Assimilation of Atlas in Indian Dry Skulls

Background: A congenital fusion of the atlas to the base of the occiput is defined as assimilation of atlas. It may produce narrowing of foramen magnum which may compress the spinal cord or brain stem. Rarely, it also results in vertebral artery compression, leading to dizziness, seizures and syncope. Multiple variations of partial assimilation have been reported and may involve any aspect of atlanto-occipital articulation. Therefore the knowledge of such anomaly is essential for orthopedic, anesthetist, and clinician. Aims and Objectives: Aim of the present study was to find the incidence of assimilation of atlas in Indian dry adult skulls of unknown sex and age for which 150 skulls were examined. Results: Only in one skull, we observed fusion of atlas vertebra with occipital bone. The posterior arch and two superior facets of atlas had completely fused with the occipital condyles. The anterior arch had incompletely fused with occipital bone, showing nonunion in the midline. Only right transverse process was fused with occipital bone. Conclusions: Assimilation of atlas may cause orthopedic problems and occasionally it produces neurological effects especially when the lumen of foramen magnum is reduced. Therefore, improved knowledge on the fusion of the atlas with the occipital bone is important in clinical practice as it shows multiple variations and combinations