The Role of Temporal Changes in Pain Response After Transforaminal Epidural Steroid Injection on Treatment Success

Transforaminal epidural steroid injection (TFESI) is widely utilized in patients with lumbar disc herniation-related radiculopathy who do not respond adequately to conservative treatment and are not immediate candidates for surgery. While previous studies have demonstrated the overall effectiveness of TFESI, there is limited evidence regarding the temporal characteristics of pain relief following the procedure and how these patterns influence long-term outcomes.

In routine clinical practice, patients may exhibit heterogeneous pain trajectories after TFESI, including early responders, delayed responders, transient responders, or those with minimal or no response. Identifying early pain response patterns that predict treatment success may help clinicians optimize patient counseling, follow-up strategies, and decisions regarding repeat interventions.

In this prospective observational cohort study, adult patients undergoing fluoroscopy-guided TFESI as part of routine clinical care will be followed longitudinally. Pain intensity will be assessed using the Numeric Rating Scale (NRS) before the procedure; at 1 hour post-procedure; every 72 hours during the first 21 days; and at 1, 3, and 6 months. Demographic data, clinical characteristics, and radiological findings from lumbar magnetic resonance imaging will be recorded.

The primary objective is to determine whether early temporal changes in pain intensity following TFESI are associated with treatment success at 3 months. Secondary objectives include evaluating treatment success at 6 months and identifying early pain response thresholds that predict favorable outcomes.

• Transforaminal epidural steroid injection (Procedure): Fluoroscopy-guided transforaminal epidural steroid injection performed as part of routine clinical care. After confirmation of correct needle placement with contrast medium and exclusion of intravascular uptake, a mixture of betamethasone, bupivacaine, and normal saline is injected slowly into the epidural space. This procedure is not assigned by the study and is performed according to standard clinical practice.

Primary outcomes

• Role of Early Temporal Changes in Pain Response on Treatment Success [Baseline to 6 months after transforaminal epidural steroid injection]: Association between temporal changes in pain response following transforaminal epidural steroid injection and clinical treatment success. Pain intensity will be assessed using the Numeric Rating Scale (NRS) at baseline (pre-procedure), at 1 hour post-procedure via face-to-face assessment, every 72 hours during the first 21 days, and at 1, 3, and 6 months via telephone follow-up. Temporal patterns of pain response over these time points will be analyzed in relation to clinical treatment success, defined as a ≥50% reduction in NRS score at 3 months compared with baseline.Clinical treatment success is defined as a ≥50% reduction in NRS score at 3 months compared with baseline.

Secondary outcomes

• Clinical Treatment Success at 3 Months [3 months after transforaminal epidural steroid injection]: Proportion of participants achieving a ≥50% reduction in Numeric Rating Scale (NRS) pain score at 3 months compared with baseline (pre-procedure).
• Clinical Treatment Success at 6 Months [6 months after transforaminal epidural steroid injection]: Proportion of participants achieving a ≥50% reduction in Numeric Rating Scale (NRS) pain score at 6 months compared with baseline.
• Time to Maximum Pain Relief [Up to 6 months after the procedure]: Time (in days) from transforaminal epidural steroid injection to the lowest recorded Numeric Rating Scale (NRS) pain score during follow-up.
• Association Between Radiological Findings and Pain Response [Baseline to 6 months]: Relationship between lumbar magnetic resonance imaging characteristics (disc herniation level, location, size, and nerve root compression) and temporal pain response patterns following transforaminal epidural steroid injection.

Sex: All, ages: 18 Years to 65 Years

Inclusion Criteria:

* Age between 18 and 65 years
* Pre-procedural Numeric Rating Scale (NRS) pain score of 4 or higher
* Presence of segmental lumbar disc herniation demonstrated on magnetic resonance imaging (MRI) consistent with clinical findings
* Undergoing fluoroscopy-guided transforaminal epidural steroid injection due to insufficient response to conservative treatments, as determined by the algology clinic

Exclusion Criteria:

* Presence of spondylolisthesis, scoliosis, or lumbar spinal stenosis accompanying lumbar disc herniation
* Presence of malignancy
* History of lumbar spine surgery for disc herniation
* Transforaminal epidural steroid injection within the previous 6 months
* Requirement for repeat epidural steroid injection during the data collection or follow-up period
* Inability to be contacted for follow-up assessments by telephone