Aplasia of the os odontoideum: Skeletal manifestation from Thailand.

Os odontoideum is a rare craniocervical abnormality of the axis resulting in absence (aplasia) of the dens and, possibly, dislocation of the atlantoaxial articulation. Skeleton 0202 from the Osteology Collection at Khon Kaen University, Thailand exhibits aplasia of the os odontoideum with torticollis, accompanied by an unusual constellation of skeletal features that include craniosynostosis, platybasia with mild basilar invagination, unilateral Kimmerle anomaly, disuse atrophy resulting in "wasting" of the upper and lower limbs, and marked stenosis of the right foramen transversarium of the axis. The remains of this individual provide anthropologists and clinicians the rare opportunity to study the combined effects of os odontoideum, craniosynostosis, torticollis, platybasia and skeletal atrophy in a known-identity individual from Thailand.