Bipartite/Split Atlas Studies

Posted by A on January 08, 2019 in bipartite atlas, c1 vertebrae, cervical spine, congenital anomalies,

If you read just one paper to understand these anomalies, you could just check out this one:

The Split Atlas Anomaly: A Comprehensive Review (2017)

The “split atlas” is a rare congenital finding occurrence arising from the non-?fusion of the anterior and posterior arches of the C1 vertebra. In most cases, this anomaly is asymptomatic and is discovered incidentally. However, it may be difficult to distinguish between fractures of the atlas, hence further imaging modalities are required to analyse the atypical appearance of the anterior and posterior arches of C1. Using standard search engines, the embryology, classification, clinical presentation, diagnosis, and treatment of the split atlas are reviewed. Clinicians who treat patients with issues near the cervical spine or interpret imaging of the craniocervical junction should be familiar with variations involving the first cervical vertebrae.

More Bipartate/Split Atlas Studies

Aplasia of the Posterior Arch of the Atlas: A Proposal for a New Clinical Classification (2009)

Partial or complete aplasia of the posterior arch of the atlas is often detected incidentally when a patient has cervical X-rays. Patients with this anomaly are generally asymptomatic. However, some cases demonstrate neurological symptoms. It is important to predict cases of this anomaly that may be accompanied with neurological symptoms. Between April 2001 and March 2005, three patients were encountered who had an anomalous posterior arch of the atlas. The anomalies encountered in the three patients were midline cleft (two patients) and an absence of the posterior arch with persistent posterior tubercle (one patient). Based on our clinical experience and a review of the literature, we developed a new clinical classification system for this condition. From a clinical point of view, aplasia of the posterior arch of the atlas can be classified into three types. Type I is complete aplasia. Type II is partial aplasia with the isolated posterior fragment. Type II is divided into subtypes depending on the inward mobility of the isolated posterior fragment (Type II- a without and Type II - b with mobility). Type III is partial aplasia without the isolated posterior fragment. Our new classification simple is simple and unambiguous and it also provides a clear direction for developing appropriate diagnostic and treatment strategies.

Bipartite Atlas –A Rare Entity, a Study of Its Incidence in North Indians. (2017)

Combined anterior and posterior C1 bifidity i.e BIPARTITE ATLAS or SPLIT ATLAS is a rare entity Our goal in this study was to examine the incidence of this anomaly in North India. review the literature and the clinical implications of this cleft defects

Complex developmental abnormality of the atlas mimicking a Jefferson fracture: Diagnostic tips and tricks (2013)

Congenital atlas abnormalities are rare — often asymptomatic — findings, not requiring any specific treatment. They are frequently discovered, by chance, in trauma patients, in the course of the radiological work flow at the Emergency Department. In these cases they may represent a diagnostic challenge, since physicians are expected to differentiate them from complex C1 fractures (isolated Jefferson’s fractures or associated with Anderson and d’Alonzo’s fractures) requiring surgical treatment. Although difficult to identify, a correct diagnosis is mandatory in order to optimize the patient’s treatment. In this article we report a case of congenital atlas abnormality, and discuss the tips and tricks to make a correct differential diagnosis through the most appropriate clinical and radiological work flow.

Hypertrophy of the anterior arch of the atlas associated with congenital nonunion of the posterior arch: a retrospective case-control study (2014)

 Nonunion of the posterior arch of the atlas is an uncommon but normal developmental variant. It is usually asymptomatic in the patient but may be associated with greater incidence of fracture because of increased stress on the anterior arch. It has long been subjectively recognized but not objectively quantified, until the present study, that the anterior arch of the atlas is hypertrophied in cases of posterior arch nonunion. Anterior arch hypertrophy may represent an adaptive response to chronically elevated mechanical stress and loss of hoop strength in cases of posterior nonunion.

Median deficiency in the posterior arch of the atlas vertebra: a case report (2011)

Isolated cases of partial agenesis of atlas were initially considered benign variations, without any clinical or pathological significance. However, there is increasing evidence that neurological symptoms may occur even after minor cervical trauma in subjects with defects in the posterior arch of the atlas. The present case study describes a rare case of median deficiency in the posterior arch of atlas vertebra. The knowledge of this benign variation is crucial as it may aid clinicians in correct management of subjects presenting with resolution of symptoms and avoid excessive investigations.

Ossification Patterns of the Atlas Vertebra (2011)

 The objective of this study was to characterize ossification patterns of the C1 (atlas) vertebra in children, to better differentiate normal variants from traumatic injury

Posterior arch anomalies of Atlas and its clinical significance (2014)

 Introduction: Congenital anomalies of posterior arch of atlas are very rare. Most of the time detection of this developmental anomaly is incidental while investigating for neck pain and stiffness or injury involving the region of head and neck. Aim: Our aim was to determine the incidence of posterior arch anomaly of atlas in Maharashtra region. 75 dried human atlas vertebrae were included for this study. Observations: We detected Type A and B in our study. Results: The incidence of posterior arch anomaly is 4% i.e. 3 out of 75 vertebrae. We detected Type A and B in our study and these types are generally asymptomatic. Type C to E may be associated with neurological deficit. Conclusion: It is essential for the clinicians to recognize the condition and the specific type of anomaly in order to distinguish it from fractures secondary to trauma and for the proper guidance of the patients accordingly.

The Incidence and Clinical Implications of Congenital Defects of Atlantal Arch (2009)

Objective : Atlantal arch defects are rare. Few cadaveric and imaging studies have been reported on the variations of such anomalies. Our goal in this study was to examine the incidence and review the clinical implications of this anomaly. Methods : A retrospective review of 1,153 neck or cervical spine computed tomography (CT) scans was performed to identify patients with atlantal arch defects. Neck CT scans were performed in 650 patients and cervical spine CT scans were performed in 503 patients. Posterior arch defects of the atlas were grouped in accordance with the classification of Currarino et al. In patients exhibiting this anomaly, special attention was given to defining associated anomalies and neurological findings. Results : Atlantal arch defects were found in 11 (11/1153, 0.95%) of the 1,153 patients. The type A posterior arch defect was found in nine patients and the type B posterior arch defect was found in two patients. No type C, D, or E defects were observed. One patient with a type A posterior arch defect had an anterior atlantal-arch midline cleft (1/1153, 0.087%). Associated cervical spine anomalies observed included one C6-7 fusion and two atlantal assimilations. None of the reviewed patients had neurological deficits because of atlantal arch anomalies. Conclusion : Most congenital anomalies of the atlantal arch are found incidentally during investigation of neck mass, neck pain, radiculopathy, and after trauma. 

The prevalence of congenital C1 arch anomalies (2017)

Purpose To determine the prevalence, radiographic features and reporting rate of, and the association between the congenital anterior and posterior C1 arch anomalies. Methods The computed tomography (CT) images of the cervical spines of all patients over 18 years who had CT examinations in our hospital during the study period were reviewed to evaluate for congenital anomalies of the anterior and posterior C1 arches. Radiology reports of the corresponding CT examinations were reviewed to determine the reporting rate of these defects. Results Of 3273 subjects, 185 (5.65%) had congenital atlas anomalies: 169 isolated posterior (5.16%), 15 combined anterior and posterior (bipartite, 0.46%), and one isolated anterior (0.031%) arch defects. Females had a higher prevalence than males (7.46 versus 4.72%, P = 0.0013). Eighty-three cases (44.9%) of C1 arch anomalies were not reported. The Currarino type A, B, C and E posterior arch defects accounted for 81.6, 8.1, 1.1, and 0.5% of all arch anomalies while type D was not observed. Fifteen patients (0.46%) had combined anterior and posterior arch anomalies (bipartite atlas) versus only one with an isolated anterior C1 defect, indicating a significant association between the anterior and posterior arch defects (P\0.0001). Conclusions Although some types of congenital C1 arch anomalies are rare, type A defects are relatively common radiological findings that are unreported approximately 45% of the time. Based on the significant association between the anterior and posterior arch defects, we propose possible mechanisms for the formation of the bipartite atlas.

 Case studies listed here.