Spinal Cord Stimulation for Complex Pain: Initial Experience with a Dual Electrode, Programmable, Internal Pulse Generator

Abstract

Abstract: The objective of this study was to engage in an 18-month follow-up of 20 chronic complex pain patients using a dual electrode, programmable, fully implantable internal pulse generator (IPG) for spinal cord stimulation (SCS). Implant status, stimulation mode, anode-cathode configuration (array), cathode position, paresthesia overlap, complications, Visual Analog Scores (VAS), and overall satisfaction were prospectively examined in 20 patients implanted with dual 4 contact, staggered, percutaneous electrodes (Pisces 3487A, Medtronic, Minneapolis, Minnesota) internalized to a fully implantable, programmable IPG (Synergy 7466, Medtronic, Minneapolis, Minnesota). All patients had undergone initial implantation for chronic complex axial and extremity pain (eg, Failed Back Surgery Syndrome (FBSS), Complex Regional Pain Syndrome (CRPS)) with dual octapolar, radiofrequency (RF) SCS systems (Advanced Neuromodulation Systems 2098, Plano, Texas).1–3 All patients required conversion to the current dual IPG systems due to RF system receiver sensitivity, preventing further antenna coupling).1 Dual quadrupolar IPG SCS outcomes were compared to previous long-term, dual octapolar RF SCS complex pain reports.1–3 Data was collected and analyzed by a disinterested third party. At 18 months, all 20 patients remained implanted. All patients reported using 1 or 2 “best” guarded tripolar or bipolar arrays to maintain favorable paresthesia overlap (77.5%), VAS reduction (9.78 → 4.40), and overall patient satisfaction (80%). Eighty-five percent of “best” anode-cathode configurations were activated on both electrode columns about the physiologic midline of the C 3/4 vertebral segments for upper extremity pain, and the T 9/10 vertebral segments for low back and lower extremity pain. Sixty-seven and one half percent of all electrodes were thoracic and 32.5% were cervical. “Best” arrays were activated as narrow (adjacent contact) guarded cathode tripoles (75%), extended (nonadjacent contact) bipoles/tripoles (15%), or as narrow bipoles (10%). The mean number of active contacts per “best” array was 5.6, with 3.75 anodes and 1.85 cathodes. All patients preferred the current IPG to the prior RF SCS implant, citing RF receiver site sensitivity, difficulty maintaining coupling of the RF antennae, and time intensive RF programming. Conversely, 13 patients (65%) reported IPG site sensitivity that did not affect overall satisfaction. That is, none would convert their current IPG to a smaller IPG to resolve this issue, unless it was of equal longevity. Sixteen patients (80%) were satisfied with the overall level of pain relief, and all (100%) would repeat the IPG SCS implant. This study demonstrates improved overall outcome and patient satisfaction after long-term, dual octapolar RF SCS conversion to dual quadrupolar IPG SCS systems in the same patient population. It also validates prior dual SCS electrode reports of common array configuration, electrode positioning about the physiologic midline, and patient preference of single or dual programmability in the treatment of chronic complex pain.1,4,5 Follow-up of this initial experience with a multicenter study is warranted.