Cranio-vertebral junction anomaly: atlanto-occipital assimilation.

Cranio-vertebral junction is a pivot which holds the globe of the head. Bony anomalies at this point are particularly significant because they lodge the spinal cord and lower part of the brain stem. Clinically fusion of the atlas with the lower part of the occiput is known as Atlanto-occipital assimilation or atlas occipitalization, which can be either partial or complete depending upon the extent of fusion. It can present as totally asymptomatic accidental finding or can be a cause behind major neuro-vascular compression. The present case study is an endeavor to explain occipitalization of atlas bone on the basis of embryology and explain its clinical relevance.