Os odontoideum with cervical mylopathy due to posterior subluxation of C1 presenting sleep apnea

Sleep apnea is a breathing disorder that manifests as repetitive cessation of breathing during sleep. It has been reported that patients with upper cervical lesions caused by rheumatoid arthritis [1-5], Arnold-Chiari type 1 malformation [6] and anterior C1-2 osteochondroma [7] have sleep apnea. Os odontoideum is characterized by the radiolucent defect between the dens and the body of the axis. In some cases with os odontoideum, C1 is very unstable and causes compression of the spinal cord at the upper cervical level. We encountered a patient with os odontoideum presenting as sleep apnea. The patient had cervical myelopathy caused by posterior subluxation of C1. Spinal cord atrophy due to the compression was marked at the C1-2 level. To our knowledge, there are no reports of such a case. Here, we present the clinical findings of this patient, and the pathogenesis of sleep apnea is discussed.