Serum Levels of the Inflammatory Cytokines in Patients with Lumbar Radicular Pain Due to Disc Herniation

STUDY DESIGN Cohort study. PURPOSE This study primarily aimed to evaluate the serum levels of tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-4 in patients with lumbar radiculopathy 1 and 12 months after microdiscectomy. OVERVIEW OF LITERATURE Lumbar radiculopathy is possibly caused by inflammatory changes in the nerve root. The intraneural application of pro-inflammatory cytokines induces behavioral signs associated with pain. Anti-inflammatory cytokine treatment effectively reduces hyperalgesia. METHODS The role of TNF-α and IL-4 in long-lasting lumbar radiculopathy was addressed. A total of 262 patients were recruited from Anqing Hospital, Anhui Medical University. During inclusion at 1 and 12 months, serum concentrations of TNF-α and IL-4 were analyzed by enzyme-linked immunosorbent assay, and pain intensity was reported on a 0-10 cm visual analog scale (VAS). RESULTS Sixty six patients had VAS <3 and 196 patients had VAS ≥3. Serum concentrations of pro-inflammatory TNF-α and anti-inflammatory IL-4 in patients with lumbar radiculopathy related to disc herniation were measured at 1- and 12-month follow-up. TNF-α decreased in both VAS groups with time. In contrast, IL-4 increased in both groups at 1 month and then decreased gradually until month 12. The changes in serum levels of TNF-α and IL-4 over time between the VAS ≥3 and VAS <3 groups were significantly different. CONCLUSIONS Chronic lumbar radiculopathy may be associated with high level of pro-inflammatory substances, such as TNF-α, in serum after disc herniation, and elevated anti-inflammatory cytokine in patients with lumbar radiculopathy may indicate a favorable outcome.