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Infolding of the base of the skull from upward movement of the C2 vertebra
Medical condition
Riew, K. Daniel; Hilibrand, Alan S.; Palumbo, Mark A.; Sethi, Navinder; Bohlman, Henry H. (2001). "Diagnosing Basilar Invagination in the Rheumatoid Patient". The Journal of Bone and Joint Surgery-American Volume. 83 (2). Ovid Technologies (Wolters Kluwer Health): 194–200. doi:10.2106/00004623-200102000-00006. ISSN0021-9355. PMID11216680.