Arcuate Foramen: Anatomy, Embryology, Nomenclature, Pathology, and Surgical Considerations

Imaging of the Craniocervical Junction: A Pictorial Review

The craniocervical junction (CCJ) is a complex anatomical structure comprising the occiput, the atlas, and the axis. The CCJ plays an important role in maintaining stability, providing protection, and supporting neurovascular structures. The CCJ can be affected by a wide range of congenital variants and traumatic, degenerative, inflammatory, and tumoral pathologies. This pictorial review the normal anatomy of the CCJ and presents the most common anatomical variants and pathologic conditions affecting the CCJ.

The segmentation of the vertebral artery: An ambiguous anatomical concept

The course of the vertebral artery from its subclavian artery origin up to its termination at the vertebrobasilar junction is divided into four segments (V1-V4). This segmentation, based on schemes that have evolved since the late nineteenth century, should be a consistent and reproducible anatomical concept. However, the current literature offers conflicting definitions of that scheme, not infrequently within a single article or monograph. The principal inconsistency found in modern publications concerns the termination of the V2 segment, which is either set at the C2 or C1 transverse foramen depending on the scheme considered. Consequently, the portion of the vertebral artery extending between C2 and C1-a frequent site of pathological involvement-either belongs to the V2 or V3 segment. This discrepancy can affect the validity of studies evaluating the diagnosis and management of vertebral artery disorders. A V3 segment extending from the transverse foramen of C2 to the posterior atlanto-occipital membrane and subdivided into vertical, horizontal, and oblique subsegments-a pattern suggested by Barbieri in 1867 and adopted in some modern publications-would provide a simple, precise, and reliable solution without significantly altering the widely accepted division of the vertebral artery into four segments (V1-V4).

Course of the V3 segment of the vertebral artery relative to the suboccipital triangle as an anatomical marker for a safe far lateral approach: A retrospective clinical study

Background:

The third segment of the vertebral artery (V3) is vulnerable during far lateral and retrosigmoid approaches. Although the suboccipital triangle (SOT) is a useful anatomical landmark, the relationship between V3 and the muscles forming the triangle is not well-described. We aimed to demonstrate the relationship between the V3, surrounding muscles, and SOT in clinical cases.

Methods:

Operative videos of patients with the vertebral artery (VA) and posterior inferior cerebellar artery (PICA) aneurysms treated with occipital artery-PICA bypass through the far lateral approach were examined. Videos from January 2015 to October 2021 were retrospectively reviewed to determine anatomy of the V3 and the SOT.

Results:

Fourteen patients were included in this study. The ipsilateral V3 was identified without injury in all patients using the bipolar cutting technique. The lateral 68.2% of the horizontal V3 segment, including the V3 bulge, was covered by the inferomedial part of the superior oblique muscle (SO). The medial 23.9% was covered by the inferolateral part of the rectus capitis posterior major muscle. The inferomedial part of the horizontal V3 segment is located within the SOT.

Conclusion:

Most of the V3, including the V3 bulge, were located beneath the SO and the inferomedial part of V3 located within the SOT. Elevation of the SO should be performed carefully using the bipolar cutting technique to avoid injury to the V3. To the best of our knowledge, this is the first description of the V3 relative to the SOT in the clinical setting.

Calcification of the Atlanto-Occipital Ligament (Ponticulus Posticus) in Orthodontic Patients: A Retrospective Study

Background: Ponticlus Posticus (PP) is a rare anomaly of the first cervical vertebra easily identifiable in lateral cephalometric radiograph and typically required for orthodontic diagnosis. The aim of this study is to evaluate the PP prevalence in lateral Cephalograms in a cohort of orthodontic patients treated at the Dental School of the University of Bari ‘Aldo Moro’, Italy, and to find possible connection between PP and other dental anomalies, as well as the patient’s cephalometric characteristics. Methods: A total of 150 panoramic radiographs and 150 lateral Cephalograms, obtained for orthodontic use only, were evaluated. No patients were referred to for congenital syndromes or disease, or a history of previously occurred maxillofacial trauma. A detailed cephalometric study was performed for each patient, and the whole cohort was divided according to the common three dental malocclusion classes. The values obtained were analyzed using the Chi-Square Test. Results: PP prevalence was 8% (12 of 150 cases), where the complete and partial forms observed 4.7% and 3.3%, respectively. Although females were more affected (9.6%), no statistically significant sex-related difference was found. Furthermore, no statistically significant relationship regarding age or dental anomalies (dental agenesis/palatal impacted canines) among the groups was observed either. Cephalometric analyses revealed that half of the subjects with PP were sagittal skeletal class I and had vertical hyper-divergence. Conclusions: PP is a frequent anatomical variation of the cervical vertebra, apparently unrelated to the skeletal malocclusion type or dental anomalies. The current study needs to further confirm the congenital hypothesis of PP’s origin already reported in literature.

Research Progress of Ponticulus Posticus: A Narrative Literature Review

Study Design

Narrative review.

Objective

The purpose of this review was to consolidate the current literature related to ponticulus posticus (PP) and to improve the systematic understanding of this anatomical variant of atlas among spine surgeons.

Methods

Articles reviewed were searched in PubMed, Ovid MEDLINE, and Embase. All articles of any study design discussing on PP were considered for inclusion. Two independent authors read article titles and abstracts and included appropriate articles. The relevant articles were studied in full text.

Results

A total of 113 literatures were reviewed and consolidated in this narrative review. These articles are roughly divided into the following five subcategories: (1) epidemiology, (2) pathology and anatomy, (3) clinical presentation, (4) surgical significance, and (5) radiographic examination.

Conclusion

The PP is non-negligible with a high prevalence. The PP compresses the V3 segment of the artery, the suboccipital nerve, and the venous plexus, consequently contributing to the incidence of neurological pathologies. When a PP is observed or suspected on a lateral radiograph, we recommend that a computed tomography (CT) scan of a patient who is about to receive a C1 lateral mass screw (C1LMS) should be performed, which could determine a safe entry point and the right trajectory of screw insertion.

The computed tomographic evaluation of bony bridge of C1 as bleeding risk factor at the screw placement

PURPOSE

To investigate the prevalence and morphological characteristics of ponticulus posticus (PP) and ponticulus lateralis (PL) using computed tomography (CT) images on a large study sample of the Anatolian population. The presence of the PP and PL bridges can limit gap available for placement procedure through the bony elements of C1. Routine screw techniques are contraindicated because of high risk of fatal bleeding of vertebral artery (VA).

METHODS

The CT images of 1000 subjects (500 males, 500 females) were examined for the morphological characteristics and presence of PP and PL. The anteroposterior diameter, superoposterior (transverse) diameter, surface area, and central thickness of the bony bridge of the PP, PL, and transverse foramina (TF).

RESULTS

The prevalence of PP was 14.8%, and bilateral complete PP was the most common PP type at 6.8%. The prevalence of PL was 4.1% and left-side complete PL was the most common PL type at 1.2%. The prevalence of both PP and PL was more common in males and bilateral complete PP were more predominant in males (p = 0.004, p = 0.038, and p = 0.010, respectively). The surface area of PP and PL were determined to be smaller than the surface area of the ipsilateral TF (p < 0.001 and p = 0.042, respectively).

CONCLUSION

PP is not an uncommon anatomic anomaly and PL is even less frequently encountered. The prevalence of PP and PL was more common in males and bilateral complete PP was more predominant in males. Detailed information about the prevalence and morphometry of the PP and PL obtained in the present study could guide the clinicians dealing with neurosurgery, physical medicine and rehabilitation, and radiology in their practice.

Three-Dimensional Assessment of Cervical Vertebrae Anomalies in Patients With Cleft Lip and Palate

OBJECTIVE

To evaluate the occurrence of cervical vertebrae anomalies (CVA) in patients with unilateral (UCLP) and bilateral cleft lip and palate (BCLP) using cone beam computed tomography (CBCT) examinations.

DESIGN

Retrospective assessment of CBCT images. Descriptive statistics were calculated. Fisher exact test or χ² test was performed to evaluate the differences among each CVA between sex and type of cleft.

SETTING

School of Dentistry.

PARTICIPANTS

One hundred fifty-one patients with cleft lip and palate (103 UCLP/48 BCLP).

INTERVENTIONS

No relevant intervention.

MAIN OUTCOME MEASURES

Cone beam computed tomography images were assessed for the presence or absence of 12 most commonly observed CVA: spina bifida, dehiscence, cleft of the posterior arch, cleft of the anterior arch, fusion between cervical vertebrae, block fusion, occipitalization, narrowing of the intervertebral space, posterior ponticle, os odontoideum, ossiculum terminale, and subdental cartilaginous remnants.

RESULTS

The presence of subdental cartilaginous remnants was the most frequently observed alteration-found in 81.45% of the sample-and it was the only CVA with statistically significant frequencies in the individuals with BCLP. Considering only the other CVA, 22.51% presented 1 and 5.29% presented 2 or more CVA.

CONCLUSIONS

Patients with cleft lip and palate may present an overall high incidence of CVAs. However, when comparing the distribution of the CVAs among sex and types of cleft, the only significant difference noted was a higher incidence of subdental cartilaginous remnants among patients with BCLP.

Variant Anatomy and Its Terminology

Variant anatomy, which is an integral part of anatomical science, is related to abnormalities in the human body structure. Our understanding of variant anatomy is based on thousand years of anatomical experience. These abnormalities generally do not interfere with the function of the human body and do not typically manifest as pathological nosological units. However, under certain conditions, these abnormalities can worsen existing pathological states or even evoke new ones. Understanding variant anatomy is a basic skill not only of mere anatomists, but also of clinicians who work in fields involving both diagnostic techniques and therapeutic interventions. To gain and retain a good knowledge of the most frequent and clinically relevant anatomical variations, a simple, clear, and exactly defined nomenclature of variant structures is needed. A list of items comprising variant anatomy, which have been incorporated into the internationally accepted nomenclatures Terminologia Anatomica (1998) and Terminologia Neuroanatomica (2017), is described and analyzed. Examples of the most common anatomical variations related to terminology are mentioned, and variant anatomy as a whole and its role in understanding current anatomy are discussed.

Posterior atlantoaxial fusion: a comprehensive review of surgical techniques and relevant vascular anomalies

Posterior atlantoaxial fusion is an important surgical technique frequently used to treat various pathologies involving the cervical 1-2 joint. Since the beginning of the 20th century, various fusion techniques have been developed with improved safety profile, higher fusion rates, and superior clinical outcome. Despite the advancement of technology and surgical techniques, posterior C1-2 fusion is still a technically challenging procedure given the complex bony and neurovascular anatomy in the craniovertebral junction (CVJ). In addition, vascular anomalies in this region are not uncommon and can lead to devastating neurovascular complications if unrecognized. Thus, it is important for spine surgeons to be familiar with various posterior atlantoaxial fusion techniques along with a thorough knowledge of various vascular anomalies in the CVJ. Intimate knowledge of the various surgical techniques in combination with an appreciation for anatomical variances, allows the surgeon develop a customized surgical plan tailored to each patient's particular pathology and individual anatomy. In this article, we aim to provide a comprehensive review of existing posterior C1-2 fusion techniques along with a review of common vascular anomalies in the CVJ.

Atlanto-occipital ligament calcification: a novel imaging finding in pediatric rotational vertebral artery occlusion

We describe a 2-year-old girl with bow hunter syndrome complicated by vertebral artery dissection and multiple ischemic infarcts. Pediatric bow hunter syndrome is a rare and likely under-recognized disorder. Interestingly, our patient had atlanto-occipital ligament calcification on CT scan, an imaging finding that has not been reported in association with bow hunter syndrome and one that might help increase recognition of this dynamic disorder of the posterior circulation.

Arcuate foramen: "Anatomical variation shape or adaptation legacy?"

PURPOSE

The groove of the vertebral artery on the posterior arch of the atlas (sulcus arteriae vertebralis) may become a complete or partial osseous foramen: the arcuate foramen. The presence of a complete or partial arcuate foramen is a rare anatomical variant described in a minority of patients and it seems to be associated with vertigo, vertebro-basilar insufficiency, posterior circulation strokes, and musculoskeletal pain. As the number and morphology of cervical vertebrae is highly preserved, we questioned about its significance from an evolutionary point of view. We thus investigated through an extensive literature review if the arcuate foramen is a pure anatomical variation shape or if it might represent an adaptation legacy.

METHODS

We observed five atlas of an extinct species, the Late Pleistocene Mammoths (M. primigenius), and we compared them with five atlas of a closely related existent species, the African elephant (L. africana).

RESULTS

All the mammoths' atlas had an arcuate foramen through which the vertebral artery passed before turning anteriorly and becoming intradural. This foramen was not present in elephants' atlas, where only a groove was observed, such as in the majority of patients.

CONCLUSION

We would like to raise the hypothesis that this peculiar morphology of mammoths' atlas might have contributed, in association with other factors, to their precocious extinction and that the arcuate foramen might represent a disadvantage in the evolutionary process, with a low prevalence in humans being the result of a natural selection.