A congenital anomaly of the atlas as a diagnostic dilemma: a case report

"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.

C1 fractures: a review of diagnoses, management options, and outcomes

The atlas is subject to fracture under axial load, often due to traumatic injuries such as shallow dives and automobile accidents. These fractures account for 2-13 % of injuries to the cervical spine [Marcon RM et al. Clinics (Sao Paulo) 68(11):1455-61, 2013]. Fractures of the C1 vertebra are often difficult to diagnose, as there is often no neurological deficit or easily identifiable findings on radiographs. However, injuries to the atlas can be associated with vertebral artery injury and atlantoaxial or atlanto-occipital instability, making prompt and accurate diagnosis imperative. A detailed understanding of the anatomy, inherent stability, and common injury patterns is essential for any surgeon treating spinal trauma. This chapter explores the diagnosis and management of C1 fractures, as well as outcomes after treatment.

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

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.

Athletic cervical spine injury in the setting of fusion failure of the anterior and posterior atlas

This article describes a rare congenital abnormality of anterior and posterior C1 fusion failure presenting after an acute athletic injury to the fibrous nonunion. C1 congenital malformations are rare, occurring in approximately 2% of patients; even rarer are combined anterior and posterior arch malformations in the same patient. Posterior ring abnormalities are more common than anterior ring injuries (4.5:1, respectively). To the authors' knowledge, combined anterior and posterior ring congenital malformations with subsequent injury have not been previously described. In the current patient, a congenital failure of fusion of the anterior and posterior arches of C1 was identified. The anterior fibrous nonunion was injured while the patient played football, leading to transient neurologic injury and dysphagia from soft tissue swelling. The patient was initially diagnosed with an acute fracture at another facility; however, given advanced imaging, flexion and extension views, and a normal neurologic examination, the authors diagnosed a traumatized congenital defect. The injury healed with a short period of cervical collar immobilization and supportive measures. Such malformations are usually found incidentally, but they can be symptomatic after trauma. Images to distinguish these deficits can be difficult because the differences between chronic nonunions and congenital malformations are subtle. Surgery is rarely indicated for congenital malformations because they are often stable even after injury; however, they may predispose patients to neurologic injury in the future with high-risk activities. Because the current patient had an increased chance of future injury secondary to the lack of bone formation in the C1 vertebrae, he was restricted from participating in contact sports.

Aplasia of the anterior arch of atlas associated with multiple congenital disorders: case report

BACKGROUND AND IMPORTANCE

Congenital clefts and aplasias of the atlas vertebra are rare. A nonfused posterior arch occurs in 4% of the population; in contrast, a nonfused anterior arch occurs in only 0.1%. To the best of our knowledge, this is the first description of the combination of anterior arch aplasia and a cleft of the posterior arch of the atlas associated with Klippel-Feil and Treacher-Collins syndromes and Sprengel deformity.

CLINICAL PRESENTATION

An 11-year-old girl presented with neck pain and symptoms of myelopathy, including upper- and lower-extremity paresthesia. Computed tomography revealed significant congenital bony anomalies of the cervical spine, with congenital fusion of C2 through C5. There was aplasia of the anterior ring of C1 (A 2.3-cm gap was present within the anterior aspect of the lateral masses). The posterior elements of C3 and C4 were fused, and signs of Sprengel deformity were present. Magnetic resonance imaging revealed effacement of the ventral cerebrospinal fluid space at the craniocervical junction and mild mass effect at the cervicomedullary junction. Flexion and extension views showed abnormal motion at the craniocervical junction. There was no evidence of atlantoaxial instability, basilar invagination, or Chiari malformation. Occipito-C4-scapular fusion was performed to prevent spinal cord injury and further neurological symptoms. Postoperatively, the patient did extremely well, and her preoperative symptoms resolved.

CONCLUSION

We describe a rare case of aplasia of the anterior arch of the atlas and posterior arch midline cleft in association with Treacher-Collins syndrome, Klippel-Feil syndrome, and Sprengel deformity. The patient's atlantoaxial instability was managed surgically with a unique construct that provided occipito-C4-scapular fusion.

Absent cervical spine pedicle and associated congenital spinal abnormalities - a diagnostic trap in a setting of acute trauma: case report

Background

Congenital spinal abnormalities can easily be misdiagnosed on plain radiographs. Additional imaging is warranted in doubtful cases, especially in a setting of acute trauma.

Case Presentation

This patient presented at the emergency unit of our university hospital after a motor vehicle accident and was sent to our radiology department for imaging of the cervical spine. Initial clinical examination and plain radiographs of the cervical spine were performed but not conclusive. Additional CT of the neck helped establish the right diagnosis.

Conclusion

CT as a three-dimensional imaging modality with the possibility of multiplanar reconstructions allows for the exact diagnosis and exclusion of acute traumatic lesions of the cervical spine, especially in cases of doubtful plain radiographs and when congenital spinal abnormalities like absent cervical spine pedicle with associated spina bifida may insinuate severe trauma.

The incidence and clinical implications of congenital defects of atlantal arch

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 C(6-7) 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.