Is there a clinical correlate to the histological and radiological evidence of inflammation in trans-ligamentous extruded and sequestered lumbar disc herniaton?

The pain of lumbar disc herniation is related to direct compression of the nerve root and to the foreign-body inflammatory response to the herniated disc material. In this study, we attempted to identify disc-related inflammation in trans-ligamentous extruded and sequestered lumbar disc herniation using gadolinium-DPTA-enhanced T1-weighted and short-time inversion recovery ( STIR) magnetic resonance imaging. We assessed how these results related to each other, and to patients' clinical status, and to immunohistochemistry findings in disc specimens removed at surgery. Forty-one patients with transligamentous extruded or sequestered disc herniation were investigated clinically and radiologically. Twenty-five patients who did not respond to initial medical treatment or who had progressive neurological deficits underwent discectomy. Specimens of disc material removed during surgery were studied immunohistochemically and inflammatory cell types were identified. The other 16 patients showed good response to treatment, and were given further medical therapy and monitored for a mean of 6.3 months of follow-up. All radiological diagnoses in the operated cases were confirmed at surgery. There were no significant differences among the rates of detection of inflammation by contrast MRI, STIR technique, and immunohistochemistry in the surgical treated cases. In the medically treated cases, the frequency of radiological evidence of inflammation on the initial contrast enhanced T1-weighted and STIR images was similar to the frequency observed on the most recent scans done during follow-up. The study showed that the radiological and immunohistochemical evidence of inflammation in these cases does not correspond with patients' clinical pain profiles over time. It also revealed that STIR and contrast T1W are equally reliable for detecting inflammation in trans-ligamentous extruded or sequestered lumbar disc herniation. In future, studies that focus on physical and chemical mechanisms of pain in lumbar disc herniation in larger series of conservatively and surgically treated patients may clarify the link between inflammation and radicular pain in these types of disc herniation.