Spinal Cord Stimulation-Naïve Patients vs Patients With Failed Previous Experiences With Standard Spinal Cord Stimulation: Two Distinct Entities or One Population?

INTRODUCTION: Nowadays, the success of spinal cord stimulation (SCS) is evaluated separately in patients who have previous experiences with standard SCS and in SCS-naïve patients. Nevertheless, it is yet to be evaluated whether both patient groups are effectively distinct patient groups. Therefore, the aims of this study are twofold: 1) Are there clusters in the data to distinguish between both patient groups? 2) Can we discriminate both patient groups based on routinely collected clinical parameters? MATERIALS AND METHODS: Baseline data from the Discover study were used, in which 263 patients with persistent spinal pain syndrome type 2 were included (185 neurostimulation-naïve patients and 78 patients with previous SCS experience). Pain intensity scores for low back and leg pain, functional disability, medication use, and health-related quality of life utility scores were used in the analysis. Model-based clustering was performed on standardized data. Discriminant analysis was performed with linear and quadratic discriminant analysis, with leave-one-out cross-validation to evaluate model performance. RESULTS: Model-based clustering revealed two different clusters in the data. None of the clusters clearly separated SCS-naïve patients from patients with previous SCS experience. Linear discriminant analysis resulted in a leave-one-out cross-validation error rate of 30.0% to discriminate between both patient groups, based on routinely collected clinical parameters. CONCLUSIONS: Clustering analysis did not result in clusters that separate SCS-naïve patients from patients with previous SCS experience. This may suggest that both patient groups should not be considered as two different patient groups when comparing them on routine clinical parameters, with potentially profound implications for research and clinical settings. CLINICAL TRIAL REGISTRATION: The Clinicaltrials.gov registration number for the Discover study is NCT02787265.

Personalised rehabilitation to improve return to work in patients with persistent spinal pain syndrome type II after spinal cord stimulation implantation: a study protocol for a 12-month randomised controlled trial-the OPERA study.

BACKGROUND: For patients with therapy-refractory persistent spinal pain syndrome type II (PSPS-T2), spinal cord stimulation (SCS) may serve as an effective minimally invasive treatment. Despite the evidence that SCS can improve return to work (RTW), only 9.5 to 14% of patients implanted with SCS are effectively capable of returning to work. Thus, it seems that current post-operative interventions are not effective for achieving RTW after SCS implantation in clinical practice. The current objective is to examine whether a personalised biopsychosocial rehabilitation programme specifically targeting RTW alters the work ability in PSPS-T2 patients after SCS implantation compared to usual care. METHODS: A two-arm, parallel-group multicentre randomised controlled trial will be conducted including 112 patients who will be randomised (1:1) to either (a) a personalised biopsychosocial RTW rehabilitation programme of 14 weeks or (b) a usual care arm, both with a follow-up period until 12 months after the intervention. The primary outcome is work ability. The secondary outcomes are work status and participation, pain intensity, health-related quality of life, physical activity and functional disability, functional capacities, sleep quality, kinesiophobia, self-management, anxiety, depression and healthcare expenditure. DISCUSSION: Within the OPERA project, we propose a multidisciplinary personalised biopsychosocial rehabilitation programme specifically targeting RTW for patients implanted with SCS, to tackle the high socio-economic burden of patients that are not re-entering the labour market. The awareness is growing that the burden of PSPS-T2 on our society is expected to increase over time due to the annual increase of spinal surgeries. However, innovative and methodologically rigorous trials exploring the potential to decrease the socio-economic burden when patients initiate a trajectory with SCS are essentially lacking. TRIAL REGISTRATION: ClinicalTrials.gov NCT05269212. Registered on 7 March 2022.

Health-related quality of life in persons post-COVID-19 infection in comparison to normative controls and chronic pain patients.

The Coronavirus disease 2019 (COVID-19) pandemic exerted a tremendous pressure on the healthcare system, people's social life, mental health and financial status with profound implications for the general population. The exact impact of the pandemic on the overall physical, mental and social wellbeing of COVID-19 infection survivors on the long term has not yet been explored in a thorough way. Based on the reporting of persistent pain, fatigue and dyspnea symptoms by these survivors, it is our hypothesis that their quality of life will be extremely impacted, as is observed in patients with chronic pain. Therefore, the first aim of this study was to perform an in-depth evaluation of the quality of life of post-COVID-19 infected persons. The second aim was to compare the quality of life of these persons with a normative population and with patients with chronic pain. Health-related quality of life, as a measure for a person's overall physical, mental, and social wellbeing, was measured with the 3-level EQ5D in 547 post-COVID-19 infected persons. These data were compared to reference data from normal population records for Belgium and to data from patients with chronic pain after spinal surgery with two-way analyses of variance. In total, 89.58% of the post-COVID-19 infected persons reported pain/discomfort and 82.45% indicated limitations when performing usual activities, when evaluated 287 days (SD: 150) after the infection. Self-care was preserved in most post-COVID-19 persons, whereby only 13.16% indicated problems. The mean EQ5D-3L index score was 0.57 (SD: 0.23) and EQ5D VAS mean score was 56.6 (SD: 18.2). The mean index score for the normative population was significantly higher than for COVID-19 infected persons [mean difference of 0.31 (95% from 0.29 to 0.33), p < 0.01] while the mean score of chronic pain patients was significantly lower than the score of COVID-19 infected persons [mean difference of -0.31 (95% from -0.29 to -0.33), p < 0.01]. Compared to age-and sex adjusted reference data, health-related quality of life of persons with long COVID is severely impacted. In relation to patients with chronic pain after spinal surgery, the quality of life of post-COVID-19 infected persons seemed to be better. Clinical trial registration: https://www.clinicaltrials.gov/, identifier: NCT04912778.

The Link Between Spinal Cord Stimulation and the Parasympathetic Nervous System in Patients With Failed Back Surgery Syndrome.

OBJECTIVES: In patients with chronic pain, a relative lower parasympathetic activity is suggested based on heart rate variability measurements. It is hypothesized that spinal cord stimulation (SCS) is able to influence the autonomic nervous system. The aim of this study is to further explore the influence of SCS on the autonomic nervous system by evaluating whether SCS is able to influence skin conductance, blood volume pulse, heart rate, and respiration rate. MATERIALS AND METHODS: Twenty-eight patients with Failed Back Surgery Syndrome (FBSS), who are being treated with SCS, took part in this multicenter study. Skin conductance and cardiorespiratory parameters (blood volume pulse, heart rate, and respiration rate) were measured during on and off states of SCS. Paired statistics were performed on a 5-min recording segment for all parameters. RESULTS: SCS significantly decreased back and leg pain intensity scores in patients with FBSS. Skin conductance level and blood volume pulse were not altered between on and off states of SCS. Heart rate and respiration rate significantly decreased when SCS was activated. CONCLUSIONS: Parameters that are regulated by the sympathetic nervous system were not significantly different between SCS on and off states, leading to the hypothesis that SCS is capable of restoring the dysregulation of the autonomic nervous system by primarily increasing the activity of the parasympathetic system in patients with FBSS.

Electrochemical Skin Conductance Alterations during Spinal Cord Stimulation: An Experimental Study.

Despite the well-known clinical effects of spinal cord stimulation (SCS), the mechanisms of action have not yet been fully unraveled. The primary aim of this study was to measure whether electrochemical skin conductance, as a measure of peripheral sympathetic autonomic function, is altered by SCS. A second aim was to compare skin conductance levels of patients with failed back surgery syndrome (FBSS) with age- and sex-matched healthy controls. Twenty-three patients with FBSS treated with SCS participated in this study. Sudomotor function was measured with the SudoscanTM instrument on the hands and feet during SCS on and off states. Difference scores in skin conductance between patients and age- and sex-matched healthy controls were calculated. Normal sudomotor function at the painful lower limb was revealed for 61% of the patients when SCS was activated. Skin conductance levels were not altered between on and off states of SCS. Differences in scores between patients and healthy controls were significantly different from zero. This study showed that SCS does not influencing the sympathetic nervous system in patients with FBSS, as measured by skin conductance levels. Moreover, it suggested that there is no normalization of the functioning of the sympathetic nervous system, despite the effectiveness of SCS to reduce pain intensity.

Exhaled-Breath Testing Using an Electronic Nose during Spinal Cord Stimulation in Patients with Failed Back Surgery Syndrome: An Experimental Pilot Study.

The increased awareness of discrepancies between self-reporting outcome measurements and objective outcome measurements within the field of neuromodulation has accelerated the search towards more objective measurements. The aim of this study was to evaluate whether an electronic nose can differentiate between chronic pain patients in whom Spinal Cord Stimulation (SCS) was activated versus deactivated. Twenty-seven patients with Failed Back Surgery Syndrome (FBSS) participated in this prospective pilot study. Volatile organic compounds in exhaled breath were measured with electronic nose technology (Aeonose™) during SCS on and off states. Random forest was used with a leave-10%-out cross-validation method to determine accuracy of discriminating between SCS on and off states. Our random forest showed an accuracy of 0.56, with an area under the curve of 0.62, a sensitivity of 62% (95% CI: 41-79%) and a specificity of 50% (95% CI: 30-70%). Pain intensity scores were significantly different between both SCS states. Our findings indicate that we cannot discriminate between SCS off and on states based on exhaled breath with the Aeonose™ in patients with FBSS. In clinical practice, these findings imply that with a noninvasive electronic nose, exhaled breath cannot be used as an additional marker of the effect of neuromodulation.

High-Dose Spinal Cord Stimulation Reduces Long-Term Pain Medication Use in Patients With Failed Back Surgery Syndrome Who Obtained at Least 50% Pain Intensity and Medication Reduction During a Trial Period: A Registry-Based Cohort Study.

OBJECTIVES: High-dose spinal cord stimulation (HD-SCS) revealed positive results for obtaining pain relief in patients with failed back surgery syndrome (FBSS). However, it is less clear whether HD-SCS also is able to reduce pain medication use. The aim of this registry-based cohort study is to explore the impact of HD-SCS on pain medication use in FBSS patients. MATERIALS AND METHODS: Data from the Discover registry was used in which the effectiveness of HD-SCS was explored in neurostimulation-naïve FBSS patients as well as in rescue patients. All neurostimulation-naïve FBSS patients positively responded to a four-week SCS trial period in which at least 50% pain relief and 50% medication reduction were obtained. Medication use was measured with the Medication Quantification Scale III (MQS) in 259 patients at baseline and at 1, 3, and 12 months of HD-SCS. Additionally, defined daily doses (DDD) and morphine milligram equivalents (MME) were calculated as well. RESULTS: One hundred thirty patients reached the visit at 12 months. In neurostimulation-naïve patients, a statistically significant decrease in MQS (χ2 = 62.92, p < 0.001), DDD (χ2 = 11.47, p = 0.009), and MME (χ2 = 21.55, p < 0.001) was found. In rescue patients, no statistically significant improvements were found. In both patient groups, statistically significant reductions in the proportion of patients on high-risk MME doses ≥90 were found over time. At the intraindividual level, positive correlations were found between MSQ scores and pain intensity for back (r = 0.56, r = 0.31, p < 0.001) and leg pain (r = 0.61, r = 0.22, p < 0.001) in neurostimulation-naïve and rescue patients, respectively. CONCLUSIONS: Registry data on HD-SCS in FBSS patients revealed a statistically significant and sustained decrease in pain medication use, not only on opioids, but also on anti-neuropathic agents in neurostimulation-naïve patients, who positively responded to an SCS trial period with at least 50% pain relief and 50% pain medication decrease, but not in rescue patients.

The association between pain intensity and disability in patients with failed back surgery syndrome, treated with spinal cord stimulation.

OBJECTIVE: Pain researchers demonstrated that pain intensity is not the most reliable measure of the success of chronic-pain treatment. Several research groups have proposed "core outcome domains", such as measurements of disability, to assess the effect of an intervention in pain patients. Up till now, studies investigating the relation between pain intensity and disability in patients treated with spinal cord stimulation (SCS) are lacking. Therefore, the current objective is to examine which pain-reporting strategy, routinely used in pain research, associates best with the degree of disability in these patients. METHODS: Eighty-one failed back surgery syndrome patients (37 males and 44 females, mean age 54.6 years), treated with high-dose spinal cord stimulation (HD-SCS) are recruited. Pain intensity was scored on an 11-point numerical rating scale (NRS) for leg and back pain, while disability was assessed with the Oswestry disability index (ODI). The association between both variables was investigated with Spearman's correlation and Cramér's V. RESULTS: Significant correlations (p < 0.001) are found between the absolute and relative differences of the ODI and NRS. Significant associations were found between reported cut-offs in literature (≤3, ≤5, and 50% pain relief) and the degree of disability. Finally, a significant association (p < 0.001) was found between the minimal clinical important difference. CONCLUSIONS: In this study, we showed that the degree of disability was strongly associated with the pain intensity as measured using different methods. The standard method for reporting pain intensity reduction (50%) seems to associate the strongest with the degree of disability. However, a low degree of disability does not always reflect a low pain intensity.Implications for rehabilitationThe degree of disability reveals a good association with the reporting methods of pain intensity from the literature.The Oswestry disability index could serve as a valid tool to measure the effect of spinal cord stimulation on pain.Disability measures offer a better insight in the clinical profile of chronic pain patients than a pain intensity score.

High-dose spinal cord stimulation for patients with failed back surgery syndrome: a multicenter effectiveness and prediction study.

ABSTRACT: The use of high-dose spinal cord stimulation (HD-SCS) has increased drastically during the past few years, with positive results. However, there remains a deficit of real-world data of the effectiveness of HD-SCS. Therefore, the primary aim was to evaluate the effectiveness of HD-SCS in patients with failed back surgery syndrome (FBSS). The second aim was to develop a prediction model for a holistic responder. One hundred ninety-four patients were recruited to a multicenter real-world registry. Self-reporting outcome variables were evaluated at baseline (before SCS) and at 1, 3, and 12 months of HD-SCS implant. Outcome measures were the mean pain intensity over time, sleep quality, disability, health-related quality of life, and medication use. Besides the effectiveness, logistic regression and decision tree analysis were performed to define a holistic responder (pain intensity reduction, medication reduction, Oswestry disability index reduction, and EQ5D improvement) after 12 months of HD-SCS. Of 185 FBSS patients who underwent a baseline visit, 75.13% had a successful HD trial. At 12 months, 92 patients were still receiving HD-SCS. Both low back and leg pain significantly decreased at 12 months. All outcome measures revealed a significant time-dependent effect from baseline to 12 months. Holistic responders could be predicted with a sensitivity and specificity of 90%. Clinically significant and sustained pain relief over a period of 12 months was achieved with HD-SCS in patients with FBSS. In addition, HD-SCS also achieved an improvement in sleep quality, functionality, and a decrease in pain medication.

The Long-Term Response to High-Dose Spinal Cord Stimulation in Patients With Failed Back Surgery Syndrome After Conversion From Standard Spinal Cord Stimulation: An Effectiveness and Prediction Study.

OBJECTIVES: Spinal cord stimulation (SCS) is nowadays available with several stimulation paradigms. New paradigms, such as high dose (HD-)SCS, have shown the possibility to salvage patients who lost their initial pain relief. The first aim of this study is to evaluate the effectiveness of HD-SCS after conversion from standard SCS. The second aim is to develop a model for prediction of long-term response of HD-SCS after unsatisfactory standard SCS. MATERIALS AND METHODS: Seventy-eight patients with failed back surgery syndrome (FBSS) who are treated with standard SCS were enrolled in the study. Self-reporting questionnaires and outcomes were assessed before conversion and at 1, 3, and 12 months of HD-SCS. Longitudinal mixed models were used to determine the effectiveness of HD-SCS. Logistic regression and classification and decision tree analyses were performed to predict responders (NRS decrease ≥2/10) after 12 months of HD-SCS. RESULTS: Significant time effects were found for both low back and leg pain responders, suggesting the effectiveness of HD-SCS after conversion. Logistic regression models revealed the importance of pain intensity scores, medication use, paresthesia coverage (for back pain) and EQ5D (for leg pain) as predictors for being a responder after 12 months of HD-SCS. CONCLUSIONS: Converting patients with unsatisfactory responses from standard SCS to HD-SCS may be an effective strategy to obtain and maintain pain relief in a challenging subgroup of patients with FBSS refractory to standard SCS. The prediction models may guide clinicians in their decision making when considering conversion to HD-SCS in patients with FBSS experiencing inadequate response to standard SCS.

Predicting the Response of High Frequency Spinal Cord Stimulation in Patients with Failed Back Surgery Syndrome: A Retrospective Study with Machine Learning Techniques.

Despite the proven clinical value of spinal cord stimulation (SCS) for patients with failed back surgery syndrome (FBSS), factors related to a successful SCS outcome are not yet clearly understood. This study aimed to predict responders for high frequency SCS at 10 kHz (HF-10). Data before implantation and the last available data was extracted for 119 FBSS patients treated with HF-10 SCS. Correlations, logistic regression, linear discriminant analysis, classification and regression trees, random forest, bagging, and boosting were applied. Based on feature selection, trial pain relief, predominant pain location, and the number of previous surgeries were relevant factors for predicting pain relief. To predict responders with 50% pain relief, 58.33% accuracy was obtained with boosting, random forest and bagging. For predicting responders with 30% pain relief, 70.83% accuracy was obtained using logistic regression, linear discriminant analysis, boosting, and classification trees. For predicting pain medication decrease, accuracies above 80% were obtained using logistic regression and linear discriminant analysis. Several machine learning techniques were able to predict responders to HF-10 SCS with an acceptable accuracy. However, none of the techniques revealed a high accuracy. The inconsistent results regarding predictive factors in literature, combined with acceptable accuracy of the currently obtained models, might suggest that routinely collected baseline parameters from clinical practice are not sufficient to consistently predict the SCS response with a high accuracy in the long-term.

Long-term quality of life and work status after high-dose spinal cord stimulation in patients with failed back surgery syndrome: a secondary analysis of real-world data.

OBJECTIVE: In recent years, the use of high-dose spinal cord stimulation (HD-SCS) as a treatment option for patients with failed back surgery syndrome (FBSS) has drastically increased. However, to the authors' knowledge a thorough evaluation of health-related quality of life (HRQOL) and work status in these patients has not yet been performed. Moreover, it is unclear whether patients who are treated with HD-SCS can regain the same levels of HRQOL as the general population. Therefore, the aims of this study were to compare the HRQOL of patients who receive HD-SCS to HRQOL values in an age- and sex-adjusted population without FBSS and to evaluate work status in patients who are receiving HD-SCS. METHODS: HRQOL, measured with the 3-level EQ-5D (EQ-5D-3L), and work status were evaluated in 185 FBSS patients at baseline (i.e., before SCS) and at 1, 3, and 12 months of treatment with HD-SCS. Difference scores in utility values between patients and an age- and sex-adjusted normal population were calculated. One-sample Wilcoxon tests were used to assess the EQ-5D-3L difference scores. Mixed models were used to evaluate the evolution over time in EQ-5D-3L utility scores and EQ-5D visual analog scale (VAS) scores in patients and matched controls. Quality-adjusted life-years (QALYs) were calculated using the area under the curve method. RESULTS: An overall significant increase in EQ-5D-3L utility scores and EQ-5D VAS scores was found over time in the patient group. Wilcoxon tests indicated that the difference scores in utility values between patients and the normal population were significantly different from zero at all time points. The median incremental QALY after 12 months of HD-SCS was 0.228 (Q1-Q3: 0.005-0.487) in comparison to continued conservative treatment. At 12 months, 13.75% of patients resumed work. CONCLUSIONS: HD-SCS may lead to significantly increased HRQOL at 12 months in patients with FBSS. Despite the increase, reaching the HRQOL level of matched controls was not achieved. Only a limited number of patients were able to return to work. This finding indicates that specialized programs to enhance return to work may be beneficial for patients undergoing SCS.

The Added Value of High Dose Spinal Cord Stimulation in Patients with Failed Back Surgery Syndrome after Conversion from Standard Spinal Cord Stimulation.

Patients with Failed Back Surgery Syndrome (FBSS) report a considerably lower health- related quality of life (HRQoL), compared to the general population. Spinal cord stimulation (SCS) is an effective treatment to offer pain relief in those patients. Despite initial treatment success of SCS, its effect sometimes wears off over time. This study investigates the added value of high dose SCS (HD-SCS) in patients with unsatisfactory conventional SCS, from a quality of life perspective. Seventy-eight FBSS patients who were treated with conventional SCS that failed to provide pain relief, were recruited in 15 centers. HRQoL was assessed before converting to HD-SCS (baseline) and three times after converting to HD-SCS using the EuroQol-5D-3L. Quality adjusted life years (QALY) were calculated and compared with conventional SCS. An overall significant increase over time was seen in utility values of the EQ5D-3L, as the mean value at baseline 0.283 (±0.21) increased to 0.452 (±0.29) at 12 months of HD-SCS. This average increase in utility coincides with an average increase of 0.153 (±0.24) QALY's in comparison to continued conventional SCS. Besides the potential of HD-SCS to salvage patients with failed responses to conventional SCS, this treatment seems to be a more efficient treatment than conventional SCS.

The influence of nociceptive and neuropathic pain states on the processing of acute electrical nociceptive stimulation: A dynamic causal modeling study.

INTRODUCTION: Despite the worldwide increase in prevalence of chronic pain and the subsequent scientific interest, researchers studying the brain and brain mechanisms in pain patients have not yet clearly identified the exact underlying mechanisms. Quantifying the neuronal interactions in electrophysiological data could help us gain insight into the complexity of chronic pain. Therefore, the aim of this study is to examine how different underlying pain states affect the processing of nociceptive information. METHODS: Twenty healthy participants, 20 patients with non-neuropathic low back-related leg pain and 20 patients with neuropathic failed back surgery syndrome received nociceptive electrical stimulation at the right sural nerve with simultaneous electroencephalographic recordings. Dynamic Causal Modeling (DCM) was used to infer hidden neuronal states within a Bayesian framework. RESULTS: Pain intensity ratings and stimulus intensity of the nociceptive stimuli did not differ between groups. Compared to healthy participants, both patient groups had the same winning DCM model, with an additional forward and backward connection between the somatosensory cortex and right dorsolateral prefrontal cortex. DISCUSSION: The additional neuronal connection with the prefrontal cortex as seen in both pain patient groups could be a reflection of the higher attention towards pain in pain patients and might be explained by the higher levels of pain catastrophizing in these patients. CONCLUSION: In contrast to the similar pain intensity ratings of an acute nociceptive electrical stimulus between pain patients and healthy participants, the brain is processing these stimuli in a different way.

Magnetic Resonance Imaging Exploration of the Human Brain During 10 kHz Spinal Cord Stimulation for Failed Back Surgery Syndrome: A Resting State Functional Magnetic Resonance Imaging Study.

INTRODUCTION: Apart from the clinical efficacy of high frequency spinal cord stimulation at 10 kHz, the underlying mechanism of action remains unclear. In parallel with spinal or segmental theories, supraspinal hypotheses have been recently proposed. In order to unveil hidden altered brain connectome patterns, a resting state functional magnetic resonance imaging (rsfMRI) protocol was performed in subjects routinely treated for back and/or leg pain with high-frequency spinal cord stimulation (HF-SCS) HF-SCS at 10 kHz. METHODS: RsfMRI imaging was obtained from ten patients with failed back surgery syndrome who were eligible for HF-SCS at 10 kHz. Specifically-chosen regions of interest with different connectivity networks have been investigated over time. Baseline measurements were compared with measurements after 1 month and 3 months of HF-SCS at 10 kHz. Additionally, clinical parameters on pain intensity, central sensitization, pain catastrophizing, and sleep quality were correlated with the functional connectivity strengths. RESULTS: The study results demonstrate an increased connectivity over time between the anterior insula (affective salience network) and regions of the frontoparietal network and the central executive network. After 3 months of HF-SCS, the increased strength in functional connectivity between the left dorsolateral prefrontal cortex and the right anterior insula was significantly correlated with the minimum clinically important difference (MCID) value of the Pittsburgh sleep quality index. CONCLUSION: These findings support the hypothesis that HF-SCS at 10 kHz might influence the salience network and therefore also the emotional awareness of pain.

Functional magnetic resonance imaging: cerebral function alterations in subthreshold and suprathreshold spinal cord stimulation.

BACKGROUND AND PURPOSE: Failed back surgery syndrome (FBSS) is a common and devastating chronic neuropathic pain disorder. Conventional spinal cord stimulation (SCS) applies electrical suprathreshold pulses to the spinal cord at a frequency of 40-60 Hz and relieves pain in FBSS patients. During the last decade, two major changes have emerged in the techniques of stimulating the spinal cord: paresthesia-free or subthreshold stimulation and administration of higher frequency or higher amounts of energy to the spinal cord. Despite the positive clinical results, the mechanism of action remains unclear. A functional MRI (fMRI) study was conducted to investigate the brain alterations during subthreshold and suprathreshold stimulation at different frequencies. METHODS: Ten subjects with FBSS, treated with externalized SCS, received randomly four different stimulation frequencies (4 Hz, 60 Hz, 500 Hz, and 1 kHz) during four consecutive days. At every frequency, the patient underwent sub- and suprathreshold stimulation. Cerebral activity was monitored and assessed using fMRI. RESULTS: Suprathreshold stimulation is generally accompanied with more activity than sub-threshold SCS. Suprathreshold SCS resulted in increased bilateral activation of the frontal cortex, thalamus, pre- and postcentral gyri, basal ganglia, cingulate gyrus, insula, thalamus, and claustrum. We observed deactivation of the bilateral parahippocampus, amygdala, precuneus, posterior cingulate gyrus, postcentral gyrus, and unilateral superior temporal gyrus. CONCLUSION: Suprathreshold stimulation resulted in greater activity (both activation and deactivation) of the frontal brain regions; the sensory, limbic, and motor cortices; and the diencephalon in comparison with subthreshold stimulation. Each type of frequency at suprathreshold stimulation was characterized by an individual activation pattern.

Twiddler's Syndrome and Neuromodulation-Devices: A Troubled Marriage.

OBJECTIVE: The occurrence of Twiddler's syndrome in subjects with neurostimulator devices is poorly understood and might be influenced by age, sex, BMI, use of medication or psychologic disorders. METHODS: Two hundred thiry-five patients who received a neuromodulator were included in this retrospective study in a period between 2008 and 2015. The subjects were divided into a group of Twiddler's syndrome patients (TS) and a group of non-Twiddler's patients (NTS). Outcome measures were gender, age at implantation, type of neuromodulation, use of antipsychotics, antidepressants and opioids, the presence of other psychologic disorders and BMI. RESULTS: Both groups differ significantly in age (p = 0.024), weight (p = 0.001) and BMI (p = 0.001). No statistical difference was found in the type of neuromodulation (p = 0.537), gender (p = 0.368), the use of antipsychotics (p = 0.071), antidepressants (p = 0.097), and opioids (p = 1). Forward stepwise logistic regression of all variables showed that age of implementation (p = 0.029), the use of antipsychotics (p = 0.022) and BMI (p = 0.001) were statistically significant for predicting Twiddler's syndrome. CONCLUSION: Twiddler's syndrome is an uncommon complication of neuromodulation implantable devices. Younger age, use of antipsychotics, and high BMI are risk factors that can be used to facilitate rapid diagnosis and treatment.

Disc Fragment Herniectomy Through a Facet Joint Quadrantectomy for Extraforaminal Lumbar Herniation: Technique and Results.

BACKGROUND: Extraforaminal lumbar disc herniation (EFLDH) accounts for 7%-12% of all lumbar disc herniations. We report on a surgical technique for EFLDH, which requires only minimal resection of the facet joint and also allows access to the preforaminal space, if necessary. METHODS: The medical records of 61 consecutive patients treated with disc fragment herniectomy through a facet joint quadrantectomy for EFLDH at the Universitair Ziekenhuis Brussel were critically evaluated with respect to preoperative clinical signs and symptoms, surgery-related complications and outcome at 6 weeks after intervention. Patient satisfaction after the surgery was evaluated using the MacNab classification. RESULTS: The prevalence of leg pain decreased from 100% before the intervention to 19.7% at follow-up. Only 9 patients (14.8%) suffered from residual motor deficit at follow-up, compared with 37 patients (60.7%) in the preoperative situation. The postoperative improvement was highly significant for all parameters (P < 0.0001) and this evolution is also reflected in the MacNab classification showing 62.3% excellent, 23.0% good, 13.1% fair, and only 1.6% poor satisfaction. Using logistic regression analysis, only the presence of a preoperative sensory deficit was found to be an independent predictor for excellent patient satisfaction on the MacNab classification. CONCLUSIONS: Disc fragment herniectomy through a facet joint quadrantectomy for EFLDH is a safe and minimal invasive technique resulting in very satisfactory results. Preservation of facet joint stability and the possibility to convert to a classic approach to reach for preforaminal components, if necessary, are major advantages of this technique.