A Cervical Flexion-Extension MRI Study in Down Syndrome.

To assess what kind of information MR examination in flexed and extended positions provides in Down syndrome subjects with suspected cranio-cervical instability.Between 2005 and 2008, 35 subjects with DS were recruited in the study. Ethics committee approval was granted and a signed informed consent was obtained from the parents. All the subjects were affected by hypotonic status and ligament laxity established by clinical evaluation, but were asymptomatic about focal neurological symptoms due to medullar damage caused by cranio-cervical instability. Each patient underwent lateral supine radiographs and MR imaging in the neutral, active flexed and extended positions. For evaluating the atlanto-axial and atlanto-occipital joint stability, multiple measurements were calculated.A significant reduction of anterior subarachnoid space in flexed position was evident in DS subjects compared to healthy controls in neutral and flexed positions. Both, space available for cord and ligamentous thickness showed significant differences between DS subjects and healthy controls. In DS subjects with occipito-cervical instability, the anterior subarachnoidal space reduction was significantly reduced in flexed position.In DS subjects with asymptomatic cranio-cervical instability, anterior subarachnoidal evaluation and ligamentous status could add new information about the risk of spinal cord damage.