A comprehensive review of the vertebral artery anatomy

BACKGROUND

The vertebral arteries (VA) play a critical role by supplying nearly one-third of the brain's blood flow, predominantly contributing to the posterior circulation. These arteries may need to be exposed in a various cranial and cervical procedures and offers access to investigate or treat vascular lesions by endovascular means related to the posterior circulation. Given its complex anatomy, which is subject to numerous variations, and its role in supplying vital brain regions, a thorough understanding of the VA's anatomy is paramount for any related procedure.

OBJECTIVE

To provide a comprehensive overview of vertebral artery anatomy and its relevance in contemporary clinical practice.

METHODS

Dissection of the entire vertebral artery length using cadaveric specimen, combined with a comprehensive literature review.

RESULTS

The vertebral artery can be subdivided into four segments. Each of these segments has its own unique topographic anatomy with its variations, anastomoses, and significance in surgery.

CONCLUSION

As surgical and endovascular techniques continue to evolve with technological improvements, we are now more equipped than ever to manage complex lesions involving the VA. However, with its increasingly complexity comes the necessity for a deeper and more comprehensive understanding of the VA. Possessing the detailed knowledge of the VA is vital for the successful execution of any procedure involving it.

Applied anatomy of the vertebral arteries for endovascular neurointerventions

The vertebral arteries (VAs) constitute most of the arterial supply to the posterior cerebral vascular circulation. They have anatomical specificities and may have variants that are critical for neurointerventionists to recognize in order to design open or endovascular surgical treatment. This review addresses each segment of the VA including its origin and discusses the branches and relevant anatomical features for neurointerventions.

Anatomy of the craniocervical junction - A review

An in-depth understanding of the anatomy of the craniocervical junction (CCJ) is indispensable in skull base neurosurgery. In this paper, we discuss the osteology of the occipital bone, the atlas (C1) and axis (C2), the ligaments and the muscle anatomy of the CCJ region and their relationships with the vertebral artery. We will also discuss the trajectory of the vertebral artery and review the anatomy of the jugular foramen and lower cranial nerves (IX to XII). The most important surgical approaches to the CCJ, including the far lateral approach, the anterolateral approach of Bernard George and the endoscopic endonasal approach, will be discussed to review the surgical anatomy.

Delimitation of the risk area of the vertebral artery during the paramedian suboccipital approach

OBJECTIVE

The V3 segment of the vertebral artery (V3-VA) is at risk during diverse approaches to the craniovertebral junction. Our objective is to present a system of anatomic and topographic landmarks to identify the V3-VA during the paramedian suboccipital approach (PMSOA) with the help of minimal or basic tools.

MATERIAL AND METHODS

The first was a retrospective analysis of the angiotomography (CTA) of 50 patients over 18-years old, and 9 anatomical dissections. A series of lines were defined between the different bony landmarks. Within this lines the risk area of the vertebral artery (RAsV3-VA) and the risk point of the vertebral artery (RPsV3-VA) were defined. The second stage was a prospective study, where the previously defined measurements were carried out by using neuronavigation in 10 patients (20 sides) operated with the PMSO approach in order to confirm the presence of the V3 segment in the RAsV3-VA and RPsV3-VA.

RESULTS

In the first stage, the V3 segment was found in the middle third of the X line in 96,6% of the cases. The distance between the inion and the UCP (percentile 5) was 20 mm and to the LCP (percentile 95) was 40 mm. In the range between the UCP and the LCP, in the middle third of the inion-mastoid line (RAsV3-VA), we found 90% of the V3-VA. The measurements taken during the second stage revealed that the artery was in the middle third of the X line in 97% of the cases. 85% of the patients presented the total of the V3s-VA on the RAsV3-VA and in 85% there was a direct relationship with the V3 segment and the RPV3s-VA.

CONCLUSION

We propose an easy-to-implement system to delimit the risk area of the V3-VA during the PMSOA. We believe that these landmarks provide a practical, reliable, costless and useful tool that could decrease the risk of lesion of the V3-VA during this approach without the need of using.

Kinking, coiling and diameters of vertebral artery first segment and their relationships to sex and side

INTRODUCTION

Recent information on tortuosity in the prevertebral (V1) segment of the vertebral artery is based on case reports rather than systematic data on its presence, types, diameters, and sex- or left-right differences.

Arterial Vascular Structures Running Through Retrotransverse Foramen and Retrotransverse Groove of the Atlas Vertebrae

OBJECTIVE

Retrotransverse foramen (RTF) and retrotransverse groove (RTG) are anatomic variations of the atlas (C1) vertebrae. RTF contains an anastomotic vein connecting atlanto-occipital and atlanto-axodian venous sinuses. The purpose of this study was to analyze the arterial vascular structures running though the RTF and RTG.

METHODS

Three-dimensional volume rendered computed tomography angiography (3D VR CTA) images of 427 patients (264 men, 163 women; age 17-87 years) were reviewed and evaluated using the RadiAnt DICOM Viewer (version 5.0.2; Medixant, Poznan, Poland). The incidence of RTF or RTG, the incidence of the V3 segment of vertebral artery variants, and the artery vascular structures inside the RTF and RTG anatomic variation of C1 were analyzed.

RESULTS

Fifty (11.7%) atlases presented RTF anatomical variant; 113 (26.5%) atlases presented RTG anatomical variants. The incidence of the V3 segment of vertebral artery variants was 0.94% (4 of 427). Three (0.7%) were persistent first intersegmental artery and 1 (0.2%) was the fenestration of the vertebral artery on left side. In 4 cases of C1 vertebral artery V3 segmental variants, there were no RTF and RTG. No artery vascular structure was found in RTF or RTG.

CONCLUSIONS

The RTF or RTG of C1 was a common anatomical variant. No arterial vascular structure runs though the RTF or RTG. The presence of C1 RTF and RTG variants had no effect on the V3 segmental course of the vertebral artery. Preoperative understanding of these variations using 3D CTA are helpful for the safe execution of the upper cervical posterior approach surgeries.

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

STUDY DESIGN

Observational, anatomical, radiological study.

OBJECTIVE

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.

SUMMARY OF BACKGROUND DATA

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.

METHODS

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.

RESULT

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.

CONCLUSION

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.

Rare anatomic variation on a 10,000-year-old South American skeleton: the case of Iuzu, Toca dos Coqueiros, Piauí State, Brazil

PURPOSE

A skeleton named Iuzu has been unearthed from an exceptional middle Holocene burial in Toca dos Coqueiros site, in Serra da Capivara National Park (UNESCO World Heritage Site, Piauí State, Brazil). During a bioarchaeological analysis of its remains, we discovered that Iuzu was suffering from rare vertebral malformations. A double foramen transversaria, the agenesis of a foramen on the atlas and the hypoplasia of the transverse process of the axis have been highlighted. We aimed to deduce the clinical consequences of the malformation on the patient's health.

METHODS

We proceeded to macroscopic observation and radiography of the bones, then we search for other examples of such a pathology in archaeological litterature.

RESULT

The malformation caused vascular insufficiency that may have led to neurological lesions leading to various pains and troubles. The very rare malformations Iuzu presented have not been found on a paleoindian skeleton from South America so far.

CONCLUSION

This case allowed us to examine the conditions of selection of individuals buried in southern Piauí during the Middle Holocene, during which time this rite does not seem to predominate.

Comparative analysis of surgical exposure and freedom between the subtonsillar, endoscope-assisted subtonsillar, and far-lateral approaches to the lower clivus: A cadaveric study

The far-lateral (FL)approach is a classic technique for skull base surgeries involving the lower clivus (LC).Recently, a modified suboccipital midline approach known as the subtonsillar (ST) approach, along with the endoscope-assisted subtonsillar (EST) approach, has been described as a minimally invasive technique to treat LC lesions. However, there is no quantitative study on comparing these approaches together for reaching LC. We aimed to compare surgical exposure and freedom provided by ST, EST, and FL approaches for various targets at LC. These approaches were performed on each side of five cadaveric specimens (total 10 sides), and relevant parameters were quantified and compared using a repeated measures ANOVA test. FL approach yielded the greatest surgical area (237.8 ± 56.0 mm²) and exposure, including lengths of glossopharyngeal nerve (16.2 ± 1.9 mm), hypoglossal nerve (11.4 ± 2.4 mm), vertebral artery (23.9 ± 3.3 mm), followed by EST and ST approaches. For surgical freedom, FL approach provided the greatest angle of attack (90.0 ± 14.0° at jugular foramen, 95.1 ± 15.8° at hypoglossal canal, 83.4 ± 31.4° at bifurcation point of posterior inferior cerebellar artery and vertebral artery). Our systematic comparison suggests that EST approach, compared to ST approach, can significantly increase surgical exposure to the medial side of LC, but FL approach still provides the greatest surgical exposure and freedom at LC. Despite the limitations of a cadaveric study, our quantitative data can update the literature on currently available surgical techniques for reaching LC and better inform preoperative planning in this area. Further studies should be performed to evaluate these approaches in clinical practice.

Is the asymmetry between the vertebral arteries related to cerebral dominance?

Background/aim

The two vertebral arteries (VAs) are usually unequal in size; the left one is generally larger than the right one. It was hypothesized that the asymmetry results from the need of the dominant cerebral hemisphere for more glucose and oxygen, i.e. more blood supply. In this study, we aimed to test this hypothesis in patients by evaluating their arterial diameter and hand preference, as it is the most common criterion to determine the dominance of the hemisphere.

Materials and methods

The study was performed with 844 participants who consented to participate in the study. We identified the dominant cerebral hemisphere by asking participants about their hand preference. Then we measured both the VA diameter and VA flow volume by Doppler ultrasonography. After demonstrating the asymmetry, correlation was tested.

Results

Among 844 participants included in the study, the mean diameter of the right VA was 3.14 ± 0.35 mm and that of the left VA was 3.41 ± 0.54 mm, while the mean flow volume of the right VA was 119.21 ± 44.98 mL/min and that of the left VA was 151.45 ± 57.26 mL/min. It was recorded that 771 (86.43%) participants were right-handed and 73 (8.18%) were left-handed.

Conclusion

No significant relationship was found between the increased blood demand of the dominant cerebral hemisphere and the vertebral artery dominance.

Tonic-clonic seizure during the ultrasound-guided stellate ganglion block because of an injection into an unrecognized variant vertebral artery: A case report

RATIONALE

Recent years have witnessed a marked improvement in the safety and accuracy of nerve blocks with the help of ultrasound and other visualization technologies. This study reports a challenging case of a severe complication during the ultrasound-guided stellate ganglion block.

PATIENT CONCERNS

A 28-year-old male patient with refractory migraine complained episodic pulsatile pain with photophobia, haphalgesia of the scalp for 3 years.

INTERVENTIONS

Ultrasound-guided stellate ganglion block with 4 ml of 1% lidocaine was administrated.

OUTCOMES

A sudden loss of consciousness and tonic-clonic seizure was occurred after negative aspiration and test dose. Further sonographic examination revealed a variation in the left vertebral artery, which remained unrecognized during the needle insertion because of its sliding ability under the differential pressure applied by the probe.

LESSONS

Inadvertent intra-arterial injection of a local anesthetic agent could be minimized under the ultrasound guidance with various protective strategies, including the determination of any prior variation, optimizing the block route, maintaining a constant probe pressure, and using saline for the test dosage. This case resulted in the implementation of new protocols of the ultrasound-guided stellate ganglion block in our department.

Accuracy evaluation of placements of three different alternative C2 screws using the freehand technique in patients with high riding vertebral artery

An observational study.To evaluate the safeties of placing three different alternative C2 screws using the freehand technique under high riding vertebral artery (HRVA) and to analyze the C2 morphometry in patients with HRVA.A retrospective analysis of radiologic data was performed on patients that underwent C2 instrumentation from September 2004 to December 2017. Two hundred fifty-one patients were included, and 90 of these patients (35.9%) had a unilateral or bilateral HRVA. We placed three alternative C2 screws including superior pars, inferior pars, and translaminar screws. Computed tomography was used to assess cortical breeches of screw placement and obtain morphometric measurements of C2 pars and lamina, that is, superior pars height/length, inferior pars length, and laminar thickness/length. We used the modification of the all India Institute of Medical Sciences outcome to define cortical breach.In total, 117 alternative C2 screws were inserted in 90 patients; 7 superior pars screws (6%), 69 inferior pars screws (59.0%), and 41 translaminar (35%) screws. Although cortical breaches occurred during 31 screw placements (26.5%), these were unacceptable in only two cases (1.7%). No symptomatic neurovascular complication was observed after screw placement in any case. Mean height of C2 superior pars was 3.8 ± 1.8 mm and mean thickness of C2 lamina was 5.2 ± 1.1 mm. Mean lengths of superior pars, inferior pars, and lamina were 17.8 ± 3.0 mm, 13.6 ± 2.2 mm, and 26.7 ± 3.3 mm, respectively. Superior pars height and lamina thickness < 3.5 mm that was a minimal diameter of cervical screw were 49.6% and 6.8%, alternative C2 screw was not available in these cases.Placements of alternative C2 screws using the freehand technique were achieved accurately and safely in patients with HRVA. However, preoperative morphometric evaluation is essential to determine the best option for C2 instrumentation and C2 screw length to avoid neurovascular complications.

Prevalence and Types of Aortic Arch Variants and Anomalies in Congenital Heart Diseases

RATIONALE AND OBJECTIVES

Aortic arch (AA) variants and anomalies are important to recognize in patients with congenital heart disease (CHD) before surgery or intervention. The aim was to study the prevalence of AA anomalies and variants in patients with CHD compared to a control group. The secondary outcome was to report the associations between common variations of AA and specific types of CHD.

MATERIALS AND METHODS

After institutional review board approval, computed tomography studies of 352 CHD patients and control group of 400 consecutive computed tomography scans of the thorax were evaluated. The AA was assigned to one of seven common types, and their distribution was compared between CHD and control. The distribution of the AA anomalies and variants was evaluated as regard specific types of CHD and the visceroatrial situs.

RESULTS

Normal three-vessel branching pattern was the commonest in both groups, but was present in only 50.5% in the CHD compared to 68.5% in the control group, p < 0.00001. Right AA and aberrant right subclavian artery were significantly more common in CHD than control group (18.1% versus 0.25%, p < 0.00001) and (4.5% versus 0.25%, p = 0.0001), respectively. Direct aortic origin of left vertebral artery was insignificantly more common in CHD group (4.2% versus 2.7%, p = 0.258). Brachiobicephalic trunk was significantly more common in control than CHD group (27.7% versus 19.3%, p = 0.007).

CONCLUSION

Normal three-vessel AA was significantly less common in CHD. AA anomalies (right arch and aberrant right subclavian) were more common in CHD than control, while AA variants (brachiobicephalic trunk and direct aortic origin of left vertebral artery) were not.

Like a hole in the head: Development, evolutionary implications and diseases of the cranial foramina

Cranial foramina are holes in the skull through which nerves and blood vessels pass to reach both deep and superficial tissues. They are often overlooked in the literature; however they are complex structures that form within the developing cranial bones during embryogenesis and then remain open throughout life, despite the bone surrounding them undergoing constant remodelling. They are invaluable in assigning phylogeny in the fossil record and their size has been used, by some, to imply function of the nerve and/or blood vessel that they contained. Despite this, there are very few studies investigating the development or normal function of the cranial foramina. In this review, we will discuss the development of the cranial foramina and their subsequent maintenance, highlighting key gaps in the knowledge. We consider whether functional interpretations can be made from fossil material given a lack of knowledge regarding their contents and maintenance. Finally, we examine the significant role of malformation of foramina in congenital diseases such as craniosynostosis.

Aberrant Right Vertebral Artery with a Diverticulum of Kommerell: Review of a Rare Aortic Arch Anomaly

The normal aortic arch branching pattern is of a three-vessel arch with the vertebral arteries arising from the subclavian arteries. There are a variety of well-known symptomatic and asymptomatic aortic branching patterns widely reported in the literature. An anomalous right vertebral artery with a diverticulum of Kommerell is an extremely rare variant, with few other cases reported in the literature. Herein, we review the embryology of the aortic arch and vertebral artery, the various types of Kommerell's diverticula and the clinical significance of this anomaly.

Variations of Occipital Artery-Posterior Inferior Cerebellar Artery Bypass: Anatomic Consideration

BACKGROUND

Advances in diagnosis of posterior inferior cerebellar artery (PICA) aneurysms have revealed the high frequency of distal and/or dissecting PICA aneurysms. Surgical treatment of such aneurysms often requires revascularization of the PICA including but not limited to its caudal loop.

OBJECTIVE

To examine the microsurgical anatomy involved in occipital artery (OA)-PICA anastomosis at various anatomic segments of the PICA.

METHODS

Twenty-eight PICAs in 15 cadaveric heads were examined with the operating microscope to take morphometric measurements and explore the specific anatomy of bypass procedures.

RESULTS

OA bypass to the p2, p3, p4, or p5 segment was feasible with a recipient vessel of sufficient diameter. The loop wandering near the jugular foramen in the p2 segment provided sufficient length without requiring cauterization of any perforating arteries to the brainstem. Wide dissection of the cerebellomedullary fissure provided sufficient exposure for the examination of some p3 segments and all p4 segments hidden by the tonsil. OA-p5 bypass was placed at the main trunk before the bifurcation in 5 hemispheres and at the larger hemispheric trunk in others.

CONCLUSION

Understanding the possible variations of OA-PICA bypass may enable revascularization of the appropriate portion of the PICA when the parent artery must be occluded. A detailed anatomic understanding of each segment clarifies important technical nuances for the bypass on each segment. Dissection of the cerebellomedullary fissure helps to achieve sufficient exposure for the bypass procedures on most of the segments.

Quantitative assessment of vertebral artery anatomy in relation to cervical pedicles: surgical considerations based on regional differences

OBJECTIVE

To quantify the anatomic relationship between the Cervical pedicle screw (CPS), vertebral artery (VA), and related anatomic structures in the Saudi population.

METHODS

This retrospective single center study included 50 consecutive patients (35 males) with normal neck findings on computed tomography angiography performed for trauma or vascular evaluation between 2012 and 2014. Radiologic parameters were assessed and correlated with age, weight, height, and body mass index (BMI).

RESULTS

Mean age, weight, height, and BMI were 45.74+/-18.93 years, 79.72+/-21.80 kg, 164.74+/-11.53 cm, and 29.38+/-6.13 kg/m2, respectively. Mean cervical pedicle diameter (PD) increased from the cranial to caudal vertebrae (p=0.0001). Mean free zone (FZ) value, defined as the distance between the lateral CP border and medial VA border, was 1 mm (range 0.95-1.16 mm). The VA entry into the transverse foramina was at C6 level on both the right 92% and left side in most patients 94%. However, the right and left side level of VA entry differed in 14% of individuals.

CONCLUSION

The PD and FZ are smaller in Saudi Arabians than in western populations. Assessment of VA entry at each level should be performed on an individual basis as the level of VA entry can differ in the same patient. Anatomic variations between different geographic areas should be studied to provide better surgical guidance.

[Data on ultrasonographic anatomy of precanal segment of the vertebral artery]

Described in the article are the results of using ultrasonographic duplex scanning for studying anatomical peculiarities of the precanal segment of the human vertebral artery.

PATIENTS AND METHODS

Ultrasonographic duplex scanning (USDS) of the extracranial portions of brachiocephalic vessels was performed in a total of 215 inpatients without haemodynamically significant stenoses of the arteries of the vertebrobasilar basin. The patients found to have pathological alterations in the vertebrobasilar basin were excluded from the examined group. We studied the first segment of the vertebral artery from the origin to its entry into the canal of the transverse processes of cervical vertebrae (V1 segment according to the ultrasonographic nomenclature). We measured the diameter of the vertebral artery, assessing the pattern the vessel's passage, presence of pathological tortuosity, topographic interrelations between the V1 segment of the vertebral artery and structures of the neck, as well as analysing age-specific alterations in the anatomy of the vertebral artery.

RESULTS

By means of duplex scanning we in a non-invasive manner managed to gain a deeper insight into the anatomical peculiarities of the passage and structure of the initial portion of the human vertebral artery, as well as the differences in the structure between the contralateral vertebral arteries. We determined the average values of the diameters of the vertebral artery, its area, topographical relationships with the surrounding anatomical reference points along the length of the precanal segment, available for visualization by this method of study, and age-related peculiarities of the anatomy of the vertebral artery.

CONCLUSIONS

Ultrasonographic duplex scanning of the extracranial portions of brachiocephalic vessels in humans is an effective, available and accurate technique making it possible to assess the anatomy of the initial portion of the vertebral artery. The average values of the diameters and area of the transverse section of the left vertebral artery turned out to be significantly greater than similar values of the right vertebral artery in the overwhelming majority of cases. Due to structural peculiarities of the aortic arch branches, in particular, independent origin of the left subclavian artery from the aortic arch, the left vertebral artery has, as a rule, greater length than the right one and differs by the topographical correlations with the surrounding structures on the neck, which is confirmed by the ultrasonographic method of study. The ultrasonographic method of study makes it possible to sufficiently effectively assess the difference in depth of the passage of the trunk of the vertebral artery in tissues of the fascial spaces of the neck in representatives of various types of the body-build. We also revealed a tendency towards a tortuous passage of the vertebral artery in the precanal segment in 35-44% of cases irrespective of the body-build, age and gender.

Vertebral artery terminating in posterior inferior cerebellar artery: A normal variation with clinical significance

A vertebral artery (VA) terminating in a posterior inferior cerebellar artery (PICA) is often considered to be a normal variation associated with VA hypoplasia. We aimed to investigate the clinical significance of this cerebrovascular variant. A total of 80 patients with clinically evident cerebrovascular events in posterior circulation were examined by duplex sonography and magnetic resonance angiography (MRA). Eighty healthy subjects who had MRA check-up were recruited as controls. PICA termination of the VA (PICA-VA) was identified as the VA not communicating with the basilar artery (BA) but ending into a PICA. We compared the prevalence of PICA-VA and associated hemodynamic parameters between the patients with and without PICA-VA, and investigated their relationships with VA hypoplasia. The prevalence of PICA-VA was higher in the patient group than in the controls (18.7% vs. 6.3%, p = 0.015). Most measurements (73.3%) of PICA-VA did not fit the criteria of VA hypoplasia. In comparison with the non-PICA-terminating group, the PICA-VA has a smaller diameter (3.7 ± 0.7 mm vs. 3.0 ± 0.5 mm, p < 0.001), lower mean velocity (241 ± 100 mm/sec vs. 164 ± 88 mm/sec, p < 0.01), and higher pulsatility index (1.3 ± 0.5 vs. 1.9 ± 0.6, p < 0.001). Moreover, a smaller diameter of the BA (3.2 ± 0.5 mm vs. 2.5 ± 0.9 mm, p = 0.004) and the posterior cerebral artery (PCA) (2.0 ± 0.1 mm vs. 1.6 ± 0.1 mm, p = 0.006) were also noted in the PICA-VA group. The higher prevalence of PICA-VA in the patient group with smaller diameter of VA, BA and PCA reflected its clinical significance, suggesting that PICA-VA may have a detrimental impact on cerebral hemodynamics. However, the sample is small, and further studies are needed with larger sample size for confirmation.

The Anatomy and Physiology of the Vertebral Nerve in Relation to Cervical Migraine

The anatomy of the vertebral nerve was investigated in humans and in monkeys. The effect of stimulation of the vertebral nerve and the cervical sympathetic trunk in the monkey was studied. The vertebral nerves in man and monkey represent a series of deep grey rami communicantes which form intersegmental neural arcades around the vertebral artery between C7 and C3. Above C3 the vertebral artery is accompanied by direct branches from the C1–3 ventral rami. Electrical stimulation of either the vertebral nerve or the cervical sympathetic trunk had a minimal effect on vertebral blood flow. In contrast, sympathetic stimulation had pronounced effects on carotid flow and resistance. Anatomically and physiologically there are no grounds to support the hypothesis that irritation of the “vertebral nerve” is the pathogenetic mechanism of cervical migraine.

Management of the Vertebral Artery at the Craniocervical Junction

OBJECTIVES: To study the surgical anatomy of the vertebral artery at the craniocervical junction and its related structures defining reliable landmarks for its safe exposure.

DESIGN: Ten sides of 5 fresh cadavers were dissected using the lateral approach to the craniocervical junction.

RESULTS: Experience gained in studying the anatomic details of the vertebral artery at the craniocervical junction in cadavers from its exit at the transverse foramen of the second cervical vertebra to the vertebrobasilar junction provided the initial background for us to use the lateral approaches to the skull base to safely manage 4 cases with pathology reaching the close vicinity of vertebral artery at the craniocervical junction.

CONCLUSION: Thorough knowledge of the anatomy of the vertebral artery is mandatory before attempting surgery at the craniocervical junction. There are reliable landmarks that, when followed, could facilitate safe exposure and identification of the artery.

The Sternomastoid Branch of the Occipital Artery: A Surgical Landmark for the Spinal Accessory Nerve in Selective Neck Dissections

OBJECTIVE: To evaluate the anatomic relationship between the spinal accessory nerve (SAN) and the sternomastoid branch of the occipital artery (SBOA) and its utility as a surgical landmark during a selective neck dissection (SND).

STUDY DESIGN AND SETTINGS: Consecutive patients undergoing SND for squamous cancer from October 1, 2004 to February 28, 2005 were enrolled in this study. During surgery the distance between the SBOA and the point of insertion of the SAN into the sternomastoid muscle (SMM) was measured.

RESULTS: Twenty-four patients underwent 33 SND. The distance between the SBOA and SAN ranged between 1 and 11 mm, with a mean of 6.2 mm and a median of 6 mm.

CONCLUSION: The relationship between these 2 structures has a range and constancy that is acceptable as a landmark.

SIGNIFICANCE: This article presents a useful adjunct for location of the SAN in the anterior neck during SND.

EBM RATING: C

Diagnosis of a C3 segmental type of vertebral artery by magnetic resonance angiography: report of two cases

We report two cases in which the vertebral artery (VA) entered the spinal canal via the intervertebral foramen at the C2-C3 disc level, an extremely rare variation regarded as a C3 segmental type of VA, that we diagnosed by magnetic resonance angiography. The C2 segmental type of VA, in which the VA enters the spinal canal via the C1-C2 intervertebral space, is relatively common. It is important to identify these variations before surgery of the craniovertebral junction or interventional procedures to prevent complications.

[Construction of a human cervical spine with bilateral vertebral artery fluid-solid coupling model]

OBJECTIVE

To construct a human cervical spine with bilateral vertebral artery fluid-solid coupling model.

METHODS

Helical CT images under the principle of reverse engineering and meshed in finite element model（FEM） related software were used to establish a human cervical spine with bilateral vertebral artery fluid-solid coupling model. In the process of modeling of vertebral body, vertebral artery, ligament, intervertebral disc, cartilage and endplate large anatomic data and cadaver experiments results were referenced. From the morphology and function the simulation of model with real physiological status was tested.

RESULTS

The study showed that the stress concentration on the surface of vertebral body and the blood wall of the bilateral vertebral artery, and the result of the volume flow rate-time curve of bilateral vertebral artery of the model were consistent with the published literatures. This model was well consistent with the clinical phenomenon.

CONCLUSION

The three-dimensional FEM of the human cervical spine established by the introduced method has been effectively verified. The modeling method would provide a new tool for research on the cervical spine biomechanics.

[The specific features of the anatomical structure of the artery of labyrinth (an anatomical and topographical study)]

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).

[MORPHO-FUNCTIONAL CHARACTERISTICS OF KIMMERLE ANOMALY]

The study material included 105 isolated bone preparations of the atlas, 100 radiographs of the cervical region of the spine, 650 spiral computed tomography (SCT) scans and 224 protocols of duplex ultrasound scanning of extracranial portions of brachiocephalic arteries and transcranial duplex scanning. Kimmerle anomaly was detected in 18% of cases in the bone material, in 17% of the cases of SCT and in 15% of cases during radiological examination. The anomaly more often is unilateral, rarely--bilateral; it may be located medially or laterally, while the vertebral artery canal more frequently is closed, less commonly--open. Among the patients with Kimmerle anomaly, hemodynamically significant asymmetry of blood flow velocity in the vertebral arteries was detected in 78.5% of cases. Thus, the most important method of Kimmerle anomaly detection is SCT with contrast-enhanced artery imaging. However, each of the research methods successively. Each of research methods used consistently allows to obtain information both on anatomical variability of atlas developmental abnormalities (morphological characteristics) and on possible functional disorders, morphological basis of which is Kimmerle anomaly.

Application of vertebral artery ultrasonography in enlistment-age male student pilots

The aim of this study was to investigate the vertebral artery (VA) morphology of enlistment-age male student pilots with ultrasound to provide a basis for early diagnosis of potentially asymptomatic cervical vertigo. Ultrasound results of the origin position, diameter and hemodynamics of the VA in 935 cases of student pilots with a mean age of 18.0 y were analyzed. The inner diameters of both sides of the VA differ: the left is larger than the right statistically (p < 0.001). Moreover, the peak systolic velocity of the left VA is significantly greater than that of the right (p < 0.001). Congenital VA anomalies in age-appropriate male student pilots included inner diameter variation, course variation and origin position variation. The incidence of course variation or origin position proportion was low (3.46%, 32/925), and origin position variation was often accompanied by inner diameter variation or course variation. This study confirms that there are a variety of congenital abnormalities in the vertebral arteries of enlistment-age male student pilots, and a VA diameter <2.5 mm may be a reasonable criterion for diagnosis of VA hypoplasia.

[Anatomical study on vertebral artety and its application in transpedicle screw fixation for upper cervical vetebrae]

OBJECTIVE

To investigate the relationship of upper cervical pedicle and vertebral artery (VA) location in order to improve the safety of transpedicular screw insertion.

METHODS

The vertebral arteries on 12 sides of 6 adult pate cadaverous specimens were dissected. The distance between VA and VA groove at the atlas needling point of transpedicle screw, and the distance between VA and the inner edge of axis cervical foramen, and the VA external diameter in axis cervical foramen were measured respectively.

RESULTS

The distance between VA and VA groove was (1.96 ± 0.72) mm on the left and (1.99 ± 0.61)mm on the right at the atlas needling point of transpedicle screw, the distance between VA and the inner edge of axis cervical foramen was (2.23 ± 0.43) mm on the left and (2.30 ± 0.39) mm on the right, the VA external diameter in axis cervical foramen was (3.03 ± 0.48) mm on the left and (2.98 ± 0.75) mm on the right.

CONCLUSION

It is unlikely to injury VA when the transpedicle screws of upper cervical vertebrae were implanted correctly besides high straddled VA, and the individualization must be performed in the process.

Vascular geometry of vertebrobasilar tree with and without aneurysm

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.

Ipsilateral arcuate foramen and high-riding vertebral artery: implication on C1-C2 instrumentation

BACKGROUND CONTEXT

Several methods for C1-C2 stabilization have been described in the literature. These include C1-C2 transarticular and C1 lateral mass screws. In patients with aberrant anatomy such as a high-riding vertebral artery (VA) or the presence of an arcuate foramen at C1, there exists a higher risk of VA injury. This may lead to excessive bleeding, stroke, and possibly death. There have been several studies determining the incidence of arcuate foramen and high-riding VA occurring individually in the general population, but none have determined their occurrence simultaneously.

PURPOSE

To determine the prevalence of ponticulus posticus and high-riding VA occurring simultaneously in the general population.

STUDY DESIGN

Radiological study.

METHODS

One hundred consecutive computed tomography (CT) scans of the cervical spine were reviewed. Scans that contained an arcuate foramen were identified, and it was indicated whether the foramen was right sided, left sided, or bilateral. In the same group, the thickness of the isthmus and the internal height of the lateral mass of C2 were measured. The VA was considered high riding if the isthmus thickness was less than 5 mm or the isthmus internal height was less than 2 mm.

RESULTS

Fourteen out of one hundred (14%) patients had a fully formed arcuate foramen. Of these, six were left sided, three were right sided, and five were bilateral. In addition, there were 24 (24%) patients with partially formed ponticulus posticus. Thirty-two (32%) patients were identified to have a high-riding VA. Of these, 13 were left sided, 9 were right sided, and 10 were bilateral. Five (5%) had an ipsilateral arcuate foramen and high-riding VA.

CONCLUSIONS

The arcuate foramen and high-riding VA are common anomalies that are often not recognized. Although ipsilateral high-riding VA and arcuate foramen rarely occur in the general population, proper identification of these anomalies on preoperative CT scan facilitates planning the safest technique for C1-C2 instrumentation.

Variations in diameters of vertebro-basilar tree in patients with or with no aneurysm

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.

[Clinical significance of vertebral artery MRA to vertebral artery type of cervical spondylosis' diagnosis and treatment]

OBJECTIVE

To study clinical significance of vertebral artery magnetic resonance angiography (MRA) to vertebral artery type of cervical spondylosis' diagnosis and treatment.

METHODS

There were two groups in the study, which were observation group and control group. There were 53 patients in observation group,including 19 males and 34 females,with a mean age of (52.51 +/- 11.29) years. There were 30 subjects in control group,including 10 males and 20 females,with a mean age of (48.11 +/- 12.21) years. Based on the vertebral artery MRA picture,the course and caliber of vertebral artery were compared between two groups.

RESULTS

The abnormal incidence of course and caliber of vertebral artery in observation group was higher than that of control group, which had statistic difference (P=0.000). Furthermore, the patterns of abnormal course and caliber of vertebral artery in observation group were complicated and diverse, but the regional circuity and stegnosis was the most common pattern,about 47.18%(25/53). The cause of circuity and stegnosis was vertebra Gu-Cuofeng,about 43.41% (23/53).

CONCLUSION

The vertebral artery MRA provides a guidance for the diagnosis of abnormal course and caliber of vertebral artery in vertebral artery cervical spondylosis.

Mapping of cerebral perfusion territories using territorial arterial spin labeling: techniques and clinical application

A knowledge of the exact cerebral perfusion territory which is supplied by any artery is of great importance in the understanding and diagnosis of cerebrovascular disease. The development and optimization of territorial arterial spin labeling (T-ASL) MRI techniques in the past two decades have made it possible to visualize and determine the cerebral perfusion territories in individual patients and, more importantly, to do so without contrast agents or otherwise invasive procedures. This review provides an overview of the development of ASL techniques that aim to visualize the general cerebral perfusion territories or the territory of a specific artery of interest. The first efforts of T-ASL with pulsed, continuous and pseudo-continuous techniques are summarized and subsequent clinical studies using T-ASL are highlighted. In the healthy population, the perfusion territories of the brain-feeding arteries are highly variable. This high variability requires special consideration in specific patient groups, such as patients with cerebrovascular disease, stroke, steno-occlusive disease of the large arteries and arteriovenous malformations. In the past, catheter angiography with selective contrast injection was the only available method to visualize the cerebral perfusion territories in vivo. Several T-ASL methods, sometimes referred to as regional perfusion imaging, are now available that can easily be combined with conventional brain MRI examinations to show the relationship between the cerebral perfusion territories, vascular anatomy and brain infarcts or other pathology. Increased availability of T-ASL techniques on clinical MRI scanners will allow radiologists and other clinicians to gain further knowledge of the relationship between vasculature and patient diagnosis and prognosis. Treatment decisions, such as surgical revascularization, may, in the near future, be guided by information provided by T-ASL MRI in close correlation with structural MRI and quantitative perfusion information.

An anatomic consideration of C2 vertebrae artery groove variation for individual screw implantation in axis

STUDY DESIGN

Retrospective case series.

OBJECTIVES

To identify the variation of C2 vertebral artery groove (VAG) based on the thin-slice computed tomography (CT) scan and choose an individual screw placement method to decrease risk of malposition.

BACKGROUND

C2 pedicle screws can be successful anchors for a variety of cervical disorders. However, variations of VAG may cause malposition and breach when C2 transpedicle screw was inserted. Recognizing the variations of vertebrae artery groove (VAG) in C2 and choosing an individual screw placement method (transpedicle or translaminar) may be helpful for avoiding violation and decreasing the operation risk in upper cervical surgery.

METHODS

From January 2009 to December 2010, a total 45 patients with upper cervical disorders underwent 1-mm-thin-slice CT scans along the C2 pedicle direction to obtain the consecutive spectrum of C2 VAG were included in this study. The C2 VAG (types I, II, III, and IV) was subgrouped based on parameter e (the vertical distance from the apex of VAG to the upper facet joint surface) and parameter a (horizontal distance from the entrance of VAG to the vertebrae canal). Subsequently, individual strategy was used to avoid the VAG violation.

RESULTS

The variations of C2 VAG in these 45 patients include the following: type I 53 (58.9%), type II 16 (17.8%) type III 13 (14.4%), and type IV 8 (8.9%). Transpedicle screws of C2 were used in types I, III, and IV VAGs (n = 74); translaminar screws were inserted in type II subgroup (n = 16). Postoperative CT scans showed that there were two pedicle screws violated into the artery groove, and no translaminar screw breached into the vertebrae canal. All the other screws were in right position. None of the 45 patients had severe complications such as spinal cord injury, dura tear, and infection.

CONCLUSION

Thin-slice CT scan along the C2 pedicle direction to analysis the variations of C2 VAG can help choose an individual screw placement method (transpedicle or translaminar) with minimal complication for C2 screw fixation.

Morphological expression of the anterior spinal artery and the intracranial segment of the vertebral artery: a direct anatomic study

Given its importance for clinical diagnosis and management, the purpose of this study was to determine the morphological expression of the intracranial segment of both vertebral and spinal arteries. Ninety-five fresh cadaveric specimens autopsied at the Instituto de Medicina Legal of Bucaramanga (Colombia) were perfused with polyester resins at the vertebrobasilar vascular bed, by canalizing the proximal segment of the internal carotids and vertebral arteries. The intracranial segment of the vertebral arteries (VA) had a length of 33.2±5.2 mm and a caliber of 3.03±0.81 mm. The left vertebral artery had a caliber of 3.12±0.85 mm, this being greater than the caliber of the right artery in 59.6% of the cases. The VA junction was seen at the level of the ponto-medullary sulcus in 44.2%, above this level in 30.5%, and below it in 25.3%. The distance from the origin of the anterior spinal branches (ASBs) to the VA junction was 7.34±2.71 mm, with a greater distance corresponding to the right ASBs, a difference that did not reach statistical significance (p=0.32). The anterior spinal arteries (ASA) had a bilateral origin in 65.3% of the cases, with the caliber being balanced in 37 (39%) and dominant at the right side in 15.8%. A right unilateral origin of the ASA was observed in 13.7% and a left unilateral origin in 9.5% of the specimens. There is disagreement in the literature as to the level of the junction of the two vertebral arteries. The unilateral origin of the spinal arteries is more frequent than most prior studies have indicated.

Morphological characteristics of the first part of the vertebral artery

Because of their anatomical localization, vertebral arteries were neglected in research for a long period of time. Vertebral arteries are responsible for about 30% of the brain blood supply. The aim of this study was to examine the vertebral artery's course in the first segment, and to define the anatomic variations and percentage of their appearance in the adult population using CT angiography. The data derived from this study may find useful application in a wide range of medical fields, such as anatomy, radiology and surgery. For that purpose during a 6-month period we examined 30 patients with CT angiography. The origin of the vertebral artery in all 30 patients was from the subclavian artery. The diameter of the left vertebral artery was from 1.6-5.20 mm., average 3.35 mm. The diameter of the right vertebral artery was from 1.64-5.40 mm., average 3.19 mm. Hypoplasia of the vessel was found in four patients. We found no aplasia of the vessel in this series. A contorted course was found in 12 (40%) patients. In all 30 (100%) patients the vertebral artery entered the foramen transversum at the level of the sixth cervical vertebra. Although the incidence of anatomical variations is rare, their presence is significant in the diagnostic and surgical procedures in the head and neck region. Insufficient knowledge can lead to serious iatrogenic injures.

Anomalous branching pattern of the aortic arch and its clinical applications

The aortic arch gives rise to three classical branches, namely the brachiocephalic trunk, the left common carotid artery and the left subclavian artery. We report a rare variation of the left common carotid artery and the right vertebral arteries originating from the brachiocephalic trunk, and the left vertebral artery that was arising from the arch of the aorta, proximal to the origin of the left subclavian artery. Variations in the branching pattern of the arch of aorta can alter the cerebral haemodynamics that leads to cerebral abnormalities. Knowledge of the variations in the classical branches of the arch of aorta is important in the diagnosis of intracranial aneurysm after subarachnoid haemorrhage.

[Topographic-anatomic grounding cervical-distalvertebral reconstruction of V3 segment vertebral artery vertebral artery]

Using 10 block-mounts "brain-base of skull- cervical spine" there were detected morphometric peculiarities of vertebral artery on the level C(I)-C(II) of spines of vertebra and of premastoidal part of cervical artery. Were effectuated 20 distalvertebral reconstructions. Were precised stages and technique of realization.

[Microsurgical anatomy and clinic significance of posterior inferior cerebellar artery]

OBJECTIVE

To study the microsurgical anatomy of the posterior inferior cerebellar artery (PICA) for neurosurgery.

METHODS

Twenty Chinese adult brain samples (40 sides) were measured with microscope for the diameters, lengths, origins, courses, and the branches of the PICA. The relationship between the PICA and cranial nerves was also checked.

RESULTS

There were 35 PICAs in 20 brain samples. The mean diameter of the PICAs was (1.6 +/- 0.6) mm, the mean length from PICAs' origin of vertebral artery to the vertebrobasilar junction was (16 +/- 5) mm. In 35 PICAs, 28 PICAs go through the rootlets of XII cranial nerves, 7 PICAs go through inferior XII cranial nerves, and 32 PICAs go through the rootlets of XI cranial nerves.

CONCLUSIONS

PICA is an important branch artery with more variation and complex relationship to the cranial nerves trend in the vertebral artery system. It is necessary to master the microsurgical anatomy of PICA and to be careful protection during the neurosurgical operations.

Vascular anatomy: the head, neck, and skull base

Knowledge of the anatomy of the vasculature of the head and neck from the thorax to the skull base is critical to the approach to diagnosis and treatment of cerebrovascular disease. Awareness of the anatomic variations that may be encountered, common and uncommon, is necessary to avoid diagnostic pitfalls and to avert therapeutic disasters. Careful anatomic analysis and understanding of collateral pathways and dangerous anastomoses facilitates cross-sectional and angiographic diagnosis and the development of surgical and endovascular treatment strategies.

Simple identification of the third segment of the extracranial vertebral artery by extreme lateral inferior transcondylar-transtubercular exposure (ELITE)

PURPOSE

The exposure of the third segment of the extracranial vertebral artery (V3) is an important step in the extreme lateral inferior transcondylar-transtubercular exposure (ELITE) approach. The muscular suboccipital triangle provides one of the landmarks to identify the V3 segment; however, identification of this triangle and dissection of the V3 segment is not always straightforward in the actual surgery. Blind dissection below the level of the foramen magnum can lead to vertebral artery injury. While the surgeon may be able to readily define the V3 segment of the vertebral artery by feeling its pulse, it is important to have a safe systematic approach to finding the V3 segment when the vessel is illusive. We propose a simple method to identify the V3 segment avoiding accidental injury of the vertebral artery.

METHODS

Sixteen cadaver heads (using both sides) were prepared by injecting red- or blue-coloured silicone into their arteries and veins, respectively. We performed an ELITE bilaterally on each cadaver head following four key bony landmarks. A postauricular lazy S-shaped skin incision was made centered just behind the mastoid tip. The posterior neck muscles were cut along the line of the skin incision behind the attachment of the sternocleidomastoid muscle to expose the occipital bone. All the incised muscles were reflected anteriorly as the ELITE is a dorsolateral approach. A suboccipital craniotomy was made exposing the posterior half of the sigmoid sinus up to the inferior retrosigmoid point (point A). The foramen magnum was opened after the craniotomy was completed. The dura on the foramen magnum was followed posteriorly in order to identify the occipital midline dural point (point B) that is identified by the bony ridge at the junction of the posterior fossa dura on the foramen magnum and the posterior most aspect of the spinal dura. The posterior tubercle of C1 (point C) was identified directly inferior to Point B. The posterior arch of C1 was followed anteriorly from the tubercle to find the "J-groove", which cradles the vertebral artery (point D). The V3 segment lies above this groove, covering the paravertebral venous plexus. We measured the distances between the landmarks introduced above after completion of the exposure.

RESULTS

The distance between points A and B was 30.5 +/- 5.6 mm, points B-C was 10.4 +/- 2.3 mm, points C-D was 19.1 +/- 3.8 mm. The V3 segment was identified using the anatomical relationships described above in all heads. In no cadaver specimen was the artery injured.

CONCLUSIONS

Identification of the V3 segment of the vertebral artery by systematically detecting the four anatomical points defined above is simple and much safer than a direct dissection below the foramen magnum.

Image fusion for preoperative evaluation of vertebral artery in a patient with atlantoaxial vertical subluxation and chronic renal failure

For preoperative evaluation of the vertebral artery (VA) at the craniovertebral junction, 3-dimensional (3-D) computed tomography (CT) angiography can simultaneously and precisely depict the location of the VA and the circumferential osseous tissues. However, this procedure has the risk of contrast-induced nephropathy, especially when patients have pre-existing renal impairment. We report the case of a 73-year-old woman with rheumatoid arthritis and concomitant chronic renal failure in whom severe myelopathy developed due to atlantoaxial vertical subluxation and subaxial subluxation. We planned to perform C1 laminectomy and C3-C7 laminoplasty, but to avoid the risk of intraoperative VA injury, we applied a fusion image technique of 3-D magnetic resonance (MR) angiography and co-registered 3-D CT that allowed for virtual assessment preoperatively of the VA courses, instead of 3-D CT angiography. Through the 3-D hybrid MR angiography-CT images, we could predict, in detail, the VA courses and the surrounding bony structures. At surgery, we found that the locations of the VAs were identical to that predicted on the preoperative image fusion analysis. We conclude that our image fusion techniques possess accurate diagnostic value for detecting arterial course, and could be applicable for patients in whom administration of contrast media should be avoided due to specific conditions, such as drug allergy and chronic renal failure.

Subarachnoid haemorrhage due to a lateral spinal artery aneurysm misdiagnosed as a posterior inferior cerebellar artery aneurysm: case report and literature review

CLINICAL DESCRIPTION

A 61 year old man presenting with subarachnoid haemorrhage had a distal posterior inferior cerebellar artery (PICA) aneurysm diagnosed on the initial cerebral angiogram. However, a PICA aneurysm was not found during surgery. A follow-up, super-selective vertebral artery (VA) performed demonstrated a saccular aneurysm located on the lateral spinal artery (LSA). A right sub-occipital craniotomy was performed and the aneurysm arising was identified and obliterated with a small titanium clip.

CONCLUSION

We describe the first example of an LSA aneurysm without occlusion or severe stenosis of the VA and PICA. This extremely rare lesion illustrates how knowledge of the angiographic features and super-selective cerebral angiography aids the precise diagnosis and the prevention of surgical complications.

Is mechanical deformation of the suboccipital vertebral artery during cervical spine rotation responsible for vertebrobasilar insufficiency?

PURPOSE

The atlanto-axial region of the vertebral artery (VA) has traditionally been considered at risk for injury during cervical spine rotation, leading to compromised blood flow to the hindbrain and vertebrobasilar insufficiency or ischaemia (VBI). The anatomical relationships of the suboccipital VA (VA3) and related haemodynamic changes associated with cervical spine movements have been neglected, however. The present review aims to provide a new perspective on possible causes of reduced blood flow to the hindbrain, with particular reference to the functional anatomy of VA3 and related biomechanics of cervical spine rotation, to inform evidence-based practice.

METHOD

To support the hypothesis that it is VA3, not the VA in the atlanto-axial region, that is compressed or stretched during cervical spine rotation, current studies of blood flow changes in the VA distal to the region of rotation and possible arterial deformation were retrieved, using AMED, CINAHL, Embase, Pedro and PubMed, and reviewed.

RESULTS

Possible sites for VA3 deformation, based on a re-examination of its anatomy and biomechanics, are described. However, no research reports of VA3 blood flow measurements associated with cervical spine rotation have been published to date. Five studies on blood flow changes in the intracranial VA after cervical spine rotation were reviewed. The subjects for four of these reports were young, healthy individuals, and the fifth included older patients and young non-patients. The analysis of these studies demonstrated that more rigorous control of variables is necessary before meaningful conclusions can be made.

CONCLUSION

The paucity of studies of VA3 emphasises the need for research based on informed understanding of the anatomy and biomechanics of this area. This view on mechanical deformation of VA3 associated with cervical spine rotation as a possible cause of compromised blood flow to the hindbrain and VBI provides further argument for avoiding full-range or sustained cervical spine rotation in clinical practice.

Bilateral variations of the vertebral arteries: the left originating from the aortic arch and the left and right entering the C5 transverse foramina

During the dissection course for second year medical students at the University of Toyama in 2005, we encountered variations of the bilateral vertebral arteries: the left directly came off from the aortic arch as the third branch between the left common carotid artery and the left subclavian artery and entered the transverse foramen of C5, instead of C6, whereas the right originated from the right subclavian artery and entered the transverse foramen of C5. The present vertebral artery of each side was possibly formed by the 6th cervical intersegmental artery linked with the longitudinal anastomoses between the cervical intersegmental arteries. Detailed knowledge of vertebral artery variations is crucially important for surgical treatment of blood vessels in the brain, neck and chest.