RESUMEN
BACKGROUND: Several biochemical mediators, such as substance P, calcitonin gene-related peptide (CGRP) and prostaglandin E2, have been demonstrated to be involved in herniated or degenerated disc-induced radiculopathy. The authors tested the hypothesis that these mediators would existed in the epidural space of humans. METHODS: Thirty nine patients were divided into two groups; 27 patients, who were diagnosed with spinal stenosis (stenosis group), and 12 scheduled for epidural anesthesia, without a history of back pain (control group). Under fluoroscopic guidance, an epidural catheter was introduced through the caudal space and placed into the anterior and posterior spaces, up to and around the epidural adhesive area, in the stenosis group. In the control group, the catheter was placed into the posterior epidural space through the L3 4 or L4 5 intervertebral space. Epidural irrigation was performed with 10 ml of saline, via an epidural catheter. Aspirated lavage fluid was collected, and the concentrations of biochemical mediators (substance P, CGRP and prostaglandin E2) measured using an enzyme immunoassay kit. RESULTS: Substance P, CGRP and prostaglandin E2 were detected in all the epidural lavage fluids from both groups. The concentrations of substance P and prostaglandin E2 in the stenosis group were higher than those of the control (P < 0.05). However, there was no difference in the CGRP levels between the two groups. In the stenosis group, the concentrations of these three mediators in the anterior epidural space were no different to those in the posterior space. CONCLUSIONS: These results suggest that biochemical mediators, such as substance P and prostaglandin E2, in the epidural space might be partly involved in pain mechanism associated with spinal stenosis.