Occipital vertebrae

Occipital vertebrae are very rare anatomical variants that result from incomplete or aberrant fusion of occipital bone ossification centers. There is a broad spectrum of occipital vertebrae variations and the four most common include:

• third condyle (condylus tertius)
• basilar process
• paracondylar process
• prebasioccipital arch

Clinical presentation

Symptoms are rare but may include:

• neck pain
• reduced movement at the atlanto-occipital joint

Radiographic features

Plain radiography and CT help in the diagnosis of this condition in which a bony projection or arch is seen between the occipital bone and atlas.