Occipitalisation of the atlas is one of the most frequent osseous anomalies of the atlas. It is characterised by the adhesion of the first cervical vertebra with the basilar part of the occipital bone. The most probable cause of the occipitalisation is a congenital disorder. The atlanto-occipital fusion may lead to narrowing of the space for medulla oblongata, spinal cord and vertebral artery. This in turn may lead to many physiological symptoms. The skull from Twardogóra, Southern Poland, showed partial atlanto-occipital fusion and presented an asymmetry in structure and shape of apertures for the vessels and nerves around the foramen magnum. Copyright © 2011 John Wiley & Sons, Ltd.