Examining the Duration of Carryover Effect in Patients With Chronic Pain Treated With Spinal Cord Stimulation (EChO Study): An Open, Interventional, Investigator-Initiated, International Multicenter Study.

OBJECTIVES: Spinal cord stimulation (SCS) is a surgical treatment for severe, chronic, neuropathic pain. It is based on one to two lead(s) implanted in the epidural space, stimulating the dorsal column. It has long been assumed that when deactivating SCS, there is a variable interval before the patient perceives the return of the pain, a phenomenon often termed echo or carryover effect. Although the carryover effect has been problematized as a source of error in crossover studies, no experimental investigation of the effect has been published. This open, prospective, international multicenter study aimed to systematically document, quantify, and investigate the carryover effect in SCS. MATERIALS AND METHODS: Eligible patients with a beneficial effect from their SCS treatment were instructed to deactivate their SCS device in a home setting and to reactivate it when their pain returned. The primary outcome was duration of carryover time defined as the time interval from deactivation to reactivation. Central clinical parameters (age, sex, indication for SCS, SCS treatment details, pain score) were registered and correlated with carryover time using nonparametric tests (Mann-Whitney/Kruskal-Wallis) for categorical data and linear regression for continuous data. RESULTS: In total, 158 patients were included in the analyses. A median carryover time of five hours was found (interquartile range 2.5;21 hours). Back pain as primary indication for SCS, high-frequency stimulation, and higher pain score at the time of deactivation were correlated with longer carryover time. CONCLUSIONS: This study confirms the existence of the carryover effect and indicates a remarkably high degree of interindividual variation. The results suggest that the magnitude of carryover may be correlated to the nature of the pain condition and possibly stimulation paradigms. CLINICAL TRIAL REGISTRATION: The Clinicaltrials.gov registration number for the study is NCT03386058.

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.

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.

Implanter's Integrated Information (I3) System: An Aid for Spinal Cord Stimulation Procedures.

OBJECTIVES: In spinal cord stimulation (SCS), the electrical stimulation of the spinal cord with an implanted lead evokes a tingling peripheral sensation known as paresthesias. Newer stimulation paradigms allow paresthesia-free treatment, but during the implantation of the lead, paresthesias must cover the painful area to achieve optimal treatment effect. The localization of the evoked paresthesias can be difficult to accurately describe for the patient, and furthermore depends on a complex and only partially predictable set of parameters that includes the anatomical localization and the programming of the electrical field. We aimed to optimize SCS implantation procedures by devising a way to aid the patient in making useful descriptions of the evoked paresthesias, then to visually convey the full set of information-anatomical position of the lead, programming parameters, and evoked paresthesias-directly to the implanting physician. MATERIALS AND METHODS: To aid the patient in making accurate descriptions of the evoked paresthesia, we use an app dedicated to creating pain drawings on a tablet. We used Chromecast and Apple TV to project the information from the pain drawing tablet and the programming device to two monitors placed in the implanter's field of vision, right next to the fluoroscopy monitor. RESULTS: The three monitors combined provide a direct visual representation of the dynamic dataset used during SCS implantation: Position, Programming, and Paresthesias, essentially creating the equivalent of the dashboard of a car. CONCLUSIONS: We present an Implanter's Integrated Information (I3) system; a simple, inexpensive solution for gathering, integrating, and conveying the complex set of information necessary for a successful SCS procedure.

Virtual Reality Treatment of Severe Neuropathic Pain in an Adolescent Child: A Case Report.

We describe virtual reality (VR) used as an effective intervention to treat severe chronic neuropathic pain in an otherwise healthy adolescent boy. The patient presented with severe pain and allodynia in the right foot after calcaneus extension surgery. Multiple medical and psychological interventions were unsuccessful over 3 years, with the pain leading the patient to drop out of school. VR gaming intervention provided the patient with significant pain relief and substantial improvement in functionality. This case report details the VR intervention and its effect on the patient's severe, medically refractory pain syndrome.

Multiple Limb Involvement in a Severe Case of Complex Regional Pain Syndrome Treated With Spinal Cord Stimulation: A Case Report.

Complex regional pain syndrome (CRPS) can be a debilitating, persistent, and treatment-resistant pain condition. This report presents a case of severe CRPS affecting multiple limbs, resistant to standard treatment modalities. Treatment with spinal cord stimulation (SCS) had an initial good effect. Nevertheless, the CRPS continued to progress, eventually affecting all 4 extremities. A lead fracture resulted in a rapidly developing recurrence of CRPS in the patient's arm, necessitating amputation. SCS may be an effective modality for treatment of severe CRPS. However, mechanical problems should always be considered when an SCS-implanted patient experiences rapid symptom progression or abrupt cessation of stimulation.