Bipartite Atlas –A Rare Entity, a Study of Its Incidence in North Indians

Background:Combined anterior and posterior C1 bifidityi.e BIPARTITE ATLAS or SPLIT ATLAS is a rare entity Our goal in this study was to examine the incidence of this anomaly in North India. review the literature and the clinical implications of this cleft defects.. Methods:It is retrospective study ofNCCT evaluation in 1735 patients who underwent CECT neck[900 patients] NCCTwith spine evaluation[835patients]in Pankaj diagnostic set up between jan 2012 to December 2016, and department of radiodignosis Sarojini Naidu Medical college Agra during the time interval between dec 2016 to july 2017 the images were reviewed retrospectively to identify patients with BIPARTITE ATLAS defects . Posterior arch defects of the atlas were grouped in accordance with the classification of Currarino et al ,anomalies were subsequently grouped. Results: We found only 4(4/1735) patients of bipartite atlas i.e .2% of total . anterior ach defects were midline and have a reported width ranging from 1-5 mm The type A posterior arch defect was found in 3 patients and the type B posterior arch defect was found in one patients. No type C, D, or E defects were observed in these bipartite atlas defect The CT scans of the patients show midline clefts of the anterior and the posterior arches of C1 with similar imaging features:smooth margins lined by cortical bone and no lateral offset. The patients had no neurological symptoms relating to the C1 abnormality, and no follow-up was performed.Conclusion:Bipartite atlas is a rare entity as it’s incidence was found to be just .2% . knowledge is essential as it can predispose to certain neurological compressive disorders.awareness helps in clinicoradiological diagnosis, management in patient of trauma as appearance of cleft simulate Jefferson fracture.