Anomalous Posterior Arch of Atlas: A Rare Cause for Craniovertebral Junction Compression

Congenital hypoplasia of the anterior and posterior arch of the atlas has been described in the literature. Currarino and associates classified this into various types based on the part of the arch that was hypoplastic. Gin and associates stated that posterior atlantal anomalies were more frequently encountered than anterior arch anomalies. Rarely do these anomalies present in the absence of genetic syndromes. Here, we describe our clinical experience of an anomalous posterior atlantal arch in a nonsyndromic patient.