Arachnoiditis ossificans

Findings

Sagittal T1 (Figure 1) weighted MRI image of the lumbar spine with poorly defined nerve roots of the cauda equina. A bony fusion mass is noted posteriorly from prior remote bony fusion surgery.
Sagittal T2 (Figure 2) weighted image demonstrates heterogeneous mixed low T2 signal within the thecal sac at multiple levels.
Axial T1 (Figure 3) weighted image with poorly defined and "clumped" nerve roots.
Axial T2 (Figure 4) weighted image with heterogeneous mixed low T2 signal.
Axial noncontrast CT (Figure 5) image of the lumbar spine reveals extensive intrathecal calcification.
Sagittal reconstructed noncontrast CT (Figure 6) of lumbar spine demonstrates widespread intrathecal calcification and "clumped" nerve roots.


Diagnosis: Arachnoiditis ossificans


Arachnoiditis has many causes including prior surgery, myelographic contrast agents (especially oil-based contrast agents used in past), infection, subarachnoid hemorrhage, and inflammatory disease (ie, sarcoidosis). Lymphoma, carcinomatous meningitis, Guillain-Barre, and CMV radiculitis can also cause nerve root thickening. Chronic endstage archnoiditis results in arachnoiditis ossificans. Patients with arachnoiditis ossificans often have progressive neurologic deficits.

This case illustrates the importance of noncontast CT in evaluation of arachnoiditis ossificans, since MRI can demonstrate variable T1 and T2 signal characteristics.