phantoms under various conditions and evaluated in vivo. For small vessels with moderately pulsatile flow, it is demonstrated that accurate VFRs and diameter estimates are obtained, virtually independent of the ROI selection, even in vessels covered by just a few pixels. Compared with conventional VFR analysis, both accuracy and reproducibility improve significantly.

The arterial system formed by branches of the vertebral and basilar arteries in guinea pig was compared to that of dog and human. The vertebrobasilar arterial system in particular species shows similarities and differences, considering its structure and arising branches. The differences are mainly due to the length of the basilar artery. In guinea pig the vertebrobasilar system distribute blood to the 2/3 of the brain. The same distribution is in dog. In human the carotid system predominates in the supply of the brain.

Advances in stroke treatment are discussed in the context of vertebrobasilar ischemia. The anatomy of the vertebral and basilar arteries and the pathophysiology of posterior circulation stroke are reviewed. The diagnosis and management of patients with vertebrobasilar occlusion is emphasized and the controversies surrounding the use of intra-arterial and intravenous thrombolytic therapy in posterior circulation disease are addressed.

The apex of human vertebro-basilar junctions can be sharp-edged or blunted. In the present study, the effect of blunted apex on the flow in vertebro-basilar junction models is investigated. We compared the flow phenomena in a series of junction models with blunted apices and confluence angles 45, 85, and 125 deg with the flow phenomena in a series of junction models with sharp-edged apices and the same range of confluence angles, studied in a previous paper (Ravensbergen et al., 1996b). The blunting of the apex appears to have an effect on the size of the local recirculation area near the apex and the prevailing low velocities. Large recirculation areas are found in the models with blunted apices, especially in those with small confluence angles. In addition, the blunting of the apex has no influence on the flow further downstream, nor on the structure and strength of the secondary flow field. Furthermore, a blunted apex appears to be a geometric risk factor for atherosclerosis. This supports the hypotheses that recirculation areas and low wall shear stress influence the development of atherosclerotic plaques.

In earlier work, it was demonstrated that the flow in models of the vertebro-basilar junction is highly three-dimensional and the geometry exerts a strong influence on the hemodynamics. The morphology of the vertebro-basilar junction is very variable amongst individuals. In a study of 85 human vertebro-basilar junctions, the angle between the vertebral arteries varied between 10 and 160 degrees. To determine how the flow is influenced by this geometrical parameter, the flow is studied both experimentally, with laser Doppler velocimetry, and numerically, with a finite element package. A series of junction models is used with a range of confluence angles (45, 85 and 125 degrees). It appears that the angle of confluence has a strong influence on the structure and strength of the secondary flow field. The secondary velocities persist far downstream. Furthermore, near the apex, a region with low velocities is present. The larger the confluence angle is, the larger this region is, and even backflow may occur. In addition, the occurrence of atherosclerotic plaques in 85 human vertebro-basilar junctions is studied. Only one preferential location was found: the apex, the other plaques seem to be randomly distributed. The magnitude of the confluence angle of junctions with sharp-edged apices has a significant influence (p = 0.006) on the occurrence of a plaque at the apex. Apparently, a large confluence angle is a geometrical risk factor for atherosclerosis.

Purpose: To describe the flow patterns in a model of the vertebrobasilar artery and use these observations to explain the appearance of the flow on the MR images., Methods: We created an anatomically precise, transparent elastic model of the human vertebrobasilar artery containing a basilar tip aneurysm and perfused the model with non-Newtonian fluid which has similar rheologic properties to blood. Flow patterns in the vessels were directly observed. MR angiogram images were obtained with commercially available two-dimensional time-of-flight, three-dimensional time-of-flight, and 3-D phase-contrast MR angiographic pulse sequences, and they were correlated with the directly seen flow patterns. Quantitative flow velocity measurements were performed with 2-D cine phase-contrast MR angiography and correlated with the flow measured with an electromagnetic flow meter., Results: Visualization studies showed the dye stream patterns in the vertebrobasilar arteries to be extremely complex and variable. During the MR experiments we found that often the same segment of a vessel could appear very different depending on the pulse sequence. In some instances, the model experiments helped to explain the MR appearance of the vessels. Flow profiles measured with 2-D cine phase contrast were found to be consistent with those measured directly with an electromagnetic flow meter., Conclusion: Clear elastic models can be used to duplicate the flow in human cranial vessels and thus provide a unique means to observe these flow patterns directly. The flow patterns helped to explain the variation in appearance of the vessels and the artifacts with different MR angiography pulse sequences. The artifacts depend on both the geometry of the vessel and the flow pattern within it. Two-dimensional cine phase-contrast MR provides temporal flow field information that is directly related to physiological information about flow volumes and velocity patterns.

Purpose: To determine the reliability of magnetic resonance (MR) angiography in depicting normal vascular anatomy and its usefulness in detecting vascular disease compared with those of digital subtraction angiography (DSA)., Materials and Methods: Sixty patients with symptoms referable to disease of the vertebrobasilar system were examined with MR angiography and DSA., Results: In patients with normal DSA results, all vertebral arteries (VAs) and basilar arteries (BAs) were also visualized with MR angiography. MR angiography demonstrated 117 of 120 superior cerebellar arteries and 80 of 90 posterior inferior cerebellar arteries but only 30 of 58 anterior inferior cerebellar arteries. MR angiography demonstrated disease of the VAs and BAs with 100% sensitivity. Stenoses were differentiated from occlusions in all cases. However, the degree of stenosis was overestimated in 63% of patients. In six patients with occlusive disease, collateral flow was correctly analyzed with selective saturation., Conclusion: Despite its limitations, MR angiography is a clinically important noninvasive technique for screening patients for macroangiopathy of the posterior arterial supply to the brain.

MRA (magnetic resonance angiography) is besides duplex sonography at present the only noninvasive method for vascular visualisation. The technical fundamentals and our initial experiences with this new technique of angiography in the visualisation of the basilar artery are presented in the following article.

Background: Anatomic variety and difficult accessibility of the vertebrobasilar arteries pose considerable problems to conventional ultrasound. We evaluated the diagnostic potential of transcranial color-coded sonography in the distal part of this system., Methods: We insonated the intracranial section of the vertebrobasilar arteries through the foramen magnum window in 24 healthy individuals using a Doppler color flow imaging system in connection with a 2.5-MHz sector transducer. Magnetic resonance images in special inclination planes were performed and compared with the color-coded duplex images in five cases., Results: The B-mode image of the craniocervical junction and the intracranial parenchymal structures in addition to the color-coded blood flow allowed an unambiguous identification of the vertebrobasilar arteries (vertebral artery, 96%; basilar artery, 79%; and posterior inferior cerebellar artery, 50%). Blood flow velocities were measured considering the insonation angles: vertebral arteries, 50/24 cm/sec (30 degrees); basilar artery, 59/28 cm/sec (4 degrees); and posterior inferior cerebellar artery, 56/30 cm/sec (20 degrees) [peak systolic/end diastolic blood flow velocity (mean angle correction)]., Conclusions: Transcranial color-coded sonography enables accurate identification and differentiation of the intracranial vertebrobasilar arteries and improves accuracy of Doppler measurements. It may prove useful for evaluation of tortuosity and for hemodynamic studies in this vascular territory.

In earlier articles it was suggested that there is a relation between vertigo and the posterior circulation. This study was designed to ascertain the course of the branches of the vertebral artery and the basilar artery, as well as the principal blood vessels of the vestibular nucleus by using radiographic three-dimensional observation. We studied 27 human brains (17 males, 10 females) fixed with the arterial embalming method at the Department of Anatomy of Kawasaki Medical School. The results were as follows: 1. Many variations in the course of the anterior inferior cerebellar artery and the posterior inferior cerebellar artery were observed, but the most frequent pattern, observed in 56% of our subjects, was the anterior inferior cerebellar arteries originating from the basilar artery and the posterior inferior cerebellar arteries from the vertebral artery. 2. Measurement of the inside diameter of both vertebral arteries showed the diameter of the left side to be thicker than that of the right side. 3. Perforating branches in the brain stem consisted of the pontine branches from the basilar artery and small branches from the anterior inferior cerebellar artery. Moreover, the transverse section showed a large number of them to originate from the ventral part of the brain stem.

Concerning the structure of connective-muscular components the authors studied the walls of the terminal segments of the vertebral arteries as well as the basilar artery, utilizing the following staining methods: Azan modified by Heidenheim, Weigert's resorcin-fuchsin, and Weigert modified by van Gieson. It was established that wall of the vertebro-basilar system exhibits a mixed structure, muscular and elastic, by means of which the vessels are adjusted to the specific blood circulation conditions. Thus, vertebral arteries show in the most external layer of tunica media an evident external elastic lamina. In contrast, in the basilar artery the elastic tissue is localized mainly in the tunica media, and is distributed heterogeneously. In its caudal segment the elastic fibers are situated in the most internal layer of tunica media, and in the cranial segment the elastic component is homogeneously distributed in the whole of tunica media.

The shape, origin, termination and number of the main arteries of the vertebrobasilar system have been analysed in 30 anatomic specimens by dissection of the injected vessels and by radiography. Five projections are described for identifying the different regions of the brain stem and cerebellum through the appearance of the arteries. A technique is proposed for obtaining a 'true' a.p. view of the vessels in vertebral angiography in patients.

Regions of supply by the posterior segment of the circle of Willis are discussed in terms of anatomo-functional organization.

Colour flow imaging was used for the visualization of the great intracranial arteries in 100 healthy infants. All children were investigated by computersonography with a 5 MHz linear transducer. Simultaneous imaging of brain tissue, displayed in gray scale and flow, displayed in colour was possible. Flow towards the transducer was displayed in red, flow away from the transducer in blud. The following arteries could be shown in sagittal and coronal sections: anterior cerebral artery, both internal carotid arteries, the basilar artery, both vertebral arteries and the posterior cerebral arteries. The middle cerebral artery could only be shown in axial sections through the temporal bone. With the help of colour flow imaging the exact course of the great intracranial arteries can be shown. Precise placement of the sample volume as well as angle correction is possible when absolute flow velocities are measured by pulsed dopplersonography. Congenital vascular abnormalities can be visualised within the image.

Topometric study of basilar arteries was performed, using 130 normal vertebral angiograms of cases consisting of 83 males and 47 females aged 2 to 67 (mean = 38.1). The cases having clinically and/or neuroradiologically had obvious positive findings such as cerebral atrophies, cerebrovascular diseases and space-taking lesions were excluded. Selective vertebral angiography using Seldinger's technique in 120 cases and retrograde brachial angiography in remaining 10 cases was carried out. The following results were obtained. 1) The position of vertebrobasilar junction was almost at the midline in frontal view with a mean distance of 0.3 mm +/- 3.6 leftward from the midline. 2) The length of basilar artery was 25.5 mm +/- 6.6 in frontal view and 32.8 mm +/- 5.8 in lateral view. 3) The position of basilar bifurcation was almost at the midline in frontal view with a mean of 0.0 mm +/- 2.0 from the midline, and 9.3 mm +/- 4.7 above the Twining's line and 24.5 mm +/- 3.4 posterior from tuberculum sellae in lateral view. 4) As for the configulation of basilar artery in frontal view, 'straight type' was common in young age and 'curved type' in old age. 'Curved type' was divided into four subtypes. The concave rightwards curved type and/ or the reversed S-formed tortuous type were almost twice many as the concave leftwards curved type and/or the S-formed tortuous type. This result seemed to support the reports on the hemodynamic mechanism of verteral arteries that the dominant flow was present on the left side at the rate of 50 to 80%. 5) Internal diameter of basilar artery at the point of 1 cm proximal to the apex was measured. The mean value was 3.3 mm +/- 0.6 in frontal view and 3.2 mm +/- 0.5 in lateral view. Maximum diameter of basilar artery was 3.5 mm +/- 0.7 in frontal view and 3.6 mm +/- 0.6 in lateral view.