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[Retroodontoid mass without atlantoaxial subluxation in an elderly patient: case report].

A Mass at the craniovertebral junction is relatively rare. We report a case of retroodontoid mass without atlantoaxial subluxation. An 84-year-old female presented to our hospital with paresthesia in the right upper and lower limb. She had no history of head or spine injury. Neurological examination revealed slight motor weakness of the right upper and lower limb. Cervical radiographs showed osteoarthrosis without atlantoaxial subluxation. MRI revealed retroodontoid, extra-dural mass that severely compressed the adjacent spinal cord. The patient underwent C1 laminectomy and posterior C1-C2 fusion with polyaxial screw and rod fixation. Simultaneously, the mass was resected partially. Histopathologically, the surgical specimen was a non-neoplastic fibrocartliginous mass and inflammatory cells were not seen. Postoperative course was uneventful and her neurological condition gradually improved. MRI revealed marked reduction of the mass and improvement of the spinal cord compression six months after the operation. We discuss the genesis of the retroodontoid mass and the strategy for surgical treatment.