Atlas Hypoplasia Combined with Atlantoaxial Subluxation is a Cause of Non-traumatic Cervical Myelopathy

Abstract

Congenital abnormalities of the posterior arch of the atlas (C-1) are uncommon. They may range from partial clefts to total agenesis of the posterior arch. Atlas hypoplasia may cause segmental compression and cervical myelopathy in elderly patients. In this report, we present a case of atlas hypoplasia combined with atlantoaxial subluxation. The patient developed cervical myelopathy gradually for 6 months without preceding trauma. Neuroimaging studies revealed a unilateral cleft of the posterior Cl arch and widening of the predental space which caused followed the removal of the hypoplastic C-l arch and the constricted ligament along with posterior occipital-C-3 fusion. Hypoplastic posterior arch of C-l may create marked focal stenosis of the spinal canal and the cord may be further compromised by atlantoaxial subluxation. Posterior decompression combined- with occipital-C-3 fusion is an effective treatment for symptomatic patients with such a condition.