Peridural Fibrosis

This 42 year-old female presented with recurrent right L5 radiculopathy after L4/5 discectomy the preceding year.
Axial T1-weighted image (click image for arrows) shows loss of fat signal around the right L5 nerve root. A gadolinium-enhanced axial T1-weighted fat-saturated image shows enhancing tissue (arrow) around the right L5 nerve root (arrowhead). This is consistent with granulation tissue or fibrosis around the nerve root, and may well be the cause of the patient’s recurrent pain.
Peridural fibrosis refers to scar formation within the epidural space following lumbar surgery. The enhancement associated with peridural fibrosis may persist for years. MRI with gadolinium-enhancement has a 96% accuracy differentiating peridural fibrosis from recurrent disc herniation. Other diagnoses to consider are epidural phlegmon or abscess, and arachnoiditis. Peridural fibrosis may be asymptomatic. Reoperative success rates are low for patients with peridural fibrosis when compared to those with recurrent disc herniation.
Reference: Ross JS et al, Diagnostic Imaging: Spine. Amirsys 2004.
Credit: Dr Laughlin Dawes
http://www.radpod.org