Nerve root signs on postoperative lumbar MR imaging. A prospective cohort study with contrast enhanced MRI in symptomatic and asymptomatic patients one year after microdiscectomy.

The association between postoperative nerve root signs and outcome was investigated in 54 out of one hundred patients operated on by lumbar microdiscectomy in a prospective cohort study with one year follow up. The patients were classified as failures or successes at the 12 month follow up according to a clinical overall score. All the 14 failures were investigated with MRI at the one year follow up, and 40 patients classified as successes were picked at random for MRI. Three patients with signs of recurrent disc herniation on MRI were excluded from the study. The MRI scans were independently read by two neuroradiologists who were ignorant of treatment outcome. No association between nerve root thickening, nerve root enhancement or nerve root displacement and the clinical outcome was found when patients with recurrent disc herniation were excluded.