Atlanto-occipital hypermobility in subjects with Down's syndrome.

Abstract

The upper cervical spines of 57 subjects with Down's syndrome were retrospectively examined, with special attention to atlanto-occipital mobility. To examine the magnitude of atlanto-occipital mobility and its clinical significance in subjects with Down's syndrome. Atlanto-occipital translation of more than 1 mm in adults implies instability. However, the normal value in children with Down's syndrome has not been established, and the value in Down's syndrome has not been evaluated based on a comparison between subjects with Down's syndrome and control subjects. Measurements were made by Wiesel and Rothman's method in 38 subjects with Down's syndrome and 34 control subjects. Atlanto-occipital translation in the Down's syndrome group ranged from 0-6.4 mm (mean, 2.3 mm), whereas in the control group it ranged from 0-2.1 mm (mean, 0.61 mm). The difference was statistically significant. Of the 38 subjects with Down's syndrome, 37 were asymptomatic. The magnitude of atlanto-occipital translation, as expected, apparently was greater in subjects with Down's syndrome than in control subjects. Although the possibility of neurologic complications should be considered whenever unusually high atlanto-occipital mobility is seen, a majority of the subjects with Down's syndrome were asymptomatic.