Congenital absence of the dens of axis.
D001368:Axis, Cervical Vertebra / Q000002:abnormalities* / Q000196:embryology; D002648:Child; D000013:Congenital Abnormalities / Q000150:complications / Q000000981:diagnostic imaging / Q000601:surgery; D006801:Humans; D008297:Male; D011782:Quadriplegia / Q000209:etiology* / Q000628:therapy; D014056:Tomography, X-Ray; D014103:Torticollis / Q000209:etiology*