N-of-1 Trials for Assessing the Efficacy of Deep Brain Stimulation in Neuropathic Pain

Rates and Predictors of Pain Reduction With Intracranial Stimulation for Intractable Pain Disorders

BACKGROUND AND OBJECTIVES

Intracranial modulation paradigms, namely deep brain stimulation (DBS) and motor cortex stimulation (MCS), have been used to treat intractable pain disorders. However, treatment efficacy remains heterogeneous, and factors associated with pain reduction are not completely understood.

METHODS

We performed an individual patient review of pain outcomes (visual analog scale, quality-of-life measures, complications, pulse generator implant rate, cessation of stimulation) after implantation of DBS or MCS devices. We evaluated 663 patients from 36 study groups and stratified outcomes by pain etiology and implantation targets.

RESULTS

Included studies comprised primarily retrospective cohort studies. MCS patients had a similar externalized trial success rate compared with DBS patients (86% vs 81%; P = .16), whereas patients with peripheral pain had a higher trial success rate compared with patients with central pain (88% vs 79%; P = .004). Complication rates were similar for MCS and DBS patients (12% vs 15%; P = .79). Patients with peripheral pain had lower likelihood of device cessation compared with those with central pain (5.7% vs 10%; P = .03). Of all implanted patients, mean pain reduction at last follow-up was 45.8% (95% CI: 40.3-51.2) with a 31.2% (95% CI: 12.4-50.1) improvement in quality of life. No difference was seen between MCS patients (43.8%; 95% CI: 36.7-58.2) and DBS patients (48.6%; 95% CI: 39.2-58) or central (41.5%; 95% CI: 34.8-48.2) and peripheral (46.7%; 95% CI: 38.9-54.5) etiologies. Multivariate analysis identified the anterior cingulate cortex target to be associated with worse pain reduction, while postherpetic neuralgia was a positive prognostic factor.

CONCLUSION

Both DBS and MCS have similar efficacy and complication rates in the treatment of intractable pain. Patients with central pain disorders tended to have lower trial success and higher rates of device cessation. Additional prognostic factors include anterior cingulate cortex targeting and postherpetic neuralgia diagnosis. These findings underscore intracranial neurostimulation as an important modality for treatment of intractable pain disorders.

Protocol for combined N-of-1 trials to assess cerebellar neurostimulation for movement disorders in children and young adults with dyskinetic cerebral palsy

BACKGROUND

Movement and tone disorders in children and young adults with cerebral palsy are a great source of disability. Deep brain stimulation (DBS) of basal ganglia targets has a major role in the treatment of isolated dystonias, but its efficacy in dyskinetic cerebral palsy (DCP) is lower, due to structural basal ganglia and thalamic damage and lack of improvement of comorbid choreoathetosis and spasticity. The cerebellum is an attractive target for DBS in DCP since it is frequently spared from hypoxic ischemic damage, it has a significant role in dystonia network models, and small studies have shown promise of dentate stimulation in improving CP-related movement and tone disorders.

METHODS

Ten children and young adults with DCP and disabling movement disorders with or without spasticity will undergo bilateral DBS in the dorsal dentate nucleus, with the most distal contact ending in the superior cerebellar peduncle. We will implant Medtronic Percept, a bidirectional neurostimulator that can sense and store brain activity and deliver DBS therapy. The efficacy of cerebellar DBS in improving quality of life and motor outcomes will be tested by a series of N-of-1 clinical trials. Each N-of-1 trial will consist of three blocks, each consisting of one month of effective stimulation and one month of sham stimulation in a random order with weekly motor and quality of life scales as primary and secondary outcomes. In addition, we will characterize abnormal patterns of cerebellar oscillatory activity measured by local field potentials from the intracranial electrodes related to clinical assessments and wearable monitors. Pre- and 12-month postoperative volumetric structural and functional MRI and diffusion tensor imaging will be used to identify candidate imaging markers of baseline disease severity and response to DBS.

DISCUSSION

Our goal is to test a cerebellar neuromodulation therapy that produces meaningful changes in function and well-being for people with CP, obtain a mechanistic understanding of the underlying brain network disorder, and identify physiological and imaging-based predictors of outcomes useful in planning further studies.

TRIAL REGISTRATION

ClinicalTrials.gov NCT06122675, first registered November 7, 2023.

Protocol for combined N-of-1 trials to assess cerebellar neurostimulation for movement disorders in children and young adults with dyskinetic cerebral palsy

Background

Movement and tone disorders in children and young adults with cerebral palsy are a great source of disability. Deep brain stimulation (DBS) of basal ganglia targets has a major role in the treatment of isolated dystonias, but its efficacy in dyskinetic cerebral palsy (DCP) is lower, due to structural basal ganglia and thalamic damage and lack of improvement of comorbid choreoathetosis and spasticity. The cerebellum is an attractive target for DBS in DCP since it is frequently spared from hypoxic ischemic damage, it has a significant role in dystonia network models, and small studies have shown promise of dentate stimulation in improving CP-related movement and tone disorders.

Methods

Ten children and young adults with DCP and disabling movement disorders with or without spasticity will undergo bilateral DBS in the dorsal dentate nucleus, with the most distal contact ending in the superior cerebellar peduncle. We will implant Medtronic Percept, a bidirectional neurostimulator that can sense and store brain activity and deliver DBS therapy. The efficacy of cerebellar DBS in improving quality of life and motor outcomes will be tested by a series of N-of-1 clinical trials. Each N-of-1 trial will consist of three blocks, each consisting of one month of effective stimulation and one month of sham stimulation in a random order with weekly motor and quality of life scales as primary and secondary outcomes. In addition, we will characterize abnormal patterns of cerebellar oscillatory activity measured by local field potentials from the intracranial electrodes related to clinical assessments and wearable monitors. Pre- and 12-month postoperative volumetric structural and functional MRI and diffusion tensor imaging will be used to identify candidate imaging markers of baseline disease severity and response to DBS.

Discussion

Our goal is to test a cerebellar neuromodulation therapy that produces meaningful changes in function and well-being for people with CP, obtain a mechanistic understanding of the underlying brain network disorder, and identify physiological and imaging-based predictors of outcomes useful in planning further studies.

Trial registration

ClinicalTrials.gov NCT06122675, first registered November 7, 2023.

The Influence of Etiology and Stimulation Target on the Outcome of Deep Brain Stimulation for Chronic Neuropathic Pain: A Systematic Review and Meta-Analysis

OBJECTIVES

Deep brain stimulation (DBS) to treat chronic neuropathic pain has shown variable outcomes. Variations in pain etiologies and DBS targets are considered the main contributing factors, which are, however, underexplored owing to a paucity of patient data in individual studies. An updated meta-analysis to quantitatively assess the influence of these factors on the outcome of DBS for chronic neuropathic pain is warranted, especially considering that the anterior cingulate cortex (ACC) has emerged recently as a new DBS target.

MATERIALS AND METHODS

A comprehensive literature review was performed in PubMed, Embase, and Cochrane data bases to identify studies reporting quantitative outcomes of DBS for chronic neuropathic pain. Pain and quality of life (QoL) outcomes, grouped by etiology and DBS target, were extracted and analyzed (α = 0.05).

RESULTS

Twenty-five studies were included for analysis. Patients with peripheral neuropathic pain (PNP) had a significantly greater initial stimulation success rate than did patients with central neuropathic pain (CNP). Both patients with CNP and patients with PNP with definitive implant, regardless of targets, gained significant follow-up pain reduction. Patients with PNP had greater long-term pain relief than did patients with CNP. Patients with CNP with ACC DBS gained less long-term pain relief than did those with conventional targets. Significant short-term QoL improvement was reported in selected patients with CNP after ACC DBS. However, selective reporting bias was expected, and the improvement decreased in the long term.

CONCLUSIONS

Although DBS to treat chronic neuropathic pain is generally effective, patients with PNP are the preferred population over patients with CNP. Current data suggest that ACC DBS deserves further investigation as a potential way to treat the affective component of chronic neuropathic pain.

Comparison of Bayesian Networks, G-estimation and linear models to estimate causal treatment effects in aggregated N-of-1 trials with carry-over effects

BACKGROUND

The aggregation of a series of N-of-1 trials presents an innovative and efficient study design, as an alternative to traditional randomized clinical trials. Challenges for the statistical analysis arise when there is carry-over or complex dependencies of the treatment effect of interest.

METHODS

In this study, we evaluate and compare methods for the analysis of aggregated N-of-1 trials in different scenarios with carry-over and complex dependencies of treatment effects on covariates. For this, we simulate data of a series of N-of-1 trials for Chronic Nonspecific Low Back Pain based on assumed causal relationships parameterized by directed acyclic graphs. In addition to existing statistical methods such as regression models, Bayesian Networks, and G-estimation, we introduce a carry-over adjusted parametric model (COAPM).

RESULTS

The results show that all evaluated existing models have a good performance when there is no carry-over and no treatment dependence. When there is carry-over, COAPM yields unbiased and more efficient estimates while all other methods show some bias in the estimation. When there is known treatment dependence, all approaches that are capable to model it yield unbiased estimates. Finally, the efficiency of all methods decreases slightly when there are missing values, and the bias in the estimates can also increase.

CONCLUSIONS

This study presents a systematic evaluation of existing and novel approaches for the statistical analysis of a series of N-of-1 trials. We derive practical recommendations which methods may be best in which scenarios.

A prototype closed-loop brain-machine interface for the study and treatment of pain

Chronic pain is characterized by discrete pain episodes of unpredictable frequency and duration. This hinders the study of pain mechanisms and contributes to the use of pharmacological treatments associated with side effects, addiction and drug tolerance. Here, we show that a closed-loop brain-machine interface (BMI) can modulate sensory-affective experiences in real time in freely behaving rats by coupling neural codes for nociception directly with therapeutic cortical stimulation. The BMI decodes the onset of nociception via a state-space model on the basis of the analysis of online-sorted spikes recorded from the anterior cingulate cortex (which is critical for pain processing) and couples real-time pain detection with optogenetic activation of the prelimbic prefrontal cortex (which exerts top-down nociceptive regulation). In rats, the BMI effectively inhibited sensory and affective behaviours caused by acute mechanical or thermal pain, and by chronic inflammatory or neuropathic pain. The approach provides a blueprint for demand-based neuromodulation to treat sensory-affective disorders, and could be further leveraged for nociceptive control and to study pain mechanisms.

Assessment of a Mobile Health iPhone App for Semiautomated Self-management of Chronic Recurrent Medical Conditions Using an N-of-1 Trial Framework: Feasibility Pilot Study

BACKGROUND

Management of chronic recurrent medical conditions (CRMCs), such as migraine headaches, chronic pain, and anxiety/depression, remains a major challenge for modern providers. Our team has developed an edge-based, semiautomated mobile health (mHealth) technology called iMTracker that employs the N-of-1 trial approach to allow self-management of CRMCs.

OBJECTIVE

This study examines the patterns of adoption, identifies CRMCs that users selected for self-application, and explores barriers to use of the iMTracker app.

METHODS

This is a feasibility pilot study with internet-based recruitment that ran from May 15, 2019, to December 23, 2020. We recruited 180 patients to pilot test the iMTracker app for user-selected CRMCs for a 3-month period. Patients were administered surveys before and after the study.

RESULTS

We found reasonable usage rates: a total of 73/103 (70.9%) patients who were not lost to follow-up reported the full 3-month use of the app. Most users chose to use the iMTracker app to self-manage chronic pain (other than headaches; 80/212, 37.7%), followed by headaches in 36/212 (17.0%) and mental health (anxiety and depression) in 27/212 (12.8%). The recurrence rate of CRMCs was at least weekly in over 93% (169/180) of patients, with 36.1% (65/180) of CRMCs recurring multiple times in a day, 41.7% (75/180) daily, and 16.1% (29/180) weekly. We found that the main barriers to use were the design and technical function of the app, but that use of the app resulted in an improvement in confidence in the efficiency and safety/privacy of this approach.

CONCLUSIONS

The iMTracker app provides a feasible platform for the N-of-1 trial approach to self-management of CRMCs, although internet-based recruitment provided limited follow-up, suggesting that in-person evaluation may be needed. The rate of CRMC recurrence was high enough to allow the N-of-1 trial assessment for most traits.

Status of N-of-1 Trials in Chronic Pain Management: A Narrative Review

N-of-1 trials are randomized controlled clinical trials conducted exclusively on a single patient. The ultimate aim of N-of-1 trials is to optimize a strategy in a particular individual. Chronic pain is a common but refractory clinical problem. Its diverse etiologies and broad variations among patients often lead to the requirement of individualizing medicine. Thus, chronic pain represents a classical condition for N-of-1 clinical trials. Studies have indicated that N-of-1 benefits patients with chronic pain, multiple comorbidities, and uncertain variations during therapies; however, this approach it is not yet adopted as the first choice in pain clinics. To dissect the current status of N-of-1 in chronic pain management, as well as the limitations for its implementation, we herein studied all N-of-1 studies related to chronic pain by searching three major databases (PubMed, ClinicalTrial.gov, Cochrane Library) for publications between 1985 and 2020. Of 35 eligibility papers, 19 were selected for analysis. Results confirmed that N-of-1 trials have solved the refractory cases including osteoarthritis, chronic musculoskeletal pain, and neuropathic pain; however, none of the trials dealt with cancer pain. Longer time and more efforts are needed from investigators when carrying out N-of-1 trials, which inevitably result in implementation difficulties. Of note, all recruited trials were conducted in developed countries. As mobile devices have been introduced and protocols improve, renewed interest in the implementation of N-of-1 trials will occur. Collectively, a previously underestimated conflict between "precision medicine" and "poor implementation" has put N-of-1 in a challenging position for chronic pain management.

N-of-1 Trials in Neurology: A Systematic Review

ObjectiveTo perform a systematic review of published N-of-1 trials (e.g. single patient cross-over trials) in neurological disorders, including an assessment of methodological quality and reporting.MethodsWe searched PubMed, MEDLINE and Embase, from inception date - the first of December 2019, for reports on N-of-1 trials in neurological disorders. Basic trial information on design, disease, intervention, analysis and treatment success was extracted. Strengths and weaknesses of the N-of-1 trials were assessed using the CONSORT extension for N-of-1 trials (CENT) 2015 criteria checklist and the Jadad score as measures of quality and reporting.ResultsWe retrieved 40 reports of N-of-1 trials in neurological disorders (19 individual N-of-1 trials, 21 series of N-of-1 trials). Most N-of-1 trials were performed in neuromuscular and neurodegenerative / movement disorders. Unlike the majority of trials that studied the main symptom(s) of a chronic stable condition, nine N-of-1 trials studied a stable chronic symptom of a progressive or acute neurological disorder. Besides pharmacological interventions, electrical stimulation protocols and nutritional products were studied. A mean total CENT score of 20.88 (SD, 9.10; range 0-43) and mean total Jadad score of 2.90 (SD, 2.15; range 0-5) were found as methodological measures of quality and reporting across all N-of-1 trialsConclusionsN-of-1 trials have been reported in numerous neurological disorders, not only in chronic stable disorders, but also in progressive or acute disorders with a stable symptom. This indicates the emerging therapeutic area of N-of-1 trials in Neurology.Methodological quality and reporting of N-of-1 trials were found suboptimal and can easily be improved in future trials by appropriately describing the methods of blinding and randomization and follow CENT guidelines. As most N-of-1 trials remain unreported in medical literature, this systematic review probably only represent the tip of the iceberg of conducted N-of-1 trials in neurological disorders. In addition to conventional trial designs, N-of-1 trials can help to bridge the gap between research and clinical care by providing an alternative, personalized level 1 evidence-base for suitable treatments.

Frequency Dependent Electrical Stimulation of PFC and ACC for Acute Pain Treatment in Rats

As pain consists of both sensory and affective components, its management by pharmaceutical agents remains difficult. Alternative forms of neuromodulation, such as electrical stimulation, have been studied in recent years as potential pain treatment options. Although electrical stimulation of the brain has shown promise, more research into stimulation frequency and targets is required to support its clinical applications. Here, we studied the effect that stimulation frequency has on pain modulation in the prefrontal cortex (PFC) and the anterior cingulate cortex (ACC) in acute pain models in rats. We found that low-frequency stimulation in the prelimbic region of the PFC (PL-PFC) provides reduction of sensory and affective pain components. Meanwhile, high-frequency stimulation of the ACC, a region involved in processing pain affect, reduces pain aversive behaviors. Our results demonstrate that frequency-dependent neuromodulation of the PFC or ACC has the potential for pain modulation.

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.

Brain and spinal stimulation therapies for phantom limb pain: a systematic review

BACKGROUND

Although many treatments exist for phantom limb pain (PLP), the evidence supporting them is limited and there are no guidelines for PLP management. Brain and spinal cord neurostimulation therapies are targeted at patients with chronic PLP but have yet to be systematically reviewed.

OBJECTIVE

To determine which types of brain and spinal stimulation therapy appear to be the best for treating chronic PLP.

DESIGN

Systematic reviews of effectiveness and epidemiology studies, and a survey of NHS practice.

POPULATION

All patients with PLP.

INTERVENTIONS

Invasive interventions - deep brain stimulation (DBS), motor cortex stimulation (MCS), spinal cord stimulation (SCS) and dorsal root ganglion (DRG) stimulation. Non-invasive interventions - repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS).

MAIN OUTCOME MEASURES

Phantom limb pain and quality of life.

DATA SOURCES

Twelve databases (including MEDLINE and EMBASE) and clinical trial registries were searched in May 2017, with no date limits applied.

REVIEW METHODS

Two reviewers screened titles and abstracts and full texts. Data extraction and quality assessments were undertaken by one reviewer and checked by another. A questionnaire was distributed to clinicians via established e-mail lists of two relevant clinical societies. All results were presented narratively with accompanying tables.

RESULTS

Seven randomised controlled trials (RCTs), 30 non-comparative group studies, 18 case reports and 21 epidemiology studies were included. Results from a good-quality RCT suggested short-term benefits of rTMS in reducing PLP, but not in reducing anxiety or depression. Small randomised trials of tDCS suggested the possibility of modest, short-term reductions in PLP. No RCTs of invasive therapies were identified. Results from small, non-comparative group studies suggested that, although many patients benefited from short-term pain reduction, far fewer maintained their benefits. Most studies had important methodological or reporting limitations and few studies reported quality-of-life data. The evidence on prognostic factors for the development of chronic PLP from the longitudinal studies also had important limitations. The results from these studies suggested that pre-amputation pain and early PLP intensity are good predictors of chronic PLP. Results from the cross-sectional studies suggested that the proportion of patients with severe chronic PLP is between around 30% and 40% of the chronic PLP population, and that around one-quarter of chronic PLP patients find their PLP to be either moderately or severely limiting or bothersome. There were 37 responses to the questionnaire distributed to clinicians. SCS and DRG stimulation are frequently used in the NHS but the prevalence of use of DBS and MCS was low. Most responders considered SCS and DRG stimulation to be at least sometimes effective. Neurosurgeons had mixed views on DBS, but most considered MCS to rarely be effective. Most clinicians thought that a randomised trial design could be successfully used to study neurostimulation therapies.

LIMITATION

There was a lack of robust research studies.

CONCLUSIONS

Currently available studies of the efficacy, effectiveness and safety of neurostimulation treatments do not provide robust, reliable results. Therefore, it is uncertain which treatments are best for chronic PLP.

FUTURE WORK

Randomised crossover trials, randomised N-of-1 trials and prospective registry trials are viable study designs for future research.

STUDY REGISTRATION

The study is registered as PROSPERO CRD42017065387.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Neuromodulation for Pain Management

Pain is a salient and complex sensory experience with important affective and cognitive dimensions. The current definition of pain relies on subjective reports in both humans and experimental animals. Such definition lacks basic mechanistic insights and can lead to a high degree of variability. Research on biomarkers for pain has previously focused on genetic analysis. However, recent advances in human neuroimaging and research in animal models have begun to show the promise of a circuit-based neural signature for pain. At the treatment level, pharmacological therapy for pain remains limited. Neuromodulation has emerged as a specific form of treatment without the systemic side effects of pharmacotherapies. In this review, we will discuss some of the current neuromodulatory modalities for pain, research on newer targets, as well as emerging possibility for an integrated brain-computer interface approach for pain management.

Single-Subject Studies in Translational Nutrition Research

There is a great deal of interest in personalized, individualized, or precision interventions for disease and health-risk mitigation. This is as true of nutrition-based intervention and prevention strategies as it is for pharmacotherapies and pharmaceutical-oriented prevention strategies. Essentially, technological breakthroughs have enabled researchers to probe an individual's unique genetic, biochemical, physiological, behavioral, and exposure profile, allowing them to identify very specific and often nuanced factors that an individual might possess, which may make it more or less likely that he or she responds favorably to a particular intervention (e.g., nutrient supplementation) or disease prevention strategy (e.g., specific diet). However, as compelling and intuitive as personalized nutrition might be in the current era in which data-intensive biomedical characterization of individuals is possible, appropriately and objectively vetting personalized nutrition strategies is not trivial and requires novel study designs and data analytical methods. These designs and methods must consider a very integrated use of the multiple contemporary biomedical assays and technologies that motivate them, which adds to their complexity. Single-subject or N-of-1 trials can be used to assess the utility of personalized interventions and, in addition, can be crafted in such a way as to accommodate the necessarily integrated use of many emerging biomedical technologies and assays. In this review, we consider the motivation, design, and implementation of N-of-1 trials in translational nutrition research that are meant to assess the utility of personalized nutritional strategies. We provide a number of example studies, discuss appropriate analytical methods given the complex data they generate and require, and consider how such studies could leverage integration of various biomarker assays and clinical end points. Importantly, we also consider the development of strategies and algorithms for matching nutritional needs to individual biomedical profiles and the issues surrounding them. Finally, we discuss the limitations of personalized nutrition studies, possible extensions of N-of-1 nutritional intervention studies, and areas of future research.

Thalamic Deep Brain Stimulation for Neuropathic Pain: Efficacy at Three Years' Follow-Up

OBJECT

Chronic neuropathic pain is estimated to affect 3-4.5% of the worldwide population, posing a serious burden to society. Deep Brain Stimulation (DBS) is already established for movement disorders and also used to treat some "off-label" conditions. However, DBS for the treatment of chronic, drug refractory, neuropathic pain, has shown variable outcomes with few studies performed in the last decade. Thus, this procedure has consensus approval in parts of Europe but not the USA. This study prospectively evaluated the efficacy at three years of DBS for neuropathic pain.

METHODS

Sixteen consecutive patients received 36 months post-surgical follow-up in a single-center. Six had phantom limb pain after amputation and ten deafferentation pain after brachial plexus injury, all due to traumas. To evaluate the efficacy of DBS, patient-reported outcome measures were collated before and after surgery, using a visual analog scale (VAS) score, University of Washington Neuropathic Pain Score (UWNPS), Brief Pain Inventory (BPI), and 36-Item Short-Form Health Survey (SF-36).

RESULTS

Contralateral, ventroposterolateral sensory thalamic DBS was performed in sixteen patients with chronic neuropathic pain over 29 months. A postoperative trial of externalized DBS failed in one patient with brachial plexus injury. Fifteen patients proceeded to implantation but one patient with phantom limb pain after amputation was lost for follow-up after 12 months. No surgical complications or stimulation side effects were noted. After 36 months, mean pain relief was sustained, and the median (and interquartile range) of the improvement of VAS score was 52.8% (45.4%) (p = 0.00021), UWNPS was 30.7% (49.2%) (p = 0.0590), BPI was 55.0% (32.0%) (p = 0.00737), and SF-36 was 16.3% (30.3%) (p = 0.4754).

CONCLUSIONS

DBS demonstrated efficacy at three years for chronic neuropathic pain after traumatic amputation and brachial plexus injury, with benefits sustained across all pain outcomes measures and slightly greater improvement in phantom limb pain.

Surgical Neurostimulation for Spinal Cord Injury

Traumatic spinal cord injury (SCI) is a devastating neurological condition characterized by a constellation of symptoms including paralysis, paraesthesia, pain, cardiovascular, bladder, bowel and sexual dysfunction. Current treatment for SCI involves acute resuscitation, aggressive rehabilitation and symptomatic treatment for complications. Despite the progress in scientific understanding, regenerative therapies are lacking. In this review, we outline the current state and future potential of invasive and non-invasive neuromodulation strategies including deep brain stimulation (DBS), spinal cord stimulation (SCS), motor cortex stimulation (MCS), transcutaneous direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) in the context of SCI. We consider the ability of these therapies to address pain, sensorimotor symptoms and autonomic dysregulation associated with SCI. In addition to the potential to make important contributions to SCI treatment, neuromodulation has the added ability to contribute to our understanding of spinal cord neurobiology and the pathophysiology of SCI.

N-of-1 Design and Its Applications to Personalized Treatment Studies

N-of-1 trial is a type of clinical trial which has been applied in chronic recurrent conditions that require long-term non-curative treatment. In this type of trials, each patient will be randomly assigned to one of the treatment sequences and repeatedly crossed over two or more treatments of interests. Through this cross-comparing method (cross-over phase), investigator can identify an optimal treatment (medicine or therapy) for the patient and treat the patient with the optimal treatment in an extension phase. This design could efficiently reduce the placebo effect, which is often seen in clinical trials, and maximize the true treatment effect. This type of design has been used in some traditional Chinese medicine (TCM) clinical trials lately. However, it brings some challenges for collecting and analyzing the data. Research on statistical methodology of this type of design is rarely found in the literature. The goal of this research is to discuss the application of the N-of-1 design to personalized treatment studies. We will demonstrate a real study conducted in TCM and present some theoretical and simulation results.

Characterising the Analgesic Effect of Different Targets for Deep Brain Stimulation in Trigeminal Anaesthesia Dolorosa

Background

Several deep brain stimulation (DBS) targets have been explored for the alleviation of trigeminal anaesthesia dolorosa. We aimed to characterise the analgesia produced from the periaqueductal grey (PAG) and centromedian-parafascicular (CmPf) nucleus using a within-subject design.

Method

We report a case series of 3 subjects implanted with PAG and CmPf DBS systems for the treatment of anaesthesia dolorosa. At follow-up, testing of onset and offset times, magnitude, and thermal and mechanical sensitivity was performed.

Results

The mean pain score of the cohort was acutely reduced by 56% (p < 0.05) with PAG and 67% (p < 0.01) with CmPf stimulation at mean time intervals of 38 and 16 min, respectively. The onset time was 12.5 min (p < 0.05) for PAG stimulation and 2.5 min (p < 0.01) for CmPf. The offset time was 2.5 min (p < 0.05) for PAG and 12.5 min (p < 0.01) for CmPf. The two targets were effective at different stimulation frequencies and were not antagonistic in effect.

Conclusion

The mechanisms by which stimulation at these two targets produces analgesia are likely to be different. Certain pain qualities may respond more favourably to specific targets. Knowledge of onset and offset times for the targets can guide optimisation of stimulation settings. The use of more than one stimulation target may be beneficial and should be considered in anaesthesia dolorosa patients.

Deep brain stimulation for chronic pain: intracranial targets, clinical outcomes, and trial design considerations

For over half a century, neurosurgeons have attempted to treat pain from a diversity of causes using acute and chronic intracranial stimulation. Targets of stimulation have included the sensory thalamus, periventricular and periaqueductal gray, the septum, the internal capsule, the motor cortex, posterior hypothalamus, and more recently, the anterior cingulate cortex. The current work focuses on presenting and evaluating the evidence for the efficacy of these targets in a historical context while also highlighting the major challenges to having a double-blind placebo-controlled clinical trial. Considerations for pain research in general and use of intracranial targets specifically are included.

Simultaneous trial of deep brain and motor cortex stimulation in chronic intractable neuropathic pain

BACKGROUND/OBJECTIVES

Both motor cortex stimulation (MCS) and deep brain stimulation (DBS) of the ventralis caudalis (Vc) thalamus have been shown to be effective in chronic neuropathic pain, and the modulation of thalamic and thalamocortical activity is regarded as a possible mechanism. Although Vc DBS and MCS have a common analgesic mechanism, the application of MCS and DBS is still considered empirical, and there is no consensus on which method is better.

METHODS

We performed a simultaneous trial of thalamic Vc DBS and MCS in 9 patients with chronic neuropathic pain and investigated the results of the stimulation trial and long-term pain relief.

RESULTS

Of the 9 patients initially implanted with both DBS and MCS electrodes, 8 (89%) had a successful trial; 6 of these 8 patients (75%) responded to MCS, and the remaining 2 responded to Vc DBS. During the long-term follow-up, the mean numeric rating scale score decreased significantly (p < 0.05). The percentages of pain relief in the chronic MCS group and the chronic DBS group were 37.9 ± 16.5 and 37.5%, respectively, and there was no statistically significant difference (p = 0.157).

CONCLUSION

Considering the initial success rate and the less invasive nature of epidural MCS compared with DBS, we think that MCS would be a more reasonable initial means of treatment for chronic intractable neuropathic pain.

Neuropathic pain and deep brain stimulation

Deep brain stimulation (DBS) is a neurosurgical intervention the efficacy, safety, and utility of which are established in the treatment of Parkinson's disease. For the treatment of chronic, neuropathic pain refractory to medical therapies, many prospective case series have been reported, but few have published findings from patients treated with current standards of neuroimaging and stimulator technology over the last decade . We summarize the history, science, selection, assessment, surgery, programming, and personal clinical experience of DBS of the ventral posterior thalamus, periventricular/periaqueductal gray matter, and latterly rostral anterior cingulate cortex (Cg24) in 113 patients treated at 2 centers (John Radcliffe, Oxford, UK, and Hospital de São João, Porto, Portugal) over 13 years. Several experienced centers continue DBS for chronic pain, with success in selected patients, in particular those with pain after amputation, brachial plexus injury, stroke, and cephalalgias including anesthesia dolorosa. Other successes include pain after multiple sclerosis and spine injury. Somatotopic coverage during awake surgery is important in our technique, with cingulate DBS under general anesthesia considered for whole or hemibody pain, or after unsuccessful DBS of other targets. Findings discussed from neuroimaging modalities, invasive neurophysiological insights from local field potential recording, and autonomic assessments may translate into improved patient selection and enhanced efficacy, encouraging larger clinical trials.

Deep brain stimulation: indications and evidence

Deep brain stimulation is a minimally invasive targeted neurosurgical intervention that enables structures deep in the brain to be stimulated electrically by an implanted pacemaker. It has become the treatment of choice for Parkinson's disease, refractory to, or complicated by, drug therapy. Its efficacy has been demonstrated robustly by randomized, controlled clinical trials, with multiple novel brain targets having been discovered in the last 20 years. Multifarious clinical indications for deep brain stimulation now exist, including dystonia and tremor in movement disorders; depression, obsessive-compulsive disorder and Tourette's syndrome in psychiatry; epilepsy, cluster headache and chronic pain, including pain from stroke, amputation, trigeminal neuralgia and multiple sclerosis. Current research argues for novel indications, including hypertension and orthostatic hypotension. The development, principles, indications and effectiveness of the technique are reviewed here. While deep brain stimulation is a standard and widely accepted treatment for Parkinson's disease after 20 years of experience, in chronic pain it remains restricted to a handful of experienced, specialist centers willing to publish outcomes despite its use for over 50 years. Reasons are reviewed and novel approaches to appraising clinical evidence in functional neurosurgery are suggested.

Long-term outcomes of deep brain stimulation for neuropathic pain

BACKGROUND

Deep brain stimulation (DBS) to treat neuropathic pain refractory to pharmacotherapy has reported variable outcomes and has gained United Kingdom but not USA regulatory approval.

OBJECTIVE

To prospectively assess long-term efficacy of DBS for chronic neuropathic pain in a single-center case series.

METHODS

Patient reported outcome measures were collated before and after surgery, using a visual analog score, short-form 36-question quality-of-life survey, McGill pain questionnaire, and EuroQol-5D questionnaires (EQ-5D and health state).

RESULTS

One hundred ninety-seven patients were referred over 12 years, of whom 85 received DBS for various etiologies: 9 amputees, 7 brachial plexus injuries, 31 after stroke, 13 with spinal pathology, 15 with head and face pain, and 10 miscellaneous. Mean age at surgery was 52 years, and mean follow-up was 19.6 months. Contralateral DBS targeted the periventricular gray area (n = 33), the ventral posterior nuclei of the thalamus (n = 15), or both targets (n = 37). Almost 70% (69.4%) of patients retained implants 6 months after surgery. Thirty-nine of 59 (66%) of those implanted gained benefit and efficacy varied by etiology, improving outcomes in 89% after amputation and 70% after stroke. In this cohort, >30% improvements sustained in visual analog score, McGill pain questionnaire, short-form 36-question quality-of-life survey, and EuroQol-5D questionnaire were observed in 15 patients with >42 months of follow-up, with several outcome measures improving from those assessed at 1 year.

CONCLUSION

DBS for pain has long-term efficacy for select etiologies. Clinical trials retaining patients in long-term follow-up are desirable to confirm findings from prospectively assessed case series.

Deep brain stimulation for pain

Deep brain stimulation (DBS) is a neurosurgical intervention whose efficacy, safety, and utility have been shown in the treatment of movement disorders. For the treatment of chronic pain refractory to medical therapies, many prospective case series have been reported, but few have published findings from patients treated during the past decade using current standards of neuroimaging and stimulator technology. We summarize the history, science, selection, assessment, surgery, and personal clinical experience of DBS of the ventral posterior thalamus, periventricular/periaqueductal gray matter, and, latterly, the rostral anterior cingulate cortex (Cg24) in 100 patients treated now at two centers (John Radcliffe Hospital, Oxford, UK, and Hospital de São João, Porto, Portugal) over 12 years. Several experienced centers continue DBS for chronic pain with success in selected patients, in particular those with pain after amputation, brachial plexus injury, stroke, and cephalalgias including anesthesia dolorosa. Other successes include pain after multiple sclerosis and spine injury. Somatotopic coverage during awake surgery is important in our technique, with cingulate DBS considered for whole-body pain or after unsuccessful DBS of other targets. Findings discussed from neuroimaging modalities, invasive neurophysiological insights from local field potential recording, and autonomic assessments may translate into improved patient selection and enhanced efficacy, encouraging larger clinical trials.

N-of-1 trials in the medical literature: a systematic review

BACKGROUND

N-of-1 trials (multiple crossover studies conducted in single individuals) may be ideal for determining individual treatment effects and as a tool to estimate heterogeneity of treatment effects (HTE) in a population. However, comprehensive data on n-of-1 trial methodology and analysis is lacking. We performed this study to describe n-of-1 trial characteristics, examine treatment changes resulting from n-of-1 trial participation, and to determine if trial reporting is adequate for estimating HTE.

METHODS

We undertook a systematic review of n-of-1 trials published between 1985 and December 2010. Included trials were those having individual treatment episodes as the unit of randomization and reporting individual-specific treatment effects. We abstracted trial characteristics, treatment change information, and analytic methods.

RESULTS

We included 108 trials reporting on 2154 participants. Approximately half (49%) of the trials used a statistical cutoff to determine a superior treatment, whereas the remainder used a graphical comparison (25%) or a clinical significance cutoff (20%). Sixty-seven trials, reporting on 488 people, provided treatment change information: 54% of participants had subsequent treatment decisions consistent with the results of the trial, 8% had decisions inconsistent with trial results, and 38% had ambiguous results. Less than half of the trials (45%) reported adequate information to facilitate the calculation of HTE.

CONCLUSION

N-of-1 trials are a useful tool for enhancing therapeutic precision in a range of conditions and should be conducted more often. To facilitate future meta-analysis, and the estimation of HTE, researchers reporting n-of-1 trial results should clearly describe individual data.

Deep brain stimulation for neuropathic pain

Deep brain stimulation (DBS) for pain was one of the earliest indications for the therapy. This study reports the outcome of DBS of the sensory thalamus and the periventricular and peri-aqueductal grey area (PVG/PAG) complex for different intractable neuropathic pain syndromes. Forty-seven patients (30 males and 17 females) were selected for surgery; they were suffering from any of the following types of pain: post-stroke neuropathic pain, phantom limb pain, post-herpetic neuralgia, anaesthesia dolorosa, brachial plexus injury and neuropathic pain secondary to neural damage from a variety of causes. Of the 47 patients selected for trial stimulation, 38 patients proceeded to permanent implantation. Patients suffering from post-stroke pain were the most likely to fail trial stimulation (33%), in contrast to individuals with phantom limb/post-brachial plexus injury pain and anaesthesia dolorosa, all of whom underwent permanent implantation. PVG stimulation alone was optimal in 17 patients (53%), whilst a combination of PVG and thalamic stimulation produced the greatest degree of analgesia in 11 patients (34%). Thalamic stimulation alone was optimal in 4 patients (13%). DBS of the PVG alone was associated with the highest degree of pain alleviation, with a mean improvement of 59% (p <0.001) and a > or =50% improvement in 66% of patients. Post-stroke pain responds in 70% of patients. We conclude that the outcomes of surgery appear to vary according to aetiology, but it would appear that the effects are best for phantom limb syndromes, head pain and anaesthesia dolorosa.

Regional cerebral perfusion differences between periventricular grey, thalamic and dual target deep brain stimulation for chronic neuropathic pain

Regional cerebral blood flow changes were evaluated in different subcortical brain targets following deep brain stimulation (DBS) for chronic pain. Three patients with intractable neuropathic pain were assessed; one had stimulating electrodes in the ventroposterolateral thalamic nucleus (VPL), one in the periventricular grey (PVG) area, and one had electrodes in both targets. Pain relief was achieved in all patients. Cerebral perfusion was measured by single-photon emission computed tomography to determine the effects of DBS. Comparison was made between individual scans using subtraction analysis. DBS consistently increased perfusion in the posterior subcortical region between VPL and PVG, regardless of the site of stimulation. Furthermore, thalamic and dual target DBS increased thalamic perfusion, yet PVG DBS decreased perfusion in the PVG-containing midbrain region and thalamus. Dual target stimulation decreased anterior cingulate and insular cortex perfusion. The study demonstrates regional differences in cerebral perfusion between three accepted and efficacious targets for analgesic DBS.

Deep brain stimulation for the alleviation of post-stroke neuropathic pain

Our aim was to asses the efficacy of deep brain stimulation in post-stroke neuropathic pain. Since 2000, 15 patients with post-stroke intractable neuropathic pain were treated with deep brain stimulation of the periventricular gray area (PVG), sensory thalamus (Ventroposterolateral nucleus-VPL) or both. Pain was assessed using both a visual analogue scale and the McGill's pain questionnaire. VAS scores show a mean improvement of 48.8% (SD 8.6%). However, there is a wide variation between patients. This study demonstrates that it is an effective treatment in 70% of such patients.