Published 15 July 2009, doi:10.1136/bmj.b2645
Cite this as: BMJ 2009;339:b2645

Endgames

Picture quiz

Cervical radiography

¹ Department of Trauma and Orthopaedics, Colchester General Hospital, Colchester

Case history

A 46 year old white man presented to the accident and emergency department following a traffic accident. He was sitting in the passenger seat of the car and was thrown out of the vehicle upon impact. The car was travelling at 60 mph. On arrival he was conscious and initial assessment revealed only superficial lacerations on his torso and limbs. Spinal assessment showed no para-spinal muscle spasm and no localised bony or soft tissue tenderness.

Standard radiographs of the pelvis, chest, and abdomen revealed no injury. His cervical radiograph (fig 1), however, caught the attention of the attending trauma team. No focal neurological deficit was present in the patient.

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Questions

1 What is the abnormality shown in the radiograph?

2 What further investigations are warranted?

3 When would surgery be considered?

Answers

Short answers

1 The radiograph shows aplasia of the posterior arch of the atlas.

2 Computerised tomography should be undertaken.

3 Surgery should be considered when symptoms of spinal cord compression are present or if a bony remnant of the posterior arch of the atlas is visible on imaging.

Long answers
1 Abnormalities of the posterior arch of the atlas
Defects of the posterior arch of the atlas are congenital abnormalities,^{1 2} with an estimated prevalence of 3-4% in the general population.³ Such defects are usually an incidental finding following cervical imaging.² When associated with traumatic injuries, however, they can cause spinal cord compression and can manifest as neurological deficits,⁴ and surgical intervention might be needed urgently.^{2 5} Asymptomatic patients should be advised to avoid contact sports, as even minor cervical trauma can cause symptoms.⁶

The most commonly used classification for congenital abnormalities of the posterior arch of the atlas is by Curriano et al⁶ (table 1). Type A defects are the most common and account for 90% of cases, with a population prevalence of 3-4% whereas the other types have a population prevalence of 0.69%.^{6 7 8 9} The cervical radiograph (fig 2) and the computed tomogram (fig 3 ) confirmed that our case had a type E defect.

View larger version (102K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 2 Lateral cervical radiograph showing aplasia of the posterior arch of the atlas

 

View larger version (140K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 3 Computed tomogram confirming complete aplasia of the posterior arch of the atlas (type E defect)

 

View this table: [in this window] [in a new window]   Table 1 Curriano classification of aplasia of the posterior arch of the atlas

 
2 Further investigations
The literature suggests that assessment of the abnormality should be done using lateral flexion/extension cervical radiographs in order to assess inward movement of any bony remnant of the posterior arch.⁷ Computed tomography is also warranted, especially if focal neurology is present or a posterior arch bony remnant is visible on radiography.^{2 5 10} Given that many of these anomalies are asymptomatic, however, the need for further investigations should be evaluated in each clinical scenario.⁷

3 Surgical treatment
Surgery should be considered if the patient shows signs of spinal cord compression in conjunction with a posterior bony remnant or tubercle (type C and D defects).^{2 5 7} Surgical opinion should also be sought in asymptomatic patients with type C or D defects but no evidence of atlanto-axial instability,² as such defects are associated with transient quadriparesis.^{1 5} A conservative approach can be considered in these cases, but the patient should be advised to avoid contact sports and seek medical attention if neurological symptoms are experienced.⁶

Unfortunately, no case based evidence exists regarding the management of type E defects because they are rare. The general consensus, however, is that type A and B defects are asymptomatic and stable, whereas type C and D defects should be readily recognised and thoroughly assessed as they are more likely to be associated with neurological symptoms and necessitate surgery.^{5 11}

Patient outcome
The patient’s immediate injuries were superficial and not life threatening. Given the radiological findings on cervical imaging, however, he remained in hospital for observations. He did not develop any neurological symptoms and was discharged after 24 hours. The patient was advised to avoid contact sports in order to prevent neck injuries, as recommended in the literature.

Cite this as: BMJ 2009;339:b2645

Provenance and peer review: Commissioned; externally peer reviewed.

Patient consent obtained.

References

1. Gangopadhyay S, Aslam M. Posterior arch defect s of the atlas: significance in trauma and literature review. Eur J Emerg Med 2003;10:238-40.[CrossRef][Medline]
2. Klimo P, Blumenthal DT, Couldwell WT. Congenital partial aplasia of the posterior arch of the atlas causing myelopathy: case report and review of the literature. Spine 2003;28:E224-8.[CrossRef][Web of Science][Medline]
3. Geipel P. Zur kenntnis der spatbildung des Atlas und Epistropheus: Teil IV. Zentralbl Allg Pathol 1955;94:19-84.[Medline]
4. O’Sullivan AW, McManus F. Occult congenital anomaly of the atlas presenting in the setting of acute trauma. Emerg Med J 2004;21:639-40.[Abstract/Free Full Text]
5. Sharma A, Gaikwad SB, Deola PS, Mishraa NK, Kalea SS. Partial aplasia of the posterior arch of the atlas with an isolated posterior arch remnant: findings in three cases. Am J Neuroradiol 2000;21:1167-71.[Abstract/Free Full Text]
6. Curriano G, Rollins N, Diehl JT. Congenital defects of the posterior arch of the atlas: a report of seven cases including an affected mother and son. Am J Neuroradiol 1994;15:249-54.[Abstract]
7. Tac EC, Soon HC, Kevin M, Se To BC. Congenital absence of the posterior arch of the atlas–a strange but benign anomaly. Malaysian Orthopaedic Journal 2007;1:30-2.
8. Page GT, Yock DH. Total aplasia of the posterior arch of the atlas. Minn Med 1981;64:666-8.[Web of Science][Medline]
9. Fiorani-Gallotta G, Luzzatti G. Complete absence of the posterior arch of the atlas. Arch Ortop 1955;68(5):753-78.[Medline]
10. Sagiuchi T, Tachibanaa S, Satoa K, Shimizua S, Kobayashia I, Okaa H, et al. Lhermitte sign during yawning associated with congenital partial aplasia of the posterior arch of the atlas. Am J Neuroradiol 2006;27:258-60.[Abstract/Free Full Text]
11. Ozdolap S, Sarikaya S, Balbaloglu O, Kalayci M. Congenital defects of the posterior arch of the atlas: a case report. Neuroanat 2007;6:72-4.

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