Int J Anat Res 2016, 4(4):3142-47. ISSN 2321-4287 3142 Original Research Article OCCIPITO-CERVICAL SYNOSTOSIS: ITS OCCURANCE AND EM BRYOLOGICAL BASIS Rakesh Kumar Diwan *, Deepshikha Kori, R.K Verma, A.K Pankaj, Garima Sehgal, Sushma Tomar. ABSTRACT Address for Correspondence: Dr. Rakesh Kumar Diwan, Associate Professor, Department of Anatomy, King George’s Medical University, Lucknow- 226003 Uttar Pradesh. India. Contact no. of corresponding author: +918005335622 E-M ail: dewanrakesh80@yahoo.com Introduction: Occipito-cervical synostosis is a rare anomaly. It is also known as assimilation or occipitalization of atlas. It is defined as a congenital fusion of atlas vertebra with the base of occipital bone, it may be complete or partial. This anomaly results due to failure in segmentation and separation of last occipital sclerotome and first cervical sclerotome during development of foetus. M aterial and M ethods: The present study was conducted on 240 skull bones in the department of Anatomy King George Medical University, Lucknow, India. We observed the synostosis of atlas vertebrae with basilar part of occipital bones. Results: Among 240 bones we noticed 7 craniums which were fused with the first cervical vertebra and the details of these are described in following article. Conclusion: This type of anomaly may alter the dimensions of foramen magnum and may compress the spinal cord and vertebral artery. Therefore, improved knowledge on the fusion of atlas with the occipital bone is important for orthopedicians, neurosurgeons, radiologist, anaesthetist, physiotherapist and anatomist, as it shows multiple variations and combinations. KEY W ORDS: Atlas, occipital bone, synostosis, variation, sclerotome . INTRODUCTION International Journal of Anatomy and Research, Int J Anat Res 2016, Vol 4(4):3142-47. ISSN 2321-4287 DOI: http://dx.doi.org/10.16965/ijar.2016.422 Access this Article online Quick Response code Web site: International Journal of Anatomy and Research ISSN 2321-4287 www.ijmhr.org/ijar.htm DOI: 10.16965/ijar.2016.422 Department of Anatomy, King George’s Medical University, Lucknow, Uttar Pradesh, India. Received: 29 Sep 2016 Peer Review: 29 Sep 2016 Revised: None Accepted: 02 Nov 2016 Published (O): 30 Nov 2016 Published (P): 30 Nov 2016 ing movements of flexion, extension and slight lateral rotation [2]. The anterior arch articulates with dens of the axis to form pivot type synovial joint. The craniovertebral anomalies are com- mon and are often seen in radiological studies, occipito-cervical synostosis is rare congenital anomaly seen at craniovertebral region [3]. It is defined as congenital fusion of atlas to the base of the occiput. The other terms for the same are occipitalization of atlas, assimilation of atlas, atlanto-occipital synostosis and atlantooccipital fusion. Motabagani & Surendra 2006 [4] quoted The occipital bone forms the back and base of cranium and its inferior surface having two occipital condyles. Atlas is first cervical vertebra which supports the skull, so also called atlas (after the mythical Greek God who supported the globe) [1]. Atlas vertebra is ring shaped, without a body having an anterior arch, posterior arch and two lateral masses. Its superior articular facets articulate with the occipital condyles to form atlanto-occipital joint which is a synovial joint of ellipsoid variety hav-