Congenital Malrotation of the Atlas with Unilateral Hypertrophy of the Atlanto-occipital Joint-A Rare Anomaly of the Craniovertebral Junction and Its Management.

Background: Congenital anomalies are commonly encountered in the craniovertebral junction because of its unique embryologic development. The craniovertebral junction usually comprises the occiput, atlas, and axis. However, malrotation of the atlas (C1) in between the occiput (C0) and axis (C2) with Chiari I malformation as well as unilateral hypertrophy of the atlanto-occipital joint and a lateral mass manifesting features of high cervical myelopathy is a rarely reported anomaly.