A bony canal in the basilar part of occipital bone

Clivus is a gradual slopping process behind the dorsum sellae that runs obliquely backwards. An unusual 6 mm long and 1 mm wide bony canal was observed on the lower one third of clivus in an adult human dry skull. The internal end of the canal was opening in the midline. The canal was directed downwards, forwards and laterally. The external opening was present antero-lateral to the pharyngeal tubercle on the left side.Presence of any canal in the clivus is a rare occurrence. There could be two possible explanations for its formation. It could be because of presence of a connecting vein or it might have contained the remnant of notochord. We believe that in the present case more likely a venous communication existed between the basilar and pharyngeal venous plexuses, which led to the formation of this bony canal. The canal of the clivus might interfere with the neurosurgical operations in the clival region or can be confused for a fracture of clivus.