Are Electrodiagnostic Study Findings Related to a Patient's Response to Epidural Steroid Injection?

Abstract

To determine if improvements in pain after epidural steroid injections (ESIs) were related to electromyographic (EMG) findings in patients with radicular symptoms and clinical findings consistent with radiculopathy. Retrospective chart review. Multisite spine clinic. Data were analyzed from 89 patients who had needle EMG within 6 months of ESI between 2005 and 2008. Clinical and demographic data and results of EMG testing from qualified patients were recorded from patient charts at least 10 days after ESI. Evidence of radiculopathy on EMG reports was classified as positive, normal, or equivocal. In all 3 EMG groups, the percentage of patients who had 50% improvement in leg pain after ESI was noted. As a secondary analysis, improvement in pre-ESI to post-ESI leg and back pain scores in the EMG groups were compared. The clinical outcome measurements were visual analog scale (VAS) scores assessing leg and back pain. ESI relief was defined as at least 50% improvement in the VAS score assessing leg pain after the injection. EMG findings were normal in 47.2%, positive in 31.5%, and equivocal in 21.3% of patients. No significant differences were found in the percentages of patients experiencing a positive response to the ESI with respect to EMG findings. Forty-three percent of patients with normal EMG findings (18/42), 25.0% of patients with positive EMG findings (7/28), and 31.6% patients with equivocal EMG findings (6/19) had relief after ESI. In all 3 EMG groups, a statistically significant improvement in mean VAS scores was found after ESI. Mean leg and back pain scores improved significantly after ESI in all 3 EMG groups: those with positive, normal, and equivocal findings. Results of this study do not suggest that ESI is contraindicated in patients with normal EMG findings.