Treatment of FBSS Low Back Pain with a Novel Percutaneous DRG Wireless Stimulator: Pilot and Feasibility Study.

OBJECTIVES: Test a miniaturized neurostimulator transforaminally placed at the dorsal root ganglion (DRG) and evaluate the device's safety and efficacy in treating failed back surgery syndrome (FBSS) low back pain. DESIGN: Pilot, two-phase study. SUBJECTS: Eleven subjects with chronic intractable neuropathic trunk and/or lower limbs pain were included. METHODS: The system consisted of an implantable, miniaturized stimulator, provided by Stimwave Technologies (Freedom-4) and an external transmitter. Only one stimulator per subject was implanted unilaterally and transforaminally at L1 to L5 levels. During Phase 1 of the study, the stimulators were not anchored. In Phase 2, the stimulators were anchored. Subjects were treated during 45 days after which the stimulator was removed. Pain reduction, implant duration, and stimulator migration were registered. RESULTS: Overall pain reduction was 59.9%, with only one device placed at one location, covering only a portion of the painful areas in the majority of the subjects. In Phase 1, the non-anchored stimulators migrated a mean of 8.80 mm and in Phase 2 a mean of 1.83 mm. Stimulator migration did not correlate with changes in pain relief. Mean time-to-implant duration was 10 minutes and no adverse events were reported during implant, follow-up period, or after explant. CONCLUSIONS: The pain reduction results indicate that the Freedom-4 spinal cord stimulation (SCS) Wireless System is a viable treatment of low back pain through stimulation of the DRG, and better overall pain reduction may be achieved by implanting multiple devices. With short percutaneous implant times and excellent safety profile, this new system may offer health cost savings.

A prospective study of dorsal root ganglion stimulation for the relief of chronic pain.

OBJECTIVE: The article aims to study the safety and effectiveness of dorsal root ganglion (DRG) stimulation with a new device in the treatment of chronic pain. DESIGN: This is a prospective, single-arm, pilot study. SETTING: Four clinical centers were used as setting for this study. PATIENTS: Ten (10) patients with chronic intractable pain of the trunk and/or limbs were included. INTERVENTION: A trial period of DRG stimulation was studied. Two to four leads, each with four electrical contacts, were inserted using a minimally invasive epidural approach and steered toward the lateral epidural space, near the DRG. Leads were attached to an external trial stimulator and stimulation therapy was provided for three to seven days. OUTCOME MEASURES: Pain reduction using a visual analog scale, subject and physician-rated improvement, adverse event (AE) rates, device programming settings, and medication utilization was evaluated at baseline and at prospective follow-up time points during stimulation. RESULTS: On average, there was a 70% reduction in pain following stimulation (p = 0.0007). Eight of the nine patients experienced a clinically meaningful (>30%) reduction in pain, and seven of the nine reduced their pain medication utilization. Pain relief in specific anatomical regions such as the leg, back, and foot was also observed. No device-related AEs were reported. CONCLUSIONS: These initial results suggest that stimulation of the DRG can reduce pain in those patients suffering from chronic pain. DRG stimulation may offer several potential benefits over other neuromodulation techniques, including the ability to target difficult-to-reach anatomies such as the low back and foot.

A voltage-controlled capacitive discharge method for electrical activation of peripheral nerves.

OBJECTIVES: A voltage-controlled capacitive discharge (VCCD) method was investigated as an alternative to rectangular stimulus pulses currently used in peripheral nerve stimulation therapies. METHODS AND MATERIALS: In two anesthetized Gottingen mini pigs, the threshold (total charge per phase) for evoking a compound nerve action potential (CNAP) was compared between constant current (CC) and VCCD methods. Electrical pulses were applied to the tibial and posterior cutaneous femoralis nerves using standard and modified versions of the Medtronic 3778 Octad. RESULTS: In contrast to CC stimulation, the combined application of VCCD pulses with a modified Octad resulted in a marked decrease (-73 ± 7.4%) in the stimulation threshold for evoking a CNAP. This was consistent for different myelinated fiber types and locations of stimulation. CONCLUSIONS: The VCCD method provides a highly charge-efficient means of activating myelinated fibers that could potentially be used within a wireless peripheral nerve stimulator system.

Peripheral Nerve Stimulation for Facial Pain Using Wireless Devices.

Since its original introduction several decades ago, peripheral nerve stimulation (PNS) of the craniofacial region has been traditionally performed using devices intended for spinal cord stimulation applications with inevitably high rate of technical challenges and procedural complications. The lower invasiveness of recently developed wireless neurostimulation systems makes them much better suited for craniofacial applications. Here, we discuss the preliminary clinical data from several published reports and the ongoing multicenter prospective study of wireless PNS in the craniofacial region. Advances in wireless transmission of electrical signals may make wireless neurostimulation even more attractive in the future. Since most of the evidence supporting PNS for facial pain comes from small subsets of the population, case series and case reports, there will need to be larger, randomized controlled trials with cost efficacy analyses in order to validate the role of wireless PNS as the standard of care.

Using peripheral stimulation to reduce the pain of C2-mediated occipital headaches: a preliminary report.

BACKGROUND: Peripheral nerve stimulation (PNS) is an accepted treatment for neuropathic pain. Recent studies have focused on its potential for relieving headache pain. OBJECTIVES: To investigate the effectiveness of PNS in reducing occipital headache pain. DESIGN: A prospective, 12-week pilot study involving 11 patients evaluated before and after implantation of PNS systems to treat C2-mediated occipital headaches. METHODS: Prior to and at 4 and 12 weeks after implantation, patients completed the Short-Form McGill Pain Questionnaire (SF-MPQ), Visual Analog Scale (VAS), and Present Pain Index (PPI). Patients also answered questionnaires and kept diaries to record stimulator use, medication consumption, and numbers of headaches. RESULTS: A comparison of pre- and post-implantation evaluations showed statistically significant declines in scores on the SF-MPQ (64%; p = 0.0013), VAS (67%; p < 0.0001), and PPI (68%; p = 0.0009). Most patients (91% and 64% respectively) reported reductions in medication use and numbers of headaches. Patients also reported a reduction in headache symptoms and the impact of headaches on activities. Two adverse events were encountered, one due to a loose connection and, the other caused by lead migration. CONCLUSIONS: PNS reduced headache pain, headache frequency and medication use.

A novel miniature, wireless neurostimulator in the management of chronic craniofacial pain: Preliminary results from a prospective pilot study.

OBJECTIVE: To report a novel wireless neuromodulation system for treatment of refractory craniofacial pain. BACKGROUND: Previous studies utilizing peripheral nerve stimulation (PNS) of the occipital and trigeminal nerves reported positive outcomes for alleviating neuropathic pain localized to the craniofacial and occipital areas. However several technological limitations and cosmetic concerns inhibited a more widespread acceptance and use of neuromodulation. Also, a relatively high incidence of adverse events like electrode erosions, dislocation, wire fracture and/or infection at the surgical site mandates a change in our approach to neuromodulation technology and implant techniques in the craniofacial region. METHODS: We report a novel approach for the management of craniofacial pain with a wirelessly powered, minimally invasive PNS system. The system is percutaneously implanted and placed subcutaneously adjacent to affected facial nerves via visual guidance by the clinician. In this feasibility study, pilot evidence was gathered in a cohort of ten subjects suffering from a combination of chronic headaches, facial pain for at least 15 days per month and for at least 4h/day. RESULTS: At four weeks post-implant follow up, all patients reported sustained pain relief of the primary pain area. Electrode location and total number of electrodes used per subject varied across the cohort. The average pain reduction using the visual analog scale was ≥82%. The procedure had no adverse events or side effects. CONCLUSION: Percutaneous placement of a wireless neurostimulation device directly adjacent to affected craniofacial nerve(s) is a minimally invasive and reversible method of pain control in patients with craniofacial pain refractory to conventional medical managements. Preliminary results are encouraging and further larger scale studies are required for improved applications.

Control of growth of vestibular schwannomas with low-dose Gamma Knife surgery.

OBJECT: The treatment of solitary vestibular schwannomas by performing Gamma Knife surgery is well established. It has been reported that decreasing the surface dose reduces patient morbidity, especially facial weakness and numbness. The authors of this retrospective study examine patient data from a single center to determine if low-dose (< or = 14 Gy) GKS controls tumor growth as effectively as higher doses (> 14 Gy). METHODS: Based on the formula for ellipsoid volumes, the tumor volumes were calculated using measurements from MR images obtained at follow up in patients treated at the authors' center. Follow-up data were available in 159 patients with a mean age of 59.5 +/- 14.2 years at treatment. Fifty-six percent of the patients were women and 53.5% of the tumors were located on the right side of the brain. The mean tumor volume was 3.3 +/- 4.3 cm3 with 10% of the tumors having volumes larger than 8 cm3. After GKS, smaller tumors (> or = 40% decrease in volume) were observed in 44.8% of patients treated with a low dose and in 48.8% treated with a high dose. Enlarged tumors (> or = 40% increase in volume) were seen in 5.2% of the patients receiving a low dose and 2.3% of those receiving a high dose. These differences were not statistically significant. Patients who had been followed up for longer than 5 years after treatment had median residual volumes of only 28.2% of the starting volume in the low-dose group and 26% in the high-dose group. This difference was statistically not significant. CONCLUSIONS: No statistically significant differences were observed between tumors given low-dose radiation treatment and those given high-dose radiation treatment.

Peripheral nerve neurostimulation.

There is a renewed interest in the use of PNS for the control of intractable pain caused by peripheral mononeuropathies and sympathetically mediated chronic pain syndromes. Technical advances in neurostimulation hardware, specifically lead design and surgical advancements with percutaneous and subcutaneous techniques, fuel this interest in part. The use of multipolar electrode arrays placed percutaneously in the region of peripheral nerves or in their dermatomal distribution without the need for extensive surgical dissection should help to support the use of PNS as a reasonable alternative to potentially destructive surgical procedures for chronic pain control.

Subcutaneous occipital region stimulation for intractable headache syndromes.

Subcutaneous occipital nerve region stimulation is becoming an important part of the overall treatment regimen for a number of chronic headache syndromes refractory to nonsurgical, medical management. A combination of improved device technology and methodology, further understanding about appropriate indications and achievement of on-label FDA status should support continued use and success of this neuromodulation modality.

Spinal cord stimulation has comparable efficacy in common pain etiologies.

Objectives. The probability of success with spinal cord stimulation (SCS) depends largely on appropriate patient selection. Here, we have assessed the predictive value of pain etiology as it relates to pain relief with SCS as part of a prospective multicenter clinical trial. Methods. Sixty-five subjects with chronic and intractable pain tested an epidural SCS system. Subjects reported pain ratings (visual analog scale) with stimulation off and stimulation on at scheduled follow-up visits for up to 18 months after activation of the system. Visual analog scale scores were averaged and stratified by dominant pain etiologies, comprising failed back surgery syndrome, complex regional pain syndrome, and a subgroup of subjects with miscellaneous other pain etiologies. Results. More than 70% of subjects in each subgroup had successful outcomes during the temporary trial period and similar percentages of subjects from each etiology subgroup subsequently went on to permanent implantation. After permanent implantation, all subgroups reported more than 50% pain relief, on average, at each follow-up time point. No predictive value of pain etiology was observed. Conclusions. Spinal cord stimulation is an effective therapy for neuropathic pain arising from a variety of causes. Failed back surgery syndrome, complex regional pain syndrome, and pain of other etiologies responded equally well to SCS.