Odontoid upward migration in rheumatoid arthritis. An analysis of 45 patients with "cranial settling".

Lack of correlation between the severity of rheumatoid subluxation of the upper cervical vertebrae and supposed absence of neurological damage has led to the erroneous supposition that this finding is innocuous. Incomplete autopsy studies in rheumatoid arthritis have failed to recognize the cause of death, despite previously proven dramatic occipito-atlanto-axial dislocations. The most feared entity of rheumatoid basilar invagination, namely "cranial settling," is poorly understood. Between 1978 and 1984, the authors treated 45 rheumatoid arthritis patients who were symptomatic with "cranial settling." This consisted of vertical odontoid penetration through the foramen magnum (9 to 33 mm), occipito-atlanto-axial dislocation, lateral atlantal mass erosion, downward telescoping of the anterior arch of C-1 on the axis, and rostral rotation of the posterior arch of C-1 producing ventral and dorsal cervicomedullary junction compromise. Cervicomedullary junction dysfunction has mistakenly been called "entrapment neuropathy," "progression of disease," or "vasculitis." Occipital pain occurred in all 45 patients, myelopathy in 36, blackout spells in 24, brain-stem signs in 17, and lower cranial nerve palsies in 10. Four patients had prior tracheostomies. Four previously asymptomatic patients with "cranial settling" presented acutely quadriplegic. The factors governing treatment were reducibility and direction of encroachment determined by skeletal traction and myelotomography. Transoral odontoidectomy was performed in seven patients with irreducible pathology. All patients underwent occipitocervical bone fusion (with C-1 decompression if needed) and acrylic fixation. Improvement occurred during traction, implying that compression might be the etiology for the neurological signs. There were no complications. Thus, "cranial settling" is a frequent complication of rheumatoid arthritis; although it is poorly recognized, it has serious implications and is treatable.