The prevalence of congenital C1 arch anomalies

Anatomical variations of the atlas arches: prevalence assessment, systematic review and proposition for an updated classification system

Objective and background

This study focuses on the atlas, a pivotal component of the craniovertebral junction, bridging the cranium and spinal column. Notably, variations in its arches are documented globally, necessitating a thorough assessment and categorization due to their significant implications in clinical, diagnostic, functional, and therapeutic contexts. The primary objective is to ascertain the frequency of these anatomical deviations in the atlas arches among a Colombian cohort using cone-beam computed tomography (CBCT).

Methodology

Employing a descriptive, cross-sectional approach, this research scrutinizes the structural intricacies of the atlas arches in CBCT scans. Analytical parameters included sex distribution and the nature of anatomical deviations as per Currarino's classification. Statistical analyses were conducted to identify significant differences, including descriptive statistics and Chi-square tests. A systematic review of the literature was conducted in order to enhance the current Currarino's classification.

Results

The study examined 839 CBCT images, with a nearly equal sex distribution (49.7% female, 50.3% male). Anatomical variations were identified in 26 instances (3%), displaying a higher incidence in females (X2 [(1, N = 839) = 4.0933, p = 0.0430]). The most prevalent variation was Type A (2.5%), followed by Type B (0.4%), and Type G (0.2%) without documenting any other variation. The systematic review yielded 7 studies. A novel classification system for these variations is proposed, considering global prevalence data in the cervical region.

Conclusion

The study highlights a statistically significant predominance of Type A variations in the female subset. Given the critical nature of the craniovertebral junction and supporting evidence, it recommends an amendment to Currarino's classification to better reflect these clinical observations. A thorough study of anatomical variations of the upper cervical spine is relevant as they can impact important functional aspects such as mobility as well as stability. Considering the intricate anatomy of this area and the pivotal function of the atlas, accurately categorizing the variations of its arches is crucial for clinical practice. This classification aids in diagnosis, surgical planning, preventing iatrogenic incidents, and designing rehabilitation strategies.

Radiological Study of Atlas Arch Defects with Meta-Analysis and a Proposed New Classification

This study consists of a retrospective cohort study, a systematic review, and a meta-analysis which were separately conducted. This study aimed to investigate the prevalence of atlas arch defects, generate an evidence-based synthesis, and propose a common classification system for the anterior and combined atlas arch defects. Atlas arch defects are well-corticated gaps in the anterior or posterior arch of the atlas. When both arches are involved, it is known as a combined arch defect. Awareness of these defects is essential for avoiding complications during surgical procedures on the upper spine. The prevalence of arch defects was investigated in an open-access OPC-Radiomics (Radiomic Biomarkers in Oropharyngeal Carcinoma) dataset comprising 606 head and neck computed tomography scans from oropharyngeal cancer patients. A systematic review and meta-analysis were performed to generate prevalence estimates of atlas arch defects and propose a classification system for the anterior and combined atlas arch defects. The posterior arch defect was found in 20 patients (3.3%) out of the 606 patients investigated. The anterior arch defect was not observed in any patient, while a combined arch defect was observed in one patient (0.2%). A meta-analysis of 13,539 participants from 14 studies, including the present study, yielded a pooled-posterior arch defect prevalence of 2.07% (95% confidence interval [CI], 1.22%-2.92%). The prevalences of anterior and combined arch defects were 0.00% (95% CI, 0.00%-0.10%) and 0.14% (95% CI, 0.04%-0.25%), respectively. The anterior and combined arch defects were classified into five subtypes based on their morphology and frequency. The present study showed that atlas arch defects were present in approximately 2% of the general population. For future studies, larger sample sizes should be used for studying arch defects to avoid the small-study effect and to predict the prevalence accurately.

Floating Laminoplasty for the Treatment of Compressive Myelopathy Accompanied by C1 Posterior Ring Hypoplasia: A Technical Note and Case Series

Posterior ring hypoplasia of the atlas (C1) is not common and in most cases is found by chance without symptoms. This disorder is sometimes accompanied by a mild C1-C2 instability or the presence of a space-occupying lesion such as ossification of posterior longitudinal ligament, pannus, or retro-odontoid pseudo-tumor, which are indications for surgery if symptomatic cord compression is present. A C1 posterior arch resection has been the procedure of choice but is associated with several fatal complications. We here present a novel posterior arch decompression technique that is relatively safer and easier and that involves mobilization and posterior translation of the posterior arch as a whole, similar to a vertebral body sliding osteotomy.

A pictorial review of imaging findings associated with upper cervical trauma

The diagnosis of cervical spine injury in the emergency department remains a critical skill of emergency room physicians as well as radiologists. Such diagnoses are often associated with high morbidity and mortality unless readily identified and treated appropriately. Both computed tomography (CT) and magnetic resonance imaging (MRI) often are crucial in the workup of spinal injury and play a key role in arriving at a diagnosis. Unfortunately, missed cervical spine injuries are not necessarily uncommon and often precede detrimental neurologic sequalae. With the increase in whole-body imaging ordered from the emergency department, it is critical for radiologists to be acutely aware of key imaging features associated with upper cervical trauma, possible mimics, and radiographic clues suggesting potential high-risk patient populations. This pictorial review will cover key imaging features from several different imaging modalities associated with upper cervical spine trauma, explore patient epidemiology, mechanism, and presentation, as well as identify confounding radiographic signs to aid in confident and accurate diagnoses.

Resection of cervical hemivertebra with occipitocervical - fusion: report on two torticollis cases and literature review

The objective of this study is to present the two cases of cervical hemivertebra and torticollis, and To describe technique and result of cervical hemivertebra resection and torticollis correction via a anterior-posterior surgical approach and occipitocervical fusion. Cervical hemivertebra, accompanied by abipartite atlas, agenesis of odontoid and C2 segmental type of vertebral artery (VA), is a rare, but complex congenital anomalies, associated with cervical scoliosis and occipitocervical instability. To the best of our knowledge, this is the first report on such congenital anomaly and deformity correction via anterior-posterior hemivertebra resection with occipitocervical fusion. Two patients were presented with torticollis due to congenital cervical hemivertebra accompanied by abipartite atlas, agenesis of odontoid and C2 segmental type of VA. Deformity correction was executed by an anterior-posterior hemivertebra resection and occipitocervical fusion with segment instrumentation. The treatment course was uneventful and clinical outcomes was favorable. The radiographs showed a satisfactory deformity correction with a well-balanced coronal and sagittal alignment. Hemivertebra resection with occipitocervical fusion could correct torticollis with satisfactory clinical and radiographical outcome.

Radiologic evaluation of congenital anomalies of anterior and posterior arch of atlas in Omani subjects

The atlas (C1) is known to present congenital anomalies in its anterior and posterior arches. The reported incidence of C1 anomalies is varied among the ethnic groups. We sought to determine the prevalence and various existing variations of C1 arch congenital anomalies in Omani subjects. This study was carried out by reviewing the cervical spine computed tomography scans of all the patients who had been referred to the Radiology Department, Sultan Qaboos University Hospital. Descriptive statistics and chi-square test were employed to analyse the data. A total of 663 subjects aged ≥18 years were included in the present study. Overall prevalence of C1 arch anomalies was 4.37% with 4.07% of isolated posterior arch anomalies, 0.3% of combined anterior and posterior arch anomalies. Among isolated posterior arch anomalies, type A and type B posterior arch defects were found in 3.77% and 0.3% of cases, respectively. Atlanto-occipital assimilation was noted in one case of total study subjects. The prevalence rate of C1 arch anomalies is relatively high in Omani subjects. The baseline data of C1 arch anomalies reported in the present study has a great impact on clinical practice, due to the fact that studying and evaluating the types of congenital anomalies helps in their accurate diagnosis and early intervention.

A surgical case of C1 arch stenosis: A case report and review of literature

Background:

Isolated symptomatic cervical stenosis of the atlas is quite rare; there have been 11 cases reported in literature.

Case Description:

A 76-year-old male presented with myelopathy attributed to C1 arch stenosis. Neuroimaging studies revealed posterior atlas compression of the spinal cord. Following a cervical laminectomy involving excision of the arch of the atlas, and the patient’s symptoms resolved.

Conclusion:

C1 stenosis resulting in cervical myelopathy due to posterior compression from the arch of the atlas is easily missed. Notably, C1 arch laminectomy may be very effective in resolving this entity.

"Split atlas" in a trauma and nontrauma patient: two different case reports for a rare congenital malformation

Congenital atlas abnormalities are rare and often asymptomatic findings, accidentally detected in trauma and, more rarely, in nontrauma patients. Rachischisis in both anterior and posterior atlas arches, condition defined as ‘‘split atlas,” is extremely uncommon and it may well be confused with fracture. Being able to discriminate between these 2 conditions is an essential step in patient care management. In this article, we report 2 cases of split atlas ascertained in both trauma and nontrauma patients. The first concerning a 54-year-old man fell from a 2 m scaffold, and the second related to a 25-year-old woman suffering from treatment-resistant headaches. Subsequently we proceed to analyse the embryology of these abnormalities, and later to discuss pitfalls, tips and tricks useful to a correct diagnosis, in order to achieve an accurate management of split atlas. Specifically, we outline the crucial radiological features to identify, that are beneficial to an efficient differential diagnosis between congenital atlas abnormalities and fracture. These include smooth corticated margins of the cleft, and <3 mm lateral displacement of C1 lateral masses.

Incidental findings of posterior arch defects of the atlas in orthodontic patients: A case series

INTRODUCTION

Congenital defects of the posterior arch of atlas are uncommon anomalies that may go unnoticed. Radiographs and cone-beam computed tomography scans made for orthodontic purposes often show the atlas; therefore, these rare defects might first be noted as incidental findings on orthodontic records.

METHODS

A series of 7 cases of posterior arch defects of atlas (C1) that were detected during routine radiographic examination are presented here.

RESULTS

The distribution of the defects was as follows: type A, 2; type B, 1; type C, none; type D, 1; and type E, 3.

CONCLUSION

As the potential complications associated with these defects may be quite concerning, a thorough analysis of the radiographs for these defects is imperative.

Incidentalomas in Spine and Spinal Cord Imaging

Incidentalomas are common in magnetic resonance imaging (MRI) of the spine. These incidental findings (IFs) can be seen involving the spinal cord, nerve root, vertebral body, posterior arch and the extraspinal region. This review article describes the imaging findings, stratifies the IFs similar to the computed tomography (CT) colonography reporting and data system and briefly mentions the current recommendations for further evaluation and management of IFs. Radiologists are the first to detect these lesions, suggest further evaluation and management of IFs. It is therefore mandatory for them to be aware of recommendations in clinical practice in order to avoid increased patient anxiety, excessive healthcare expenditure and inadvertent therapeutic procedures.

Prevalence of anatomic variations of the atlas vertebra

BACKGROUND CONTEXT

The retrotransverse foramen (RTF), arcuate foramen (AF), unclosed transverse foramen (UTF) and posterior atlas arch defects (PAAD) are anatomic variations of the atlas vertebra that surgeons must be aware of before spine surgery is performed.

PURPOSE

To analyze the prevalence of the AF, RTF, UTF, and PAAD.

STUDY DESIGN

Ex-vivo anatomical study.

PATIENT SAMPLE

Two hundred eighteen atlas vertebrae obtained from 100 Caucasian subjects and 118 sub-Saharan African subjects (48 Sotho subjects, 35 Xhosa subjects and 35 Zulu subjects).

METHODS

We studied 218 atlas vertebrae from skeletons of the Raymond A. Dart Collection in order to analyze the prevalence of AF, RTF, UTF, and PAAD in both Caucasian and sub-Saharan African subjects.

OUTCOME MEASURES

Not applicable.

RESULTS

Sixty-nine (31.2%) atlases presented anatomical variants: 64 (29.3%) presented one anatomical variant, 4 (1.8%) presented two, and 1 (0.5%) presented three. AF, RTF, UTF, Type A and Type E defects were present in 35 (16.1%), 17 (7.8%), 17 (7.8%), 5 (2.3%), and 1 (0.5%) vertebrae, respectively. The vertebrae with two anatomical variants presented a bilateral UTF and a Type A defect, a bilateral AF and a Type A defect, a right UTF and a left AF, and a right UTF and a Type E defect. The vertebra with three anatomical variants presented a bilateral RTF, a left UTF, and a left AF. No sex differences in prevalence of the RTF (p=.775), AF (p=.605), UTF (p=.408) and Type A defects (p=1.000) were found in the sub-Saharan African and Caucasian groups (RTF, p=.306; AF, p=.346; UTF, p=.121; Type A defects, p=.561). Comparison between the sub-Saharan African (all subjects) and the Caucasian group revealed no differences in the UTF (p=.105), AF (p=.144), RTF (p=.542) and Type A defects (p=.521) prevalence. Also, no differences in the prevalence of the UTF (p=.515), AF (p=.278), and RTF (p=.857) between Zulu, Xhosa and Sotho subjects were found. Neither were found sex differences in the prevalence of UTF, RTF and AF in Zulu (p=.805, p=.234, p=.129), Xhosa (p=.269, p=.181, p=.309), and Sotho subjects (p=.062, p=.590, p=.106).

CONCLUSIONS

The present study has revealed no sex differences in the prevalence of AF, UTF, RTF or PAAD in both Caucasian and sub-Saharan African subjects. This research has also indicated no differences in the prevalence of the UTF, AF and RTF between Zulu, Xhosa and Sotho subjects. In addition, this study has revealed no differences in the Type A, UTF, AF, and RTF prevalence between the sub-Saharan African (all subjects) and the Caucasian subjects. These variations may be known by surgeons before spine surgery for better planning.