Dorsal root ganglion stimulation for multifactorial refractory foot pain: A case report

Abstract

Background

Dorsal root ganglion (DRG) stimulation has emerged as an effective, targeted neuromodulation therapy for refractory pain of the lower extremities, particularly in the setting of complex regional pain syndrome. However, preliminary evidence supporting DRG for other applications, such as peripheral neuropathy or refractory nociceptive pain, is currently limited to patient populations with discrete pain sources. We report a case of chronic, multifactorial foot pain successfully treated with a right S1 DRG stimulation after failure of multiple prior interventions including physical therapy, corticosteroid injections, and surgeries.

Case report

A 74-year-old male presented with chronic refractory right foot pain, diagnosed with L5-S1 radiculopathy, peripheral neuropathy, persistent post-surgical pain following multiple procedures, including partial toe pain, which significantly impaired his mobility and quality of life. DRG stimulation was pursued after multiple prior interventions, including physical therapy, corticosteroid injections, surgeries, and a trial of peripheral nerve stimulation (PNS) that provided only temporary relief. Following a successful stimulation trial, a permanent DRG device was implanted at the S1 level, resulting in meaningful, sustained pain relief and functional improvement.

Conclusion

DRG stimulation represents a promising treatment for refractory lower extremity pain, especially in cases where traditional therapies have failed. This case illustrates its therapeutic potential in patients with complex refractory neuropathic pain of mixed etiologies.

1. Background

Chronic foot pain is a complex and often multifactorial condition that can arise from various etiologies, including peripheral nerve entrapment, radiculopathy, post-surgical changes, and localized neuropathies. When persistent, it can lead to significant functional impairment, reduced mobility, and diminished quality of life [1,2]. Management is often challenging, particularly when standard treatments such as pharmacotherapy, physical therapy, corticosteroid injections, and surgical interventions fail to provide adequate relief [3].

Dorsal root ganglion (DRG) stimulation is an emerging neuromodulation technique that offers precise targeting of affected dermatomes, making it especially suitable for focal neuropathic conditions like complex regional pain syndrome (CRPS) and post-surgical pain [4]. Unlike traditional spinal cord stimulation (SCS), DRG stimulation delivers electrical stimulation directly to the sensory neurons located within the dorsal root ganglia, providing localized and consistent pain relief with minimal paresthesia [5,6]. Clinical trials such as the ACCURATE study have demonstrated DRG stimulation to be superior to traditional SCS in treating lower extremity CRPS [7]. Although supported by high level Class I evidence with a Grade A recommendation for CRPS [8], its application in other neuropathic pain conditions such as peripheral neuropathy and post-surgical pain, as well as nociceptive pain syndromes remains limited. Herein, we present a case of refractory chronic right foot pain following foot surgery, successfully managed with S1 DRG stimulation.

2. Case presentation

A 74-year-old male with a long-standing history of right foot pain was referred to our clinic in 2024 for evaluation of chronic, severe neuropathic pain consistent with multifactorial L5-S1 radiculopathy, post-surgical pain, and peripheral neuropathy. He was diagnosed with hallux valgus et rigidus deformity with transfer metatarsalgia of the second through fourth metatarsophalangeal (MTP) joints in 2019 after initially presenting to Orthopedics with forefoot pain of one year that interfered with daily and recreational activities. He proceeded to foot arthrodesis surgery later that year after exhausting conservative therapies, including custom orthotics and anesthetic/steroid injections. Approximately five months after the surgery, he was diagnosed with metatarsalgia involving the second and third MTP joints. He was fitted with custom-made orthotics featuring medial arch support, a metatarsal pad, and a comfort surface, which provided minimal relief.

Over the following months, the patient developed progressive neuropathic symptoms, including paresthesia, numbness, and burning dysesthesia. He was referred to a podiatrist and underwent further conservative measures, which again did not yield significant improvement. Subsequently, he underwent hardware removal and plantar condylectomy of the second metatarsal which provided temporary pain relief. In 2022, he elected to undergo partial amputation of the second toe at the proximal interphalangeal (PIP) joint on the right foot. While this also provided some relief, the pain remained significant and continued to interfere with ambulation and quality of life.

He was then referred to a Physical Medicine and Rehabilitation (PM&R) specialist with expertise in sports medicine and ultrasound-guided interventions, who ordered lower limb EMG and diagnosed him with peripheral neuropathy. The patient subsequently received a corticosteroid injection at the right second MTP joint, followed a month later by a phenol injection targeting the first digital nerve. Both interventions failed to provide relief.

Due to the focal and refractory nature of his symptoms, a diagnostic block of the right sciatic nerve was performed to evaluate candidacy for temporary percutaneous peripheral nerve stimulation (PNS). After a positive block response, PNS leads were placed at the mid-thigh level for right sciatic/tibial division nerve stimulation, resulting in significant improvement in pain and function during the 90-day stimulation period, but which failed to provide lasting relief after the lead removal.

Throughout the years, he had previously trialed multiple treatments, including physical therapy, oral analgesics, all of which failed to provide meaningful or lasting benefit. Due to the refractory nature of his symptoms, he was referred to our clinic in March 2024 for evaluation of neuromodulation options. Based on the dermatomal distribution of his pain and partial response to PNS, DRG stimulation at the S1 level was selected to more effectively target both distal and proximal pain generators.

An S1 DRG trial led to approximately 85 % pain relief with improved sleep and mobility. During the trial, he was found to have a severe adhesive allergy, requiring topical treatment. In August 2024, he underwent successful implantation of a permanent DRG stimulator at the S1 level (Fig. 1). In the following months, the patient reported sustained 85 % pain relief, enhanced function and mood. It is also important to note that he experienced a lead malfunction and underwent lead replacement surgery 5 weeks after the initial DRG placement. However, after the replacement, he continued to report 85 % pain relief.

Fig. 1.

Fluoroscopic images of DRG procedure lead placement for targeting right S1. (A) AP view. (B) Lateral view. AP = Anteroposterior; DRG = Dorsal Root Ganglion.

3. Discussion

This case underscores the complex and refractory nature of multifactorial foot pain, which began after foot arthrodesis surgery and evolved despite extensive treatment. The patient had trialed oral neuropathic agents, anti-inflammatories, muscle relaxants, physical therapy, and local injections, with little relief. Even partial surgical amputation provided only limited benefit and introduced further challenges.

Neuromodulation emerged as a pivotal intervention in this patient's trajectory. While PNS has shown to be effective in treating refractory lower extremity pain [9], this modality offered short-term improvement in the present case. DRG stimulation, which has proven to be an effective treatment for CRPS [7] has low level evidence for treating post-surgical and peripheral neuropathic pain [8] but ultimately delivered significant and lasting pain relief, improved function, and quality of life. This improvement aligns with the findings of Liem et al. [10], who reported that 89 % of patients with foot pain experienced significant pain relief at six months following treatment with DRG stimulation.

Although current evidence for DRG stimulation in peripheral neuropathy remains limited, classified as Level III evidence with a Grade C recommendation by Chapman et al. [8] it is nonetheless an area of growing clinical interest. Existing reports include case series and small retrospective analyses showing potential benefit in patients with diabetic neuropathy [11,12] chemotherapy-induced neuropathy [13,14], small fiber neuropathy [15], and idiopathic or hereditary axonal polyneuropathies [16]. Falowski et al. [17] contributed a multicenter retrospective series that further supports this application, reporting favorable outcomes in patients with various peripheral neuropathy etiologies including polysensory neuropathy, diabetic neuropathy, chronic radiculopathy, and cases with prior spinal surgery or failed SCS. Notably, in a prospective pilot study, Koetsier et al. [18] reported a significant reduction in NRS pain scores at both 1, 3 and 6 months among seven participants treated with DRG stimulation for intractable painful polyneuropathy. However, these studies largely involve patients with clearly defined, monotypic neuropathic conditions who had failed conservative treatments. In contrast, our case demonstrates the utility of DRG stimulation in a far more complex scenario, marked by overlapping nociceptive and neuropathic drivers, multiple surgical interventions, and temporary sciatic PNS treatment which failed to provide more sustained relief. This multifactorial pain syndrome does not fit neatly within traditional peripheral neuropathy classifications. The patient's significant and sustained benefit highlights the versatility of DRG stimulation beyond classical indications, suggesting that it may also be considered in refractory, mixed-mechanism pain syndromes when other neuromodulatory and surgical interventions have failed.

In this case, several factors may explain the limited durability of pain relief following peripheral nerve stimulation. While the patient initially experienced functional improvement during the 90-day stimulation period, the benefits did not persist after lead removal. One plausible explanation is that the peripheral approach of PNS, targeting the sciatic/tibial division at the mid-thigh level, may have inadequately modulated deeper or more proximal pain generators. This is particularly relevant in patients with overlapping radiculopathy or possible central sensitization, where distal nerve stimulation may fall short in addressing the full spectrum of pain drivers [19]. Given the patient's dermatomal distribution of symptoms and partial response to PNS, DRG stimulation at the S1 level was selected to more effectively target both proximal and distal components of his pain. Other options, such as repeat PNS or conventional SCS, were considered; however, SCS was deemed less optimal due to its broader and less focal paresthesia patterns, which did not match the patient's symptom localization [20]. DRG stimulation ultimately offered a more precise and targeted neuromodulatory strategy for this complex, refractory presentation.

This case illustrates the potential of DRG stimulation as an effective therapy not only for classical neuropathic pain syndromes such as CRPS but also for complex, refractory pain with mixed neuropathic and nociceptive components. The patient's multifactorial pain profile underscores the limitations of traditional treatments and peripheral nerve stimulation, while the sustained benefit observed with DRG stimulation supports its emerging role as a targeted neuromodulation strategy capable of modulating both proximal and distal pain generators. These findings emphasize the importance of a stepwise, multimodal strategy in managing refractory foot pain, including the careful consideration of surgical therapies and the potential for neuromodulation, particularly DRG stimulation, in cases where traditional and even invasive treatments fail to achieve long-term relief.

Importantly, while the patient presented with overlapping neuropathic and nociceptive features, DRG stimulation was approved under the indication of causalgia, consistent with current payer requirements for labeled use. This reflects real-world practice, in which labeled diagnoses are often required despite complex or overlapping pain phenotypes. This case also serves as a proof-of-concept encouraging further research and broader clinical application of DRG stimulation in mixed-mechanism pain syndromes.

4. Conclusion

This case illustrates the challenges of managing refractory foot pain, as the patient failed to respond to multiple conservative treatments and interventions, including oral neuropathic agents, physical therapy, PNS, and surgeries. Ultimately, the patient achieved significant pain relief and functional improvement with DRG stimulation, despite its limited evidence base for applications outside of CRPS. This outcome highlights the potential effectiveness of DRG stimulation in complex refractory cases, offering a promising treatment option for patients with complex neuropathic pain unresponsive to traditional therapies.

Consent

The patient's consent was obtained for disclosure of the case details.

Funding

None.

Declaration of competing interest

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Zachary McCormick reports a relationship with International Pain & Spine Intervention Society that includes: board membership. Zachary McCormick reports a relationship with Avanos Medical Inc that includes: consulting or advisory and funding grants. Zachary McCormick reports a relationship with Boston Scientific Corporation that includes: funding grants. Zachary McCormick reports a relationship with Relievant Medsystems Inc that includes: funding grants. Zachary McCormick reports a relationship with Saol International Ltd that includes: consulting or advisory and funding grants. Zachary McCormick reports a relationship with Spine Biopharma that includes: funding grants. Zachary McCormick reports a relationship with SPR Therapeutics Inc that includes: funding grants. Zachary McCormick reports a relationship with Stratus that includes: funding grants. Zachary McCormick reports a relationship with Stryker that includes: consulting or advisory. Zachary McCormick reports a relationship with Orthoson that includes: consulting or advisory. Aaron Conger reports a relationship with Stratus that includes: funding grants. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.