Four year follow-up of dual electrode spinal cord stimulation for chronic pain

This paper reports on 80 patients using dual electrode spinal cord stimulation (SCS) over a four-year period. Implant status, stimulation mode, anode-cathode configuration (array), cathode position, paresthesia overlap, explantation rates, complications, Visual Analog Scores (VAS), and overall satisfaction were examined in patients implanted with dual 8 contact, staggered, percutaneous electrodes. All patients had undergone implantation for chronic axial and extremity pain (e.g., Failed Back Surgery Syndrome (FBSS), Complex Regional Pain Syndrome (CRPS)). Outcomes were evaluated in view of our previous reports in this same group at 24 and 30 months (1,2). Data was collected by a disinterested third party. At 48 months, 18 of the original 80 patients were lost to follow-up. Of the 62 patients contacted, 33 remained implanted and 29 (47%) had been explanted. After an average evaluation of 85 arrays (PainDoc, Advanced Neuromodulation Systems, Plano, Texas), 88% of patients reported using one or two "best" arrays (bipolar or guarded tripolar) to maintain favorable paresthesia overlap (89%), VAS reduction (8.1 to 4.9), and overall patient satisfaction (63%). These arrays were most commonly positioned about the physiologic midline of the C3-4 vertebral segments for upper extremity pain, and the T9-10 vertebral segments for low back and lower extremity pain. In contrast to our initial reports where essentially all patients preferred more than two arrays to maintain "best" paresthesia overlap and outcome, only 12% of these same patients maintained this trend in this long-term follow-up study. The arrays most commonly selected long-term as the "best" ones (88% of all electrodes) were narrow (adjacent contact) bipoles and guarded cathode tripoles (<8 contacts). Thirty-five percent of patients with thoracic implants achieved paresthesia in the low back at 48 months. Explantation rates and overall patient satisfaction were significantly affected by painful radio frequency (RF) antenna coupling. This data supports the efficacy of dual electrodes in optimizing long-term SCS paresthesia overlap and complex pain outcomes.