Recovery of function in adjacent nerve roots after surgery for lumbar discherniation: Use of quantitative sensory testing in the exploration of different populations of nerve fibers

Results from experimental and clinical studies indicate that adjacent nerve roots may be affected in sciatica because of lumbar disc herniation. This may be caused by proinflammatory mediators in the epidural space being tran sported into nerve roots at the same or neighboring lumbar segments. The ai m of the present study was to investigate the recovery of function of senso ry nerve fibers in the adjacent noncompressed nerve roots. Thirty-nine pati ents undergoing microdiscectomy for monoradiculopathy were investigated wit h quantitative sensory testing immediately before surgery, and at 6 weeks, 4 months, and 12 months after the operation. Twenty-one healthy volunteers were used as controls. The patients were classified as having a good or a p oor result at the 1-year follow-up according to a clinical score. Significa nt improvement of function in the noncompressed nerve roots were only obser ved in the 31 patients with a good result. The improvement in small myelina ted nerve fibers came within 12 months in the adjacent nerve roots in both the symptomatic as well as the asymptomatic leg. The improvement of functio n in small unmyelinated fibers also came within 12 months after surgery; ho wever, significant improvement was only observed in the ipsilateral neighbo ring nerve root. The function in large myelinated fibers did not improve in any of the adjacent nerve roots during the observation period. The observe d recovery of function in adjacent noncompressed nerve roots after successf ul surgical decompression in monoradiculopathy may be because of less produ ction of proinflammatory mediators when the disc herniation is removed.