INTRODUCTION: We often treat patients with lumbar disk herniation on whom radicular symptoms improve relatively soon after surgery, although postoperative magnetic resonance (MR) imaging shows a mass protruding into the spinal canal from the posterior aspect of the intervertebral disk that compresses the nerve root and dural sac persisting for a long period. In the present study, we observed the changes of the protruding mass and radicular symptoms.
METHODS: Thirty‐four patients with the diagnosis of lumbar disc herniation who underwent nucleotomy were followed up for more than 2 years. MR imaging was performed before surgery and 3,6,12, and 24 months afterward. MR imaging studies were performed on a 1.5‐T permanent magnet (Signa General Electric) using a 12‐cm diameter planar circular surface coil operated in the receive mode. We measured the distance between the posterior edge of the intervertebral disk and the top of the mass protruding into the spinal canal before surgery and after surgery, and calculated the reduction rate using MR imaging.
RESULTS: Radicular symptoms improved in all patients within 3 months after surgery, although only 36% of the patient showed a significant protruding mass reduction (rate over 75%); but after 2 years, 67% of the residual mass after surgery had disappeared. Thus, clear progressive mass reduction has been demonstrated in the follow up. No clear correlation has been found between the improvement of the symptoms and the presence of a residual mass in the postoperative MR imaging.
CONCLUSIONS: This study indicated that there are patients who have a residual mass in the spinal canal even after the improvement of radicular symptoms by surgery for lumbar disc herniation. This should be kept in mind when following up these patients postoperatively.