en Basic Neurosurgery Case report <div style="text-align: justify;"><strong>Background & Importance:</strong> Atlas assimilation is the congenital Atlas fusion with the base of the occipital bone.<br> <strong>Case Presentation: </strong>A patient was presented with neck pain, dysaesthesia and tingling of hands and feet and difficulty in walking for 4 years. On examinations, the patient had a short neck with&nbsp;rigidity in neck muscles and there were&nbsp;exaggerated jerks with bilateral Babinski sign. Cervical<br> spinal x-ray indicated basilar invagination with the absence of a C1 arch and CT scan of the&nbsp;cervical spine showed assimilation of C1 with basilar invagination. Occipitocervical stabilization has been commonly proposed for the operational fusion. The iliac crest interposing bone graft&nbsp;was performed for fusion and stabilization of the occipitocervical region. The patient was treated&nbsp;surgically and soon after operation became painless and was able to move easily.<br> <strong>Conclusion:</strong> In C1 assimilation with basilar invagination, bicortical occipital screws and C2&nbsp;pedicle screws with interposition bone graft can be the way to optimize the shortest segmental&nbsp;stabilization and fusion procedure for occipitocervical fusion.<br> <br> <br> &nbsp;</div> Quadriperesis, Atlanto-occipital, fibrosis, CVJ, unicortical 141 146 http://irjns.org/browse.php?a_code=A-10-280-1&slc_lang=en&sid=1 Moshiur Rahman Moshiur sabit.kh06@gmail.com 10031947532846005123 10031947532846005123 Yes Neurosurgery Department, Holy Family Red Crescent Medical College, Dhaka, Bangladesh S.I.M. Khairun Nabi Khan Khairun abeer.ewu932@gmail.com 10031947532846005124 10031947532846005124 No Neurosurgery Department, Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh Robert Ahmed Khan sarwardocument@gmail.com 10031947532846005125 10031947532846005125 No Neurosurgery Department, Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh Rokibul Islam Rokibul sarwartopbright2019@gmail.com 10031947532846005126 10031947532846005126 No Neurosurgery Department, Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh Mainul Haque Sarker newazanika22@gmail.com 10031947532846005127 10031947532846005127 No Neurosurgery Department, Dhaka Medical College, Dhaka, Bangladesh