Dynamic CT scan of the craniovertebral junction: a role in the management of os odontoideum

Os odontoideum is an uncommon abnormality of the cranio-vertebral junction (CVJ) that exists as a separate ossicle apart from a hypoplastic dens. Its genesis and natural history have been debated, and its proper treatment remains uncertain. A 48-year-old woman complained of persistent upper neck pain and paraesthesia of her left side. Magnetic resonance imaging of the CVJ demonstrated an os odontoideum. Dynamic computed tomography scan of the CVJ showed a reduction of the space available for the spinal cord to 50% from extended to flexed position. The patient underwent posterior spinal fusion of C1-C2 using a sublaminar titanium hook and rods fixed in moderate extension. We discuss the usefulness of the dynamic computed tomography (CT) scan in the evaluation of atlantoaxial motion and the management of this pathology.