[Incidence of occipito-cervical instability in Down syndrome].

Seventy children with Down Syndrome (22 boys and 48 girls), ages ranging between five and seventeen years, were evaluated for instability of the upper cervical-spine. X-ray study of this region in lateral projection was did, in neutral position and flexion-extension of the neck. The distance between the anterior arch of the atlas and odontoid process as well as the displacement of the basion in relation to the first cervical vertebrae were examined. Twelve patients (17.14 percent) exhibited motion alterations of the region studied: atlanto-axial instability in eight cases (interval bigger than 4.5 mm) and atlanto-occipital instability in four cases.