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Preoperative plain radiography and magnetic resonance imaging (MRI).. Plain radiographs showing that atlantoaxial subluxation is reduced in the extension position (A-B). MRI showing high-signal intensity within the spinal cord at the level between the basal dental segment and the posterior arch of C1 (C).
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Plain radiographs of the cervical spine revealed a separation of the dens from the axis as well as atlantoaxial subluxation (Fig. 1A), which was reduced in the extended neck position (Fig. 1B). T2-weighted magnetic resonance imaging (MRI) revealed areas of hyperintensity in the spinal cord at the level between the body of the axis and the posterior arch of the atlas (Fig. 1C).
Preoperative computed tomography (CT) myelography.. CT showing the anterior arch of C1 fused with the apical segment of the dens separated from the basal segment of the dens (A). Sagittal reconstruction CT showing the right and left C0-C1-C2 articulations (B-C). Atlantoaxial dislocation in the flexion position (D) is reduced in the neutral position (E).
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Computed tomography (CT) myelography revealed fusion of the apical segment of the dens and the anterior arch of C1 and narrowing of the spinal canal between the basal dens and the posterior arch (Fig. 2A and D-E). Other anomalous conditions were not identified in the atlantooccipital and atlantoaxial joints (Fig. 2B-C), and there was no additional anomaly in the subaxial cervical spine.
Atlantoaxial fusion surgery.. Atlantoaxial arthrodesis was performed using the Magerl and Brooks technique.
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The operation was performed using the Magerl and Brooks technique (Fig. 3), after which the patient's motor impairment improved over time, with slight numbness in the upper extremities.
Embryology of the axis.. The odontoid process comprises the apical dental segment from the caudal proatlas, the basal dental segment from the first cervical sclerotome, and the body of the axis from the second cervical sclerotome.. PA: proatlas, CSo: cervical somite, CSc: cervical sclerotome
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After resegmentation of cervical sclerotomes, the odontoid process is composed of the apical dental segment from the caudal proatlas, the basal dental segment from the first cervical sclerotomes, and the body of the axis from the second cervical sclerotomes) (Fig. 4).
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