 There is an ossific fragment that represents the upper portion of the dens, which is displaced anterosuperiorly in relation to the remainder portion of the dens. There is approximately 55 degrees of angulation between the dens and the displaced ossific fragment. The distance between the displaced ossific fragment and the mildly hypertrophy anterior arch of C1 is 1 mm. The degree of displacement of the odontoid fragments is approximate 8 mm. There is anterior subluxation of the lateral mass of C1 in respect to C2, better visualized on CT.There is impingement of the hypoplastic dens remnant on the left ventral cord with moderate central spinal canal stenosis. There is a subtle diffuse increased T2 signal in the cord at this level. There is no significant volume loss. Fluid signal is seen between the displaced ossified fragment and the remainder of the dens.Remainder of the cervical spine is unremarkable.
1. Findings consistent with dystopic os odontoideum. The os odontoideum is anterosuperiorly displaced and angulated with the remainder of the hypoplastic remnant dens. 2. Impingement of the dens remnant on the left ventral cord with moderate spinal stenosis. High T2 signal on the cord may represent a degree of chronic myelomalacia although there is no significant cord volume loss and the possibility of superimposed cord edema cannot be excluded. Please correlate clinically.4. Trace fluid between the displaced os odontoideum and the remainder of the dens, possibly indicating atlantoaxial instability. Flexion/extension radiographs recommended.