Abstract and Introduction
Cervical spine involvement commonly occurs in patients with rheumatoid arthritis (RA), especially those with inadequate treatment or severe disease forms. The most common site affected by RA is the atlantoaxial joint, potentially resulting in atlantoaxial instability, with cervical pain and neurological deficits. The second most common site of involvement is the subaxial cervical spine, often with subluxation, resulting in nerve root or spinal cord compression.
In this paper, the authors review the most commonly used plain radiographic criteria to diagnose cervical instabilities seen with RA. Finally, we discuss the advantages and disadvantages of cervical CT and MRI in the setting of cervical involvement in RA.
Rheumatoid arthritis (RA) is a systemic inflammatory disease that predominantly affects adult women (2 to 4 times as frequently as men). Although this autoimmune condition involves mainly bone, joints, and ligaments, extra-articular involvement has been described in nearly every organ, including the lungs, eyes, skin, and vessels.[16,18]
The cervical spine is involved in up to 86% of patients with RA, especially in those with inadequate treatment or more severe forms of the disease.[18,22,27,33,38,44] Cervical involvement is probably a consequence of the intense chronic synovitis that occurs in the joints, progressing to bone erosion and consequent ligamentous laxity and finally clinical and radiological instability.[15,18]
The most common site of involvement is the atlantoaxial region.[4,42,43] There is an important predilection for chronic inflammatory infiltration and pannus formation at the C1–2 joints that precedes bone destruction. This inflammatory process results in laxity of the ligamentous complex and loss of ligamentous restriction, leading to atlantoaxial instability. As a natural tendency, the head drops forward, resulting most commonly in anterior atlantoaxial subluxation (AAS) craniocervical kyphosis, decreasing the craniocervical angle.[15,18] Clinically, cervical pain can be secondary to instability or C-2 nerve root compression. Stroke and sudden death have been reported in patients with RA involvement of the upper cervical spine due to vertebrobasilar insufficiency.[4,38] Considering atlantoaxial instability, anterior AAS is the most common form, followed by lateral AAS, which represents about 20% of cases, and posterior AAS, which represents about 7% of all cases of AAS in association with RA. Posterior AAS generally occurs in the setting of an odontoid base erosion or fracture. Posterior subluxation is associated the highest rate of neurological deficits of all forms of AAS.[18,28] Additionally, all cases of AAS can also be classified as reducible, partially reducible, or fixed, according to the response to traction or dynamic radiological studies.
In some cases, atlantoaxial instability can progress and result in vertical migration of the odontoid into the cranial cavity—also known as cranial settling. Many other terms are found in the medical literature and used as synonyms for cranial settling, including basilar impression or invagination, vertical subluxation, atlantoaxial impaction, and superior migration of the odontoid.
Lastly, cervical involvement in RA patients can also affect the subaxial cervical spine, defined as the segments from C-3 to C-7. The most common form of presentation is subaxial subluxation (SAS), with pain, radiculopathy or even myelopathy secondary to canal stenosis. Multilevel subluxations can produce a "staircase" deformity, associated with severe systemic RA.[18,22,27]
In this paper, we review and discuss the limitations and benefits of each radiological method used to diagnose cervical instability, as well as the criteria used to classify the most common forms of cervical spine involvement in RA.
Neurosurg Focus. 2015;38(4):e4 © 2015 American Association of Neurological Surgeons