Fig. 5

A 45-year-old male patient was admitted for numbness of limbs and walking instability for 2 years. Preoperative dynamic radiographs (a, b) showed successful reduction of the atlantoaxial dislocation in a hyperextended position, so it was classified as type I. Preoperative T1-weighted MRI showed atrophy of the spinal cord (c), and T2-weighted MRI showed high signal intensity of the spinal cord (d). Following posterior fixation and fusion, satisfactory reduction and internal fixation were achieved (e, red arrow). Postoperative MRI showed that spinal cord compression was relieved (f, g), and the patients had further neurological deterioration within 6 months after operation