The clinical presentation is consistent for cervical myelopathy due to atlantoaxial subluxation in a patient with rheumatoid arthritits.
Boden et al found "The most important predictor of the potential for neurological recovery after the operation was the preoperative posterior atlanto-odontoid interval (PADI). In patients who had paralysis due to atlanto-axial subluxation, no recovery occurred if the PADI was less than 10mm, whereas recovery of at least one neurological class always occurred when the PADI was at least 10mm. All patients who had paralysis and a PADI or diameter of the subaxial canal of 14mm had complete motor recovery after the operation." They found no correlation with the anterior atlanto-odontoid interval (ADI) with the severity of paralysis or the potential for recovery.
Monsey et al report that the most helpful radiographic measurements to evaluate atlantoaxial subluxation are the anterior atlantodens interval (ADI) and the posterior atlantodens interval (PADI). Atlantoaxial subluxation greater than 9 mm and a posterior atlantodens interval less than 14 mm correlate with neurologic deficit. They argue nonoperative management does not change the natural history of cervical disease, and recommend posterior arthrodesis in patient's with neurologic deficits.
Boden SD, Dodge LD, Bohlman HH, Rechtine GR. Rheumatoid arthritis of the cervical spine. A long-term analysis with predictors of paralysis and recovery. J Bone Joint Surg Am. 1993 Sep;75(9):1282-97.
PMID:8408150 (Link to Abstract)
Monsey RD. Rheumatoid Arthritis of the Cervical Spine. J Am Acad Orthop Surg. 1997 Oct;5(5):240-248.
PMID:10795060 (Link to Abstract)