PMC4508738_01
An X-ray demonstrating atlantoaxial subluxation (AAS) and assimilation of C1. The subluxation was slightly increased in the extended position (A), and it was not reduced even in the neutral (B) and flexed positions (C).
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F1
X-ray revealed AAS and assimilation of C1, and the subluxation (which had not reduced) was slightly increased in the extended position (Fig. 1).
Preoperative three-dimensional computed tomography angiography (3DCTA) demonstrates the persistent first interseg-mental artery (PFIA) on the left side, which courses abnormally below the arch of atlas.
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F2
Preoperative three-dimensional computed tomography angiography (3DCTA) revealed the PFIA on the left side (Fig. 2) and stenosis of the foramen magnum.
A T2-weighted sagittal magnetic resonance imaging (MRI) revealed myelomalacia in the upper cervical cord. The odontoid process compressed the ventral cervical cord in flexed (A) and neutral (B) positions, and caused cervical cord impingement in extended position (C). The atlantoaxial distance is slightly increased in the extended position.
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F3
A magnetic resonance imaging (MRI) revealed myelomalacia in the upper cervical cord as a result of the compression of the posterior arch of C1 and the odontoid process (Fig. 3).
An X-ray revealing a sufficient reduction between C1 and C2 (A). A three-dimensional computed tomography angiography (3DCTA) shows C1-C2 rod construct (D). Axial and sagittally reconstructed computed tomography (CT) reveals the C1 screw inserted into the lateral mass on the right side (B, E) and penetrating the occipital condyle on the left side (C, F).
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F4
A postoperative CT scan revealed that all the screws were properly placed (Fig. 4).