PMC3176433_01
Preoperative dynamic lateral plain radiographs. Flexion view (a) and extension (b) view. Preoperative plain radiographs in flexed position (a) and in extended position (b) showed ossified mass behind dens and irreducible atlantoaxial subluxation. The atlantodental interval is 6 mm and the space available for the spinal cord is 7 mm in each positions.
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Dynamic lateral plain radiographs of cervical spine revealed irreducible atlantoaxial subluxation (AAS) (Figure 1).
Reconstructed computed tomogram (CT). (a) Sagittal reconstructed CT. Ossified mass behind dens (arrow) and osteophyte continuing from the dens (arrowhead) can be seen. The dens itself is degenerated and hypertrophied. (b) Axial CT. Most of the spinal canal is occupied by ossification of transverse ligament of atlas. (c) Coronal reconstructed CT. The joint space of atlantoaxial joint and the spaces between dens and lateral masses of atlas were narrowed. Coalition of bilateral atlantooccipital joints can be seen (arrow).
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fig2
There was no ossification of posterior longitudinal ligament (Figure 2(a)). A space between dens and posterior arch decreased (Figure 2(b)). CT. Coalition of bilateral atlantooccipital joints was seen (Figure 2(c)).
Preoperative MRI on T2-weighted image. (a) Sagittal plane. The spinal cord is compressed at the level of C1, C3-4, and C4-5, with high intensities within the spinal cord at C1 level. (b) Axial plane. The spinal cord is compressed by the mass behind dens and posterior arch of the atlas.
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The spinal cord was compressed between the mass and posterior arch of atlas, and there was no subarachnoid space around the spinal cord. The spinal cord was also compressed at the level of C3-4 and C4-5 (Figure 3(a)). Axial planes of MRI also showed compressed spinal cord at the level of C1 between the mass and posterior arch of atlas (Figure 3(b)).
Postoperative dynamic lateral plain radiographs. Flexion (a) and extension (b) view. Atlantoaxial subluxation had not progressed.
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Follow-up plain lateral radiographs showed no deterioration of AAS after surgery (Figures 4(a) and 4(b)).
Postoperative MRI on T2-weighted image. Sagittal (a) and axial (b) plane. The spinal cord had been decompressed.
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The follow-up MRI revealed an adequate decompressed spinal cord (Figures 5(a) and 5(b)).