[A radiological study of the cervical alterations in Down syndrome. New findings on computerized tomography and three dimensional reconstructions].

OBJECTIVE

We studied a large proportion of the population in our health district who have Down's syndrome to determine the incidence and variety of changes in the spine and to define the guidelines for preventive diagnosis advisable in relation to atlanto-axial instability, a common disorder in these patients.

PATIENTS AND

METHODS

First phase: a plain X-ray of the cervical spine in a neutral lateral projection and in flexion in 188 patients, measuring the atlanto-odontoid distance. Second phase: computerized tomography (CT) studies and three dimensional reconstructions in 25 patients (13.3%) chosen at random. The axial cuts from the upper portion of C3 to the occiput were 3 mm in thickness with 3 mm intervals and a standard reconstruction algorithm.

RESULTS

The incidences of atlanto-axial instability with an atlodontoid distance (3)5 mm were not comparable with the published series. There was a lower incidence (4.2%), with no difference between measurements in flexion and in the neutral lateral views. There was a greater incidence of malformations than in other reports, including a rare case of os odontoideum and also constant asymmetry of the occipital condyles (100%) in the patients of the CT series and consequently instability of the atlas (96%) and off-centered odontoides (84%).

CONCLUSIONS

The study showed that there was deficient asymmetrical development of the occipital bone, which caused different heights of the occipital condyles and led to cervico-cranial mal-position. For study of the degree of error of position and congenital anomalies. We recommend replacing plain X-ray studies by CT with three dimensional reconstructions.