Congenital hypoplasia of the posterior arch of the atlas: case report and extensive review of the literature.

Congenital hypoplasia of the posterior arch of the atlas (C1), a developmental failure of chondrogenesis, is a rare anomaly and may range from partial clefts to total agenesis of the posterior arch. Ossification of the posterior arch usually occurs between the 3rd and 5th years of life. The incidence of posterior arch anomalies of the atlas is between 0.69% and 2.95%. For the evaluation of the patient, cervical lateral plain radiography, 2D or 3D reconstructed CT and MRI are very useful and important tools in initial diagnosis. Surgery is the treatment of choice in symptomatic compression. Excision of the posterior arch is performed. during surgery. After the surgery, patients may be followed up for instability and treated as necessary. A patient, admitted to the emergency department with head and neck trauma after a traffic accident is presented in this article. C1 hypoplasia was determined after detailed imagining studies and the radiology department consulted. When upper cervical anomalies are found in a young patient, the patient should be evaluated in detail with advanced radiological studies to avoid misinterpretation as fractures, luxation, osteolysis or instability. Consulting a radiologist could help making an accurate diagnosis and deciding on current therapeutic interventions.