DRGS for Postherpetic Neuralgia: Promising Results Demand Further Research

Can DRGS Transform PHN Treatment?

Dorsal root ganglion stimulation (DRGS) is emerging as a promising therapeutic approach for postherpetic neuralgia (PHN), according to a comprehensive scoping review recently published in the clinical literature. This pilot review meticulously examined 23 studies investigating DRGS for PHN management, revealing encouraging preliminary results while highlighting significant research gaps that must be addressed before widespread clinical implementation can be recommended.

PHN represents one of the most challenging neuropathic pain conditions to treat, often persisting long after the resolution of herpes zoster infection. Conventional treatments frequently provide inadequate relief, leaving patients with limited options and reduced quality of life. DRGS offers a theoretical advantage over traditional spinal cord stimulation (SCS) by precisely targeting the dorsal root ganglia—key structures in pain signal transmission that may be particularly relevant to the focal, dermatomally concentrated pain characteristic of PHN. The current review synthesizes the available evidence to evaluate whether this theoretical benefit translates to meaningful clinical outcomes.

How Was This Review Conducted?

The review methodology followed Joanna Briggs Institute guidelines, with comprehensive searches across MEDLINE, Embase, CINAHL, and the Cochrane Library for literature published from 2010 onward, with the most recent search conducted in January 2025. Of 117 references initially identified, 23 studies met inclusion criteria and underwent detailed data extraction. The included studies spanned a range of designs, from case reports and retrospective case series to limited randomized controlled trials (RCTs), reflecting the evolving nature of this therapeutic approach. This methodological heterogeneity represents one of several limitations that complicate data interpretation and comparative analysis.

Are the Clinical Outcomes Consistent?

Case reports demonstrated promising individual outcomes, with several PHN patients experiencing substantial pain reductions following DRGS implementation. For instance, Bara et al. reported a remarkable reduction in Visual Analog Scale (VAS) scores from 90mm to 30mm in a 51-year-old female patient, while Lynch et al. documented significant pain relief in an 80-year-old patient who was able to discontinue all pain medications following treatment. These encouraging results were supported by small case series, such as the 2024 study by Verma et al., which reported greater than 40% pain reduction at 12 months post-implant in three patients with refractory PHN, along with improvements in functional status, mental health, and reduced reliance on analgesics. Similarly, Semenov et al. documented a median pain reduction of 62.3% in six elderly patients with refractory PHN, with most patients experiencing substantial improvements in daily functioning and sleep quality.

However, not all studies reported uniformly positive outcomes for PHN patients. Anthony et al. examined six patients with thoracic neuralgia of various etiologies and found that all three PHN patients failed to respond to DRGS during the trial phase, with two reporting no pain improvement and one experiencing lead-related pain necessitating device removal. This contrasted with findings from Papa et al., who noted that while their overall cohort demonstrated substantial pain relief (74% reduction at 48 months), the PHN subgroup specifically showed a less robust response compared to other pain etiologies. These discrepancies underscore the complex and potentially variable efficacy of DRGS across different PHN presentations and highlight the need for more refined patient selection criteria and larger, more homogeneous study populations.

The limited prospective evidence available provides additional insights. Eldabe et al. conducted a prospective cohort study of 42 patients (including two with PHN) and reported a mean VAS reduction of 1.7 points at 24 months, though PHN-specific outcomes were not separately reported. Piedade et al. conducted a randomized double-blind crossover trial evaluating different stimulation frequencies and found that low-frequency stimulation (4 Hz) produced the lowest pain scores compared to 20 Hz, 60 Hz, and sham conditions, though the small sample size (including just one PHN patient) limits generalizability. Perhaps most intriguingly, Parker et al. examined potential synergistic effects between DRGS and transcranial direct current stimulation (tDCS), finding that DRGS alone resulted in a 37% mean pain reduction, while DRGS paired with active tDCS yielded a 57% reduction compared to DRGS-OFF conditions.

Are Safety Concerns Under Control?

Safety considerations remain paramount in evaluating DRGS for PHN. Adverse events, though inconsistently reported across studies, commonly included lead migration, infection, skin erosion, and device failure or reduced efficacy requiring reprogramming or explantation. In the prospective study by Eldabe et al., procedural revisions were necessary in 14 patients, highlighting the ongoing safety concerns that must be balanced against potential therapeutic benefits. Kim et al. reported infection and lead dislodgement in their small case series, requiring explantation and reimplantation in one case and surgical revision in another. These complications underscore the importance of meticulous surgical technique, appropriate patient selection, and careful postoperative monitoring to optimize outcomes and minimize risks.

Could DRGS Impact Clinical Practice?

From a clinical perspective, these findings suggest that DRGS may provide meaningful pain relief for selected PHN patients who have not responded adequately to conventional treatments. The potential for improved pain control and reduced reliance on systemic analgesics positions DRGS as an emerging option for refractory cases within a comprehensive pain management strategy. However, the significant methodological limitations across available studies—including small sample sizes, heterogeneous populations, varied stimulation parameters, and inconsistent outcome reporting—preclude definitive conclusions or broad clinical recommendations at this time. The authors appropriately emphasize that their scoping review serves as a foundational synthesis and pilot mapping of the available evidence, laying the groundwork for more rigorous future investigations.

Looking ahead, the authors highlight several critical research priorities. There is an urgent need for well-designed, large-scale RCTs focused exclusively on PHN populations, employing standardized stimulation protocols and validated outcome measures with adequate long-term follow-up. Comparative effectiveness studies evaluating DRGS against alternative neuromodulation techniques or medical management strategies would further clarify its optimal role in clinical practice. Additionally, establishing consensus guidelines for study design and reporting would enhance consistency and facilitate meaningful data synthesis across investigations.

Could the observed variability in treatment response across studies reflect underlying differences in PHN pathophysiology or chronicity that might inform more tailored patient selection criteria? How might the development of standardized protocols for lead placement, programming parameters, and outcome assessment accelerate clinical translation and improve generalizability of research findings? These questions represent important considerations for researchers and clinicians as they navigate this evolving therapeutic landscape and work to address the significant unmet need for effective treatments for refractory PHN.

What Innovations Could Enhance DRGS Effectiveness?

The neurophysiological basis for DRGS effectiveness in PHN warrants further exploration. Parker et al.'s 2021 study examining cortical activity provided intriguing insights, demonstrating that pain relief was associated with a shift from low-frequency theta to higher-frequency low beta activity. This suggests potential biomarkers for DRGS efficacy that could eventually guide patient selection and optimize treatment protocols. The exploration of novel technical approaches, such as Wang et al.'s dual-function stimulator capable of delivering both DRGS and pulsed radiofrequency neuromodulation, points toward evolving innovations that might further enhance treatment outcomes through more flexible targeting of affected dermatomes.

The technical aspects of lead placement also emerged as a critical consideration across studies. Johnson et al.'s case report highlighted the surgical implantation of DRGS leads through laminectomies and foraminotomies, while Isagulyan et al. noted the use of standard SCS systems for DRGS due to lack of dedicated devices. These variations in technical approach and equipment underscore the need for standardization and optimization of implantation techniques to maximize therapeutic benefit while minimizing procedural risks. The development of specialized devices designed specifically for DRGS may further improve outcomes by addressing the unique anatomical and physiological characteristics of the dorsal root ganglia.

This comprehensive scoping review provides valuable insights into the current state of evidence for DRGS in PHN management while establishing a clear roadmap for future research. By systematically identifying knowledge gaps and methodological limitations, it serves as an essential reference point for investigators designing the next generation of studies in this promising but still emerging field. For clinicians managing patients with refractory PHN, it offers a balanced assessment of potential benefits and limitations, supporting informed discussions about this therapeutic option within the context of a multidisciplinary treatment approach.

Summary

A comprehensive scoping review examining 23 studies has evaluated dorsal root ganglion stimulation (DRGS) as a potential treatment for postherpetic neuralgia (PHN), a challenging neuropathic pain condition that persists after herpes zoster infection. The review, which followed Joanna Briggs Institute guidelines and searched literature from 2010 to January 2025, reveals encouraging preliminary results alongside significant research gaps. Case reports and small series demonstrated promising outcomes, with some patients experiencing substantial pain reductions—ranging from 40% to over 60% improvement—along with reduced medication dependence and improved quality of life. However, results were inconsistent across studies, with some PHN patients failing to respond to treatment during trial phases. Safety concerns included lead migration, infection, skin erosion, and device failure requiring revision or explantation. The review identified critical methodological limitations including small sample sizes, heterogeneous populations, varied stimulation parameters, and inconsistent outcome reporting. DRGS offers theoretical advantages over traditional spinal cord stimulation by precisely targeting dorsal root ganglia structures involved in pain transmission, potentially addressing the focal, dermatomally concentrated pain characteristic of PHN. The authors emphasize that while DRGS may provide meaningful relief for selected refractory PHN patients, current evidence remains insufficient for broad clinical recommendations. They call for well-designed, large-scale randomized controlled trials with standardized protocols, validated outcome measures, adequate long-term follow-up, and comparative effectiveness studies against alternative treatments. Emerging innovations include exploration of cortical biomarkers for treatment efficacy and dual-function stimulators combining DRGS with other neuromodulation approaches. The review establishes a foundation for future research and provides clinicians with a balanced assessment to support informed treatment discussions within comprehensive pain management strategies.