The MSCT and MRI features and diagnosis of Os Odontoideum:A case series of 15 patients

HU Xianhua; HU Yundi; CAO Zhigang; ZHU Tingting

Abstract：Objective Os odontoideum(OsO)is rare, often accompanying with atlanto-axial instability(C1/C2), cervical spinal canal stenosis and spinal cord degeneration,etc.MSCT and MR imaging findings of OsO were reviewed retrospectively,so that to improve the diagnosis of OsO.Methods 15 cases of OsO were collected and reviewed during 2010 to 2014 year in our hospitals.MSCT and MRI of cervical spine were performed to verify OsO.Results MSCT revealed that the ossicles were found in 100%,the dissociating ossicles in 93.3%,C2 odontoid base displacement in 100%,spinal canal stenosis in 100%,C1/C2 instability in 100%,spinal cord compression in 93.3%.MRI revealed that the ossicles were found in 80.0%, the malposition ossicles in 80.0%.C2 odontoid base displacement and spinal canal stenosis were 100%,C1/2 instability was 100%,the com-pression of the spinal cord was 93.3%,myelopathy was 93.3%.There was significant difference betwen MSCT and MRI to reveal the spinal cord degenerative myelopathy(P <0.00),there were no significant differences(P >0.00)among the other results of MSCT and MRI.Conclusion MSCT and /or MRI can diagnose OsO if they find out a dissociating ossicle with surrounding com-plete bone cortex above C2 odontoid base.The results reveal that MSCT be better than MRI to show the bone cortex of the ossicles and the very tiny ossicles in this series,and MRI is obviously better than MSCT to show the myelopathy.