Congenital absence of the posterior arch of the atlas.
D000293:Adolescent; D001368:Axis, Cervical Vertebra / Q000002:abnormalities* / Q000000981:diagnostic imaging; D001270:Cervical Atlas / Q000002:abnormalities* / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011859:Radiography; D014054:Tomography