Bifid clivus
Numbers
- Rare
Pathophysiology
- Failure of midline integration of basioccipital primordium
- Failure of midline integration of the axial sclerotome of the proatlas --> a split primordium of the basioccipital --> may affect anchorage of the tectorial membrane ( which normally straps the odontoid complex to the back of the clivus)
- atlanto-occipital joint may become unstable and the cervical spine may appear to have drifted away from the skull
- If the failure involves the other occipital sclerotomes, the bifidity may extend up to the sphenoclival synchrondrosis
Radiology
- A
- Left: Axial CT shows the gap in the lower clivus (arrow).
- Right: Sagittal CT shows the odontoid process is far anterior to its usual position below the clivus. Fusion of the C2, C3 and C4 centra is also seen.
- B, CT 3-D rendering of the skull base.
- Left: View from the back shows widely bifid basiocciput and an oval defect (arrow) higher in the clivus. The posterior C1 arch is deficient.
- Right: view from the front shows the odontoid is far forward from the bifid clivus (mostly covered by the dens), and the anterior C1 arch is also bifid. Note upper clival defect (arrow). incomplete posterior C1 arch; Incomplete anterior C1 arch
Management
- C0-C1/2 fusion