Abstract| Volume 14, ISSUE 4, SUPPLEMENT , S65, April 2013

Thoracic wall pain from spinal cord stimulator electrode malfunction

      Spinal cord stimulators (SCSs) produce electrical signals to suppress perception of chronic neuropathic pain, but they can have complications. We present a case of thoracic wall dysesthesia associated with spinal cord stimulator use due to leakage current from electrode degeneration. Case: A 51 y/o female presented with new left sided chest pain with usage of her SCS. Patient had history of multiple back surgeries and failed back surgery syndrome. Ten year previously, she had a SCS implanted with 2 Medtronic Pisce percutaneous-style 4 contact electrodes at the T8-T9 spinal levels for low back and left leg pain. She had excellent pain relief until 14 months after initial implantation, when the SCS was revised due to increasing voltage demands. Electrodes were replaced with a Specify 4x2 paddle electrode at T8-T9. After 7 years she abruptly started to experience left sided chest wall pain consistently during SCS activation despite multiple attempts at reprogramming. Imaging displayed perfect midline and dorsal electrode alignment with no migration from previous studies. There were, however, signs of discontinuity in some contacts. After multidisciplinary discussions between pain medicine, neurosurgery, neuroradiology, we hypothesized that leakage current could be causing the thoracic dysesthesias, and the patient was offered another revision with a new paddle electrode. During surgery the left electrode appeared to have a defect in the insulation. A Specify 8x2 paddle electrode was then placed. Excellent relief of the patient’s neuropathic pain was achieved, with complete resolution of the thoracic dysesthesias during stimulation. New SCS related dysesthesia in a previously well-functioning system is not commonly reported in the absence of lead migration. This case demonstrates the possibility of aberrant electrical current paths that can develop over time, particularly as electrodes age and fray. Electrode revision should be considered, particularly if impedance values in the existing electrode are abnormal.