"The prevalence of this variant is 1–5% 2-7."
"complete (multiple openings in the clivus)"
"incomplete (blind-ending canals or deep recesses in the clivus)"
"Canalis basilaris medianus was first described by Gruber in 1880 8, but it remains not well known. It is not included in Terminologia Anatomica. In 1987, Zhang and Yen asserted they were the first to describe such canals and termed them inferior median clival canals 5."