Congenital defects of C1 arches and odontoid process in a child with Down's syndrome: A case presentation.

We present the case of a 2-year-old child with Down's syndrome who presented to our unit with torticollis. Imaging studies revealed the rare occurrence of anterior and posterior C1 arch defects, absent odontoid process, and atlantoaxial subluxation. We managed her conservatively for 3 years without neurological deficits or worsening of atlantoaxial subluxation. We discuss the rare occurrences of anterior and posterior arch defects of the atlas, the radiological presentations of axis defects in patients, and the occurrence of atlantoaxial instability in patients with Down's syndrome. Management options with consideration to surgery in asymptomatic and symptomatic patients are also discussed.