Implantable Subdural Cortical Stimulation for Chronic Intractable Pain Treatment-The Mayo Experience and Review of Literature.

OBJECTIVES: Motor cortex stimulation (MCS) is an effective technique in treating chronic intractable pain for some patients. However, most studies are small case series (n < 20). Heterogeneity in technique and patient selection makes it difficult to draw consistent conclusions. In this study, we present one of the largest case series of subdural MCS. MATERIALS AND METHODS: Medical records of patients who underwent MCS at our institute between 2007 and 2020 were reviewed. Studies with at least 15 patients were summarized for comparison. RESULTS: The study included 46 patients. Mean age was 56.2 ± 12.5 years (SD). Mean follow-up was 57.2 ± 41.9 months. Male-to-female ratio was 13:33. Of the 46 patients, 29 had neuropathic pain in trigeminal nerve territory/anesthesia dolorosa; nine had postsurgical/posttraumatic pain; three had phantom limb pain; two had postherpetic pain, and the rest had pain secondary to stroke, chronic regional pain syndrome, and tumor. The baseline numeric rating pain scale (NRS) was 8.2 ± 1.8 of 10, and the latest follow-up score was 3.5 ± 2.9 (mean improvement of 57.3%). Responders comprised 67% (31/46)(NRS ≥ 40% improvement). Analysis showed no correlation between percentage of improvement and age (p = 0.352) but favored male patients (75.3% vs 48.7%, p = 0.006). Seizures occurred in 47.8% of patients (22/46) at some point but were all self-limiting, with no lasting sequelae. Other complications included subdural/epidural hematoma requiring evacuation (3/46), infection (5/46), and cerebrospinal fluid leak (1/46). These complications resolved with no long-term sequelae after further interventions. CONCLUSION: Our study further supports the use of MCS as an effective treatment modality for several chronic intractable pain conditions and provides a benchmark to the current literature.

What's New in Peripheral Nerve Stimulation.

Peripheral nerve stimulation (PNS) is a powerful interventional option for the management of otherwise intractable pain. This technique involves the implantation of electrodes to apply electrical stimulation to named peripheral nerves, thereby alleviating pain in the territory of the target nerves. Recent advancements, largely driven by physician-industry relationships, have transformed the therapy into one that is minimally invasive, safe, evidence-based, and effective. Ongoing research has expanded the indications beyond chronic neuropathic pain in a peripheral nerve distribution. This article provides an overview of recent advances in this field.

Wireless Subcutaneous Trigeminal Nerve Field Stimulation for Refractory Trigeminal Pain: A Single Center Experience.

INTRODUCTION: Subcutaneous trigeminal nerve field stimulation (sTNFS) is a neuromodulatory treatment for neuropathic trigeminal pain with the ability to reduce the intensity and frequency of pain attacks. However, hardware issues including lead migration, skin erosion, infection, so-called pocket pain at the site of the implanted neurostimulator are reported. Implantable wireless neurostimulation technology promises not only an even less invasive sTNFS treatment and thinner and more flexible electrodes better suited for facial implants, but also provides further advantages such as lack of an implantable neurostimulator and 3T magnetic resonance imaging compatibility. MATERIAL AND METHODS: All patients who had received trial stimulation with a partially implantable sTNFS system were analyzed for ICHD-3 (3rd edition of the International Classification of Headache Disorders) diagnosis, success of trial stimulation, pre- and postoperative pain intensity, frequency of attacks, complications, and side-effects of sTNFS. RESULTS: All patients (N = 3) responded to sTNFS (≥50% pain reduction) during the trial period. According to ICHD-3, N = 2 of the patients were classified with trigeminal neuralgia (TN) with concomitant persistent facial pain and N = 1 patient with multiple sclerosis associated TN. The time of the test period was 44 ± 31.24 days (mean ± SD). The average daily duration of stimulation per patient amounted 2.5 ± 2.2 hours (range 1-5). The pain intensity (defined on a visual analog scale) was reduced by 80% ± 17% (mean ± SD). Reduction or cessation in pain medication was observed in all patients. No surgical complications occurred in the long-term follow-up period of 18.84 ± 6 (mean ± SD) months. CONCLUSION: The partially implantable sTNFS device seems to be safe, effective, and reliable. Compared to conventional devices, the equipment is not limited to the length of trial stimulation. Furthermore, the daily stimulation duration was much shorter compared to previous reports.

A Clinical Review of Slipping Rib Syndrome.

ABSTRACT: Slipping rib syndrome is pain created at the lower, anterior border of the rib cage when performing upper-extremity activities, coughing, laughing, or leaning over. Defects in the costal cartilage of ribs 8 to 10 result in increased movement of the ribs, impinging soft tissue and intercostal nerves. Advancements have been made in the diagnosis of slipping rib syndrome by dynamic ultrasound. Ultrasound can identify abnormalities in the rib and cartilage anatomy, as well as soft tissue swelling. Although the mainstays of treatment continue to be reassurance, nonsteroidal anti-inflammatory drugs, physical therapy, intercostal nerve injections, osteopathic manipulative treatment, surgery for refractory pain, and botulinum toxin injections have been attempted, and there may be a role for prolotherapy in treatment. Surgical techniques are being examined secondary to recurrence of pain following resection. The hooking maneuver and surgery remain important for identification and treatment, respectively.

Programming Parameters and Techniques in Trigeminal Ganglion Stimulation for Intractable Facial Pain.

OBJECTIVES: Atypical facial pain syndromes are challenging disorders to manage and often incur limited benefit with surgery for classical trigeminal neuralgia presentations, such as microvascular decompression or ablative procedures. Neurostimulation of the trigeminal ganglion and peripheral nerves can be effective at treating atypical presentations of trigeminal facial pain affecting the V1-3 dermatomes, and the surgical techniques are well described. The stimulation parameters, however, have thus far received limited description; we therefore sought to describe programming strategies. MATERIALS AND METHODS: We performed a retrospective chart review, examining patients that underwent trigeminal ganglion stimulation (TGS) and nerve branch stimulation for atypical facial pain and trigeminal neuropathic pain, and describe the programming strategies in detail. RESULTS: We describe the use of high-frequency stimulation (1000 Hz), with alteration in pulse width (60-220 msec) and amplitude (0.5-3 V) to achieve effective treatment of refractory trigeminal facial pain. These parameters differ from existing published parameters for trigeminal nerve branch stimulation. We also describe the programming of specific contacts on each lead to target specific aspects of the individual patients' facial pain. CONCLUSIONS: The use of effective programming strategies is critical to the success of neurostimulation surgical treatments; however, the critical details in programming strategies typically receive limited description. We report on the use of several successful programming strategies for TGS, to assist pain providers in successfully applying these surgical techniques in these difficult to manage atypical facial pain syndromes.

Ultrasound-Guided Percutaneous Peripheral Nerve Stimulation for the Treatment of Chronic Intractable Pain Originating From a Lipofibromatous Hamartoma of the Median Nerve.

This case report presents an application of peripheral nerve stimulation to the median nerve to treat a patient with intractable pain due to a lipofibromatous hamartoma of the left upper extremity. Ultra high-frequency ultrasound was used to determine the boundaries of the hamartoma. The patient then underwent an ultrasound-guided implantation of 2 stimulator electrodes distal to the elbow along the median nerve with stimulation coverage achieved at 1.2 and 1.4 mA, respectively. After an uneventful procedure, the pain score immediately decreased from 9 out of 10 to less than 6 on a numeric rating scale. Two weeks after the procedure, the patient reported substantial pain relief, with an average pain level of 5 to 6 out of 10. Twelve months after implantation, the patient maintained significant pain relief, rating her average pain level as a 4 to 6 out of 10. Placement of a percutaneous peripheral nerve stimulator was safe and effective with no adverse events being reported at the 12-month follow-up.

An evidence-based review of neuromodulation for the treatment and management of refractory angina.

Angina pectoris is defined as substernal chest pain that is typically exacerbated by exertion, stress, or other exposures. There are various methods of treatment for angina. Lifestyle modification and pharmacological management are considered as conservative treatments. If these medications do not result in the resolution of pain, more invasive approaches are an option, like coronary revascularization. Refractory angina (RA) is differentiated from acute or chronic angina based on the persistence of symptoms despite conventional therapies. Overall, the prevalence of RA is estimated to be 5%-15% in patients with coronary artery disease, which can account for up to 1,500,000 current cases and 100,000 new cases in the United States per year. Spinal cord stimulation treatment is a viable option for patients who are suffering from RA pain and are either not candidates for revascularization surgery or are currently not being well managed on more traditional treatments. Many studies show a positive result.

Proclaim™ DRG Neurostimulator System for the management of chronic, intractable pain.

Chronic pain is consistently listed as one of the most costly and disabling health problems worldwide. In an effort to treat these suffering individuals, significant amounts of time and energy have been devoted to discover safe and effective pain relieving treatments. Dorsal root ganglion stimulation is the newest treatment modality to be created for chronic intractable pain. In this manuscript, we review the history and development, published research and safety profile of the Proclaim™ DRG Neurostimulator System (Abbott, TX, USA). At last, we offer our outlook on future developments with dorsal root ganglion stimulation.

Percutaneous Trigeminal Stimulation for Intractable Facial Pain: A Case Series.

BACKGROUND: Facial pain syndromes can be refractory to medical management and often need neurosurgical interventions. Neuromodulation techniques, including percutaneous trigeminal ganglion (TG) stimulation, are reversible and have emerged as alternative treatment options for intractable facial pain. OBJECTIVE: To report the complication rates and analgesic effects associated with TG stimulation and identify potential predictors for these outcomes. METHODS: A retrospective chart review of 59 patients with refractory facial pain who underwent TG stimulation was conducted. Outcomes following trial period and permanent stimulation were analyzed. Patients with >50% pain relief during trial stimulation received permanent implantation of the stimulation system. RESULTS: Successful trial stimulation was endorsed by 71.2% of patients. During the trial period, 1 TG lead erosion was identified. History of trauma (facial/head trauma and oral surgery) was the only predictor of a failed trial compared to pain of idiopathic etiology (odds ratio: 0.15; 95% CI: 0.03-0.66). Following permanent implantation, approximately 29.6% and 26.5% of patients were diagnosed with lead erosion and infection of the hardware, respectively. TG lead migrations occurred in 11.7% of the patients. The numeric rating scale score showed a statistically significant reduction of 2.49 (95% CI: 1.37-3.61; P = .0001) at an average of 10.8 mo following permanent implantation. CONCLUSION: TG stimulation is a feasible neuromodulatory approach for the treatment of intractable facial pain. Facial/head trauma and oral surgery may predict a nonsuccessful trial stimulation. Future development of specifically designed electrodes for stimulation of the TG, and solutions to reduce lead contamination are needed to mitigate the relatively high complication rate.

Effect of subcutaneous needling on visual analogue scale, IgG and IgM in patients with lumbar disc herniation: Study protocol clinical trial (SPIRIT Compliant).

BACKGROUND: Lumbar disc herniation (LDH) is a disease commonly seen in clinical practice. In the majority of such patients presenting in clinic, the symptoms can be relieved or even abolished after non-surgical treatment. Floating needle therapy has attracted considerable attention as a promising non-surgical technique to treat LDH, as demonstrated in previous studies. The purpose of the present study was to evaluate the outcomes of patients treated using this therapy in a single blind and randomized controlled trial by recording patient report questionnaires and objective test data, and to explore the feasibility and preliminary effects of floating needle therapy for patients with LDH. METHODS: A total of 80 patients who fulfilled the inclusion criteria were randomly divided into a Fu's subcutaneous needling (FSN) group and an acupuncture group then treated in accordance with procedures appropriate for a single blind and randomized controlled trial. The FSN group received 12 FSN therapy sessions over a 3-week period, and the acupuncture group received acupuncture therapy at specified points using acupuncture needles. The principal measurements were scored using the visual analogue scale (VAS), Japanese Orthopedic Association (JOA) Score, and Oswestry disability index (ODI) before and 3 weeks after treatment. Secondary measurements included immune function IgG and IgM measurements performed at the same time and adverse reactions during treatment. RESULTS: The results of this trial will be published on the website of China Clinical Trial Registration Center (http://www.chictr.org.cn/searchprojen.aspx) and in peer-reviewed journals or academic conferences. CONCLUSIONS: This study will explore the feasibility and preliminary effects of floating needle therapy for the treatment of patients with LDH. REGISTRATION: PROSPERO (registration number ChiCTR1900024045).

Deep Brain Stimulation for Pain in the Modern Era: A Systematic Review.

BACKGROUND: Deep brain stimulation (DBS) has been considered for patients with intractable pain syndromes since the 1950s. Although there is substantial experience reported in the literature, the indications are contested, especially in the United States where it remains off-label. Historically, the sensory-discriminative pain pathways were targeted. More recently, modulation of the affective sphere of pain has emerged as a plausible alternative. OBJECTIVE: To systematically review the literature from studies that used contemporary DBS technology. Our aim is to summarize the current evidence of this therapy. METHODS: A systematic search was conducted in the MEDLINE, EMBASE, and Cochrane libraries through July 2017 to review all studies using the current DBS technology primarily for pain treatment. Study characteristics including patient demographics, surgical technique, outcomes, and complications were collected. RESULTS: Twenty-two articles were included in this review. In total, 228 patients were implanted with a definitive DBS system for pain. The most common targets used were periaqueductal/periventricular gray matter region, ventral posterior lateral/posterior medial thalamus, or both. Poststroke pain, phantom limb pain, and brachial plexus injury were the most common specific indications for DBS. Outcomes varied between studies and across chronic pain diagnoses. Two different groups of investigators targeting the affective sphere of pain have demonstrated improvements in quality of life measures without significant reductions in pain scores. CONCLUSION: DBS outcomes for chronic pain are heterogeneous thus far. Future studies may focus on specific pain diagnosis rather than multiple syndromes and consider randomized placebo-controlled designs. DBS targeting the affective sphere of pain seems promising and deserves further investigation.

Neurostimulation for the Treatment of Chronic Head and Facial Pain: A Literature Review.

BACKGROUND: Head and facial pain is a common and often difficult to treat disorder. Routine treatments sometimes fail to provide acceptable relief, leaving the patient searching for something else, including narcotics and surgery. Recently, neuromodulation has been expanding to provide another option. Secondary to its potentially temporary nature and relatively manageable risk profile, several reviews have suggested trialing neuromodulation prior to starting narcotics or invasive permanent surgeries. There is evidence that neuromodulation can make a difference in those patients with intractable severe craniofacial pain. OBJECTIVES: To provide a basic overview of the anatomy, epidemiology, pathophysiology and common treatments of several common head and facial disorders. Furthermore, to demonstrate the suggested mechanisms of neuromodulation and the evidence currently existing for the use of neuromodulation. METHODS: A comprehensive review was performed regarding the available literature through targeting articles reporting on the use of neuromodulation to treat pain of the head and face. RESULTS: We compiled and discuss the current evidence available in treating head and facial pain. The strongest evidence currently for neuromodulation is for occipital nerve stimulation for migraine, transcutaneous vagal nerve stimulation for migraine and cluster headache, sphenopalatine ganglion microstimulation for cluster headache, and transcutaneous supraorbital and supratrochlear nerve stimulation for migraine. In addition, there is moderate evidence for occipital nerve stimulation in treating occipital neuralgia. LIMITATIONS: Neuromodulation has been trialed and is promising in several craniofacial pain disorders; however, there remains a need for large-scale, randomized, placebo-controlled clinical trials to further evaluate the efficacy and safety of most treatments. Much of the current data relies on case reports without randomization or placebo controls. CONCLUSIONS: With advancing techniques and technology, neuromodulation can be promising in treating intractable pain of the head and face. Although more randomized controlled trials are warranted, the current literature supports the use of neuromodulation in intractable craniofacial pain. KEY WORDS: Neuromodulation, headache, facial pain, craniofacial pain, migraine, cluster headache, trigeminal neuralgia, occipital neuralgia, peripheral nerve stimulator, high cervical spinal cord stimulator, peripheral nerve field stimulator.

Spinal Stimulation for the Treatment of Intractable Spine and Limb Pain: A Systematic Review of RCTs and Meta-Analysis.

OBJECTIVE: To synthesize the evidence regarding the effect of spinal stimulation (SS) vs medical therapy (MT) and the effect of newer SS technologies vs conventional SS on pain reduction in patients with intractable spine or limb pain. METHODS: A comprehensive literature search was conducted by a reference librarian. The literature search encompassed January 1, 1995 - December 31, 2017. Reviewers worked independently to select and appraise trials. Random-effect meta-analysis and frequentist indirect comparison methods were used to compare the three interventions. Results were expressed as odds ratio (OR) or weighted mean difference (WMD) with 95% CIs. RESULTS: We identified 12 trials enrolling 980 patients. Compared with MT, SS significantly increased the odds of reducing pain by 50% or more in three trials (OR, 13.01; 95% CI, 4.96-34.17) and significantly reduced pain as measured by visual analogue scale scores in three trials (WMD, 1.43 scale points; 95% CI, 0.16-2.71). Using the common comparator of MT, newer stimulation technology (eg, high-frequency 10 kilohertz spinal stimulation, Burst, dorsal root ganglion) was associated with increased odds of pain relief compared with conventional SS (OR, 2.07; 95% CI, 1.35-3.19). CONCLUSIONS: In patients with intractable spine/limb pain, SS was associated with better pain reduction than MT. New stimulation technology was likely associated with better pain reduction than conventional stimulation.

The Effectiveness and Safety of 42°C Pulsed Radiofrequency Combined with 60°C Continuous Radiofrequency for Refractory Infraorbital Neuralgia: A Prospective Study.

BACKGROUND: Infraorbital neuralgia, one of the rare causes of facial pain, lacks systematic treatment guidelines because few studies on the topic have been published. We previously found that 42°C percutaneous nondestructive pulsed radiofrequency (PRF) treatment could achieve satisfactory pain relief for infraorbital neuralgia patients. However, patients who responded poorly to PRF had no other ideal treatment options until now. Recently, standard PRF combined with 60°C continuous radiofrequency (CRF) was successfully performed on trigeminal neuralgia patients and achieved a promising effective rate with mild complications. However, the efficacy of the combined therapy in the treatment of infraorbital neuralgia has not yet been reported. OBJECTIVES: To evaluate the effectiveness and safety of 42°C PRF combined with 60°C CRF in infraorbital neuralgia patients who responded poorly to 42°C PRF and were reluctant to receive destructive therapies or nerve decompression surgery. STUDY DESIGN: Prospective, single-center, observational clinical trial. SETTING: The interventional pain management center in Beijing Tiantan Hospital. METHODS: We prospectively investigated the effects of 10 minutes of 3-dimensional computer tomography-guided 42°C PRF combined with 270 seconds of 60°C CRF in the treatment of 28 patients with refractory infraorbital neuralgia. The response criterion was a postoperative verbal pain numeric rating scale score reduction of > 50%. The response rates at different time points during a 2-year follow-up were calculated. RESULTS: The effective rates of combined PRF and CRF treatment were 95.5%, 86.4%, 81.8%, 72.7%, 72.7%, and 72.7% postoperative at 1 month, 3 months, 6 months, 1 year, 18 months, and 2 years, respectively. Except for 16 patients (72.7%) experiencing mild numbness that gradually disappeared within 1 week to 2 months after the operation, no obvious complications were observed. LIMITATIONS: This study examined the therapeutic effectiveness over a period of only 2 years; no further follow-up was conducted. In addition, this study is a single-center observational clinical study with small sample sizes. CONCLUSIONS: For patients with intractable infraorbital neuralgia, 42°C PRF combined with 60°C CRF is an effective and safe treatment. Prospective, double-blind randomized controlled trials with longer follow-up periods are needed to evaluate whether the combined treatment could become an alternative option for those who do not respond to conservative treatment, sparing those patients from destructive therapies or more invasive nerve decompression surgery. KEY WORDS: Infraorbital neuralgia, effectiveness, safety, pulsed radiofrequency, continuous radiofrequency, combined therapy.

Ultrasound-Guided Percutaneous Peripheral Nerve Stimulation for the Treatment of Lower Extremity Pain: A Rare Case Report.

OBJECTIVE: This case report presents an application of percutaneous peripheral nerve stimulation to the right superficial peroneal nerve to treat a patient with chronic intractable L5-S1 radiculopathy pain that conventional treatment failed to ameliorate. METHODS: The patient underwent an uneventful implantation of a percutaneous peripheral nerve stimulator. The implanted lead (15 cm in length and 1.2 mm in diameter) containing the receiver coil and 3 stimulation electrodes (Bioness Stimrouter® , Valencia, CA, U.S.A.) was implanted parallel with the trajectory of the right superficial peroneal nerve. RESULTS: Two weeks after implantation of the percutaneous peripheral nerve stimulator, the patient experienced excellent pain relief and reported a significant increase in mobility. At the 3-month follow-up consultation, the patient reported maintenance of the reduction of pain in his right lower extremity as well as improved performance in his daily activities. CONCLUSION: Percutaneous peripheral nerve stimulation offers an alternative treatment option for intractable pain associated with chronic radiculopathy, especially for patients in whom conventional treatment options have been exhausted. Further clinical series involving larger numbers of patients are warranted in order to assess the definitive role of percutaneous peripheral nerve stimulation for the treatment of chronic intractable radiculopathy pain.

Peripheral nerve stimulation: black, white and shades of grey.

Unbearable chronic neuropathic pain, which can often not be resolved by conservative pain management techniques, calls for peripheral nerve stimulation. The technique, based on the Gate control hypothesis, uses low intensity current to block depolarization and conduction of neuronal membrane. Conditions such as intractable migraine, occipital and trigeminal neuralgia, burn injury pain, transformed migraine, among others, which cause intense pain can be treated by PNS, especially when the pain is localised and can be traced back to a specific nerve. Complication rates in PNS vary from 5% in some cases to 43% in others. Common complications include lead breakage, electrode migration, etc., meanwhile complications associated with every surgery like risks of anaesthesia, bleeding etc., are also present. PNS shows great potential in the treatment of intractable pain, and with its less invasiveness, high success rate, and development of advanced technologies like BION and SAINT, it is bound to become a standard procedure in the future for neuropathic pain management.

Evolving Techniques and Indications in Peripheral Nerve Stimulation for Pain.

Peripheral nerve stimulation is the direct electrical stimulation of named nerves outside the central neuraxis to alleviate pain in the distribution of the targeted peripheral nerve. These treatments have shown efficacy in treating a variety of neuropathic, musculoskeletal, and visceral refractory pain pathologies; although not first line, these therapies are an important part of the treatment repertoire for chronic pain. With careful patient selection and judicious choice of stimulation technique, excellent results can be achieved for a variety of pain etiologies and distributions. This article reviews current and past practices of peripheral nerve stimulation and upcoming advancements in the field.

Motor cortex stimulation: a systematic literature-based analysis of effectiveness and case series experience.

BACKGROUND: Aim to quantitatively analyze the clinical effectiveness for motor cortex stimulation (MCS) to refractory pain. METHODS: The literatures were systematically searched in database of Cocharane library, Embase and PubMed, using relevant strategies. Data were extracted from eligible articles and pooled as mean with standard deviation (SD). Comparative analysis was measured by non-parametric t test and linear regression model. RESULTS: The pooled effect estimate from 12 trials (n = 198) elucidated that MCS shown the positive effect on refractory pain, and the total percentage improvement was 35.2% in post-stroke pain and 46.5% in trigeminal neuropathic pain. There is no statistical differences between stroke involved thalamus or non-thalamus. The improvement of plexus avulsion (29.8%) and phantom pain (34.1%) was similar. The highest improvement rate was seen in post-radicular plexopathy (65.1%) and MCS may aggravate the pain induced by spinal cord injury, confirmed by small sample size. Concurrently, Both the duration of disease (r = 0.233, p = 0.019*) and the time of follow-up (r = 0.196, p = 0.016*) had small predicative value, while age (p = 0.125) had no correlation to post-operative pain relief. CONCLUSIONS: MCS is conducive to the patients with refractory pain. The duration of disease and the time of follow-up can be regarded as predictive factor. Meanwhile, further studies are needed to reveal the mechanism of MCS and to reevaluate the cost-benefit aspect with better-designed clinical trials.

Systematic Review and Neural Network Analysis to Define Predictive Variables in Implantable Motor Cortex Stimulation to Treat Chronic Intractable Pain.

Implantable motor cortex stimulation (iMCS) has been performed for >25 years to treat various intractable pain syndromes. Its effectiveness is highly variable and, although various studies revealed predictive variables, none of these were found repeatedly. This study uses neural network analysis (NNA) to identify predictive factors of iMCS treatment for intractable pain. A systematic review provided a database of patient data on an individual level of patients who underwent iMCS to treat refractory pain between 1991 and 2017. Responders were defined as patients with a pain relief of >40% as measured by a numerical rating scale (NRS) score. NNA was carried out to predict the outcome of iMCS and to identify predictive factors that impacted the outcome of iMCS. The outcome prediction value of the NNA was expressed as the mean accuracy, sensitivity, and specificity. The NNA furthermore provided the mean weight of predictive variables, which shows the impact of the predictive variable on the prediction. The mean weight was converted into the mean relative influence (M), a value that varies between 0 and 100%. A total of 358 patients were included (202 males [56.4%]; mean age, 54.2 ±13.3 years), 201 of whom were responders to iMCS. NNA had a mean accuracy of 66.3% and a sensitivity and specificity of 69.8% and 69.4%, respectively. NNA further identified 6 predictive variables that had a relatively high M: 1) the sex of the patient (M = 19.7%); 2) the origin of the lesion (M = 15.1%); 3) the preoperative numerical rating scale score (M = 9.2%); 4) preoperative use of repetitive transcranial magnetic stimulation (M = 7.3%); 5) preoperative intake of opioids (M = 7.1%); and 6) the follow-up period (M = 13.1%). The results from the present study show that these 6 predictive variables influence the outcome of iMCS and that, based on these variables, a fair prediction model can be built to predict outcome after iMCS surgery. PERSPECTIVE: The presented NNA analyzed the functioning of computational models and modeled nonlinear statistical data. Based on this NNA, 6 predictive variables were identified that are suggested to be of importance in the improvement of future iMCS to treat chronic pain.