A comparative immunohistochemical study of inflammatory cells in acute-stage and chronic-stage disc herniations.

STUDY
DESIGN: Herniated lumbar disc specimens were obtained from patients undergoing surgical discectomy for persistent radicular pain (radiculopathy) and stained for inflammatory cells to determine their occurrence in relation to the duration of radicular pain and to analyze the role of the time factor in the inflammatory response.
OBJECTIVES: To analyze the presence of inflammatory cells and their involvement in the pathophysiology of radicular pain and to determine whether there is a clear difference in the occurrence of inflammatory cells between the earlier phase of radicular pain (after herniation) and the later chronic stage. SUMMARY OF BACKGROUND DATA: Previously, inflammatory cells were reported in herniated disc tissues, and macrophages were most prevalent. Biologically active inflammatory mediators have also been repeatedly observed. However, there have been no observations regarding possible differences in the occurrence of inflammatory cells in radicular pain of different durations.
METHODS: Forty-four herniated lumbar discs were obtained from 44 patients undergoing disc surgery. Two groups of 22 age- and gender-matched patients with comparable affected disc levels were studied. In the first group (acute group) pain duration ranged from 3 days to 21 days. In the second group (chronic group) pain duration was 6 months or longer. All disc herniation specimens were subjected to indirect immunocytochemistry to study and compare the presence of inflammatory cells.
RESULTS: Inflammatory cells, predominantly macrophages, were observed in both groups. Macrophages were abundantly present in eight (36%) disc samples in the acute group; in three (14%) samples only few scattered macrophages were observed. In the chronic group, in nine (41%) disc samples, abundant macrophages were observed; in six (27%) there were a few scattered macrophages. In the acute group, in three (14%) disc samples abundant activated T lymphocytes were observed; in two (9%) there were only a few activated T lymphocytes, whereas in the chronic group abundant activated T lymphocytes were not seen; only a few scattered activated T lymphocytes were observed in five (23%) disc tissue samples. In two (9%) samples in the acute group, B cells were abundantly present, and in two (9%) only a few B cells were observed. In the chronic group, abundant B cells were seen in no samples, and only a few B cells were noted in one (5%) sample. Only in the acute group and only in lateral disc herniations were abundant lymphocytes observed. In disc samples from intraspinal herniations, acute and chronic, there were only abundant macrophages, not lymphocytes.
CONCLUSIONS: Because of the small size of the study groups and the low prevalence particularly of lymphocytes in both groups, no major group differences were noted. The prevalence of macrophages was highest, similar in both groups, and was similar to the results in prior studies. The results indicate no major differences in the occurrence of inflammatory cells in acute and chronic disc herniations. They also indicate that only macrophages may have a clinical relevance in disc tissue inflammation.