Spinal Cord Electrical Stimulation in Severe Angina Pectoris: Surgical Technique, Intraoperative Physiology, Complications, and Side Effects

Twenty patients with angina pectoris were treated with spinal cord stimulation (SCS) at the T₁, T₂ level of the spinal cord since June 1985. These patients were not candidates for angioplasty or coronary bypass or those procedures had failed. There were no injections. One lead broke and one lead migrated. Both were corrected migrally and regained some relief. The relief of pain with SCS may be an alternative treatment to coronary bypass or angioplasty in some patients.     

Stimulation Characteristics, Complications, and Efficacy of Spinal Cord Stimulation Systems in Patients with Refractory Angina: A Prospective Feasibility Study

Objectives: In a prospective study with a 1-year follow-up we evaluated: (1) the feasibility of a method for the adjustment of spinal cord stimulator (SCS) parameters, (2) complications of SCS, and (3) efficacy of SCS. Methods: In patients receiving an SCS for severe angina unresponsive to standard therapies, SCS characteristics were evaluated within 1 week and at 4, 14, 26, and 52 weeks after SCS treatment. Step-by-step adjustment of pulse output parameters was performed at the electrode configuration at which paresthesias occurred (‘sensory threshold”), covered the anginal area (“adjusted setting”), or provoked pain (“motor threshold”). In addition, the number of anginal attacks and intake of glyceryl trinitrate (GTN) tablets were recorded at regular intervals. Results: Twenty-two patients with either a bipolar (14) or a unipolar (8) system were evaluated. In the 14 patients with bipolar systems, alteration in paresthesias required 26 reprogrammings of the configuration. In the eight patients with bipolar systems who completed the followup without lead dislocation, the mean “sensory threshold” was 3.3 V (1.7–5.6), the mean “adjusted stimulation” output was 4.5 V (2.8–7.6), and the mean “motor threshold” was 4.9 V (2.8–7.7) after 4 weeks SCS. The mean stimulation duration per 24 hours was 14.1% (5%–24%), and the mean standardized impedance was 821 Ω (748–893) after 4 weeks SCS. The unipolar group demonstrated comparable results. After 1-year follow-up the parameters had not changed significantly. During the 1-year follow-up, 6 of 22 patients experienced lead dislocation that required surgery. In all patients, anginal attacks (P < 0.003) and GTN intake (P < 0.005) were reduced significantly with SCS. The effect lasted during the 1 year. Conclusions: During a 1 -year follow-up, the stimulation parameters did not change significantly in the 16 patients without lead dislocations. Our standardized method appears to be feasible for follow-up of SCS. Moreover, SCS seems to be an effective adjuvant therapy for intractable angina, despite a relatively frequent dislocation of the electrode.     

Experimental Spinal Cord Stimulation and Neuropathic Pain: Mechanism of Action,Technical Aspects,and Effectiveness

Abstract: Spinal cord stimulation (SCS) is a valuable treatment for chronic intractable neuropathic pain. Although SCS has gone through a technological revolution over the last four decades, the neurophysiologic and biochemical mechanisms of action have only been partly elucidated. Animal experimental work has provided some evidence for spinal as well as supraspinal mechanisms of neuropathic pain relief of SCS. A SCS computer model of the electrical properties of the human spinal cord revealed many basic neurophysiologic principles that were clinically validated later on. The main question in clinical SCS is how to further improve the effectiveness of SCS as there is still a significant failure rate of 30%. In this context, experimental studies are needed to elucidate which target pain neuron(s) are involved, as well as with what exact electrical stimulation this target neuron can be influenced to produce an optimal supapression of neuropathic pain. This article reviews the basic clinical and experimental technical aspects in relation to the effectiveness of SCS in view of recent understanding of the dorsal horn pain circuit involved. These data may then result in experiments needed for an improved understanding of the mechanisms underlying SCS and consequently lead to improvement and increased effectiveness of SCS in neuropathic pain as a clinical therapy.     

Retrospective Review of 707 Cases of Spinal Cord Stimulation: Indications and Complications

Appropriate patient selection and minimizing complications are critical for successful spinal cord stimulation (SCS) therapy in managing intractable pain. We thus reviewed electronic medical records of 707 consecutive cases of patients who received SCS therapy in the Cleveland Clinic from 2000 to 2005 with an emphasis on indications and complications. SCS was used to treat complex regional pain syndrome (CRPS) (345 cases), failed back surgery syndrome (235 cases), peripheral vascular disease (20 cases), visceral pain in the chest, abdomen, and pelvis (37 cases), and peripheral neuropathy (70 cases). CRPS and failed back surgery syndrome accounted for 82% of the cases. The implant‐to‐trial ratio was 75% on average, with the highest for CRPS type 2 (83%) and the lowest for peripheral vascular diseases (65%). The only documented complication associated with SCS trials was lead migration in 5 of 707 patients (0.7%). There were no permanent neurological deficits or deaths as a result of SCS implant or its complications. Hardware‐related complications were common (38%) and included lead migration (22.6%), lead connection failure (9.5%), and lead breakage (6%). Revisions or replacements were required in these cases. Biologically related complications included pain at the generator site (12%) and clinical infection (4.5%; 2.5% with positive culture). The rates of infection varied among the different diagnoses with the highest in failed back surgery syndrome (6.3%). Patients with diabetes had an infection rate of 9%, over the 4% in non‐diabetics. Infections were managed successfully with explantation and antibiotic therapy without permanent sequela.     

Predictors of Pain Relief Following Spinal Cord Stimulation in Chronic Back and Leg Pain and Failed Back Surgery Syndrome: A Systematic Review and Meta‐Regression Analysis

We sought to assess the extent to which pain relief in chronic back and leg pain (CBLP) following spinal cord stimulation (SCS) is influenced by patient‐related factors, including pain location, and technology factors. A number of electronic databases were searched with citation searching of included papers and recent systematic reviews. All study designs were included. The primary outcome was pain relief following SCS, we also sought pain score (pre‐ and post‐SCS). Multiple predictive factors were examined: location of pain, history of back surgery, initial level of pain, litigation/worker's compensation, age, gender, duration of pain, duration of follow‐up, publication year, continent of data collection, study design, quality score, method of SCS lead implant, and type of SCS lead. Between‐study association in predictive factors and pain relief were assessed by meta‐regression. Seventy‐four studies (N = 3,025 patients with CBLP) met the inclusion criteria; 63 reported data to allow inclusion in a quantitative analysis. Evidence of substantial statistical heterogeneity (P < 0.0001) in level of pain relief following SCS was noted. The mean level of pain relief across studies was 58% (95% CI: 53% to 64%, random effects) at an average follow‐up of 24 months. Multivariable meta‐regression analysis showed no predictive patient or technology factors. SCS was effective in reducing pain irrespective of the location of CBLP. This review supports SCS as an effective pain relieving treatment for CBLP with predominant leg pain with or without a prior history of back surgery. Randomized controlled trials need to confirm the effectiveness and cost‐effectiveness of SCS in the CLBP population with predominant low back pain.