A Prevalence Anatomic-Imaging Study of the Posterior Inferior Cerebellar Artery's Origin.

Background and Objectives: Typically, the vertebral arteries (VAs) enter the posterior fossa through dural rings and further unite, forming the basilar artery. The posterior inferior cerebellar artery (PICA) is usually a branch of the V4 segment of the VA (intradural origin). It may also leave the V3 suboccipital segment of the VA (extradural origin). The transdural origin of the PICA within the VA's dural ring has been consistently overlooked. A study was designed to determine the topographical patterns of the PICA's origin. Materials and Methods: Determinations were performed in a retrospective sample of 225 computed tomography angiograms. Four types of PICA origin were documented: type 0, absent PICA; type 1, the extradural origin of the PICA from the V3 segment of the VA; type 2, the transdural origin of the PICA within the dural ring; and type 3, the intradural origin of the PICA from the V4 segment of the VA. The bilateral symmetry of types was also investigated. Results: Out of 450 VAs, type 0 (absent PICA) was found in 36%, type 1 (extradural) in 0.44%, type 2 (transdural) in 5.56%, and typical type 3 in just 58%. In types 1 and 2, the PICA entered the posterior fossa through the dural ring and the marginal sinus. In the overall group (N = 225), the type combinations 1_1, 1_2 and 1_3 were not found. Bilaterally absent PICAs occurred in 18.67%. The bilateral combinations 0_1/0_2/0_3/2_2/2_3/3_3 were found, respectively, in 0.89%/3.11%/30.67%/1.78%/4.44%/40.44%. Four of the seventy-eight PICAs opposite to an absent one, three intradural and one transdural, were true bihemispheric PICAs. Conclusions: The PICAs with extradural or transdural origins are facultative contents of the dural ring and are at risk during neurosurgical approaches in the foramen magnum. Rare bihemispheric PICAs could originate either intradurally or within the dural ring.

Anatomical differences of the vertebrobasilar artery between normal subjects and patients with cerebral infarction.

Previous studies have reported various anatomical differences in the cerebral artery between healthy subjects and patients with posterior circulation cerebral infarction. In particular, basilar artery angulation has been associated with posterior circulation cerebral infarction. We compared anatomical variations and the degree of anterior and lateral vertebrobasilar artery angulation and deviation to compare the incidence of cerebral infarction of healthy subjects and patients with posterior circulation cerebral infarction. We compared basilar artery anatomy using brain magnetic resonance angiography in 97 patients who underwent brain magnetic resonance angiography during health checkups at our hospital and in 92 patients diagnosed with posterior circulation cerebral infarction between 2012 and 2022. Anatomical variations, including fetal-type posterior cerebral artery, hypoplastic P1 segment, vertebrobasilar dolichoectasia, and dominant vertebral artery, as well as the degree of anterior and lateral deviation and angulation, were evaluated. Correlations between these variations and the occurrence of cerebral infarction were analyzed. The prevalence of hypoplastic P1 was significantly differences in patients with posterior circulation cerebral infarction (odds ratio: 5.655). Furthermore, patients with posterior circulation cerebral infarction exhibited more acute anterior and lateral angulation, as well as lateral deviation. Hypoplastic P1 and more acute anterior or lateral angulation of the vertebrobasilar artery are associated with increased frequency of cerebral infarction.

Does ponticulus posticus affect vertebral artery diameter.

PURPOSE: Ponticulus Posticus, atlantooccipital ligament ossification-induced anomaly, surrounds the vertebral artery and the first cervical nerve root. It is believed to wrap around the first cervical nerve root and the vertebral artery, causing compression. We hypothesized that it would also reduce the diameter of the vertebral artery. METHODS: Between January 1, 2022, and December 31, 2022, cervical spine CT scans taken for any reason were retrospectively reviewed. The images of 1365 patients suitable for evaluation were evaluated by two expert radiologists in 3 dimensions. Among patients with PP, those who underwent cervical angiography were identified for vertebral artery diameter measurement. RESULTS: The average age of the 1365 individuals included in the study (732 males, 633 females) was 55.78 (± 18.85) with an age range of 1-96. Among this group, PP was detected in 288 individuals, resulting in a total prevalence of 21.1%. Right and left vertebral artery diameters were significantly lower in patients with complete PP compared to the absent group (p < 0,001, p < 0,001, respectively). Additionally, it was observed that width and height diameters and artery diameters were positively correlated in patients with Complete PP. CONCLUSIONS: Ponticulus posticus can cause vertebrobasilar insufficiency by reducing the diameter of the vertebral artery. Therefore, imaging and detailed evaluation of this region are important in symptomatic patients.

[Anatomical Variations to the Vertebral Artery and Posterior Inferior Cerebellar Artery are Associated with the Partial Persistence of Primitive Lateral Basirovertebral Anastomosis].

The angioarchitecture of the hindbrain is homologous to that of the spinal cord, and its vascular system can be analyzed at the longitudinal and axial structures. During embryonic development, there are two main longitudinal arteries: the longitudinal neural artery and the primitive lateral basilovertebral anastomosis. Commonly observed variations are formed by the fenestration and duplication of either the vertebrobasilar artery, or cerebellar artery, which can be observed when the primitive lateral basilovertebral anastomosis partially persists. Understanding the pattern and development of blood supply to the hindbrain provides useful information of various anomalies in the vertebrobasilar junction and cerebellar arteries.

Anatomy of vertebral artery hypoplasia and its relationship with clinical implications: a systematic review and meta-analysis of prevalence.

PURPOSE: The vertebral artery (VA) is a vital branch of the subclavian artery, coursing through the transverse foramina of the cervical vertebrae, and playing a crucial role in irrigating the posterior region of the arterial cerebral circle, also known as the Polygon of Willis. Among the various possible alterations that can affect the VA, vertebral artery hypoplasia (HAV) emerges as a significant variant. This study aims to discern the anatomical features of HAV and its correlation with the clinical conditions of the posterior cerebral circulation. METHODS: The databases Medline, Scopus, Web of Science, Google Scholar, CINAHL, and LILACS were searched until January 2024. Two authors independently performed the search, study selection, and data extraction. Methodological quality was evaluated with an assurance tool for anatomical studies (AQUA). Pooled prevalence was estimated using a random effects model. RESULTS: A total of 24 studies met the established selection criteria, with a total of 8847 subjects. In this study, 6 articles were included for the meta-analysis with a total of subjects. The average prevalence of VAH reported in each study was 11% (95% CI 10-12%); the studies had a heterogeneity of 41% based on the funnel plot and a low risk of bias. CONCLUSION: The prevalence of VAH is low, but in the presence of this condition, the changes are mainly in diameter rather than morphological. If it is present, some clinical safeguards must be taken to avoid complications such as stroke.

Extracranial Vertebral Artery Injuries.

Paired vertebral arteries (VAs) travel from the subclavian artery through the cervical spine and into the intracranial space where they contribute to posterior cerebral circulation. Blunt and penetrating injuries to the cervical spine risk injury to the VA. Among the most feared complications of vertebral artery injury (VAI) is posterior circulation stroke. Appropriate screening and treatment of these injuries in the trauma setting remain vitally important to aid in the prevention of devastating neurologic sequelae. A robust knowledge of the VA anatomy is required for spine surgeons to avoid VAI during cervical spine approaches and instrumentation. Both anterior and posterior cervical spine surgeries can place the VA at risk. Careful preoperative assessment with the appropriate advanced imaging studies is necessary to verify the course of the VA in the cervical spine and thus prevent iatrogenic injury because anatomic variations along the course of the artery can prove hazardous if not properly anticipated. Iatrogenic VAI can be treated successfully with tamponade. However, in some cases, ligation, repair, or endovascular procedures may be indicated.

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.

Radiologic Evaluation of Uncinate Processes of the Cervical Spine and the Relationship Between the Uncinate Process and Vertebral Artery: Implication in Anterior Cervical Spine Surgery.

OBJECTIVE: To determine the relationship between the uncinate process (UP) and vertebral artery (VA) from a radiologic view and to confirm the surgical safety margin to minimize the risk of VA injury during anterior cervical approaches. METHODS: We retrospectively reviewed computed tomography angiography of 205 patients by using a contrast-enhanced computed tomography angiography protocol of the VA. Four kinds of images were simultaneously reconstructed to measure all the parameters associated with VA and UP of cervical spine. RESULTS: The shortest distance from the UP's tip to the VA's medial border (P < 0.001) was at the C-6 level (2.9 ± 0.9 mm on the left and 3.2 ± 1.3 mm on the right), and the longest distance (P < 0.001) was at the C-3 level on both sides. The distance between UP's tip and the medial border of the ipsilateral VA was statistically significantly different at each cervical level, and the right distance was larger than the left (P < 0.05). We found the height of UP gradually increased from C-3 to C5-level and then decreased from C-5 to C-7 level for both sides. The mean distance between the medial borders of left UP and left VA was on average 7.5 ± 1.4 mm. The diameter of VA was on average 3.4 ± 0.6 mm on the left side and 3.2 ± 0.7 mm on the right. The diameter of the VA was statistically significantly different on both sides, and the left side was larger than the right (P < 0.05). CONCLUSIONS: Detailed radiologic anatomy of VA and UP was reviewed in this study. A deep understanding of the correlation between the UP and VA is essential to perform anterior cervical spine surgery safely and ensure adequate spinal canal decompression.

A primer to vascular anatomy of the brain: an overview on anterior compartment.

PURPOSE: Knowledge of neurovascular anatomy is vital for neurosurgeons, neurologists, neuro-radiologists and anatomy students, amongst others, to fully comprehend the brain's anatomy with utmost depth. This paper aims to enhance the foundational knowledge of novice physicians in this area. METHOD: A comprehensive literature review was carried out by searching the PubMed and Google Scholar databases using primary keywords related to brain vasculature, without date restrictions. The identified literature was meticulously examined and scrutinized. In the process of screening pertinent papers, further articles and book chapters were obtained through analysis and additional assessing of the reference lists. Additionally, four formalin-fixed, color latex-injected cadaveric specimens preserved in 70% ethanol solution were dissected under surgical microscope (Leica Microsystems Inc, 1700 Leider Ln, Buffalo Grove, IL 60089 USA). Using microneurosurgical as well as standard instruments, and a high-speed surgical drill (Stryker Instruments 1941 Stryker Way Portage, MI 49002 USA). Ulterior anatomical dissection was documented in microscopic images. RESULTS: Encephalic circulation functions as a complex network of intertwined vessels. The Internal Carotid Arteries (ICAs) and the Vertebral Arteries (VAs), form the anterior and posterior arterial circulations, respectively. This work provides a detailed exploration of the neurovascular anatomy of the anterior circulation and its key structures, such as the Anterior Cerebral Artery (ACA) and the Middle Cerebral Artery (MCA). Embryology is also briefly covered, offering insights into the early development of the vascular structures of the central nervous system. Cerebral venous system was detailed, highlighting the major veins and tributaries involved in the drainage of blood from the intracranial compartment, with a focus on the role of the Internal Jugular Veins (IJVs) as the primary, although not exclusive, deoxygenated blood outflow pathway. CONCLUSION: This work serves as initial guide, providing essential knowledge on neurovascular anatomy, hoping to reduce the initial impact when tackling the subject, albeit the intricate vasculature of the brain will necessitate further efforts to be conquered, that being crucial for neurosurgical and neurology related practice and clinical decision-making.

Posterior vascular anatomy of the encephalon: a comprehensive review.

PURPOSE: This article presents a comprehensive exploration of neurovascular anatomy of the encephalon, focusing specifically on the intricate network within the posterior circulation and the posterior fossa anatomy; enhancing understanding of its dynamics, essential for practitioners in neurosurgery and neurology areas. METHOD: A profound literature review was conducted by searching the PubMed and Google Scholar databases using main keywords related to neurovascular anatomy. The selected literature was meticulously scrutinized. Throughout the screening of pertinent papers, further articles or book chapters were obtained through additional assessment of the reference lists. Furthermore, four formalin-fixed, color latex-injected cadaveric specimens preserved in 70% ethanol solution were dissected under surgical microscope (Leica Microsystems Inc, 1700 Leider Ln, Buffalo Grove, IL 60089, USA), using microneurosurgical as well as standard instruments, and a high-speed surgical drill (Stryker Instruments 1941 Stryker Way Portage, MI 49002, USA). Ulterior anatomical dissection was performed. RESULTS: Detailed examination of the basilar artery (BA), a common trunk formed by the union of the left and right vertebral arteries, denoted a tortuous course across the basilar sulcus. Emphasis is then placed on the Posterior Inferior Cerebellar Artery (PICA), Anterior Inferior Cerebellar Artery (AICA) and Superior Cerebellar Artery (SCA). Each artery's complex course through the posterior fossa, its divisions, and potential stroke-related syndromes are explored in detail. The Posterior Cerebral Artery (PCA) is subsequently unveiled. The posterior fossa venous system is explained, categorizing its channels. A retrograde exploration traces the venous drainage back to the internal jugular vein, unraveling its pathways. CONCLUSION: This work serves as a succinct yet comprehensive guide, offering fundamental insights into neurovascular anatomy within the encephalon's posterior circulation. Intended for both novice physicians and seasoned neuroanatomists, the article aims to facilitate a more efficient clinical decision-making in neurosurgical and neurological practices.

An In-Depth Analysis of the Artery of Salmon: Anatomy and Neurosurgical Implications.

BACKGROUND: Michel Salmon was a prominent person in the field of plastic surgery during the early 20th century. His pioneering work contributed significantly to our understanding of human anatomy, particularly with the identification of the artery of Salmon (AOS). The objective of this study is to thoroughly investigate the AOS by conducting a comprehensive literature review, providing insights into its anatomy and surgical implications. METHODS: This review was undertaken after a thorough examination of literature encompassing papers about the AOS. Right up until January 2024, databases like PubMed, ScienceDirect, and Web of Science were explored. The search was conducted using specific terms such as "Artery of Salmon," "suboccipital artery," and "vertebral artery anatomy." An in-depth assessment was conducted to examine the anatomy, and surgical significance of the AOS. RESULTS: The AOS is a branch of the V3 segment of the vertebral artery that supplies the suboccipital muscles. The ability, to identify it, is critical for distinguishing the origins of intraoperative hemorrhage. Through careful surgical intervention, the artery was able to devascularize tumors and vascular lesions. We also touched on the technical issues of its possible application in bypass operations for aneurysms of the posterior inferior cerebellar artery or vertebral artery. CONCLUSIONS: The AOS is sometimes vital in neurosurgery, facilitating precise interventions and serving as a conduit in suboccipital bypass surgeries. Understanding its variations is essential for neurosurgeons, showcasing ongoing advancements in patient care.

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.

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.

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.

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.

Bilateral Variation of the Vertebral Artery: Report of a Case and its Clinical Implication / Variación Bilateral de la Arteria Vertebral; Reporte de un Caso y su Implicancia Clínica

SUMMARY: There are many reports on anatomical variations of the vertebral arteries, which may be related to origin, trajectory, caliber, and side. Bilateral variations are less frequent, however, and less common are bilateral variants that differ from each other. The aim of this work was to report the presence of a bilateral variation of the vertebral artery and its functional and clinical implications. Dissection of a female cadaver, fixed in 10 % buffered formaldehyde, which had not undergone any previous surgeries in the study area and had anatomical variations in both vertebral arteries. In each one, follow-up was done from its origin to its end, determining its trajectory, diameters, branching, and anatomical relations. A left vertebral artery was found, starting in the aortic arch and making a sinuous trajectory of 4 curvatures to enter the transverse foramen of C4. The right vertebral artery began as the first branch of the subclavian artery. Its initial trajectory was rectilinear, followed by a right concave curve, a 360° loop that included a second ascending curve, and ended straight before entering the transverse foramen of C6. The coexistence of bilateral variations in the vertebral arteries is possible. This atypical situation can potentially generate vascular and neurological pathologies, but with different symptoms and causes. Knowing these variations and deliberately searching for them will enable the specialist to make a suitable differential diagnosis.

Existen múltiples reportes sobre variaciones anatómicas de las arterias vertebrales, las que se pueden relacionar con origen, trayecto, calibre y lateralidad. Sin embargo, las variaciones bilaterales son menos frecuentes, y menos común es que las variantes bilaterales sean diferentes entre ellas. El objetivo de este trabajo fue reportar la presencia de una variación bilateral de la arteria vertebral y su implicancia funcional y clínica. Disección en un cadáver de sexo femenino, fijado en formaldehido tamponado al 10 %, el cual no presentaba intervenciones quirúrgicas previas en la región de estudio y que tenía variaciones anatómicas en ambas arterias vertebrales. En cada una se realizó seguimiento desde su origen hasta su terminación, pudiendo determinar su trayecto, diámetros, ramificaciones y relaciones anatómicas. Se encontró una arteria vertebral izquierda originada en el arco aórtico, que realizaba un trayecto sinuoso de 4 curvaturas e ingresaba al foramen transverso de C4. La arteria vertebral derecha se originaba como primera rama de la arteria subclavia. Su trayecto inicial era rectilíneo seguido por una curva de concavidad derecha, un loop (giro) de 360° que incluía una segunda curva ascendente y terminaba en dirección recta antes de ingresar al foramen transverso de C6. La coexistencia de variaciones bilaterales en las arterias vertebrales es posible. Esta situación atípica, potencialmente puede generar en la persona patologías neurológicas de origen vascular, pero con sintomatología y causas diferentes. Conocer estas variaciones y realizar una búsqueda intencionada de ellas permitirá el especialista realizar un adecuado diagnóstico diferencial.

Medullary branches of the vertebral artery: microsurgical anatomy and clinical significance.

BACKGROUND: Since the medullary arteries are of a great neurologic and neurosurgical significance, the aim was to perform a detailed microanatomic study of these vessels, as well as of the medullary infarctions in a group of patients. METHODS: The arteries of 26 halves of the brain stem were injected with India ink and gelatin, microdissected and measured with an ocular micrometer. Neurologic and magnetic resonance imaging (MRI) examinations were performed in 11 patients. RESULTS: The perforating medullary arteries, averaging 6.7 in number and 0.26 mm in diameter, most often originated from the anterior spinal artery (ASA), and rarely from the vertebral (VA) (38.5%) and the basilar artery (BA) (11.6%). They supplied the medial medullary region. The anterolateral arteries, 4.8 in number and 0.2 mm in size, most often arose from the ASA and PerfAs, and nourished the anterolateral region. The lateral arteries, 2.2 in number and 0.31 mm in diameter, usually originated from the VA and the posterior inferior cerebellar artery (PICA). They supplied the lateral medullary region. The dorsal arteries, which mainly arose from the PICA and the posterior spinal artery (PSA), nourished the dorsal region, including the roof of the 4th ventricle. The anastomotic channels, averaging 0.3 mm in size, were noted in 42.3%. Among the medullary infarctions, the lateral ones were most frequently present (72.8%). CONCLUSION: The obtained anatomic data, which can explain the medullary infarctions symptomatology, are also important in order to avoid damage to the medullary arteries during neurosurgical and neuroradiologic interventions.

Photorealistic 3-Dimensional Models of the Anatomy and Neurosurgical Approaches to the V2, V3, and V4 Segments of the Vertebral Artery.

BACKGROUND: The vertebral artery (VA) has a tortuous course subdivided into 4 segments (V1-V4). For neurosurgeons, a thorough knowledge of the 3-dimensional (3D) anatomy at different segments is a prerequisite for safe surgery. New technologies allowing creation of photorealistic 3D models may enhance the anatomic understanding of this complex region. OBJECTIVE: To create photorealistic 3D models illustrating the anatomy and surgical steps needed for safe neurosurgical exposure of the VA. METHODS: We dissected 2 latex injected cadaver heads. Anatomic layered dissections were performed on the first specimen. On the second specimen, the two classical approaches to the VA (far lateral and anterolateral) were realized. Every step of dissection was scanned using photogrammetry technology that allowed processing of 3D data from 2-dimensional photographs by a simplified algorithm mainly based on a dedicated mobile phone application and open-source 3D modeling software. For selected microscopic 3D anatomy, we used an operating microscope to generate 3D models. RESULTS: Classic anatomic (n=17) and microsurgical (n=12) 3D photorealistic models based on cadaver dissections were created. The models allow observation of the spatial relations of each anatomic structure of interest and have an immersive view of the approaches to the V2-V4 segments of the VA. Once generated, these models may easily be shared on any digital device or web-based platforms for 3D visualization. CONCLUSIONS: Photorealistic 3D scanning technology is a promising tool to present complex anatomy in a more comprehensive way. These 3D models can be used for education, training, and potentially preoperative planning.

Anatomical variations of human vertebral and basilar arteries: A current review of the literature.

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

Entrance and origin of the extracranial vertebral artery found on computed tomography angiography.

To investigated morphological variability of vertebral artery (VA) origin and its entrance level into cervical transverse foramina by computed tomography angiography (CTA). To retrospectively investigated CTA of 223 subjects (446 VA courses). Investigated were origin of the VA and its level of entrance into vertebral transverse foramen with notification of the sex and side of variation. The VA entered the C6 transverse process in 91.70% of specimens (409 out of 446 VA courses). Abnormal entrance of VA was observed in 8.30% of specimens (37 VA courses), with the level of entrance into the C3, C4, C5, or C7 transverse foramen at 0.22%, 2.47%, 4.71% and 0.90% respectively. Comparably, the overall variability of abnormal origin of VA was 1.57% (7 out of 466 VA courses), in which the left vertebral arteries all arose from aortic arch. The variation rate of vertebral entrance rose up to 50% in abnormal origin subgroup. When comparing subgroups of subjects with normal and abnormal origin, there was significance difference in the frequency of entrance variation in the level of transverse foramen (p < 0.001). Abnormal entrance and origin of VA were observed in 8.30% and 1.57% of VA courses, which can be accurately appeared by CTA. Regarding to the subgroups of abnormal origin, the frequency of entrance variation was significantly increased in the level of transverse foramen compared to that of normal origin.