A case of nonrheumatoid retro-odontoid pseudotumor in Klippel-Feil syndrome with C1 occipitalization

Background: Patients with both nonrheumatoid retro-odontoid pseudotumors (ROPTs) and congenital craniocervical junction (CCJ) abnormalities are rare. Here, a 73-year-old female presented with neck pain and myelopathy due to MR-documented ROPT with intramedullary hyperintensity at the CCJ warranting an occipital-cervical fusion. Case Description: A 73-year-old female originally developed occipitalgia and became quadriparetic within the subsequent 7 months. The cervical MR showed a ROPT with intramedullary hyperintensity at the CCJ. Further, the CT demonstrated C1 occipitalization and a congenital C2-3 fusion without radiological instability. After she underwent an occipito-C2 fusion, her symptoms improved. Conclusion: For patients with C1 occipitalization and a Klippel-Feil syndrome, ROPT may occur due to loading of C1-2 complex. These patients typically favorably respond to occipito-C2 fusion.