Effects of corticosteroids on nerve root recovery after spinal nerve root compression

Corticosteroids have been used in the treatment of radiculopathy and postoperative pain after lumbar disc surgery. Although the effects of steroids are thought to be antiinflammatory, the underlying nature of action may be more complex and may involve a direct effect on pain mediators like substance P. A feline model of nerve root compression and decompression was used to study the effect of steroids on the expression of cytokine differentiation antigens 4 and 5, and substance P. Ten adult cats were used. The animals were divided equally into a steroid treatment group and a control group. The sixth lumbar nerve root was compressed surgically and subsequently decompressed followed by local application of betamethasone or saline. The cats then were perfused and the corresponding nerve root and dorsal root ganglion were removed and immunostained for cytokine differentiation antigens 4 and 5, and substance P, respectively. The relative absence of cytokine differentiation antigens 4- and 5-labeled lymphocytes at the compression site in the steroid treated group is consistent with an antiinflammatory effect of the steroid. Substance P expression at the dorsal root ganglion in the steroid treated group was decreased significantly. These findings may help explain clinical observations of efficacy of steroids after spinal nerve root decompression.