Fusion of atlas with occipital bone, superior migration of dens of C2, projecting above foramen of magnum and causing compression and kinking at the cervicomedullary junction.
Intramedullary hyperintensity is seen in cord at C2-3 level.
Degenerative changes are seen with disc-osteophyte complexes at multiple levels causing varying degrees of cord, thecal sac and neural foraminal compression.