Bilateral ossification of the carotico clinoid ligament: clinical and surgical considerations

The carotico clinoid foramen (CCF) is an anomalous foramen that is formed due to ossification of carotico clinoid ligament (CCL) in the sphenoid bone with a reported prevalence of around 8%. Ossified CCL is of tremendous clinical relevance considering its intimate relationship with important neurovascular structures in the parasellar region such as internal carotid artery, cavernous sinus, optic nerve and the pituitary gland.

This report describes a case of bilateral ossification of CCL that was incidentally observed in a dry human skull during routine demonstration to medical undergraduate students. In the present case, ossified CCLs were observed spanning the tips of the anterior and the middle clinoid processes bilaterally and they formed two distinct oval CCF on either side.

Variable incidence of ossified CCL has been reported in anatomical studies. The exact reason for the ossification of CCL and other periclinoid ligaments are not known. Developmental anomalies of the sphenoid bone, ossification of fibrous tissue of the ligaments or the folds of dura mater bridging the interclinoid region are thought to be underlying reasons. The presence of a complete or partially ossified CCL can affect the internal carotid artery (ICA), cavernous sinus, its contents and the pituitary gland etc. Ossified CCL and CCF can lead to misinterpretation in radiological investigations and might pose difficulty in neurosurgical access and interventions in the skull base.

Considering the modest prevalence of carotico clinoid ligament across all major races, preoperative recognition of the same in imaging studies is warranted before approaching any parasellar intra- cranial lesions.