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Neuroradiology Case of the Week

Case 80

Ravinder Sidhu MD, Lawrence Buadu MD, PhD, Yuji Numaguchi MD, PhD,
and P-L Westesson MD, PhD, DDS

Clinical Presentation: A 46-year-old female with history of rheumatoid arthritis presented with cervical pain.

Radiological Findings:  PA view of both hands showed late sequale of rheumatoid arthritis (Fig. 1). Sagittal T1-weighted MR images revealed an increased signal intensity soft tissue mass anterosuperior to dens. No evidence of atlantoaxial dislocation was seen (Fig. 2A). Sagittal T2-weighted MR images showed hyperintense signal of the lesion along with few low signal areas within it (Fig. 2B). A note is made of degenerative changes at C4/5 and C5/6 level.

Diagnosis: Pannus at cervicocranial junction

Discussion:  Involvement of the upper cervical spine, specifically the atlantoaxial segment of the cervical spine, is a well-known manifestation of rheumatoid arthritis. Enlargement of the retro-dental pannus can induce or aggravate compressive myelopathy [1]. Pannus is described as hypertrophied synovitis with production of inflammatory joint fluid containing several different types of enzymes. These inflammatory changes result in destruction of ligaments, cartilage, and adjacent subchondral bone, which in turn result in progressive atlantoaxial instability and cranial migration of the dens due to erosion of the lateral masses of atlas [2].
     Plain radiography of the neck can show the typical skeletal deformities but does not reveal the presence of cord compression. Computed tomography can demonstrate the craniocervical junction in the transaxial plane with delineation of the soft tissues including the spinal cord. Calcification and ossification can be much better delineated with computed tomography [3].
     However, due to excellent soft tissue details, MR excels in revealing the effect of the inflammatory process on the neural tissue and on the ligaments, bursae, and the fat pads. Pannus is usually seen as low-signal intensity on T1 and high-signal intensity on T2-weighted MR images. It is thought that high-signal on T2 reflects an increased water content in active inflammatory tissue. Rarely is increased signal seen on both T1 and T2-weighted images that represents associated fatty proliferation in chronic stage. MRI allows visualization of erosions in three orthogonal planes. MR imaging is also the preferred technique in demonstrating the cord compression [4].

References:

1. Dvorak J, Grob D, Baumgartner H, Gschwend N, Grauer W, Larsson S. Functional evaluation of the spinal cord by magnetic resonance imaging in patients with rheumatoid arthritis and instability of upper cervical spine. Spine 1989; 14:1057-1064.
2. Robinson DR, Tashjian AH, Levine L. Prostaglandin-stimulated bone resorption by rheumatoid synovia: A possible mechanism for bone destruction in rheumatoid arthritis. J Clin Invest. 1975; 56:1181-1188.
3. Fagerlund M, Bjornebrink J, Ekelund L, Toolanen G. Ultra low field MR imaging of cervical spine involvement in rheumatoid arthritis. Acta Radiol. 1992; 33:89-92.
4. Glew D, Watt I, and Dieppe PA, Goddard PR. MRI of the cervical spine: rheumatoid arthritis compared with cervical spondylosis. Clin Radiol. 1991; 44:71-76.