Electromyographic Findings After Epidural Steroid Injections in Patients with Radicular Low Back Pain: A Prospective Open-Label Study

Epidural steroid injections (ESIs) are commonly used in the management of chronic lower back and leg pain. The aim of this study was to investigate the short- and long-term electromyographic and clinical outcome of patients with chronic radicular pain after ESIs. This prospective, open-label study, included patients with chronic radicular pain due to disc herniation or spinal stenosis, who underwent interlaminar, fluoroscopy-guided ESIs. Patients were assessed before ESIs, as well as after 6 and 12 months, clinically (VAS 0-10, BPI, DN4, Rolland Morris, DASS, STAI) and electromyographically for the improvement of spontaneous activity (SA) and of motor unit recruitment/interference pattern (IP/MUR). A total of 39 patients were studied, 20 (51.3%) who had a significant improvement in VAS, RM, DN4 and BPI were revealed, mainly during the first 6 months (P < 0.05). Statistically significant improvement was revealed in MUR/SA for almost all nerve roots studied. Patients with disc herniation showed a greater improvement in mean difference of MUR/SA (P < 0.05) (with a prognostic value of radicular LBP versus spinal stenosis in short- [VAS P = 0.042] and long-term improvement of pain [VAS P = 0.009]. The independent variables "MUR" and "SA" had a significant prognostic value for improvement of pain (VAS: R² = 0.287, P = 0.032 and VAS: R² = 0.277, P = 0.036 respectively). Electromyographic and clinical findings indicated a benefit from epidural steroid injections. Patients with disc herniation exhibited a better outcome, especially during the first 6 months post-treatment.