Gadolinium enhancement in newly diagnosed patients with lumbar disc herniations are associated with inflammatory peridiscal tissue reactions--evidence of fragment degradation?

Objective: It is debatable whether a local inflammatory tissue response caused by herniated disc material contributes to sciatic pain and/or sensorimotor deficits. The impact of inflammatory changes on local tissue remodelling, the healing process and the clinical course of disease remains unclear.

Methods: In this prospective observational study, we included a total of 31 patients with a single-level, unilateral lumbar disc herniation. The diagnosis was confirmed by magnetic resonance imaging (MRI)±gadolinium. The presence of peridiscal contrast enhancement was correlated with the extent of inflammatory reactions in the herniated fragments as confirmed by immunohistochemistry; clinical symptoms, including the duration of radicular pain; and the incidence of sensorimotor deficits.

Results: Peridiscal contrast enhancement was found in 17 patients (55%) and was encasing the adjacent rootlet in 4 cases. There was no significant correlation between gadolinium uptake and the presence of sensorimotor deficits or the duration of radicular symptoms. Degenerative changes were observed in all 31 disc specimens. Overall, 18 cases exhibited increased cellularity in the marginal areas, which were mostly populated by CD68(+) macrophages and fibroblasts. Additionally, these areas displayed a limited number of CD3(+) T-lymphocytes and different degrees of concomitant neovascularisation, which represented a chronic and unspecific immune response. Peridiscal contrast enhancement on MRI was significantly correlated with the histopathological characteristics of tissue inflammation. However, no correlation was found between the histological evidence and the degree of inflammation and neurological symptoms.

Conclusion: Gadolinium-enhanced MRI is a sensitive method to detect unspecific inflammatory reactions in therapy-naïve disc herniations. However, the neuroradiological and histological evidence of peridiscal inflammation was not correlated with the severity of pain or sensorimotor deficits in our patients. Additional research is needed because the occurrence of local inflammation may indicate an ongoing degradation of herniated fragments and thus be helpful in therapeutic decision-making.