Retro-Odontoid Pseudotumor Without Radiographic Instability with Congenital C1 Assimilation and C2-C3 Fusion: A Case Report.

Case The authors present a case of retro-odontoid pseudotumor (ROP) with congenital C1 assimilation and C2-C3 block vertebra without radiological instability who presented with cervical myelopathy with spastic quadriparesis. The patient was managed with occipitocervical fusion and C1 laminectomy. She had rapid neurological recovery in 3 months postoperatively and at 2 years had complete resolution of the retro-odontoid mass. Conclusion C1 assimilation without apparent radiographic instability as a cause of ROP is underappreciated. This case report and review of literature highlight that C1 assimilation and C2-C3 fusion can lead to ROP even in the absence of apparent radiographic instability with posterior atlantoaxial fusion alone providing good results.