Anatomical variation of vertebral artery at the craniovertebral junction in patients with occipitalization of the atlas: radiographic study using three ⁃ dimentional CT angiography

Abstract

Objective To study the anatomical variation of vertebral artery (VA) at the craniovertebral junction (CVJ) in patients with occipitalization of the atlas. Methods Through reviewing the image studies of 48 patients with occipitalization of the atlas admitted to Department of Neurosurgery, Xuanwu Hospital from January 2007 to October 2010, the anatomical characteristics of VA were studied retrospectively. Results According to the branches and anatomical course of VA, 48 patients (96 sides) were divided into 5 types. Type 1: the VA is single trunk, running between the occipitalized atlantal posterior arch and axial plate (19 sides, 19.79%); type 2: single trunk VA runs through a bony canal between the assimilated atlas and occipital cranium (43 sides, 44.79% ); type 3: single trunk VA runs between the normal occipital cranium and atlantal posterior arch (29 sides, 30.21% ); type 4: VA has a fenestration, with one branch running below the occipitalized atlantal posterior arch and the other branch running above the atlantal posterior arch (3 sides, 3.13%), 2 branches merge as one VA trunk after entering into the dura; type 5: hypogenesis or agenesis of VA (2 sides, 2.08% ). Conclusion The vertebral artery has a high rate of anatomical variation in patients with assimilation of the atlas. The risk to be injured is high for type 1 and type 4 variations during surgical dissection. For type 2 and type 3, careful subperiosteal dissection can decrease the risk. Preoperative computed tomography (CT) angiography combined with bone reconstruction can provide important information in the preoperative evaluation, thus decrease surgical risk. DOI：10.3969/j.issn.1672-6731.2011.05.019