Congenital anomalies of the cervical spine.

There are numerous congenital anomalies of the cervical spine. They can be simple and clinically inconsequential to complex with serious neurologic and structural implications. They can occur in isolation or as one of several maldeveloped organs in the patients. Many are discovered incidentally. The more common anomalies seen by pediatric spine surgeons include defects of the anterior or posterior arches of C1, occipital assimilation of the atlas, basilar invagination or impression, os odontoideum, and Klippel-Feil syndrome. Management begins with a detailed history, physical examination, and imaging studies. In general, those lesions that are causing or have caused neurologic injury, chronic pain, or spinal deformity or place the patient at high risk for developing these require treatment.