Congenital Posterior Arch Defect of the Atlas: Report of a Rare Anomaly

CY Chu, RTM Chan, VKP Fung, CS Cheng

Hong Kong J Radiol 2011;14:102-7

Congenital defects of the posterior arch of the atlas are rare, with a reported prevalence of 0.95 to 4%. The defects have been classified into five types (A-E), with type A being most common and types B-E being found only in 0.69% of the general population. Although most patients are asymptomatic, some may present with chronic neck pain, headache, Lhermitte’s sign, transient quadriparesis or even acute neurological deficits. The defects may also mimic a Jefferson fracture leading to a wrong diagnosis. Despite its rarity, knowledge of this congenital posterior arch defect of the atlas is important for avoiding diagnostic errors and to provide information on its management. We are therefore reporting a case with this congenital defect discovered as an incidental finding and provide a literature review about this rare anomaly.





先天性寰椎後弓缺陷症非常罕見,據文獻報告,發病率只有0.95%至4%。這症狀被分為A至E五種類 型,其中A型最常見,而B至E型只佔一般人口的0.69%。雖然大部分患者並沒有病徵,有些患者卻出 現慢性頸部疼痛、頭痛、拉密特徵(Lhermitte’s sign)、暫時性的四肢輕癱或急性神經功能缺損。寰 椎後弓缺陷症的病徵可能會與Jefferson骨折相似,引致誤診。雖然寰椎後弓缺陷症很罕見,認識此症 對於治療及避免誤診很重要。所以特此報告這宗因偶然而發現的寰椎後弓缺陷症病例,並對此病症 作文獻回顧。