Effect of lumbar epidural steroid injection on neuropathic pain: a prospective observational study

Background: Low back pain (LBP) is caused by disc herniation, spinal stenosis, facet syndrome or etc. This LBP could be either nociceptive or neuropathic pain (NP). In addition, these neuropathic pain is a major contributor to chronic low back pain. It is already known that lumbar epidural steroid injection (ESI) is effective for low back pain, but no study has assessed both nociceptive and neuropathic pain separately. This study investigated whether neuropathic or nociceptive pain was better improved after an epidural steroid injection. Methods: This was a prospective study. Patients were classified according to the pre-procedure painDETECT questionnaire (PD-Q) score. If the PD-Q score was <= 12, it was considered as nociceptive pain, and it the PD-Q was >= 19, it was considered NP. The patients were given a transforaminal (TF) or interlaminar (IL) epidural steroid injection (ESI). The PD-Q was filled out by each patient prior to the ESI (baseline), and again at 4 weeks after the ESI. Outcomes was assessed using a numerical rating scale (NRS) score, short form McGill Pain Questionnaire (MPQ), and revised Oswestry Back Disability Index (ODI) at 1 month later. Results: A total of 114 patients were enrolled and of these, 54 patients with a PD-Q score of <= 12 were classified into the nociceptive pain, and 60 patients with a PD-Q score >= 19 were classified into the neuropathic pain group. At 1 month after treatment, both groups had significantly lower than improved their mean NRS score. Not withstanding these improvements and difference between NRS, the differences in MPQ and ODI after treatment between the groups (nociceptive vs. neuropathic) not significant. After the procedure (TF-ESI or IL-ESI), the patients in group 1 (PD-Q score <= 12, n = 54) had no change in their PD-Q score. Among the patients in group 2 (pre-treatment PD-Q score >= 19, n = 41), 13 patients moved to a PD-Q score <= 12 and 15 patients had a PD-Q score of 13-18. Conclusion: For the short-term relief of neuropathic pain, ESI was effective for both nociceptive and neuropathic pain, therefore ESI could be treat the try neuropathic pain component in patients with low back pain.