Analgesic Efficacy of "Burst" and Tonic (500 Hz) Spinal Cord Stimulation Patterns: A Randomized Placebo-Controlled Crossover Study.

OBJECTIVES: The aim of this study was to compare the efficacy in reducing pain intensity in adult subjects suffering from chronic back and leg pain of burst (BST) and tonic sub-threshold stimulation at 500 Hz (T500) vs. sham stimulation delivered by a spinal cord stimulation (SCS) device capable of automated postural adjustment of current intensity. MATERIALS AND METHODS: A multicentre randomized double-blind, three-period, three-treatment, crossover study was undertaken at two centers in the United Kingdom. Patients who had achieved stable pain relief with a conventional SCS capable of automated postural adjustment of current intensity were randomized to sequences of BST, T500, and sham SCS with treatment order balanced across the six possible sequences. A current leakage was programmed into the implantable pulse generator (IPG) in the sham period. The primary outcome was patient reported pain intensity using a visual analog scale (VAS). RESULTS: Nineteen patients were enrolled and randomized. The mean reduction in pain with T500 was statistically significantly greater than that observed with either sham (25%; 95% CI, 8%-38%; p = 0.008) or BST (28%; 95% CI, 13%-41%; p = 0.002). There were no statistically significant differences in pain VAS for BST versus Sham (5%; 95% CI, -13% to 27%; p = 0.59). Exploratory sub-group analyses by study site and sex were also conducted for the T500 vs. sham and BST versus sham comparisons. CONCLUSIONS: The findings suggest a superior outcome versus sham from T500 stimulation over BST stimulation and a practical equivalence between BST and sham in a group of subjects with leg and back pain habituated to tonic SCS and having achieved a stable status with stimulation.

Analgesic efficacy of high-frequency spinal cord stimulation: a randomized double-blind placebo-controlled study.

INTRODUCTION: Spinal cord stimulation is a recognized treatment of chronic neuropathic and vascular pain. Recent data suggest that the use of very high-frequency (HF) stimulation modes does produce analgesia without paresthesia. AIM OF THE STUDY: To compare the efficacy of HF stimulation (HF spinal cord stimulation [HFSCS]) and sham stimulation on the patient's global impression of change (PGIC), pain intensity, and quality of life. PATIENTS AND METHODS: Forty patients who have achieved stable pain relief with conventional SCS have been recruited. After randomization, HFSCS and sham are initiated in a double-blind randomized two-period-crossover design. RESULTS: Complete data were available from 33 patients. The primary outcome was a minimal improvement in the PGIC. The proportion of patients responding under HFSCS was 42.4% (14/33 patients) vs. 30.3% (10/33 patients) in the sham condition. The mean benefit of HF vs. sham was not statistically significant with a proportion of 11.2% in favor of HFSCS (p = 0.30). There was a highly statistically significant "period effect," irrespective of treatment received, with 51.5% of patients (N = 17) improving at visit 3 vs. 21.2% (N = 7) at visit 5 (p = 0.006). The mean pain visual analog scale (VAS) on sham was 4.26 vs. 4.35 on HFSCS (p = 0.82) and the mean EuroQol five-dimensional (EQ-5D) index with HFSCS was 0.480 vs. 0.463 with sham (p = 0.78). CONCLUSION: This is the first randomized double-blind study on SCS. HFSCS was equivalent to sham for the primary outcome (improvement of PGIC) as well as for both the secondary outcomes (VAS and EQ-5D index). There was a highly statistically significant "period effect" (p = 0.006) with improved PGIC scores in the first study period regardless of the treatment. The same trend was seen for VAS and EQ-5D. It appears that the effect of HFSCS and sham is equal and only the order in the sequence, not the nature of the treatment, seems to dictate the effect.

Prospective analysis of the trial period for spinal cord stimulation treatment for chronic pain.

OBJECTIVE: To determine patient preferences regarding the duration of trial period. MATERIALS AND METHODS: Forty patients were given a trial of spinal cord stimulation. They were questioned daily if they would like to proceed to a permanent implant. Three consecutive affirmative answers implied a successful trial; three negative replies implied a failed trial. Patients rated daily the pain from the surgery, original pain, satisfaction with the stimulator, and the duration of the use of the stimulator. RESULTS: The trial duration varied from 3 to 15 days. Patients with a failed trial took longer to make a decision and also experienced prolonged surgical pain. The majority of patients with a successful trial experienced more than 50% pain reduction. The rate of infection was 7.5%, which has reduced to 2.8% after changing the dressing protocol. CONCLUSIONS: In this study, all patients could make a decision in 15 days, with successful trials requiring a shorter duration. The conversion rate was similar to rates in literature despite patients making a decision without physician input.

Effects of flow rate modifications on reported analgesia and quality of life in chronic pain patients treated with continuous intrathecal drug therapy.

OBJECTIVE: We compared the analgesia and the quality of life of a constant daily dose of intrathecal drug administered at different flow rates in patients treated for chronic pain. We postulate that the quality of the analgesia, at the same daily dose, will show an infusion rate dependent pattern with decreased pain at higher flow rates. PATIENTS: Twenty consecutive patients on stable intrathecal treatment were included in a double-blind three-period crossover study where the same daily dose was administered at single, double, and quadruple flow rates in a randomized sequence. OUTCOMES MEASURES: The mean daily pain score and the quality of life (EuroQol measure of health outcome [EQ-5D]) were measured following each flow rate change, after 1 week of stabilization. Results. Visual analog scale (VAS) scores remained unchanged with all flow rates. Compared with the lowest flow rate, the EQ-5D index decreased with double and even more with quadruple flow rate, suggesting a clinically relevant worsening of the health state with higher flow rates. Adverse events were equally distributed in all groups. CONCLUSION: Pain VAS did not significantly change with flow rate. This is consistent with preclinical data showing very limited increase in drug distribution in the cerebrospinal fluid with much larger flow rate augmentation. However, the quality of life decreased consistently as the flow rate increased. This was entirely due to a worsening of the pain and anxiety dimension of the EQ-5D questionnaire, caused presumably by a slight increase in pain rather than adverse events. We suggest that at higher flow rates increased drug dilution results in a decreased effect at the receptor site.