By Chris Faubel, MD –

Patients undergoing transforaminal epidural steroid injections show greater functional improvement if they have positive EMG findings of lumbar radiculopathy.

J Pain. 2008 Jan;9(1):64-70.

Right L4 Transforaminal Epidural Steroid Injection

The use of electromyography to predict functional outcome following transforaminal epidural spinal injections for lumbar radiculopathy.
Fish DE, Shirazi EP, Pham Q.
Department of Orthopedics, UCLA School of Medicine, Los Angeles, California 90404
Get the abstract here

Summary of Study

• Purpose: to determine if objective EMG findings can predict functional benefit after a lumbar transforaminal epidural steroid injection
• Retrospective chart review
• Study Participants
  • Patients who presented to the Veterans Affairs (VA) hospital in Los Angeles between July 1, 2000, and June 30, 2002.
  • Pain level and functional status (using the Oswestry Disability Index – ODI) was filled out before the injection, and at a follow-up visit (and these were kept electronically).
  • Inclusion criteria
    • EMG completion before the procedure with a diagnosis of an L5 or S1 radiculopathy
    • Transforaminal epidural steroid injection (TF-ESI) performed at L4 and/or L5
    • Symptomatic pain in only one extremity
    • Completion of self-assessment surveys before the interventional spine procedure and at follow-up
  • To be considered “EMG-positive”
    • Evidence of denervation or reinnervation on needle EMG
    • Two muscles innervated by 2 nerves from the same spinal cord level needed to be positive .
  • Baseline characteristics
    • Number of patients = 39
    • Age = 60 (mean; ± 12.5 years)
• Methods
  • The level of injection was based on the EMG findings, physical examination, magnetic resonance imaging (MRI), and clinical symptoms.
  • No patient received more than two levels of injections.
  • Injectate used
    • 40-mg triamcinolone acetonide (Kenalog) + an unknown amount of 1% lidocaine
    • If two levels were injected, the injectate was divided equally between the two levels.
• Results
  • The pre-injection ODI (Oswestry Disability Index) scores were essentially equal.
  • The pre-injection pain scores on the VAS were similar as well.
  • Two groups
    • EMG-positive patients
      • 18 patients
      • Post-injection ODI improvement = 7.11
    • EMG-negative/normal patients
      • 21 patients
      • Post-injection ODI improvement = 3.2
  • The post-injection VAS scores were improved after the injection, but the difference between the  groups was not statistically different.
• Limitations of the study
  • No evaluation of medications taken or changed during the pre- and post-injection ODI
  • No comparison of prior surgical interventions to the lumbar spine
  • No standardized time between symptom onset and EMG testing
  • Not a heterogenous group of patients
  • The injectionists were not blinded to the EMG results

• Conclusion
  • Patients undergoing transforaminal epidural steroid injections show greater functional improvement if they have positive EMG findings of lumbar radiculopathy.
  • Analog pain scores do not help in the decision-making of treatment options for patients with lumbar radiculopathy.
  • This study shows the diagnostic value of needle EMG in the prognostic success of patients prior to lumbar TF-ESIs, while simple pain scores are of little value.

Future Research

• Evaluate the psychological and medication factors that may determine a patient’s relief from lumbar epidural steroid injections.
• Also look at interlaminar vs transforaminal ESI relief in EMG-positive vs EMG-negative patients.

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