Variations Of Vertebral Artery Research Articles

Arcuate foramen prevalence in South African subjects: A cadaveric study based on 120 atlas vertebrae

BackgroundThis study was a prospective cadaver-derived skeletal study looking at the skeletal remains of a modern human population. The complete arcuate foramen (AF) is an anatomical variant of the atlas vertebra with a complete osseous bridge over the groove for the vertebral artery (VA). Awareness of the anatomic variations of the atlas related to the course of the VA, such as the AF, is important because the course and variations of VAs are critical to spine surgeons. We aimed to detect the prevalence of AF in sub-Saharan African subjects. Materials and methodsWe analyzed the prevalence of AF in 120 atlas vertebrae from the Raymond A Dart Collection of the University of the Witwatersrand, Johannesburg, South Africa. ResultsTwelve (13.3 %) atlases of the 90 that were from sub-Saharan African ancestry subjects presented at least one AF: the presence of AF frequency was 6.7 % in the Sotho sample, 23.3 % in the Xhosa sample and 10.0 % in the Zulu sample. However, no significant difference was found in their distribution regarding the presence of AF ratios (p = 0.221). The AF frequency was 3.3 % in the South African Caucasian subjects. No significant differences were found in their distribution regarding the presence of AF ratios between the Caucasian and the Sotho (p = 1.000), Zulu (p = 0.612) and Xhosa (p = 0.052) samples. ConclusionsOur research shows a tendency for a higher AF presence in Xhosa subjects. It has increased the knowledge of the AF prevalence in sub-Saharan Africa, drastically increasing the population.

Characteristics and evaluation of C1 posterior arch variation for transpedicular screw placement between patients with and without basilar invagination.

C1 transpedicular screw (C1TS) placement provided satisfactory pullout resistance and 3D stability, but its application might be limited in patients with basilar invagination (BI) due to the high incidences of the atlas anomaly and vertebral artery (VA) variation. However, no study has explored the classifications of C1 posterior arch variations and investigated their indications and ideal insertion trajectories for C1TS in BI. To investigate the bony and surrounding arterial characteristics of the atlas, classify posterior arch variations, identify indications for C1TS, evaluate ideal insertion trajectories for C1TS in BI patients without atlas occipitalization (AO), and compare them with those without BI and AO as control. A total of 130 non-AO patients with and without BI (52 patients and 78 patients, respectively) from two medical centers were included at a 1:1.5 ratio. The posterior arch variations were assessed using a modified C1 morphological classification. Comparisons regarding the bony and surrounding arterial characteristics, morphological classification distributions, and ideal insertion trajectories between BI and control groups were performed. The subgroup analyses based on different morphological classifications were also conducted. In addition, the factors possibly affecting the insertion parameters were investigated using multiple linear regression analyses. The BI group was associated with significantly smaller lateral mass height and width, sagittal length of posterior arch, pedicle height, vertical height of posterior arch, and distance between VA and VA groove (VAG) than control group. Four types of posterior arch variations with indications for different screw placement techniques were classified; Classifications I and II were suitable for C1TS. The BI cohort showed a significantly lower rate of Classification I than the control cohort. In the BI group, the subgroup of Classification I had significantly larger distance between the insertion point (IP) and inferior aspect of the posterior arch. In addition, it had the narrowest width along ideal screw trajectory, but a significantly more lateral ideal mediolateral angle than the subgroup of Classification II. Multiple linear regression indicated that the cephalad angle was significantly associated with the diagnosis of BI (B = 3.708, P < 0.001) and sagittal diameter of C1 (B = 3.417, P = 0.027); the ideal mediolateral angle was significantly associated with BMI (B = 0.264, P = 0.031), sagittal diameter of C1 (B = - 4.559, P = 0.002), and pedicle height (B = - 2.317, P < 0.001); the distance between the IP and inferior aspects of posterior arch was significantly associated with age (B = - 0.002, P = 0.035), BMI (B = - 0.007, P = 0.028), sagittal length of posterior arch (B = - 0.187, P = 0.032), pedicle height (B = - 0.392, P < 0.001), and middle and lower parts of posterior arch (B = 0.862, P < 0.001). The incidence of posterior arch variation in BI patients without AO was remarkably higher than that in control patients. The insertion parameters of posterior screws were different between the morphological classification types in BI and control groups. The distance between VA V3 segments and VAG in BI cohort was substantially smaller than that in control cohort. Preoperative individual 3D computed tomography (CT), CT angiography and intraoperative navigation are recommended for BI patients receiving posterior screw placement.

Multidetector computed tomography evaluation of origin, V2 segment variations and morphology of vertebral artery.

The current study aimed to determine the origin of vertebral artery (VA) on both sides and the levels of entry into respective foramen transversarium (FT), to evaluate possible effects of sex on the entry levels, and to investigate the frequency of VA dominance and VA hypoplasia based on the VA V2 segment. For this study, archived images of patients undergoing multidetector computed tomography (MDCT) examination of the chest and headneck for various reasons at Gaziantep University Medical Faculty Hospital were reviewed retrospectively. Three-dimensional reconstructions were performed for a total of 644 VA images from 322 patients using Horos software, and VA origin, the level of entry to FT and transverse diameters of both VA and FT were measured at the point of entry. It was found that, among males, the VA originated from the truncus brachiocephalicus on the right side in only 1 patient and from the aortic arch in 2 patients on the left side. Left VA emerging from the aortic arch was observed in 2 females. The right VA was found to enter the FT at C3 in 1 male, at C4 in 6 patients (5 males, 1 female), at C5 in 19 patients (3 males, 16 females), and at C6 in 300 patients (141 males, 159 females). The left artery entered the FT at C5 in 23 patients (9 males, 14 females) and at C6 in 298 patients (141 males, 157 females). Looking at the relationship between variations of VA origin and the levels of entry to the FT, it was observed that only one of the left VAs originating from the arcus aorta entered the FT at C6 and at C5 in all others. On the right side, there was only one VA originating from the truncus brachiocephalicus, which entered the FT at C3. Of the remaining 248 VAs originating from the subclavian artery, 5 VAs entered the FT at C4, 14 VAs at C5 and 229 VAs at C6. The measurements of VA diameters showed right VA hypoplasia in 14 patients and left VA hypoplasia in 17 patients. Also, the right VA dominance was found in 110 patients and the left VA dominance in 128 patients. A moderate, positive correlation was observed between VA and FT diameters in both sides. A regression analysis showed that a 1 mm change in the right VA diameter was associated with a 75% change in the FT diameter and a 1 mm change in the left VA diameter caused a 72% change in the FT diameter. An understanding of VA variations and FT morphometry is crucial for informed clinical practice. This will clearly affect the success rates of physicians in the diagnosis and treatment of pathologies involving cervical region. The presence of any VA variation in a patient should be investigated on computed tomography or magnetic resonance imaging images prior to surgery.

Radiological Assessment of Extracranial Vertebral Artery Variations: A Computed Tomography Angiography Study

We evaluated the incidence of intraforaminal and extraforaminal variations of the vertebral artery (VA) in the Omani population using computed tomography angiography (CTA). CTA results of 579 consecutive Omani patients (1158 VAs) were reviewed retrospectively for the analysis of unusual entrance transverse foramen (UE-V2), midline migration (MM), persistent first intersegmental artery (PFIA), and paracondylar process (PP) variations of VA. The anomalous origin and VA dominance were also determined. The sex and side differences in the incidence of these variations were analyzed using the Chi-square test. The incidence of UE-V2 was observed in 10.44% (121 out of 1158) of cases. The incidence of UE-V2 at different vertebral levels was observed in the sequence of C5 (71%) &gt; C4 (20.7%) &gt; C7 (7.43%) &gt; C3 (0.8%). The incidence of MM variation was 1.29%. PFIA and PP variations were found in 0.17% and 0.60% of cases, respectively. Left-dominant VA was identified in 44.7% (259 out of 579) of subjects. The incidence of VA variations was not significantly associated with either sex or side. Anomalous VA origin from arch aorta (3.5%) and right common carotid artery (CCA) (0.08%) was identified. The incidence of UE-V2 in Omani subjects is comparatively higher than that reported in other Asian populations. A rare case of VA originating from the right CCA was also identified.

Retrospective Study of Normal Variations in Vertebral Artery on Computed Tomography Angiography With Special Emphasis on Relevant Embryology.

Background The vertebral arteries (VA) nourish the posterior cerebral circulation. Planning neck and cervical interventions like drilling and instrumentation, which involves VA manipulation, require an in-depth acquaintance with the normal and variant patterns encountered in the origin and course of the VA. Embryological events involved in forming these variant patterns can be correlated to their prior disposition in the lower vertebrate's understanding which becomes crucial while planning cervical interventions. Study design This is a single-center, retrospective study. Materials and methods The study involved 70 patients of both sexes and was done from September 2021 to February 2022 in the Department of Radiodiagnosis and Imaging at North Eastern Indira Gandhi Regional Institute of Health and Medical Sciences (NEIGRIHMS), Meghalaya, India. The CT angiographies were studied for variations of VA under V1 - from origin to entrance into the foramen transversarium (FT), V2 - part inside FT, V3 - from its exit from FT till it pierces the cranial dura mater, and V4 - intracranial part. Further, VA was observed for its origin, dominance, level of entry in FT, and any associated anomalies. Results The VA was found mostly to be codominant. There was an opposite directional relationship between the basilar artery curvature and the dominance of VA. The association of ischemic events with hypoplastic VA was more on the left side (66.67%). Left VA originated from the aorta in 4.3% of subjects. One case presented a dual origin of VA. The abnormal origin of the LVA from the aorta showed a higher rate of abnormal entry into FT which was also found to be statistically significant. Conclusion Our study identifies and documents the anatomical variations present in VA specific to the population of northeast India by CT angiography and thus provides a much-needed reference for the healthcare professionals working in the field of Head and Neck interventions by providing opportunities further to understand these patterns for better diagnostic and therapeutic outcomes.

Anomalous Origin of the Left Vertebral Artery from the Aortic Arch: A Case Report

This study presents and describes the anatomical variation of the left vertebral artery arising from the aortic arch in two female cadavers, discovered during dissection in an anatomical laboratory setting. This anomaly was initially discovered during a routine cadaveric dissection of the neck of a 64‐year‐old female cadaver. This finding prompted an evaluation of the remaining twenty‐five cadavers in the lab, leading to the discovery of the same variation in an 83‐year ‐old female. In both cadavers, the left vertebral artery originated from the aortic arch in between the origins of the left common carotid artery and the left subclavian artery. This is a variation, as the vertebral artery is typically known to branch off of the first part of the subclavian artery on both the right and left side. Following this discovery of the anomaly in the laboratory, a literature review was conducted to understand the prevalence of this variation in the general population as well as its clinical implications.

Morphological characteristics of subaxial cervical pedicles and surrounding critical structures in patients with vertebral artery dominance - an anatomical study based on computed tomographic imaging

BackgroundNo study has assessed the feasibility and safety of cervical pedicle screw implantation in patients with vertebral artery dominance (VAD), a common vertebral artery (VA) variation which can increase VA injury (VAI) risk. This study was to assess morphological characteristics of the subaxial cervical pedicles and surrounding critical structures, and identify their correlations in patients with VAD.MethodsComputed tomography arteriography scans of 152 patients were used for retrospectively measuring parameters including pedicle outer width (POW), the distance from the lateral pedicle border to the closest part of VA (DPVA), diameter of VA (DVA), area of VA (AVA), area of transverse foramen (ATF) and occupational ratio of transverse foramen (TF). Moreover, correlations among some critical parameters were assessed.ResultsOne hundred eight males and 44 females, with a mean age of 55.9 years were included. POW was smaller on the dominant side than on the non-dominant side, whereas DPVA, DVA, AVA, ATF, and TF were larger on the dominant side than those on the non-dominant side. On both sides, POW < 4 mm and POW + DPVA < 5 mm were observed most frequently at C3 and C4. On both sides, POW was correlated to ATF, and ATF was correlated to DVA and AVA. DPVA was correlated to ATF on the dominant side.ConclusionPatients with VAD exhibited smaller POW on the dominant side, most frequently at C3 and C4. Dominant VA may indirectly affect POW. TF may be a key determinant of DPVA and POW.

Vertebral Artery Variations at the Craniovertebral Junction in “Sandwich” Atlantoaxial Dislocation Patients

ObjectiveTo summarize the vertebral artery (VA) pattern of 96 “sandwich” atlantoaxial dislocation (AAD) patients and to describe the strategies of reducing the injury of VA during surgery. MethodsFrom 2009 to 2020, we retrospectively reviewed the 3-dimensional computed tomography angiography data of 96 AAD patients combined with atlas occipitalization and C2–3 fusion, which were diagnosed as “sandwich” AAD and 96 patients as control group patients who were without atlas occipitalization, C2–3 fusion and any other cervical bone deformity at our institution. The variations of each side of VA were described in 3 different parts (C0–1, C1–2, and C2–3) according to the characteristics of the 3-part pathological structures in “sandwich” subgroup. ResultsOne hundred ninety-two sides of VAs in every group of patients were analyzed and every VA was described separately at 3 different level regions. There were different variations in these 3 different regions: 4 variations in the upper fusion region, 5 variations in the sandwiched region, and 6 variations in the lower fusion region in sandwich AAD patients. And the rate of VA deformity in sandwich AAD patients was much higher and more types of VA variations existed. ConclusionIn “sandwich” AAD patients, deformities of vertebral arteries in craniovertebral junction are more common, and the same VA may have deformities at different levels that severely affect surgical procedures. Therefore, preoperative imaging examination of VA for “sandwich” AAD patients is vital of guiding surgeons to avoid injury of VA during surgery.

The vertebral Artery Anomalous, Stenosis vs Hypoplasia as the leading cause of Stroke. An anatomical cross-Sectional Study of VA anomalies in Neck three-Dimensional computed Tomography Angiography

Introduction: A thorough understanding of the vertebral artery (VA) variations and course of the artery and its related branches could significantly enhance the efficacy and safety of interventions involving the neck and spine. Here, we aimed to investigate the incidence of various VA variations in individuals presenting with signs and symptoms of stroke with our neurology team. Material and Method: In this retrospective study we investigate CTA images of patients with signs and symptom of stroke who referred to specialized medical imaging centre. An experienced board-certified radiologist evaluated the CTA images, recording the characteristics of VA, regarding dominance and any possible anomalies. These included anomalous origin, anomalous route, anomalous branching, stenosis, hypoplasia, atresia, thrombosis, and dissection. All data were analyzed using SPSS version24 and Pearson Chi-Square and Fishers test used for anomaly and gender correlation. Results: A total of 125 patients (53.6% females; mean age, 60.7 (11-87)) were included. In the case of VA dominance, 66.4% of cases were co-dominant while 16.0% were right, and 12.8% were left dominant. Overall, males had more VA anomalies than females, 24.8% and 17.6%, respectively (in general, 42.4% of all participants) (p = 0.020). Among patients, 4.0% (n = 5) had an anomalous origin and anomalous branching was reported in 5 patients (4.0%). Among the variations, significant stenosis (18.4%) and hypoplasia (17.6%) were the most prevalent anomalies with the earliest one having the higher rate. While anomalous branching was reported in 5 patients (4.0%). Conclusions: VA variations are relatively common and should be addressed during procedures involving the neck region and would allow surgeons to avoid life threatening injury.

Akutna ishemija lijeve ruke nakon TEVAR-a zbog anatomske varijante vertebralne arterije

Aim: In this case we report acute left arm ischemia after thoracic endovascular aortic repair of the saccular thoracic aortic aneurysm due to a rare anatomical variation of the left vertebral artery. Case report: Thoracic aortic stent-graft was deployed to cover the aneurysm, but six hours later acute left arm ischemia occurred due to a rare form of vertebral artery origin from the aortic arch instead of from the left subclavian artery. This hostile anatomy led to an iatrogenic acute ischemia which was the indication for an emergency left-common-carotid-to-subclavian-artery bypass grafting. Conclusion: Multidisciplinary approach and careful pre-procedural planning should always be the standard procedure in complex cases to avoid this complication.

Incidental identification of the aberrant origin of left vertebral artery using magnetic resonance angiography: A case report

Background: The vertebral arteries originate from the root of the neck as the first branches of the subclavian arteries. Variations of vertebral arteries are congenital anomalies occurring during embryonic development. Anatomic variations of the left vertebral artery are clinically symptomless and recognized incidentally during angiographic assessments or imaging techniques so the diagnosis of these anomalies is a serious challenge. Anomalous origin of vertebral arteries may lead to neurologic disorders. It is, thus, important to identify variations of the large vessels of the aortic arch when planning neck and cervical spine interventions and diagnostic radiology. For this reason, we would like to present this rare case of left vertebral artery showing a different origin. Case report: In this work, we describe a 60-year-old female patient with headache, lethargy and blurred vision. We employed magnetic resonance angiography for both the brain and neck. There was no lesion in the brain. Incidentally, we found that the root of the left vertebral artery was anatomically aberrant. The left vertebral artery arose from the nearest section of the left external carotid artery, next to the bifurcation of the left common carotid artery, which is a rare variation. Conclusion: Understanding the state of anomalous variations of the origin of the vertebral artery might have crucial implications in angiographic and surgical procedures. It is beneficial to perform more screening with noninvasive studies like neck magnetic resonance angiography in clinical cases with potential symptoms coexisting with other diseases in order to predict possible future problems in intracranial and extracranial interventions. Keywords: Vertebral artery; external carotid artery; anatomic variation; magnetic resonance angiography.

Radiological anatomy of the intracranial vertebral artery in a select South African cohort of patients

The intracranial segment of the vertebral artery (VA) is the unique part of the artery where the two VAs join to form a single vascular channel, viz. the basilar artery. In addition to this typical description, anatomical variations have been described; the presence of anatomical variation has been associated with some pathological processes, neurological complications, and the risk of vascular diseases in the posterior circulatory territory. We evaluated the typical anatomical features and variations of the VA4 component of the VA in a South African population to provide useful data on the prevalence of variation and morphometry of the distal VA. The study is an observational, retrospective chart review of 554 consecutive South African patients (Black, Indian, and Caucasian) who had been examined with multidetector computed tomography angiography (MDCTA) from January 2009 to September 2019. We observed various anatomical variations in the VA4 segment of the VA. We report the incidence of VA hypoplasia, hypoplastic terminal VA, and atresia. Fenestration and duplicate posterior inferior cerebellar artery (PICA) origin were also observed. The left intracranial VA was significantly larger than the right. Our study shows that anatomical variation of the intracranial VA is common in the population studied, with a total prevalence of 36.5%. Understanding the patterns of anatomical variations of the VAs will contribute significantly to the interpretation of ischemic areas and diagnosis of various diseases in the posterior circulatory territory.

Esophageal cancer with right vertebral artery variation observed during thoracoscopic esophagectomy: a case report

BackgroundVariation of the vertebral artery bifurcation is rare. This branching abnormality can cause unexpected vertebral artery damage and bleeding during thoracoscopic esophagectomy. There are few reports of abnormal branching of the vertebral artery associated with neurosurgery but none related to esophagectomy. We report the case together with the results of the evaluation of vertebral artery bifurcation and length in 50 patients with esophageal cancer in our hospital.Case presentationThoracoscopic esophagectomy was performed on a 70-year-old patient with esophageal cancer. During lymph node dissection around the right reccurent laryngeal nerve, an unusual blood vessel was found running along the right subclavian artery. We determined this blood vessel to be the right vertebral artery branching far more centrally than usual. Because this anatomical abnormality was clarified, we could then recognize that the right reccurent laryngeal nerve coursed around the right vertebral artery and the right subclavian artery and thus was running in a larger arch than usual.ConclusionLong right vertebral artery may appear in the surgical field of the thoracoscopic esophagectomy. Knowledge of such anatomical variation is important to prevent iatrogenic injury of the right vertebral artery and the right reccurent laryngeal nerve.

Variations of the extracranial segment of vertebral artery as a bleeding risk factor.

Standart interventional procedures such as screw instrumentation, aortic arch endovascular surgery and cervical nerve blockade may be of fatal risk due to anatomic reason of variations in the proximal part of the vertebral artery (VA). The aim of this study is to study the VA variations of the extracranial segments to evaluate the frequency of the incident to demonstrate the importance of clinical condition strategy. The prevalence of variations and morphometric measurements of the VA in three-dimensional computed tomographic angiography (3D-CTA) scans were studied. Total 400 VA was investigated for the aortic arch origin of the VA, diameter of the VA, its level of entry into the transverse foramen, the dominance sides, and related basilar artery course. 3D-CTA radiographs of 200 Anatolian patients (120 men and 80 women with age range 17-90years). In most cases (approximately 94%), both sides of VA were the first branch of subclavian artery. While all the right VAs was branched from the subclavian artery, 6% of the left VAs were branched from the aortic arch. 2/3 of them originated from the proximal of the subclavian artery and 1/3 from the distal. The VA which were originating from the proximal of the classical anatomic pattern tended to enter the transverse foramen more distally than C6 level. VAs with a different level of entry than C6 are left-sided and aortic arch originated (out of 8 cases 3 had a level of entry at C5 and 2 at C4). The outer diameter ranges of the prevertebral part of the VA of subclavian origin and left VA of aortic arch origin were 3.2-3.6mm and 3.2-3.6mm, respectively. While the diameters of the right and left VAs were almost the same in approximately 20% cases, the left VA was dominant in up to 60% of cases. A significant relationship was found between the side of the dominant VA and in the course of the basilar artery. The relationship between the dominant side of VA and the course of the basilar artery of its own vessel has never been reported elsewhere. Such anatomical variations, routine preoperative 3D-CTA evaluation is mandatory to prevent the VA injury when C5-C2 instrumentation, anterior cervical decompression, cervical nerve blockade and aortic arch surgery are planned.

Vertebral artery variations revised: origin, course, branches and embryonic development.

The vertebral artery originates from the subclavian artery and is divided into four segments. The aim of this study is to investigate the anatomical variations in the course and branches of the vertebral artery. A research was performed via PubMed database, using the terms: "variations of vertebral artery AND cadaveric study", "variations of vertebral artery AND cadavers" and "anomalies of vertebral artery AND cadavers". A total of 24 articles met the inclusion criteria, 13 of them referring to variations of the origin of the vertebral artery, 9 to variations of the course and 3 to variations of its branches. On a total sample of 1192 cadavers of different populations, origin of the left vertebral artery directly from the aortic arch was observed at 6.7%. In addition, among 311 cadavers, 17.4% were found with partially or fully ossified foramen of the atlas for the passage of the vertebral artery, while the bibliographic review also showed variants at the exit site of the artery from the transverse foramen of the axis. Despite the fact that variations of both the course and the branches of vertebral artery are in most cases asymptomatic, good knowledge of anatomy and its variants is of particular importance for the prevention of vascular complications during surgical and radiological procedures in the cervix area.

Can Intracranial Vertebral Artery Hypoplasia be an Etiopathogenetic Factor for Barré-Ličou Syndrome Other than Arcuate Foramen? A Retrospective Clinical Study and Review of Literature.

To investigate the co-occurrence of the arcuate foramen (AF) variation of atlas and intracranial vertebral artery (V4) hypoplasia and, therefore, to understand the pathophysiology of Barré-Ličou syndrome (BLS). The AF localizes on the vertebral artery (VA) sulcus posterior to the atlas and has incomplete and complete types. Complete-type AF can exert pressure on the VA that passes through it, resulting in vertebrobasilar insufficiency finding, a BLS component. By the surgical decompression of VA at the AF level, complaints could be decreased in some cases. However, a reliable theory regarding BLS has not yet been established; therefore, the cases that do not respond to AF decompression have not been fully elucidated. We assumed that V4 hypoplasia that accompanies AF might be the main factor in the pathophysiology of BLS. Cervical computed tomography and magnetic resonance angiography images of 139 patients aged 14?88 years with head and neck pain and dizziness were retrospectively evaluated. Of the patients, 19.4% exhibited complete AF and 32.4% exhibited VA hypoplasia (VAH); 10% of the patients with VAH had accompanying contralateral complete AF variation. There was no significant relationship between complete AF and contralateral and ipsilateral VAHs (right side: p=0.527 and p=0.433, respectively; left side: p=1.000 and p=0.740, respectively). Our findings indicate that V4 hypoplasia is not the main factor of BLS pathophysiology. Furthermore, the rarity of the relationship suggests why some cases do not respond to decompressive surgery.

Hypoplasia of Fourth Part of Vertebral Artery and Its Clinical Significance.

Introduction:The anatomical and morphological variation of vertebral artery has clinical importance not only to the performance of interventional or surgical procedure itself but also to ensure circulation to the hindbrain.Aim of the Study:To analyze the morphological and morphometric variations of the fourth part of vertebral arteries.Materials and Methods:The present study was conducted in the Department of Anatomy, Vinayaka Mission's Kirupananda Variyar Medical College and Hospitals, Salem, Tamil Nadu, India. Fifteen adult human brains’ specimens acquired from embalmed human cadavers were utilized for the study. Morphology and morphometric analysis of the fourth part of vertebral arteries were done to demonstrate the variations. Vernier caliper was used for morphometric analysis.Results:The mean diameter of the fourth part of the left vertebral artery has been larger in size than the right vertebral artery with a mean of 2.55 mm ± 0.30 mm. In one specimen, the fourth part of the left vertebral artery was very narrow with a diameter of 0.1 mm and the right vertebral artery measured 0.4 mm.Conclusion:Hypoplasia of the fourth part of the vertebral artery is a contributing factor in acute ischemia of the brain. Morphological variations of the vertebral artery are considered as an etiological factor for conditions such as atherosclerosis, infarction, vascular malformations, transient ischemic attack and syndromes such as Wallenberg's and Medial Medullary syndrome. Vascular variations usually subject for controversy, and detailed knowledge of such variations serves as a key role in procedures such as magnetic resonance imaging, computed tomography, and neurovascular surgeries. The study will be done extensively to support the anatomical and morphological variations of vertebral arteries to make fruitful clinical implications.

Vertebral Artery Variation in Patients With Congenital Cervical Scoliosis: An Anatomical Study Based on Radiological Findings.

Observational, anatomical, radiological study. The aim of this study was to explore the incidence and type of vertebral artery (VA) variation in patients with congenital cervical scoliosis and approach their clinical importance during surgery. Congenital scoliosis of the cervical spine is usually sporadic and caused by a variety of bone structural anomalies. Most of the cases remain asymptomatic. Surgical intervention is the main management for patients with neurological compromise or with cosmetic demands. The operation involved more screw insertion and osteotomy than the regular degenerative cases. The incidence and pattern of VA variants in these patients have not been reported. Patients with congenital cervical scoliosis treated in our department were reviewed. We measured Cobb angle of cervical spine. We observed bilateral VAs and recorded variants. We measured their diameter in each segment through CT angiography. The bilateral diameter in each patient was then compared respectively. There is a total of 44 patients enrolled. The incidence of VA variation was 41% (18/44). Fifty percent (22/44) of patients had the dominant VA with no difference between concave side and convex side. Patients with a dominant VA had a larger Cobb angle than those who had not (30.25° vs. 23.24°, P < 0.05). The courses of VA were abnormal in 18 patients. Two patients had unilateral variant in V1 segment. Twelve patients had variants in V2 segment. Eight patients had variants in V3 segment. Three patients had VA variants in multiple sites. In patients with congenital cervical scoliosis, the dominance of VA is not related to the convex side or concave side, but patients with a dominance of VA have a larger Cobb angle. The incidence of variant in V2 and V3 segment is higher. A thorough evaluation of bilateral VAs is required before surgery. Extra cautions must be taken during surgery.Level of Evidence: 5.

In Reply: Three-Dimensional Evaluation and Classification of the Anatomy Variations of Vertebral Artery at the Craniovertebral Junction in 120 Patients of Basilar Invagination and Atlas Occipitalization.

To the Editor: We appreciate the comments of Sardhara et al1 regarding our paper entitled “Three-Dimensional Evaluation and Classification of the Anatomy Variations of Vertebral Artery at the Craniovertebral Junction in 120 Patients of Basilar Invagination and Atlas Occipitalization” published in Operative Neurosurgery.2 We regretted not citing the research by Sardhara et al3 in our paper, as there were so many papers concerning the vertebral artery (VA) variations at the craniovertebral junction (CVJ). We could not cite all the information in the literatures. In your study, the anatomical parameters between VA variations and bony deformity were measured and a total score for risk stratification of VA injury during surgery was calculated.3 Your paper had given many useful and beneficial clinical experiences. However, the preventive strategies of different type of VA injury and clinical value of anatomical parameters were majorly discussed in our paper.2 There might be some misunderstanding of the comments of Sardhara et al.1 In our study,2 the traditional three-dimensional (3D) computed tomography angiography (CTA) was used just as most of the literature reported. The limitation of the traditional 3D reconstruction software is that the circumambient osseous of VA cannot be transparent and the special course of VA variations in the osseous deformities cannot be clearly recognized. In our study, the separating, fusing, opacifying and false-coloring-volume rendering technique was used to process the traditional 3D-CTA image. Based on our experiences, it only takes another 5 to 10 min to realize the differentiation of anatomical structures with a different opacity value. Therefore, we concluded that such technique is a convenient and concise method for preoperative evaluation of safety screw placement and for identifying the risk of VA injury in congenital anomalies at the CVJ. In our center, we have treated CVJ anomalies since the 1980s and have accumulated experience of over 3000 cases. We started the VA research very early. As early as 2005, we had reported a kind of VA entering subarachnoid space at the C2 to C3 intervertebral level,4 which is consistent with the abnormal VA as a C3 segmental artery mentioned in the author's letter. With the number of cases increased over the years, we did further study with the biggest cohort. Although the abovementioned kind of VA variations is rare, we found it in 3 patients in our study. The result we reported was still earlier than those reported by Moon et al.5 Patients with basilar invagination and atlas occipitalization usually present abnormal anatomy of the VAs at the CVJ. In managing such complex diseases, spine surgeons are greatly challenged with issues regarding how to intraoperatively address the VA. Failure to recognize them may lead to catastrophic complications. In fact, multiple modalities have been routinely used to detect the aberrant VA, like the 3D imaging reconstruction technique, mixed reality technique and 3D printed technique. With the assist of these techniques, the risks of VA injury would be reduced and the optimal surgical results would be achieved for patients. Funding This study did not receive any funding or financial support. Disclosures The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.

Letter: Three-Dimensional Evaluation and Classification of the Anatomy Variations of Vertebral Artery at the Craniovertebral Junction in 120 Patients of Basilar Invagination and Atlas Occipitalization.

Letter: Three-Dimensional Evaluation and Classification of the Anatomy Variations of Vertebral Artery at the Craniovertebral Junction in 120 Patients of Basilar Invagination and Atlas Occipitalization.