Atlanto-occipital fusion and other variations at the base of the skull: a case report

Fusion of the atlas with the occipital bone is called assimilation or occipitalization of atlas. Either partial or complete assimilation can alter the course of vertebral artery, compression of vertebral artery and first cervical nerve, compression of spinal cord by reducing the diameter of foramen magnum. We found a skull with partial fusion of the atlas vertebra with occipital condyles and other variations in the norma basalis. Other variations include change in the size of the jugular foramen, hypoglossal canal, distance between the transverse process of atlas and styloid process, massive mastoid process on right side. The knowledge of such a fusion and variations at the base of skull is important for radiologists, anesthesiologists,orthopedic and neurosurgeons because skeletal abnormalities at the craniocervical junction may result in sudden unexpected death.