The Aarhus Neuromodulation Database

Does Spinal Cord Stimulation Improve Sleep Disturbances Independently of Pain Relief in Patients With Chronic Pain? An Explorative, Observational Study

OBJECTIVES

Chronic pain poses a significant health challenge worldwide and is associated with both disability and reduced quality of life. Sleep disturbances are reported in 67% to 88% of patients with chronic pain. Pain and sleep affect each other reciprocally; we aimed to study this bidirectional relationship in patients treated with spinal cord stimulation (SCS) for chronic pain. Specifically, we investigated whether sleep improves after treatment with SCS and whether this improvement may be mediated by pain reduction.

MATERIALS AND METHODS

An observational cohort study was conducted in patients with chronic neuropathic pain treated with SCS at a single neurosurgical department in Denmark. Outcomes were assessed preoperatively and at three, six, and 12 months postoperatively, and thereafter annually. Primary outcomes were pain intensity (numeric rating scale) and insomnia at first follow-up (Insomnia Severity Index). The association between sleep and pain was investigated using linear regression and mediation analysis.

RESULTS

Forty-three patients were included in the study. The mean insomnia score was reduced by 25% from 18.1 (SD 6.0) to 13.5 (SD 6.6) (p = 0.0001). Pain intensity was reduced 38% from 7.4 (SD 1.6) to 4.6 (SD 2.1) at the first follow-up (p ≤ 0.0001). Changes in pain and changes in insomnia scores were significantly but weakly associated (regression coefficient = 1.3, 95% CI [0.3; 2.2], p = 0.008, r2 = 15.7%); and changes in pain score were not found to mediate changes in sleep score (β = -0.02, 95% CI [-0.15; 0.11], p = 0.76).

CONCLUSIONS

We found that patients treated with SCS showed significant improvements in both insomnia and pain intensity at first follow-up. Improvements in insomnia and pain intensity were significantly but weakly associated, and improvements in pain intensity score did not mediate improvements in insomnia score. Thus, improvements in self-reported insomnia in patients treated with SCS for chronic pain may predominantly be caused by other factors than reduced pain intensity.

Treatment of chronic cluster headache with burst and tonic occipital nerve stimulation: A case series

OBJECTIVES AND BACKGROUND

Chronic cluster headache (CCH) is a rare but severely debilitating primary headache condition. A growing amount of evidence suggests that occipital nerve stimulation (ONS) can offer effective treatment in patients with severe CCH for whom conventional medical therapy does not have a sufficient effect. The paresthesia evoked by conventional (tonic) stimulation can be bothersome and may thus limit therapy. Burst ONS produces paresthesia-free stimulation, but the amount of evidence on the efficacy of burst ONS as a treatment for intractable CCH is scarce.

METHODS

In this case series, we report 15 patients with CCH treated with ONS at Aarhus University Hospital, Denmark, from 2013 to 2020. Nine of these received burst stimulation either as primary treatment or as a supplement to tonic stimulation. The results were assessed in terms of the frequency of headache attacks per week and their intensity on the Numeric Rating Scale, as well as the Patient Global Impression of Change (PGIC) with ONS treatment.

RESULTS

At a median (range) follow-up of 38 (16-96) months, 12 of the 15 patients (80%) reported a reduction in attack frequency of ≥50% (a reduction from a median of 35 to 1 attack/week, p < 0.001). Seven of these patients were treated with burst ONS. A significant reduction was also seen in maximum pain intensity. Overall, 10 patients stated a clinically important improvement in their headache condition following ONS treatment, rated on the PGIC scale. A total of 16 adverse events (nine of which were in the same patient) were registered.

CONCLUSION

Occipital nerve stimulation significantly reduced the number of weekly headache attacks and their intensity. Burst ONS seems to function well alone or as a supplement to conventional tonic ONS as a preventive treatment for CCH; however, larger prospective studies are needed to determine whether the effect can be confirmed and whether the efficacy of the two stimulation paradigms is even.

Burst Spinal Cord Stimulation in Pregnancy: First Clinical Experiences

OBJECTIVES

Spinal cord stimulation (SCS) is a treatment for chronic neuropathic pain. It is based on the delivery of electric impulses to the spinal cord, traditionally in a regular square-wave pattern ("tonic" stimulation) and, more recently, in a rhythmic train-of-five "BurstDR" pattern. The safety of active SCS therapy in pregnancy is not established, and recommendations are based on limited casuistic evidence. We present in this study clinical data on a case series of six women treated with burst SCS during pregnancy. In addition, we present the ultrasonographic flow measurements of fetal and uteroplacental blood flow in a pregnant patient.

MATERIALS AND METHODS

Patients were included if they had been implanted with a full SCS system at Aarhus University Hospital, Denmark, between 2006 and 2020 and received active burst SCS stimulation during a pregnancy. Telephone interviews were conducted, including details on SCS therapy, medication, pregnancy course and outcome, and health status of the offspring. In one patient, the uteroplacental and fetal blood flow was assessed in gestational week 29 by Doppler flow measurements performed during both ON and OFF phases of the SCS system.

RESULTS

Six patients were included with a total of 11 pregnancies. Three pregnancies ended in miscarriages, all in the same patient who had preexisting significant risk factors for miscarriage. Eight resulted in a live-born child with normal birth weight for gestational age; seven were born at term, and one was born late preterm, in gestational week 36. Ultrasonographic Doppler flow, measured in one patient, was normal and did not reveal any immediate changes between burst SCS ON and OFF. Seven children were reported healthy with normal neurodevelopment and one physically healthy but with developmental delays.

CONCLUSIONS

The data presented in this study add to the accumulating evidence of the safety of SCS in pregnancy.

Spinal cord stimulation in severe cases of complex regional pain syndrome: A retrospective cohort study with long-term follow-up

BACKGROUND

Complex regional pain syndrome (CRPS) is a debilitating pain condition often resistant to standard treatment modalities. In these cases, spinal cord stimulation (SCS) can be an option, but the effect on CRPS remains disputed. We aimed to assess the long-term effect of SCS on CRPS.

METHODS

We retrospectively analysed 51 CRPS patients implanted with an SCS system at the University Hospitals in Aarhus or Odense, Denmark, with a median follow-up time of 4.4 years. Primary outcomes were pain intensity on a numeric rating scale (NRS) and the Patients' Global Impression of Change (PGIC). Secondary outcomes were patient satisfaction, work status, consumption of pain medication, the Major Depression Inventory (MDI), Pain Catastrophizing Scale (PCS) and quality of life (QoL) measured using the Short-Form Health Survey (SF-36). For each outcome measure, baseline data were compared to the latest collected data point.

RESULTS

A significant pain relief was found with a mean reduction in NRS score of 2.4 (95% CI: 1.7-3.0, p < 0.0001). 68.8% reported 'much improved' or 'very much improved' on the PGIC scale. 87.5% would choose SCS again for the same outcome. A significant beneficial impact was found on MDI score, PCS, SF-36 summary scores and consumption of tricyclic antidepressants, antiepileptic drugs and opioids. No statistical effect was found on work status.

CONCLUSION

Pain intensity, depression, pain catastrophizing, pain medication use and QoL were significantly improved after SCS implantation, with high patient satisfaction rates in CRPS patients. This study supports the continued use of SCS in the treatment of severe CRPS.

SIGNIFICANCE

This study presents detailed data from a large, well-characterized cohort of Danish CRPS patients treated with SCS, analyzing several outcome measures. The results serve to document SCS as an effective treatment for severe CRPS and expands the cumulative level of evidence in favor of its use. Additionally, analysis of preoperative patient characteristics suggests that SCS treatment should not be withheld in patients with a high degree of psychological distress or high consumption of analgesics.

The International Neuromodulation Registry: An Informatics Framework Supporting Cohort Discovery and Analysis

Background

Neuromodulation therapies, such as deep brain stimulation (DBS), spinal cord stimulation (SCS), responsive neurostimulation (RNS), transcranial magnetic stimulation (TMS), transcranial direct stimulation (tDCS), and vagus nerve stimulation (VNS) are used to treat neurological and psychiatric conditions for patients who have failed to benefit from other treatment approaches. Although generally effective, seemingly similar cases often have very different levels of effectiveness. While there is ongoing interest in developing predictors, it can be difficult to aggregate the necessary data from limited cohorts of patients at individual treatment centers.

Objective

In order to increase the predictive power in neuromodulation studies, we created an informatics platform called the International Neuromodulation Registry (INR). The INR platform has a data flow process that will allow researchers to pool data across multiple centers to enable population health research.

Methods

This custom informatics platform has a Neo4j graph database and includes a harmonization process that allows data from different studies to be aggregated and compared. Users of the INR can download deidentified patient imaging, patient demographic data, device settings, and medical rating scales. The INR supports complex network analysis and patient timeline visualization.

Results

The INR currently houses and allows visualization of deidentified imaging and clinical data from hundreds of patients with a wide range of diagnoses and neuromodulation therapies.

Conclusion

Ultimately, we believe that widespread adoption of the INR platform will improve population health research in neuromodulation therapy.

Pain Catastrophizing Does Not Predict Spinal Cord Stimulation Outcomes: A Cohort Study of 259 Patients With Long-Term Follow-Up

OBJECTIVE

Spinal cord stimulation (SCS) is an important treatment modality used to treat chronic neuropathic pain. However, reported success rates of 26%-70% entail an increased focus on patient selection. An area of core interest is psychological evaluation, often using scales such as the Pain Catastrophizing Scale (PCS). The aim of this study was to assess the relation between baseline PCS scores obtained before implantation and SCS outcomes defined as (1) Rating on Patients' Global Impression of Change scale (PGIC), (2) Pain relief on the Numeric Rating Scale (NRS), (3) Cessation of pain medication, and (4) Risk of permanent explantation.

MATERIALS AND METHODS

Using records from the Neurizon Neuromodulation Database, we performed a multicenter open cohort study of 259 permanently implanted SCS patients. Follow-up ranged from six months to nine years (median = three years). For each of the defined SCS outcomes, patients were grouped according to their latest follow-up registration. Subsequently, we used a one-way ANOVA and exact t-tests to compare mean baseline PCS scores between groups.

RESULTS

No difference in mean baseline PCS scores was found between PGIC groups. Baseline PCS scores was not associated with the probability of obtaining 30% or 50% pain relief on latest registration. Baseline PCS scores of patients able to cease all usage of tricyclic antidepressants, antiepileptics, or opioids during SCS treatment did not differ from baseline scores of continuous users. We found no association between baseline PCS scores and risk of permanent explantation.

CONCLUSION

This study did not demonstrate any associations between baseline PCS scores and SCS outcomes.

Complications and Effects of Dorsal Root Ganglion Stimulation in the Treatment of Chronic Neuropathic Pain: A Nationwide Cohort Study in Denmark

OBJECTIVES

Dorsal root ganglion (DRG) stimulation is a novel treatment of chronic neuropathic pain and has been shown to be efficacious across several case reports and randomized trials. However, long-term follow-up is limited, as are reports of complication rates. This study presents efficacy and complications for patients treated with DRG stimulation.

MATERIALS AND METHODS

We performed an observational, multicenter cohort study of all patients in Denmark implanted with FDA-approved DRG stimulation systems to treat chronic, neuropathic pain between 2014 and 2018. Follow-up period was one to three years.

RESULTS

Forty-three patients underwent trial DRG stimulation; 33 were subsequently fully implanted. Pain location: 58% lower extremity; 21% upper extremity; 21% thoracic/abdominal. At the end of the observation period, 58% of fully implanted patients were still implanted; 42% had fully functional systems. In these patients, average Numerical Rating Scale (NRS)-score of pain was reduced from 6.8 to 3.5 (p = 0.00049) and worst NRS-score was reduced from 8.6 to 6.0 (p = 0.0039) at 12 months follow-up. Pain Catastrophizing Score was reduced from 32 to 15 (p = 0.0039). Thirteen patients experienced complications related to defect leads (39% of implanted systems). In four patients (12%), lead removal left fragments in the root canal due to lead fracture, and three patients suffered permanent nerve damage during attempts to replace broken leads.

CONCLUSIONS

This study suggests a significant, clinically relevant effect of DRG stimulation on neuropathic pain, but also demonstrates substantial problems with maintenance and revision of currently available systems. Consequently, treatment with equipment marketed specifically for DRG stimulation is currently paused in Denmark.

Therapy-Related Explants After Spinal Cord Stimulation: Results of an International Retrospective Chart Review Study

Objectives

Clinical trials of spinal cord stimulation (SCS) have largely focused on conversion from trial to permanent SCS and the first years after implant. This study evaluates the association of type of SCS and patient characteristics with longer‐term therapy‐related explants.

Materials and Methods

Implanting centers in three European countries conducted a retrospective chart review of SCS systems implanted from 2010 to 2013. Ethics approval or waiver was obtained, and informed consent was not required. The chart review recorded implants, follow‐up visits, and date and reasons for any explants through mid‐2016. Results are presented using Cox regression to determine factors associated with explant for inadequate pain relief.

Results

Four implanting centers in three countries evaluated 955 implants, with 8720 visits over 2259 years of follow‐up. Median age was 53 years; 558 (58%) were female. Explant rate was 7.9% per year. Over half (94 of 180) of explants were for inadequate pain relief, including 32/462 (6.9%) of implants with conventional nonrechargeable SCS, 37/329 (11.2%) with conventional rechargeable and 22/155 (14.2%) with high‐frequency (10 kHz) rechargeable SCS. A higher explant rate was found in univariate regression for conventional rechargeable (HR 1.98, p = 0.005) and high‐frequency stimulation (HR 1.79, p = 0.035) than nonrechargeable SCS. After covariate adjustment, the elevated explant rate persisted for conventional rechargeable SCS (HR 1.95, p = 0.011), but was not significant for high‐frequency stimulation (HR 1.71, p = 0.069).

Conclusions

This international, real‐world study found higher explant rates for conventional rechargeable and high‐frequency SCS than nonrechargeable systems. The increased rate for conventional rechargeable stimulation persisted after covariate adjustment.

Spinal cord stimulation: Background and clinical application

Background Spinal cord stimulation (SCS) is a surgical treatment for chronic neuropathic pain refractory to conventional treatment. SCS treatment consists of one or more leads implanted in the epidural space of the spinal canal, connected to an implantable pulse generator (IPG). Each lead carries a number of contacts capable of delivering a weak electrical current to the spinal cord, evoking a feeling of peripheral paresthesia. With correct indication and if implanted by an experienced implanter, success rates generally are in the range of about 50-75%. Common indications include complex regional pain syndrome (CRPS I), angina pectoris, and radicular pain after failed back surgery syndrome, and the treatment is also used to treat stump pain after amputation, and pain due to peripheral nerve injury, peripheral vascular disease, and diabetic neuropathy. Recommended contraindications for the treatment include pregnancy, coagulopathy, severe addiction to psychoactive substances, and lack of ability to cooperate (e.g. due to active psychosis or cognitive impairment). Most common complications to the treatment include lead migration, lead breakage, infection, pain over the implant, and dural puncture. Despite extensive research in the area, the mechanisms of action are still only partially understood. Methods In this topical review the historical background behind the treatment is described and the current theories on the mechanism of action are presented. The implantation procedure is described in detail and illustrated with a series of intraoperative pictures. Finally, indications for SCS are discussed along with some of the controversies surrounding the therapy. Implications The reader is presented with a broad overview of spinal cord stimulation, including the historical and theoretical background, practical implantation technique, and clinical application.