387UNUSUAL FORAMEN ON THE POSTERIOR ARCH OF ATLASAtlas vertebra with a groove for the vertebral artery , dorsal rami of first cervical nerve and venous plexus is present on the superior surface of the posterior arch of the atlas. We found an abnormal foramina on the left posterior arch of the atlas. The vertebral artery is vulnerable to compression in its course between foramen transversarium and the foramen magnum during extreme rotation of the head and neck. This situation may be aggravated by the presence of posterior or lateral bridge of the Atlas and result in compromised blood flow. The presence of the bony ring formed by posterior bridging in the atlas vertebra has been documented in previous literatures. The knowledge of the presence of this additional foramen will be useful for chiropractioner, orthopaedic surgeons, radiologist and neurosurgeons during a spinal adjustment and surgical manipulation of the cervical spine.s4chavan@yahoo.co.incasereport5122015Atlas Vertebra,Foramina,Posterior ArchSuresh R Rao, Gangadhara Swamy,Vasudha T.K,T.Ramesh RaoDepartment of Preclinical Sciences, Faculty of Medical Sciences, The University of The West Indies, St. Augustine Trinidad & Tobago, Subbiah Institute of Medical Sciences and Research Center, Shimoga, India., Subbiah Institute of Medical Sciences and Research Center, Shimoga, India.,Department of Preclinical Sciences, Faculty of Medical Sciences, The University of The West Indies, St. Augustine Trinidad & Tobago