Objective To expand MSCT obseration and cognition in the ponticulus of atlas,and to improve the diagnosis for it. Methods 263 cases were collected among the patients undergone the examine of MSCT angiography in intracranial and cervical and volume rendering technique(VRT)with unenhance images,and observation and analysis was focused on the posterior arch of atlas. Results 69 cases(97 sides)were detected ponticulus in this group,including unilateral in 41 cases,bilateral in 28 cases.The simple type ponticulus were 82 sides,including the ponticulus posterior (PP)were 60 sides,the ponticulus lateralis (PL)were 1 5 sides,the ponticulus borderland (PB)were 5 sides,The ponticulus middle (PM)were 2 sides.According to the shape of the ponticulus:simple root in 43 sides,opposite beaked in 21 sides,complete type in 18 sides.The ponticulus compound (PC)were 1 5 sides.Conclusion The images of MSCT VRT can showed accurately the ponticulus of atlas,and it can provide reliable imaging evidence on its diagnosis and classification,and it can be used as an unearthly method for its examination.

Objective To explore the belongingness,name and clinical significance of a sort of osteal structure variation (OSV) posterior,outboard and superior to the ditch of vertebral artery of atlas.Methods 23 cases of OSV were collected among 426 patients underwent MSCT intracranial and cervical angiography with volume rendering technique (VRT)to notice the pier point,shape and direction of protuberance,and the relation and influence to the vertebral artery.Results The incidence of OSV was 5.40%(23/426) in which 31 sides were detected,and 1 5 cases in unilateral and 8 cases in bilateral.Simple type was showed at 1 9 sides,compound type at 12 sides with other ponticulus.According to the shape of the ponticulus,simple root was seen at 1 7 sides(13 inferior root and 4 lat-erial root),opposite beaked at 5 sides,complete type at 9 sides.OSV was located at posterior,outbord and superior to the ditch of vertebral artery of atlas and closed to the vertebral artery.The vertebral artery was influenced by OSV as following:in simple OSV vertebral artery stenosis was seen at 4 sides in which unite convulsion was showed at one side;in compound OSV vertebral artery ste-nosis was seen at 5 sides,in which unite convulsion was showed at 2 sides.Conclusion OSV is similar to ponticulus posticus(PP)and ponticulus lateralis(PL),and has similarly importance clinical significance,and should belong to the ponticulus of atlas,and to be named as ponticulus borderland(PB).