Objective: To determine if (a) inflammatory mediators are present in herniated intervertebral discs and (b) if their presence correlates with inflammation of nerve roots or symptoms.

Design: Inflammation was assessed with gadolinium enhancement of MRI. Neurological compromise was measured. Disc tissue was examined for inflammatory mediators IL-1α and β, IL-6, MCP-1, TSG-6, iNOS, TNFα and thromboxane.

Patients: Sixty-five discs were removed from 64 patients undergoing surgery for disc prolapse.

Outcome measures: We developed (i) an MRI score to assess inflammation radiologically prior to surgery (n=28, mean 4.9±6.8 days), (ii) a Surgical Score to assess inflammation of the nerve roots at surgery (n=44), (iii) a Clinical Score to determine pain, disability and neurological compromise (n=17) and (iv) a Mediator Score to reflect the number and amount of inflammatory mediators present (n=20).

Results: Thirty percent of the prolapses in this study were extrusions, 19% sequestrations and 51% protrusions. Sixteen of the 28 patients with gadolinium had nerve root enhancement (86% of the extrusions, 57% of sequestrations, and 43% of protrusions), whilst 19 had enhancement of or around the disc herniation itself (71% of the extrusions, 86% of sequestrations and 57% of protrusions). The Mediator Scores were highest for the sequestrations (as was the Surgical Score) and lowest for the protrusions, but extruded discs had most IL-1α and β, IL-6, TNFα and thromboxane. Extruded discs had the highest Clinical Score and sequestrated the lowest.

Conclusions: Mediators produced in prolapsed disc appear to play an important role in inflammation of adjacent tissue and nerve roots. The type of mediator present and proximity of the prolapse to the nerve root may be the important factors in determining which pro-lapses are the most painful.