ANATOMICAL VARIATIONS IN CONDUIT OF VERTEBRAL ARTERY IN ATLAS

BACKGROUND: The 1 st cervical vertebra is named as atlas.It differs from all the other vertebrae in having no body and no spine.The atlas consists of two bulky lateral masses, connected to each other in front by a short anterior arch, and behind by a long curved posterior arch it thus forms a ring of bone.The posterior arch forms three-fifths of the atlantal ring.At the root of the arch the superior surface of posterior arch bears a wide groove for the vertebral artery, venous plexus and the C1 nerve immediately behind the lateral mass.In few cases this groove is converted into the completely or partially posterior/lateral vertebral artery foramen.AIM: This study was carried out to know the variations in posterior vertebral artery groove in atlas vertebra for clinical and surgical purpose.MATERIALS AND METHODS: The present study is based on the observation of the 300 macerated Human atlas vertebrae of North Indian present in the Anthropology Museum of Department of Anatomy, GSVM Medical College, Kanpur.The atlases were randomly selected the age and sex were not taken into consideration.RESULTS: We observed the complete posterior vertebral artery foramen in 8% specimen (2.33% bilateral and 5.67% unilateral).In 3.33% it was found on left side and 2.33% on right side.Incidence of incomplete posterior vertebral artery foramen was observed in 9.33% (1.33% bilateral and 8% unilateral).In 5% it was found on left side and 3% on right side.The bilateral presence of complete or incomplete lateral vertebral artery foramen was nil.The unilateral presence of complete or incomplete lateral vertebral artery foramen was found equal in frequency i.e. 0.67%.The unilateral presence of complete lateral vertebral artery foramen on either side was found in 0.33% specimen whereas the incomplete lateral vertebral artery foramen was found only on left side (0.67%).CONCLUSION: The presence of complete/incomplete posterior or lateral vertebral artery foramen may reduce the area of the space for the vertebral artery passing through the vertebral artery groove and may compress the vertebral artery which may result into various types of neurological symptomatology.