Congenital midline cleft of the posterior arch of atlas: a rare cause of symptomatic cervical canal stenosis

Developmental symptomatic Cl canal stenosis is very rare. We describe the c omputed tomography (CT) and magnetic resonance imaging (MRI) appearances in a 8-year-old child who presented with progressive upper and lower limb neu rological symptoms and in whom imaging revealed the medial posterior hemiar ches of a bifid Cl to be inturned and compressing the cervical cord. This p articular configuration of the posterior arch of atlas is frequently associ ated with other craniocervical bony anomalies and presents with neurologica l symptoms early in life. Early CT or MRI examination of patients with symp tomatic posterior arch of Cl defects is necessary, in order to detect such an appearance, since surgical treatment may prevent neurological deteriorat ion.