The Use of Electromyography to Predict Functional Outcome Following Transforaminal Epidural Spinal Injections for Lumbar Radiculopathy

Abstract

This study aimed to determine if electromyographic (EMG) diagnostic evaluation can predict functional outcome in patients undergoing transforaminal lumbar spine epidural injections. In this retrospective study, functional outcome by Oswestry Disability Index (ODI) and verbal rating scale (VRS) for current pain severity was evaluated in 39 patients undergoing lumbar transforaminal epidural spinal injections (ESI). Subjects with low back pain (mean age, 60 +/- 12.5 years) were evaluated for functional improvement post EMG and ESI. Of 39 patients tested with EMG before injection, 18 patients were positive for radiculopathy and 21 had a normal or negative examination. The patients were followed postinjection on average of 10.8 (SD +/- 3.9) weeks. Pretreatment ODI scores were not significantly different between groups showing positive (72.3 SD +/- 12.7) and negative (65.9 SD +/- 18.6, P > .05) EMG findings. There was significantly greater improvement of ODI for EMG positive radiculopathy (7.11 SD +/- 9.5) compared with negative EMG (3.2 SD +/- 17.4, P < .05). Positive radiculopathy subjects complained of more pain by VRS before ESI than subjects with negative EMG findings, 8.1 SD +/- 1.0 and 7.3 SD +/- 0.8, respectively, which was not significant (P > .05). VRS mean improvement was not significantly different in the positive EMG group (1.8 SD +/- 1.2) compared with a negative EMG (1.2 SD +/- 1.2, P > .05). The results appear to show that patients undergoing transforaminal ESI, who have a positive radiculopathy by EMG before injection, will have significant improvement in functional outcome by ODI but not with current pain intensity by VRS. This study suggests the importance and diagnostic value of ordering electromyography studies for lumbar radiculopathy evaluation, which may lead to prediction of outcome with lumbar transforaminal epidural spinal procedures. Furthermore, the current study highlights the difficulty of pain evaluation outcome by VRS.