Cutaneous Silent Period-Based Comparison of DRG-PRF and TFESI in Lumbar Radicular Pain

Cutaneous Silent Period-Based Comparison of Dorsal Root Ganglion Pulsed Radiofrequency and Transforaminal Epidural Steroid Injection in Lumbar Radicular Pain

This prospective clinical study compares the effects of two interventional treatments, dorsal root ganglion pulsed radiofrequency (DRG-PRF) and transforaminal epidural steroid injection (TFESI), on patients with lumbar radicular pain (LRP). A third group of healthy individuals is included as a control group to provide baseline cutaneous silent period (CSP) values.

The CSP is a neurophysiological marker of spinal inhibition. The study aims to evaluate whether these treatments affect pain levels, functional disability, and CSP parameters over time. Participants with LRP will receive either DRG-PRF or TFESI, while healthy controls will undergo CSP testing only.

The findings may provide insight into the effects of these interventions on segmental nociceptive processing and inform treatment strategies for neuropathic low back pain.

Lumbar radicular pain (LRP) is one of the most common causes of low back pain (1). It frequently results from disc herniation at the L4-5 or L5-S1 levels or from irritation of spinal nerve roots due to other degenerative conditions (2). Transforaminal epidural steroid injection (TFESI) and dorsal root ganglion pulsed radiofrequency (DRG-PRF) are minimally invasive interventional procedures used in the treatment of this condition. However, data objectively comparing the effects of these interventions on segmental nociceptive processing in humans are limited (3,4).

This prospective clinical study aims to evaluate both the clinical and neurophysiological effects of DRG-PRF and TFESI in individuals with LRP. The cutaneous silent period (CSP), a non-invasive electrophysiological marker that reflects spinal inhibitory function, will be used as an objective assessment tool. CSP is a polysynaptic spinal reflex in which a nociceptive stimulus conducted via A-delta fibers causes temporary suppression of voluntary motor activity (5). It represents the electrophysiological correlate of a protective reflex involving both sensory and motor pathways and enables functional assessment of thinly myelinated sensory fibers using standard neurophysiological equipment (6).

The study will include three groups: a DRG-PRF group, a TFESI group, and a healthy control group with no spinal pathology. Participants in the DRG-PRF and TFESI groups will be randomly allocated to treatment arms according to their order of presentation at the outpatient clinic. All participants will undergo baseline CSP recordings. In the treatment groups, CSP will be reassessed on Day 1, Week 1, and Month 1 following the intervention. CSP measurements will be conducted by an experienced electrophysiologist who is blinded to the treatment group. In addition, pain severity using the Numeric Rating Scale (NRS) and functional disability using the Oswestry Disability Index (ODI) will be evaluated in the treatment groups.

The DRG-PRF group will receive fluoroscopy-guided pulsed radiofrequency treatment at the L4-5 and L5-S1 lumbar levels using a standard 42°C protocol. The TFESI group will receive transforaminal corticosteroid injections at the same spinal levels. All procedures will be performed under sterile conditions by an experienced pain specialist.

The primary outcome of the study is to assess changes in CSP parameters, specifically onset latency and duration. Secondary outcomes include changes in pain intensity and functional capacity. The inclusion of a healthy control group will allow for comparison of CSP responses against normative values.

The study is expected to yield new insights into the neurophysiological effects of interventional pain treatments and to clarify the potential utility of CSP in monitoring treatment response in lumbar radicular pain. The findings may support more personalized clinical decision-making and enhance understanding of the underlying spinal mechanisms associated with these procedures.

Inclusion Criteria:

• Age between 18 and 65 years
• Clinically and radiologically confirmed lumbar radicular pain (LRP) due to unilateral intervertebral disc herniation, confirmed by MRI and physical examination
• Symptom duration greater than 3 months
• Baseline pain score of ≥4 on the 11-point Numerical Rating Scale (NRS-11)
• Inadequate response to conservative treatment (e.g., medication or physical therapy)

Exclusion Criteria:

• Unstable or uncontrolled psychiatric illness
• Pregnancy
• Bleeding diathesis
• Known allergy to any procedural agent (e.g., local anesthetics, corticosteroids, contrast media)
• Prior lumbar surgery
• Spondylolisthesis
• Compression fracture
• Discitis
• Bilateral or sequestered disc herniation
• Moderate-to-severe spinal stenosis
• Diabetes mellitus
• Polyneuropathy
• Fibromyalgia
• Movement disorders
• Regular use of antidepressants or tramadol
• Regular use of pregabalin or gabapentin
• Chronic alcohol use
• Noncompliance with follow-up