Changes at the base of skull and cervical spine in Down syndrome.

Lateral films of the skull base and upper cervical spine in flexion, extension, and neutral positions in 165 patients with Down syndrome, ranging in age from 16 to 60 years, were analyzed. There is a 20% incidence of atlantoaxial subluxation with a marked preponderance in men (24% incidence compared to 15% in women). In addition, there is a high incidence of degenerative changes at the C2-3 and C3-4 cervical interspaces, especially in patients over 37 years of age; these are unusual sites when compared to the normal population in which the degenerative changes are most often at the C5-6 and C6-7 levels. Four patients demonstrated subluxation at cervical interspaces other than C1-2 and six had congenital fusion of either vertebral bodies or facets in the cervical region. Several patients also had flattening of cervical vertebrae; 20% of patients had nonaeration of the sphenoid sinus and 46% had partial aeration.