Course Of Vertebral Artery Research Articles

A study of variations of subclavian artery and its clinical implication

Background: When the right subclavian artery directly arises from the arch of aorta (AOA) distal to the origin of the left subclavian artery, it is known as an aberrant right subclavian artery (ARSCA). It is a most common anomaly of AOA occurs in approximately 0.5–1.8% cases and usually remains asymptomatic. In case of ARSCA, commonly it has a retroesophageal course to reach the right side of the neck. Variations in origin and course of vertebral artery (VA) found in 7% cases, more on the left side than the right side. Objectives: To study the origin, course and branching pattern of the subclavian artery and discuss its embryology and histological changes of the variant artery. Materials and Methods: The 67 embalmed cadavers were utilized for dissection for MBBS students at various Medical Colleges in Patna, Bihar in the Department of Anatomy. The course and branching pattern of both side subclavian arteries were observed. Histopathological observations of variant arteries were also noted. Results: ARSCA with the retroesophageal course along with the right VA (RVA) was originating from the right common carotid artery was noted in one case. The aberrant VA traverse through the foramen transversaria of 5th cervical vertebrae. Histopathological observation of ARSA and RVA showed atherosclerotic changes. Conclusion: The knowledge of such variation is important for carrying out surgical procedure and clinically significant during diagnostic and interventional angiographic procedures.

A New Technique for the Surgical Treatment of Atlantoaxial Instability: C1 Lateral Mass and C2-3 Transfacet Screwing.

Atlantoaxial instability is a special entity that may be caused by many disorders such as trauma, tumor, arthritis, congenital malformation and infection. Atlantoaxial fixation is needed to provide stability, prevent neurological deficits and correct deformity. The objective of this study is to introduce an alternative technique for the treatment of atlantoaxial instability in patients who have vertebral artery anomaly, anomalous C2 or osteoporosis. C1-2-3 fixation was performed in a 50-years-old, male patient with atlantoaxial instability due to os odontoideum. C1 lateral masses identified and screw placement was performed. C2 facet joints were identified bilaterally. Superior margin of junction of pedicle and the lamina was used as the entry point and 3.5x22 mm screws were inserted from C2 facet joint to the C3 facet joint in mediolateral and craniocaudal direction under fluoroscopic guidance with caution. The posterior fixation screws are interconnected with two rods. Finally, autologous grafts were placed posterolaterally to encourage the fusion. Patient's complaints relieved after the surgery. C1-C2 instability wasn't seen in the postoperative radiological examinations. In the surgical treatment of C1-2 instability, our technique could help to reduce the possibility of vertebral artery injury in patients who have a vertebral artery course anomaly or when it is difficult to place C2 pedicle screws due to anomalous C2 pedicles and osteoporosis. High fusion rate could be achived with this technique due to passing through the four cortical surfaces. No wire or allograft was required. Thus, the instrumentation cost could be reduced.

Understanding the Course of Vertebral Artery at Craniovertebral Junction in Occipital Assimilation of Atlas: Made Simplified Using Conventional Angiography.

Introduction Preoperative assessment of vertebral artery (VA) is important to avoid its injury during surgery at craniovertebral junction (CVJ). The main concern is the course of third segment of VA (V3) while performing instrumentation at CVJ, that is, segment of VA from its course through transverse foramen of C2 to its course along the posterior arch of C1. This segment of VA includes its passage through C1 transverse foramen as well. This observational study was done to analyze the course, curvature, and termination of VA in patients with occipital assimilation of atlas at CVJ, a complex congenital anomaly, and compared with the normal course for better understanding especially by young neurosurgeons and spine surgeons. Materials and Method This is an observational study that included patients with occipitalized C1 with or without associated anomalies. Out of 30 patients of CVJ anomalies, 16 patients had occipitalized atlas. Digital subtraction angiography was done in all cases. It was done by selectively catheterizing the VA using standard Seldinger's technique and both anteroposterior and lateral projections were taken. Results The course of VA was not identical on either side in any individual. It was lengthened and tortuous in all patients. Different types of anomalous course were encountered like bypassing transverse foramen of C1, close relation with C1-2 facet joints, variable course along the posterior arch of C1, abnormal termination and fenestration of VA. Conclusion Craniovertebral junction anomalies are not only bony or neural, but are vascular too. Complex CVJ anomalies are associated with higher incidence of anomalous course of the VA, an important surgical consideration.

Foramen magnum meningiomas: surgical results and risks predicting poor outcomes based on a modified classification.

OBJECTIVE This study aimed to evaluate neurological function and progression/recurrence (P/R) outcome of foramen magnum meningioma (FMM) based on a modified classification. METHODS This study included 185 consecutive patients harboring FMMs (mean age 49.4 years; 124 females). The authors classified the FMMs into 4 types according to the previous classification of Bruneau and George as follows: Type A (n = 49, 26.5%), the dural attachment of the lesion grows below the vertebral artery (VA); Type B (n = 39, 21.1%), the dural attachment of the lesion grows above the VA; Type C1 (n = 84, 45.4%), the VA courses across the lesion with or without VA encasement or large lesions grow both above and below the bilateral VA; and Type C2 (n = 13, 7.0%), Type C1 plus partial/total encasement of the VA and extradural growth. RESULTS The median preoperative Karnofsky Performance Scale (KPS) score was 80. Gross-total resection (GTR) was achieved in 154 patients (83.2%). Lower cranial nerve morbidity was lowest in Type A lesions (16.3%). Type C2 lesions were inherently larger (p = 0.001), had a greater percentage of ventrolateral location (p = 0.009) and VA encasement (p < 0.001), lower GTR rate (p < 0.001), longer surgical duration (p = 0.015), higher morbidity (38.5%), higher P/R rate (30.8%, p = 0.009), and poorer recent KPS score compared with other types. After a mean follow-up duration of 110.3 months, the most recent follow-up data were obtained in 163 patients (88.1%). P/R was observed in 13 patients (7.2%). The median follow-up KPS score was 90. Compared with preoperative status, recent neurological status was improved in 91 (49.2%), stabilized in 76 (41.1%), and worsened in 18 (9.7%) patients. The multivariate Cox proportional hazard regression model demonstrated Type C2 (HR 3.94, 95% CI 1.04-15.0, p = 0.044), nontotal resection (HR 6.30, 95% CI 1.91-20.8, p = 0.003), and pathological mitosis (HR 7.11, 95% CI 1.96-25.8, p = 0.003) as independent adverse predictors for tumor P/R. Multivariate logistic regression analysis identified nontotal resection (OR 4.06, 95% CI 1.16-14.2, p = 0.029) and pathological mitosis (OR 6.29, 95% CI 1.47-27.0, p = 0.013) as independent risks for poor outcome (KPS score < 80). CONCLUSIONS The modified classification helped to predict surgical outcome and P/R in addition to the position of the lower cranial nerves. Preoperative imaging studies and neurological function should be reviewed carefully to establish an individualized management strategy to improve long-term outcome.

Three-dimensional computed tomography angiographic study of the vertebral artery in patients with congenital craniovertebral junction anomalies

To describe vertebral artery (VA) course at the C0-C1-C2 complex in patients with congenital bony craniovertebral junction (CVJ) anomalies. We studied the course of 169 VAs in 86 patients with congenital bony CVJ anomalies [basilar invagination (42), os odontoideum (33), and irreducible atlantoaxial dislocation (11)]. Occipitalized atlas occurred in 41 patients (30 complete and 11 partial). Using axial, coronal and sagittal three-dimensional computed tomography (3D-CT) angiograms, we traced the VA bilaterally at the CVJ and correlated the course to the presence or absence of occipitalization of the atlas. Of the 73 arteries associated with occipitalization of atlas, all had an abnormal course-58 (78.4%) coursed through a canal within the C0-C1 fused complex and 15 (20.3%) coursed below the C1 posterior arch, and it was absent unilaterally in one patient. There were 96 arteries associated with a non-occipitalized atlas and only 15 (15.3%) were abnormal-eight coursed below the C1 posterior arch, four coursed above the C1 arch in the absence of a C1 foramen transversarium, one passed through a canal in C0-C1 and two arteries were absent unilaterally. Sixty vertebral arteries (34 on the right and 26 on the left side) had a redundant loop situated at a distance of≥5mm from the C1 lateral mass in patients with os odontoideum and irreducible atlantoaxial dislocation. In occipitalization of the atlas, the VA course is usually abnormal-typically passing through a canal within the C0-C1 fused complex or below the C1 arch. A redundant VA loop is more likely to be seen in os odontoideum and irreducible atlantoaxial dislocation. Careful study of the vertebral artery course with 3D CT angiography is mandatory while contemplating CVJ realignment surgery in congenital anomalies of the CVJ.

Six Different Vertebral Artery Configurations, in Three Subjects Commanding Different Approaches for C1-C2 Distraction and Fixation in Cases of CVJ Anomaly: A Case Series

Introduction There are various choices to fix up Atlanto-Axial dislocation (AAD) and Basilar invagination (BI), it may be Posterior only, Anterior only or Combined. Many surgeons refrain from “posterior only” approach of C1-C2 distraction (as described by Atul Goel and Lahiri) because of the fear of Vertebral artery (VA) injury and it's poorly understood course between C1, C2, and Occipital condyles. We describe details of preoperative work and subsequently adopted, customized surgical plans, as per VA configuration to distract &amp; fix the C1-C2 joint to achieve reduction in AAD and BI without harming the Vertebral artery. This case series covers most of the variations of VA around C1-C2 for learning purpose. After seeing this work up, many surgeons may allay their anxieties and take up this single stage corrective measure to achieve correction of deformities in cases of AAD &amp; BI. In the due course author will also explain different variations of Vertebral artery not only in different individuals, but also in same subject on either sides. We describe the adaptive surgical methods taken based on these data to avoid injury to VA, and still achieve a firm distraction and fixation at C1-C2 with this single stage. The technique can thus be extrapolated in various other cases of AAD and BI with hardly any exception. Material and Methods Three serial patients with an established diagnosis of Atlanto-axial dislocation and Basilar invagination are described. All three were evaluated with 3-D MPR CT with vertebral artery angiography (CTA-VA), and MRI at Cervico-medullary junction (MRI-CMJ). The VA in one subject was going through pedicle on one side and in another subject, it was going around the C1-C2 facet joint, while in another case it was entirely intra-spinal. The radiological evaluation was done in both pre and post operative period to describe anomalies of CVJ, different courses of VA and vectors thus used for potential instrumentation. Postoperative scans were used to see adequacy of fixation. Results There was a clear evidence of highly variable course in VA of all three subjects. There were different courses in right and left VAs as well, commanding different choices of instrumentation on both sides in a single individual. All patients achieved reduction of AAD &amp; BI and there was no injury to the vascular structure in question. They all improved in clinical signs and symptoms in the due course. Conclusion Authors conclude that it's mandatory to subject all patients to CT angiography in an order to view the Vertebral artery course wrt C1-C2 facets, which is not only variable in different individuals but also, on both sides in same individual, hence even in a single patient we may need different instrumentation to achieve the same goal. The authors also conclude that instrumentation at C1-C2 without CTA-VA is not only dangerous but can be fatal as well, hence instrumentation done without the above mentioned study should be considered a mandatory practice in the safest interest of patients and to achieve optimum and customized instrumentation.

Risks for Vascular Injury During Anterior Cervical Spine Surgery: Prevalence of a Medial Loop of Vertebral Artery and Internal Carotid Artery.

Observational study using a retrospective single-institute database. To investigate the prevalence of a medial loop (ML) of the vertebral artery (VA) and internal carotid artery (ICA), which might be an anatomical risk factor for arterial injury in anterior cervical surgeries. Anterior cervical spine surgeries are generally considered to be safe and effective. VA injury is one of the most serious complications during anterior procedures. Several articles have reported this complication, which might be because of the anomalous course of VA at V2 segment. The prevalence and anatomical features of those high-risk cases were, however, not investigated. Consecutive Japanese subjects, who underwent contrast-enhanced computed tomography (CT) or computed tomographic angiography (CTA) for reasons other than evaluation of cervical artery disease from November 2011 to October 2012 in our institution, were reviewed. Exclusion criteria included poor images, past surgery, and endovascular intervention of cervical spine and its vessels. The definition of ML was set as the course of VA and ICA extended medially inside the uncovertebral joint. We also investigated whether those anomalous courses were detectable by plain CT. A total of 1251 subjects with age ranging from 14 to 93 years with a mean of 56.1 years were surveyed. Among them, 1054 subjects were eligible and the others were excluded. A total of 421 subjects were male, and 633 were female. There were 10 cases (1%) with an ML of the VA, and 2 (0.2%) cases with a medial loop of internal carotid artery. Five of the 10 cases with a medial loop of vertebral artery were aberrant into the vertebral body, which were detectable by plain CT. Importantly, the other five cases could not be seen on the CT. One percent of all subjects showed higher anatomical risk for VA and ICA injury during anterior surgery, half of which were undetectable by plain CT. Preoperative evaluation for vascular anatomy may be necessary for safer surgical treatment. 4.

Craniovertebral junction 360°: A combined microscopic and endoscopic anatomical study.

Objectives:Craniovertebral junction (CVJ) can be approached from various corridors depending on the location and extent of disease. A three-dimensional understanding of anatomy of CVJ is paramount for safe surgery in this region. Aim of this cadaveric study is to elucidate combined microscopic and endoscopic anatomy of critical neurovascular structures in this area in relation to bony and muscular landmarks.Materials and Methods:Eight fresh-frozen cadaveric heads injected with color silicon were used for this study. A stepwise dissection was done from anterior, posterior, and lateral sides with reference to bony and muscular landmarks. Anterior approach was done endonasal endoscopically. Posterior and lateral approaches were done with a microscope. In two specimens, both anterior and posterior approaches were done to delineate the course of vertebral artery and lower cranial nerves from ventral and dorsal aspects.Results:CVJ can be accessed through three corridors, namely, anterior, posterior, and lateral. Access to clivus, foreman magnum, occipital cervical joint, odontoid, and atlantoaxial joint was studied anteriorly with an endoscope. Superior and inferior clival lines, supracondylar groove, hypoglossal canal, arch of atlas and body of axis, and occipitocervical joint act as useful bony landmarks whereas longus capitis and rectus capitis anterior are related muscles to this approach. In posterior approach, spinous process of axis, arch of atlas, C2 ganglion, and transverse process of atlas and axis are bony landmarks. Rectus capitis posterior major, superior oblique, inferior oblique, and rectus capitis lateralis (RCLa) are muscles related to this approach. Occipital condyles, transverse process of atlas, and jugular tubercle are main bony landmarks in lateral corridor whereas RCLa and posterior belly of digastric muscle are the main muscular landmarks.Conclusion:With advances in endoscopic and microscopic techniques, access to lesions and bony anomalies around CVJ is becoming easier and straightforward. A combination of microscopic and endoscopic techniques is more useful to understand this anatomy and may aid in the development of future combined approaches.

Vertebral Artery Injury during Routine Posterior Cervical Exposure: Case Reports and Review of Literature

Study Design Case series. Objective We report the unusual occurrence of vertebral artery injury (VAI) during routine posterior exposure of the cervical spine. The importance of preoperative planning to identify the course of the bilateral vertebral arteries during routine posterior cervical spine surgery is emphasized. Methods VAI is a rare but potentially devastating complication of cervical spinal surgery. Most reports of VAI are related to anterior surgical exposure or screw placement in the posterior cervical spine. VAI incurred during posterior cervical spinal exposure surgery is not adequately addressed in the existing literature. Two cases of VAI that occurred during routine posterior exposure of the cervical spine in the region of C2 are described. Results VAI was incurred unexpectedly in the region of the midportion of the posterior C1–C2 interval during the initial surgical exposure phase of the operation. An aberrant vertebral artery course in the V2 anatomical section in the region between C1 and C2 intervals was identified postoperatively in both patients. A literature review demonstrates a relatively high incidence of vertebral artery anomalies in the upper cervical spine; however, the literature is deficient in reporting vertebral artery injury in this region. Recommendations for preoperative vertebral artery imaging also remain unclear at this time. Conclusions Successful management of this unexpected complication was achieved in both cases. This case report and review of the literature highlights the importance of preoperative vertebral artery imaging and knowledge of the course of the vertebral arteries prior to planned routine posterior exposure of the upper cervical spine. In both cases, aberrancy of the vertebral artery was present and not investigated or detected preoperatively.

THE STUDY OF CERVICAL VERTEBRAE SHOWING VARIATIONAL PRESENTATION OF FORAMEN TRANSVERSARIUM

Foramen transversarium is formed by the vestigial costal element fused to the body and the true transverse process of the vertebra. Present study carried out on 60 cervical vertebrae that showing variations in the presentation of foramen transversarium. Among them, 25 vertebrae show double (accessory) foramen transversarium, 15 vertebrae having double bubble appearance (incomplete double foramen transversarium) and 20 vertebrae having asymmetrical foramen transversarium. The results of present study shows incidence of variations more common on right side as compare to left in which unilateral accessory foramen transversarium more common than bilateral, even incomplete double foramen transversarium and narrowing of foramen transversarium more common on right side. Conclusion from this study etiology of variation in foramen transversarium may be related with the variation in the course of vertebral artery due to development reason.

Anterior Extrapharyngeal Fixation of the Atlanto–Axial Joints

Introduction The atlanto–axial joints can be easily exposed from a unilateral submandibular extrapharyngeal approach. Decortication and intrajoint bone grafting can be easily accomplished. Rigid anterior fixation of the joint is possible without any risk to the vertebral arteries. Materials and Methods Between April 2008 and September 2014, 95 patients, 50 male and 45 female patients, in the age group of 12 to 82 years, were offered this procedure. 55 patients had anterior transarticular screws, 40 patients had anterior screw plate fixation (AAD 63 patients, tuberculosis 20, fixed AAD with Basilar invagination 12). All patients underwent preoperative dynamic X-rays of craniovertebral junction, computerized tomography (CT scan) of C1–C2 static and dynamic study with bone window settings and 3D reconstruction, magnetic resonance imaging (MRI), and MR angiography to study the course of vertebral artery. Stevenson technique (22 patients) for exposure to reach the prevertebral space at C1–C2. Technique 1: plate and screws (C1 lateral mass and C2 body); Technique 2: anterior transarticular screws across C1–C2 joint. Results Average procedure time was 3 hours, no case required blood transfusion, reoperation occurred in seven cases; three screw malposition both ipsilateral (right sided), reoperated within 48 hours and screw repositioned correctly. One overdistraction of C1–C2 joint due to screw not piercing the C1 lateral mass and pushing the lateral mass of C1 away from C2 (because of inadequate drilling of C1 lateral mass). Reoperated on the 3rd day and lateral mass of C1 drilled correctly and the screw passed successfully. Two inadequate excisions of odontoid process had to be removed transorally after 3 weeks because of excessive backward angulation of odontoid process. One case of screw loosening that was due to incorrect plate contouring, reoperation after 3 weeks when patient had come for first postoperative follow-up. Follow-up in 75% for 24 months. Rigid fixation in 100%, mortality 0%. Conclusion Anterior extrapharyngeal approach allows for reduction of the atlanto–axial dislocation, opportunity for bone grafting of the joint, and with anterior C1 lateral mass and C2 body screw plate fixation or anterior transarticular screws, provides rigid fixation without any risk to the vertebral artery, venous plexus, or spinal cord.

Risk stratification of vertebral artery vulnerability during surgery for congenital atlanto-axial dislocation with or without an occipitalized atlas.

Variability in dimensions and course of vertebral artery (VA) makes it vulnerable to injury during surgery for congenital atlanto-axial dislocation (AAD) with or without an occipitalized atlas. This prospective study attempts to define anatomical variations that render VA at the craniovertebral junction (CVJ) vulnerable to injury during transoral decompression and posterior stabilization procedures; and, to propose a classification that helps in preoperative risk stratification. A prospective study. 104 patients (65 with AAD; 39 controls) underwent a three-dimensional multiplanar computed tomographic angiogram to study anatomical variations in VA size, course, and anomalous medial deviation as well as in the type of axial isthmus and rotational deformity/tilt at the CVJ. The VA/foramen transversarium diameter; "stretched loop" sign of VA; and C1-2 facet joint angle were also assessed. A medial VA deviation that brought it in close proximity to the trajectory of the surgical approach was evaluated (P ≤ 0.05 significant). An increased predisposition to VA injury was present in 23 (35.4%) patients (persistent first intersegmental artery [n = 20; 30%]; fenestrated VA [n = 1; 1.53%], and low-lying posterior inferior cerebellar artery [n = 2; 3.0%]) where VA crossed the C1-2 facet joint; 8 (12%) with an anomalous medial deviation; 12 (18%) with a high-riding VA at C2 and a narrow axial isthmus; and 13 (20%) with rotation/tilt at the CVJ. A normal score of 5 was obtained in 21 patients; and a score of 6-9 (that progressively indicated an increased vulnerability of VA to iatrogenic injury) in 44 patients. The "AAD with an occipitalized atlas" group was associated with a significant medial deviation of VA (right: P = 0.00 and left: P = 0.001). A preoperative detailed risk assessment of anatomical variations in the size and course of VA at the CVJ significantly reduces chances of its iatrogenic injury.

English

Foramen transversarium are located on the transverse process of cervical vertebrae and are the cardinal features of cervical vertebrae. These foramina are known to exhibit variations in size, shape and may be absent or duplicated. Keeping this in mind, a study was done to record these variations. A hundred and twenty dry typical cervical vertebrae procured from department of anatomy were used for this study. Unilateral double foramen transversarium were seen in 2.5% cases while 4.16% cases showed bilateral double foramen transversarium. 0.83% cases showed symmetrical foramen transversarium and another 1.66% cases showed incomplete foramen transversarium. The normal factor responsible for such anomalies is developmental or related to variation in course of vertebral artery. The recognition of this variation provides safety and efficiency for the posterior approaches of the cervical spine.

Variant course of right vertebral artery - a case report

AbstractThe Vertebral artery is the first branch of subclavian artery. It is an important source of blood supply to the brain. During dissection of an adult male cadaver, a unilateral variation in the course of Vertebral artery was found. The right Vertebral artery took origin from the subclavian artery and entered foramen transversarium of fourth cervical vertebra. An understanding of the variability of the Vertebral artery remains most important in angiography &amp; surgical procedures where an incomplete knowledge of its anatomy can lead to complications.

Commentary on: "Vertebral Artery Anomalies at the Craniovertebral Junction: A Case Report and Review of the Literature".

The authors report a case of an unstable C1 fracture with magnetic resonance imaging demonstrating rupture of the transverse ligament. Posterior vertebral artery anomaly in the form of a right persistent first intersegmental artery was identified preoperatively in the region of the right posterior C1–C2 lateral mass interval. The surgical plan was altered to avoid the anomalous vertebral artery and the patient was successfully managed with an uncomplicated occiput to C3 instrumentation and fusion procedure. The literature review includes a discussion of the work by Uchino et al who have reported a persistent first intersegmental artery in up to 3.2% of normal subjects and an overall prevalence of craniovertebral junction vertebral artery anomalies of 5%.1 This article is an important addition to the existing literature as it highlights the relatively high prevalence of vertebral artery anomalies at the craniovertebral junction. The case described involves an aberrant vertebral artery with an anomalous course located posteriorly between the C1 and C2 lateral masses. This particular vertebral artery anomaly poses great risk to the conventional placement of C1 lateral mass screws through previously described techniques involving the exposure of the C1 lateral mass or placement of the screw through the C1 posterior ring. The anomaly was identified preoperatively by computed tomography angiography in this case, and intraoperative vertebral artery injury was avoided. The utility of the use of routine of preoperative imaging studies to demonstrate the course of the bilateral vertebral arteries before any planned exposure of the craniocervical junction is clearly implied in this case report. The significance of this case report and review of the literature lies in the identification of the increased risk of complication involving vertebral artery injury through a routine posterior cervical spine surgical exposure. Much of the existing literature involving vertebral artery injury in cervical spinal surgery has focused on injuries incurred with anterior cervical spinal surgical procedures. Tortuous anterior course of the vertebral artery in the subaxial cervical spine has been well described by Curylo et al in approximately 5.5% of subjects.2 Multiple reports of injury to the vertebral artery during anterior cervical decompression surgery exist in the literature.3 Five studies reported rates of 0.10 to 1.96%, depending on the type of anterior cervical spine procedure.3 There remains, however, a paucity of literature with respect to vertebral artery injury incurred with a posterior cervical surgical exposure. Molinari et al recently reported vertebral artery injury in two cases involving a persistent first intersegmental artery in the region of C1–C2. Both injuries were incurred with routine posterior exposure of the C1–C2 anatomy. A review of the existing literature demonstrates few publications on this topic.3 The authors should be applauded for this work, which raises a greater sense of awareness as to the increased potential for vertebral artery injury during posterior cervical spine exposure in the region of the craniocervical junction. Their work underscores the need for thorough preoperative evaluation of the course of the vertebral artery before performing operative procedures on the cervical spine.

Analysis of 3-dimensional course of the intra-axial vertebral artery for C2 pedicle screw trajectory: a computed tomographic study.

A retrospective radiological study. To analyze the course of intra-axial vertebral artery (IAVA) and evaluate the relationship between the 3-dimensional (3D) courses for IAVA with respect to safe trajectory for C2 pedicle screw (C2PS). The VA at the level of C2 has a distinct 3D course. The traditional concept of "high riding (HR)" VA was based on sagittal plane but does not provide all the 3D course of IAVA for safe C2PS placement. However, 3D course of IAVA has not been previously analyzed. Three-dimensional, vascular-enhanced computed tomographic scans on the cervical spine of 100 patients, 200 IAVA (male to female ratio = 50:50; mean age, 58.4 yr) were analyzed. (1) The arterial parameters including (1) "medial-shifting (MS)" (A: lateral, B: neutral, C: medial to C3 transverse foramen [TF]) and (2) "HR" (0: below C2TF, 1 within C2TF, 2: above C2TF) of IAVA was measured. (2) The bony parameters including pedicle diameter, medial convergence angle, and sagittal angle of C2PS were measured. Correlation between the arterial and bony parameters, differences between sex, laterality, dominance of VA, and age were analyzed. MS (grade A, 37.5%; B, 37%; and C, 25.5%) and HR (grade 0 in 34%, 1 in 42%, and 2 in 24%) showed significant correlation with each other (P < 0.001). The main patterns of IAVA were A-0 (26%), B-1 (26.5%), and C-2 (18.5%). Higher grade of MS and HR showed significantly smaller pedicle diameter, larger medial convergence angle, and smaller sagittal angle (P < 0.001). Female sex and older age are factors that showed significantly higher grade of MS and HR (P < 0.001). Tortuosity of IAVA was greater in the female sex and it also increased with aging. The different IAVA courses significantly influenced the pedicle diameter and the safe trajectory for C2PS; therefore, these factors should be considered before planning C2 pedicle screw placement. 3.

Vertebral artery anomalies at the craniovertebral junction in the US population.

Retrospective review. To evaluate the prevalence of anatomical variations of the vertebral artery at the craniovertebral junction and the posterior arch of the atlas in the US population. Recent studies from Asia have reported a 5% to 10% prevalence of a persistent first intersegmental vertebral artery and 1% to 2% prevalence of a fenestrated artery. These anomalous vertebral artery courses lie directly over the starting point for atlas lateral mass screw insertion. The relatively high reported prevalence of these anomalies suggests that routine preoperative computed tomographic angiogram be considered prior to upper cervical fixation. We have not observed this anomaly as commonly as reported. The authors analyzed the records of 975 patients from a level I trauma center and adjacent university hospital who underwent computed tomographic angiography to evaluate the incidence of anomalous variations in the third segment of the vertebral artery. These results were compared with similar studies performed in Korea and Japan. The mean age of the patients was 52.9 years. The ethnic distribution of the patients was as follows: 69.3% of the patients were Caucasian, 11% Asian, 10.8% African American, and 6% Hispanic. The prevalence of a persistent intersegmental artery was 0.01% (1/975); a fenestrated vertebral artery was 0.01% (1/975); and origin of a posterior inferior cerebellar artery was 0.4% (4/975). The incidence of these anomalies was significantly lower than those previously published from Korea and Japan. Vertebral artery course anomalies in the upper cervical spine were rare (0.42%) in our patient population. This finding contrasts with recent published reports from Asia, citing as high as a 10% rate of vertebral artery presence over the starting point for C1 lateral mass screw insertion. On the basis of the infrequent occurrence of this anomaly, we do not recommend routine computed tomographic angiography when planning upper cervical instrumentation. N/A

Rotational Vertebral Artery Compression Syndrome: Bow Hunter's Stroke

Rotational vertebral artery occlusion is a rare syndrome characterized by vertebrobasilar insufficiency secondary to position-dependent occlusion of the vertebral artery. Most cases reported in the literature have been attributed to osteophytic compression, either from the occipital condyle or within the transverse foramen. However, vertebral artery dissection secondary to motion in the setting of anomalous anatomy has not been reported.To the authors' knowledge, rotational vertebral artery occlusion and dissection secondary to anomalous entrance into the transverse foramen have never been reported. The authors describe the case of a 42-year-old male who presented with multiple posterior circulation transient ischemic attacks. Standard digital subtraction cerebral angiography demonstrated a non−flow-limiting right vertebral artery dissection, while dynamic digital subtraction cerebral angiography was remarkable for right vertebral artery stenosis that worsened with neck rotation. Computed tomography angiography of the neck revealed an anomalous course of the right vertebral artery, which entered the transverse foramen at C4 with preforaminal compression by the anterior tubercle of the C5 transverse process. The patient had no further symptomatic events after decompression of the vertebral artery by resecting the anterior C5 tubercle.In the setting of codominant vertebral circulation and unilateral bony compression, the authors propose that neck rotation led to vertebral artery trauma, causing dissection complicated by thromboembolism. This is a novel and unusual entity that is different from Bowhunter's syndrome.

Anomalous course and diameter of left-sided vertebral arteries – Significance and predisposing factors in clinical practice

The purpose of this study was to determine whether any correlation exists between the level of entry of vertebral arteries (VAs) into the foramen transversarium (FT) and their anomalous course or diameter. To our knowledge there are no studies in the literature concerning the diameter of the vertebral artery (VA) as an impact factor on entrance level. Computed tomography angiography (CTA) images of the aortic arch (AA) and its branches, obtained at the Department of Radiology, Medical University of Łódź from May 2009 to April 2012, were reviewed and the entrance points into the FT were determined. Left vertebral arteries arising directly from the AA more often had an anomalous entrance point to the foramen transversarium and were more frequently hypoplastic. In addition, hypoplastic VAs entered the FT at an anomalous level more often than VAs with normal diameter. The left vertebral arteries arising directly from the aortic arch are often more hypoplastic and often enter the foramen transversarium at a different level from the C6 vertebrae. In patients with hypoplastic VA detected on the basis of ultrasound Color Doppler examination, the presence of anomalies must be considered when planning surgical treatment.

Feasibility of Rigid Upper Cervical Instrumentation in Children

Tomographic analysis of occipitocervical (OC) instability in children aged between 2 and 6 years. To assess the feasibility of screw placement in various bone anchors in the OC region in young children. The use of rigid stabilization in the pediatric patients is gradually increasing. No study has comprehensively assessed the suitability of bony anatomy of the OC region for screw placement, especially in younger children. A total of 50 patients (2-6 y, 10 each) who underwent skull and cervical CT scanning were randomly queried using an x-ray database. Screw placement was considered feasible if there was at least 0.5 mm of bone around a 3.5 mm screw through its trajectory. When the bony channel measured 3.5-4.0 mm, placement was considered possible, but difficult. Statistically, most measures were similar from the right to left sides. External occipital protuberance thickness increased from a mean value of 8.60 mm to a mean value of 10.73 mm. The mean C1 lateral mass length and width varied from 15.26 to 16.67 mm (P=0.056) and 7.34 to 8.58 mm (P=0.0005), respectively, with age. The mean C2 pedicle width and length varied from 3.85 to 4.18 and 17.11 to 19.8 mm, respectively, with age. The mean C2 laminar screw length increased from 20.4 to 22.66 mm with age (P<0.001). C2 lamina widths did not vary much by age. The mean C1-C2 transarticular path length and height increased from 26.7 to 33.6 mm and 2.58 to 3.09 mm, respectively, with age. The width was less directly variable by age (2.68-3.09 mm). Standard 3.5 mm screws can be used for OC and upper cervical instabilities in children aged between 2 and 6 years. Some anchor points appeared safer compared with others. The occipital keel, C1 lateral mass, and C2 laminae offered adequate space for screw placement in almost all cases. C2 pedicles offered adequate space in 49 sides and barely adequate space in 25 pedicles. Transarticular screws could be safely placed in only 4 of 100 sides. Close radiographic assessment of the vertebral artery course and bony architecture are recommended before surgery in pediatric patients with OC and upper cervical instability.