title: Congenital absence of the anterior arch of the atlas: a normal variant.
abstract: Congenital absence of the anterior arch of the atlas is incredibly rare with only two cases reported previously in the literature. We present a third case of a medically fit patient who suffered neck trauma with an abnormal odontoid peg x-ray, which subsequently demonstrated a congenital  non-fusion of the anterior vertebral arch of C1 on computed tomography. This case highlights the need to have an open diagnosis to include congenital anomaly when interpreting abnormal odontoid peg x-rays.
authors.affiliation: Royal Berkshire Hospital, Reading, Berkshire, UK. dushanthavarajah@yahoo.com
authors.forename: D
authors.initials: D
authors.lastname: Thavarajah
authors.forename: P
authors.initials: P
authors.lastname: McKenna
mesh_terms: D001270:Cervical Atlas / Q000002:abnormalities* / Q000000981:diagnostic imaging*; D006801:Humans; D014057:Tomography, X-Ray Computed