Peripheral Nerve Stimulation or Is It Peripheral Subcutaneous Field Stimulation; What Is in a Moniker?

A Definition of Neuromodulation and Classification of Implantable Electrical Modulation for Chronic Pain

OBJECTIVES

Neuromodulation therapies use a variety of treatment modalities (eg, electrical stimulation) to treat chronic pain. These therapies have experienced rapid growth that has coincided with escalating confusion regarding the nomenclature surrounding these neuromodulation technologies. Furthermore, studies are often published without a complete description of the effective stimulation dose, making it impossible to replicate the findings. To improve clinical care and facilitate dissemination among the public, payors, research groups, and regulatory bodies, there is a clear need for a standardization of terms.

APPROACH

We formed an international group of authors comprising basic scientists, anesthesiologists, neurosurgeons, and engineers with expertise in neuromodulation. Because the field of neuromodulation is extensive, we chose to focus on creating a taxonomy and standardized definitions for implantable electrical modulation of chronic pain.

RESULTS

We first present a consensus definition of neuromodulation. We then describe a classification scheme based on the 1) intended use (the site of modulation and its indications) and 2) physical properties (waveforms and dose) of a neuromodulation therapy.

CONCLUSIONS

This framework will help guide future high-quality studies of implantable neuromodulatory treatments and improve reporting of their findings. Standardization with this classification scheme and clear definitions will help physicians, researchers, payors, and patients better understand the applications of implantable electrical modulation for pain and guide informed treatment decisions.

Efficacy of Peripheral Nerve Field Stimulation for the Management of Chronic Low Back Pain and Persistent Spinal Pain Syndrome: A Narrative Review

OBJECTIVES

Various approaches have been developed with a view to treating the back pain component in patients with chronic low back pain (CLBP) and persistent spinal pain syndrome (PSPS). Emerging evidence shows that peripheral nerve field stimulation (PNFS) may be an efficacious therapeutic modality against axial low back pain. Hence, the aim of the review was to evaluate the analgesic efficacy and safety of PNFS, when used alone or as an adjunct to spinal cord stimulation (SCS), for managing CLBP and PSPS.

MATERIALS AND METHODS

A comprehensive search for clinical studies on PNFS and PNFS + SCS used for the management of CLBP and/or PSPS was performed using PubMed, EMBASE, MEDLINE via Proquest, and Web of Science.

RESULTS

A total of 15 studies were included, of which four were randomized controlled trials (RCTs), nine were observational studies, and two were case series. For patients receiving PNFS, a significant decrease in back pain intensity and analgesic consumption, together with a significant improvement in physical functioning, was observed upon implant of the permanent system. Meanwhile, the addition of PNFS to SCS in refractory cases was associated with a significant reduction in back and leg pain, respectively.

CONCLUSIONS

This review suggests that PNFS, when used alone or in combination with SCS, appears to be effective in managing back pain. However, high-quality evidence that supports the long-term analgesic efficacy and safety is still lacking. Hence, RCTs with a larger patient population and of a longer follow-up duration are warranted.

Peripheral subcutaneous field stimulation for the treatment of spinal cord injury at-level pain: case report, literature review, and 5-year follow-up

Spinal cord injury (SCI) frequently engenders chronic pain which may be classified as occurring above, at, or below the level of injury. Since patients with SCI may have a complex combination of nociceptive and neuropathic pain, pharmacological interventions often fail. Peripheral subcutaneous field stimulation (PSFS) is a novel neuromodulation surgery for pain in which subcutaneous electrodes designed for spinal cord stimulation are placed subcutaneously in a region of pain. We report the case of a 26-year-old man who was an unrestrained driver in a motor vehicle accident and suffered a complete ASIA A spinal cord injury with paraplegia due to a T4 three-column burst fracture. He underwent successful surgical fixation of the fracture (7/27/12) and developed severe at-level SCI-associated pain which failed all conservative measures. After a successful trial, two octrode leads (Abbott Medical, Plano, TX, USA) were placed for PSFS under general anesthesia and were connected to a right flank rechargeable pulse generator (11/6/13). At 60 months postoperative, the patient continues to use the peripheral field stimulation system on a daily basis and reports near complete relief of his at-level spinal cord injury pain. He noted instantaneous relief of his pain once ideal stimulation programming was achieved and has tolerated complete cessation of all narcotic use. His current programming settings are: Frequency of 50 Hz (Hz), Pulse Width of 350 μs (μsec), Amplitude of 0.00 miliamps (mA), Comf of 7.70 mA, and Perc of 4.50 mA. Chronic pain is a challenging and expensive sequela to manage in SCI patients and newer therapies are needed. Our case suggests that SCI at-level pain may respond durably to PSFS and provides the longest published follow-up on a case of PSFS. Peripheral subcutaneous field stimulation remains an investigational treatment for chronic pain syndrome and larger, long-term follow up studies are needed for the FDA and payers to approve this modality.

The Effect of Peripheral Neuromodulation on Pain From the Sacroiliac Joint: A Retrospective Cohort Study

OBJECTIVE

To report a retrospective review of the longer-term results of peripheral neuromodulation in 12 patients with significant chronic sacroiliac joint pain who had previously failed multiple conservative and interventional pain therapies.

METHODS

To allow for the assessment of meaningful longer-term outcome, implants for all 12 patients had been in place for a minimum of 18 months to a maximum of 36 months prior to the formal review.

RESULTS

Compared to the preimplantation baseline, the longer-term follow-up revealed a significant and sustained reduction in visual analog scale pain scores from 8.7T 1.1 to 1.1T 1.0 (p < 0.001), with a 75% reduction in analgesia requirement, and improvement in pain impact on daily function from 94.1% T 5.9% to 5.8% T 6.0% (p < 0.001).

CONCLUSION

This initial case series has highlighted that SIJ neuromodulation results in the reduction in pain intensity and improved functionality in patients who have already failed conventional medical management and interventional techniques, including RF denervation. These preliminary results merit a prospective randomized trial of peripheral neuromodulation.

The Effect of Peripheral Neuromodulation on Pain from the Sacroiliac Joint: A Retrospective Cohort Study

We report here a retrospective review of the longer-term results of peripheral neuromodulation in 12 patients with significant chronic sacroiliac joint pain who had previously failed multiple conservative and interventional pain therapies. To allow for the assessment of meaningful longer-term outcome, implants for all 12 patients had been in place for a minimum of 18 months to a maximum of 36 months prior to the formal review. Compared to the preimplantation baseline, the longer-term follow-up revealed a significant and sustained reduction in visual analog scale pain scores from 8.7 ± 1.1 to 1.1 ± 1.0 (P < 0.001), with a 75% reduction in analgesia requirement, and improvement in pain impact on daily function from 94.1% ± 5.9% to 5.8% ± 6.0% (P < 0.001). These preliminary results merit a prospective randomized trial of peripheral neuromodulation.

Long-Term Clinical Outcome of Peripheral Nerve Stimulation for Chronic Headache and Complication Prevention

Background

Subcutaneous peripheral nerve stimulation (PNS) has emerged as a useful tool in the treatment of intractable headaches. However, complications such as skin erosion, infection and lead migration have adversely affected clinical outcome, and occasionally led to treatment cessation.

Objectives

Here we report the results of peripheral nerve stimulator implantation performed on 24 patients with various chronic headaches at our center over a period of 9 years. We describe the complications of the procedure and their prevention with a modified surgical technique.

Patients and Methods

We searched our database for patients with chronic refractory headaches who had undergone PNS. Patients were assessed before being considered for PNS, and their pain characteristics were reviewed. Following a successful trial, patients were implanted with a permanent peripheral nerve stimulator. Selection of target nerves was based on headache diagnosis and head pain characteristics. Patients were followed for an average of 4.9 years. Headache characteristics before and after treatment were compared.

Results

Twenty four patients were included in the study. All patients reported on improvement in head pain intensity, duration and frequency three months after permanent device implantation Mean total pain index (TPI) decreased significantly, from 516 ± 131 before the procedure to 74.8 ± 61.6 at the last follow up (P < 0.00001). There were no acute post-operative infections. Three patients had their stimulator removed. The self-rated treatment satisfaction was excellent in 54% of the patients, very good or good in 42%, and fair in 4%.

Conclusions

Our results support the use of PNS in some patients with refractory chronic headaches. Appropriate surgical planning and technique are important to achieve good clinical outcome and to minimize complications.

Peripheral neuromodulation for the treatment of refractory trigeminal neuralgia

Trigeminal neuralgia is an extremely painful condition. Treatment options for trigeminal neuralgia include anticonvulsants, opioids and surgical methods; however, some cases may be refractory to these therapies. In this article, the authors report a case involving a patient for whom conventional treatments failed; she underwent a successful trial of peripheral nerve stimulation and subsequently opted for a permanent implantation of an internal pulse generator, leading to long-term relief of her pain.

Trigeminal neuralgia is a type of orofacial pain that is diagnosed in 150,000 individuals each year, with an incidence of 12.6 per 100,000 person-years and a prevalence of 155 cases per 1,000,000 in the United States. Trigeminal neuralgia pain is characterized by sudden, severe, brief, stabbing or lancinating, recurrent episodes of pain in the distribution of one or more branches of the trigeminal nerve, which can cause significant suffering for the affected patient population.

In many patients, a combination of medication and interventional treatments can be therapeutic, but is not always successful. Peripheral nerve stimulation has gained popularity as a simple and effective neuromodulation technique for the treatment of many pain conditions, including chronic headache disorders. Specifically in trigeminal neuralgia, neurostimulation of the supraorbital and infraorbital nerves may serve to provide relief of neuropathic pain by targeting the distal nerves that supply sensation to the areas of the face where the pain attacks occur, producing a field of paresthesia within the peripheral distribution of pain through the creation of an electric field in the vicinity of the leads.

The purpose of the present case report is to introduce a new, less-invasive interventional technique, and to describe the authors’ first experience with supraorbital and infraorbital neurostimulation therapy for the treatment of trigeminal neuralgia in a patient who had failed previous conservative management.

The appropriate use of neurostimulation: stimulation of the intracranial and extracranial space and head for chronic pain. Neuromodulation Appropriateness Consensus Committee

INTRODUCTION

The International Neuromodulation Society (INS) has identified a need for evaluation and analysis of the practice of neurostimulation of the brain and extracranial nerves of the head to treat chronic pain.

METHODS

The INS board of directors chose an expert panel, the Neuromodulation Appropriateness Consensus Committee (NACC), to evaluate the peer-reviewed literature, current research, and clinical experience and to give guidance for the appropriate use of these methods. The literature searches involved key word searches in PubMed, EMBASE, and Google Scholar dated 1970-2013, which were graded and evaluated by the authors.

RESULTS

The NACC found that evidence supports extracranial stimulation for facial pain, migraine, and scalp pain but is limited for intracranial neuromodulation. High cervical spinal cord stimulation is an evolving option for facial pain. Intracranial neurostimulation may be an excellent option to treat diseases of the nervous system, such as tremor and Parkinson's disease, and in the future, potentially Alzheimer's disease and traumatic brain injury, but current use of intracranial stimulation for pain should be seen as investigational.

CONCLUSIONS

The NACC concludes that extracranial nerve stimulation should be considered in the algorithmic treatment of migraine and other disorders of the head. We should strive to perfect targets outside the cranium when treating pain, if at all possible.

Peripheral neuromodulation: a review

Peripheral nerve stimulation (PNS) is likely the most diverse and rapidly expanding area of neuromodulation. Its expansion has become possible due to both technological and clinical advances in pain medicine. The first implantable systems were surgically placed. However, it is currently commonplace to use percutaneous leads, as this approach has become instrumental in its expansion. The first percutaneous peripheral nerve stimulators were reported in 1999. Cylindrical leads were implanted to stimulate the greater occipital nerve to manage intractable headache. It has been expanded into other individual nerves or nerve plexuses to treat neuropathic, visceral, cardiac, abdominal, low back and facial pain. The use of PNS in modulating organ function in treatment of syndromes such as epilepsy, incontinence and obesity with vagal, tibial and gastric stimulation is under extensive investigation. New technologies that allow easier and safer electrode placement are expected to further expand the uses of PNS. A noninvasive stimulation will open this treatment modality to more clinicians of varying backgrounds.

Subcutaneous stimulation: how to assess optimal implantation depth

INTRODUCTION

Subcutaneous stimulation (peripheral nerve field stimulation) is a novel neuromodulation modality that has increased in its utilization during the last 10 years. It consists of introducing a lead in the subdermal level to stimulate the small nerve fibers in that layer. Unlike other neuromodulation techniques including direct peripheral nerve stimulation, spinal cord stimulation, or deep brain stimulation, the precise target is not identified.

MATERIALS AND METHODS

To date, there is no clear guideline on the appropriate depth or a method to achieve reproducibility of the appropriate depth to place these leads. From clinical experience, we have found that when electrodes are placed in a layer that is too superficial, stimulation is often painful or lacks efficacy. Further, if they are too deep, the patient may not feel adequate paresthesia or get uncomfortable stimulation including, in some circumstances, muscle contractions.

RESULTS

In this small series, we demonstrate a novel concept using a radiofrequency stimulation probe to identify the appropriate depth to place the lead. Reproducibility of results will add clarity to the accumulating data and hopefully increase the chances of adequate stimulation coverage and pain relief.