Presentation
The patient complains of chronic neck pain.
Patient Data
The scout image of the cervical spine shows a separated odontoid process from the axis with loss of the predental space, and the odontoid process is fused to the anterior arch of the atlas.
The odontoid process is separated from the axis as shown in the sagittal reformat images and fused with the anterior arch of the atlas as shown in the axial slices.
The axial slices reveal a small defect in the posterior arch of the atlas, in addition to fusion of the odontoid process to the anterior arch.
The sagittal T1 and T2 sequences of the cervical spine demonstrates a separated odontoid process from the axis, with subsequent fusion to the anterior arch of the atlas.
Case Discussion
Os odontoideum is a rare congenital anomaly of the craniovertebral junction. It is characterized by a separate ossicle of variable size and shape at the tip of the odontoid process. This ossicle, also known as the "tooth-like" bone, normally fuses with the second cervical vertebra during development. However, in os odontoideum, this fusion fails to occur, leading to the separate bone.
Os odontoideum can be asymptomatic or cause neurological symptoms due to atlantoaxial instability or compression of the spinal cord or brainstem. This instability arises from the lack of proper bony connection between the atlas (C1) and axis (C2) vertebrae, which allows excessive movement at the joint.
The etiology of os odontoideum is controversial, but it is generally believed to result from either incomplete ossification of the odontoid process during early development or a traumatic fracture of the process in early childhood.
The treatment of os odontoideum depends on the presence and severity of symptoms, the type and degree of instability, and the patient's age and general condition.
Acknowledgment: Nusaibah Ghaleb Yousef Alnahari
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