Preoperative Surveillance Thoracic MRI for Thoracic Dorsal Column Stimulation: Case Series

Background: To date, there have been no guidelines, studies, or consensus statements regarding the use of advanced imaging studies as a preoperative screening tool prior to patients undergoing spinal cord stimulation (SCS). Objectives: The purpose of this case series is to highlight the importance of obtaining thoracic imaging studies as part of a thorough initial clinical assessment prior to percutaneously or surgically placing an SCS electrode. Methods: We undertook a 3-year retrospective review of patients undergoing evaluation for SCS therapy in an academic interventional pain management and neurosurgery practice. Patients with chronic neuropathic pain underwent a trial with percutaneous dorsal column stimulation, and if response to the trial was > 50% reduction in pain and improvement in function, the patient was implanted using either a percutaneous approach or placement of a paddle electrode with an internal pulse generator (IPG). All patients had advanced thoracic imaging performed (magnetic resonance imaging [MRI] if possible, or computed tomography [CT] if contraindicated) prior to percutaneous trial or paddle electrode implantation. Results: In 3 years, 88 patients underwent a trial of SCS, of which 75 patients (85%) were referred for implantation of a permanent percutaneous or paddle stimulator with IPG. Two patients (1.2%) treated by trial and implant were found to have a thoracic lesion on surveillance imaging, which contraindicated SCS implantation. One patient had thoracic imaging prior to undergoing the trial and one patient had thoracic surveillance imaging after the trial, but before surgical paddle placement. Limitations: The retrospective nature and lack of a control group in this case series are limitations of this study. Conclusion: This case series outlines the importance of considering advanced thoracic imaging studies for screening/surveillance purposes prior to SCS therapy. Placement of SCS electrodes in the thoracic epidural space without prior understanding of spinal anatomy potentially puts patients at unnecessary risk. In the cases presented, had patients undergone SCS trial and subsequent implant without screening imaging, thoracic lesions would have been missed, increasing the likelihood of diagnostic and therapeutic complications. Our incidental findings of lesions on MRI prior to SCS trial or implant support the use of a screening protocol for other centers providing thoracic SCS therapies. Key words: Thoracic, dorsal column stimulation, chronic pain, surveillance MRI, patient selection