Congenital variations of the upper cervical spine and their importance in preoperative diagnosis. A case report and a review of the literature.

Several variations of the bony and vascular anatomy around the first and second cervical vertebrae have been reported. Failure to recognise these variations can complicate operations on the upper cervical spine. We present a patient with recent onset of cervical myelopathy due to stenosis at the C3-4 level. Preoperative evaluation identified Klippel-Feil syndrome with cervical fusion of C2-3, aplasia of posterior arch of C1, anomalous vertebral artery course and a "ponticulus posticus" of C2. The combination of these variations in a Klippel-Feil syndrome patient has never been reported. Thus, we recommend a thorough preoperative imaging evaluation, with CT scan and CT angiography or DSA, in addition to plain radiographs. This evaluation is imperative, before a cervical spine surgery, allowing a better understanding of the anatomy, in order to minimise the risks of misplacement of cervical instrumentation especially in such patients.