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