Imaging of the absent cervical pedicle syndrome.

Three cases of congenital absence of a cervical spine pedicle are described. This anomaly comprises a radiological triad of (i) the absent pedicle producing an apparently 'giant' neural foramen; (ii) a dorsally displaced ipsilateral articular mass and lamina with a dysplastic and reversed facet joint; and (iii) deficiency or absence of the ipsilateral transverse process. Recognition of this anomaly is particularly important in the context of acute injury to avoid misdiagnosis as a traumatic facet joint fracture-dislocation. The giant foramen must also be differentiated from expansion due to a neurofibroma. A correct plain radiographic diagnosis is usually possible, but in doubtful cases appearances on computed tomography are pathognomonic. Magnetic resonance imaging, performed in two of the cases, was helpful in elucidating the contents of the giant foramen, but should rarely be necessary in clinical practice.