Figure 7b. Arachnoiditis in a 52-year-old woman with postoperative back pain. (a) Sagittal, postcontrast, T1-weighted image (450/10) shows enhancement of the cauda equina nerve roots (arrows) and their adherence to the posterior surgical site. (b) Transverse, postcontrast, T1-weighted MR image (800/13) shows clumping (arrow) of the nerve roots at the L3-4 level. The findings of adhesion and enhancement represent changes of arachnoiditis.