2 cases of Spondyloepiphyseal Dysplasia congenita accompainied by hypoplasia of the odontoid process are presented. Case 1 was a 49-year-old female with primary complaints of dizziness, pain of neck and from the right shoulder to the antebranchium, and numbness from the right antebranchium to the finger tips. Case 2 was a 32-year-old male with primary complaints of left back pain and numbness of the left fingers. Both patients showed hypoplasia of the axial odontoid process and marked

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... y of the atlantoaxial joint. Myelography also indicated compression of the spinal cord by the vertebral body of the axis and posterior arch of atlas. Case 1 was treated by resection of the posterior arch of the atlas and occipitocervical fusion and application of a halo-vest for 14 weeks postoperatively. Presently, 2 years after operation, bone union has been completed, and the symptoms are alleviated. In case 2, posterior fusion by the modified McGraw method was performed, but bone union was not achieved. Therefore, transoral atrantoaxial fusion was carried out after 11 months, and a halo-vest fixation was applied for 8 postoperative weeks. The symptoms disappeared shortly after operation, and the patient has shown good bone union and an uneventful course to date 14 years after the operation.