A posterior occipitocervical fusion, in situ distraction with transarticular C1–C2 screws and iliac crest autograft fusion was performed. A postoperative radiograph is shown in Fig. 84.2. Solid fusion was observed and myelopathy improved.

• Hypoglossal, glossopharyngeal vagus, and trigeminal nerve deficit and neurogenic bladder are signs of severe dysfunction at the craniovertebral junction.1,2
• The accentuation of the symptoms in flexion and extension may suggest an atlantooccipital segment hypermobility.

• On the axial CT scan, the erosion and compression of the lateral atlantal masses as well as the penetration of the dens beyond the level of the occipital condyle in the foramen magnum are visualized. The sagittal T2-weighted MRI image of the cervical spine clearly shows some typical findings.^3,4
  • The downward separation of the anterior arch of the atlas from the clivus provokes a descent of the atlas arch onto the axis body.
  • The displacement of the posterior arch of the atlas rostrally and ventrally causes a decrease in the anteroposterior diameter of the spinal canal.

    The inflammatory rheumatoid pannus and the resulting compression of the medulla are seen in both the axial and sagittal MRI. There is no syringomyelia or Chiari malformation. The craniometric lines^3,5 in lateral view are shown in Fig. 84.3.

• Marks and Sharp² showed in 1981 that untreated myelopathic rheumatoid patients died within 6 months of presentation. Furthermore, most myelopathic rheumatoid patients (56%, n = 18) treated with conservative measures only (collar or traction alone) also died within 6 months.²
• Treatment should be planned immediately.

• Spinal and complete systemic workup are in order:
  • Flexion–extension cervical spine x-rays. Any increase in the atlantodental interval confirms the instability, which is consistently associated with the basilar invagination.^1,3,4
  • Consider dynamic MRI in flexion and extension to identify instability and sites of compression.
  • Preoperative blood work including nutritional status (lymphocyte count and liver function tests).
  • Discontinue nonsteroidal antiinflammatory agents 1 week prior to surgery. Methotrexate and steroids may be used for pain management preoperatively.
  • Cardiac status, pulmonary function assessment tests, and anesthesia consult should be obtained.

• A period of 4 to 5 days of halo traction with mild sedation and a maximum of 12 pounds of charge can reduce a basilar invagination of less than 15 mm.⁴
• Traction is contraindicated in posterior occipitoatlantal dislocation or complex rotatory luxations.

• Treatment should be designed depending on the presence of an irreducible versus reducible deformity.⁴
  • Irreducible deformity: Anterior decompression. Can be achieved through a transoral route although an endoscopic transcervical⁶ or transsphenoidal (unpublished) approach have also been described. The decompression is followed by a posterior fusion.
  • Reducible deformity: Posterior occipitocervical fusion. Many posterior fusion techniques have been described for reducing the basilar invagination, restoring craniospinal alignment, and establishing fixation of the atlantoaxial joint.⁷ The advance in osteosynthesis now allows for a solid instrumented fusion. Plates and screws at the occiput combined with C1 lateral masses and C2 pedicular screws, transarticular C1–C2 screws, or translaminar C2 screws and any combination thereof with autograft or mixed allograft fusion have achieved solid fusion.

• There is evidence in the literature suggesting the regression of the soft pannus after internal fusion.⁸
• A high rate of postoperative morbidity (42%, n = 55), and both early and 6 months mortality (13% and 25%, respectively) are reported for nonambulatory patients.⁹
• Significant postoperative motor recovery was observed for a patient with a posterior atlantodental interval of more than 14 mm.¹⁰