Cytokine assay of the epidural space lavage in patients with lumbar intervertebral disk herniation and radiculopathy.

INTRODUCTION: Lumbar disk herniation may result in a radiculopathic pattern of symptoms. Consideration for a primary biochemical inducement of pain over a mechanical mechanism is a contemporary topic of spinal research. However, the exact pathomechanism by which a degenerative intervertebral disk leads to neural inflammation and pain has not been determined. Using modern techniques of chemical analysis, biochemical markers can be identified which participate in the degenerative cascade, and possibly with the onset of pain. The purpose of this research is to identify potential biochemical markers through a novel technique of epidural space lavage that may be helpful in understanding the pathogeneses of pain in the presence of intervertebral disk degeneration and herniation.

METHODS: Fifty consecutive patients with acute radiculopathy secondary to a symptomatic herniated lumbar intervertebral disk or spinal stenosis, and who were indicated for epidural steroid injection were identified. Additionally, 3 volunteers with no history of back pain or radiculopathy volunteered to undergo epidural lavage. After needle insertion, a lavage followed by fluid aspiration of the epidural space at the level of the disc herniation, in the case of the symptomatic patients, was performed using normal saline, before the instillation of corticosteroids. The fluid samples were frozen at -20 degrees C until analysis. A biochemical evaluation for a battery of cytokines was undertaken (IL-1beta, IL-1ra, IL-2, IL-2R, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12p40, IL-13, IL-15, IL-17, TNF-alpha, IFN-alpha, IFN-gamma, GM-CSF, MIP-1alpha, MIP-1beta, IP-10, MIG, Eotaxin, RANTES, and MCP-1, and neuropeptides) using high-resolution multiplex bead immunoassays and enzyme-linked immunosorbent assay (ELISA). Additionally, polyacrylamide gel electrophoresis was carried out to verify the presence of serum proteins.

RESULTS: Despite the presence of amino acids/serum proteins in the epidural lavage fluid, none of the aforementioned mediators were isolated in a quantifiable concentration using the ELISA techniques with >5 pg/mL resolution.

DISCUSSION: The current proteomics array technology was not able to detect critical levels of biochemical markers present in the epidural space through the mentioned lavage technique. This lack of detection could be due to the absence of the factors in this environment or the inability of the technique to obtain or detect factors which may be present.

CONCLUSION: Although a novel approach, the current study was unable to identify the presence of a series of inflammatory peptides in the epidural lavage of patients with symptomatic radicular pain due to herniated disc disease. We recommend alternative experimental designs than the one we pursued for definitively identifying potential sources of pain generators.