Anteroposterior spondyloschisis of atlas with bilateral cleft defect of posterior arch: A case report

Study Design.: Case report and review of the literature. Objective.: To report on a patient presenting with anteroposterior defects of the arch of the atlas with a rare type of posterior arch defect. This report includes a literature review of the hypothesis for the development of this anomaly. Summary of Background Data.: Congenital bony defects of the atlas are uncommon. Isolated posterior clefts are the most frequent anomaly, but combined anterior and posterior defects are the least common. In particular, combined anteroposterior defects of the arch of the atlas with other types of posterior arch defects, not including type A, have not been reported. These anomalies can cause confusion, particularly in the setting of trauma when the radiologic finding may be misinterpreted as representing a fracture. Methods.: We report here on a 22-year-old man with an anteroposterior defect of the atlas who complained of neck pain after a traffic accident. The computed tomography demonstrated well-corticated defects with sclerotic changes and no evidence of soft tissue swelling adjacent to the bony discontinuities, consistent with a congenital abnormality. Suspecting anteroposterior spondyloschisis, we performed only conservative treatment. Results.: The patient improved on conservative therapy without a surgical procedure. Conclusion.: We describe combined anteroposterior defects of the arch of the atlas along with other types of posterior arch defects. Most congenital defects of the arch of the atlas are found during radiologic evaluation of neck pain after trauma. Careful diagnosis is needed for these patients to avoid confusing these defects with a fracture.