[Atlanto-axial dislocation in Down syndrome and os odontoieum. Case report and review of the literature].

A case is reported of the rare coincidence of mongolism and os odontoideum in an eleven-year-old child, leading to compression myelopathy in consequence of atlantoaxial dislocation, and an overview of literature to the present time is given. Recommendations on diagnostic and prophylactic measures are offered designed to counteract as early as possible the spinal complications of atlantoaxial instability.