Os odontoideum is a small oval or round shaped bone fragment observed as the most common congenital anomaly of theodontoid process. Since it causes a slowly increasing mobility or instability in the atlanto-axial joint, sudden death, tetraplegia, chronic neck pain, headache, torticollis and myelopathy may develop. The spinal canal widens initially at the craniocervical junction and symptoms can occur at a very late stage. In this case, clinical complaints emerged after the age of 35.There was no other neurological finding and no history of recent trauma in this case presenting with severe neck pain. Thiscase report shows how ligaments, the supporting connective tissue elements, can be thickened to maintain stability whenthe stability of the cervical spine is impaired. Since it may cause sudden death even when asymptomatic, it is important torecognize this pathology and to distinguish os odontoideum from odontoid fractures in trauma patients