Development of a Predictive Model of Effectiveness for the Implantation of Electrical Neurostimulators in Patients With Chronic Pain Using Imaging Biomarkers Extracted From Magnetic Resonance

Chronic pain is correlated with alterations in the structure and function of the brain, developed according to the phenotype of pain. Still today, the data on functional connectivity (FC), on chronic back pain, in patients with failed back surgery syndrome (FBSS), is limited. The selection process for the ideal candidate for spinal cord stimulation (SCS) is based on results from test and functional variables analysis as well as pain evaluation. In addition to the difficulties in the initial selection of patients and the predictive analysis of the test phase, which undoubtedly impact on the results in the middle and long term, the rate of explants is one of the most important concerns, in the analysis of suitability of implanted candidates. The hypothesis is that the structural and functional quantitative information provided by imaging biomarkers will improve the characterization of the patients compared to the characterization with the current clinical variables alone and this will allow establishing a CDSS that improve the effectiveness of the SCS implantation, optimizing human, economic and psychological resources.

A prospective, consecutive and observational, open-label, single-center study conducted at the Multidisciplinary Pain Management Department of our University Hospital. A total of 69 subjects were initially included in the study. The population split in 3 groups:

• Interventional Group-SCS, included 35 patients with failed back surgery syndrome (FBSS) who were treated with SCS implants.
• Comparator group included 23 patients with patients with chronic low-back pain who were treated with conventional medication (CM) for their pain.
• Control Group included 11 subjects as health controls who volunteered to participate in the study.

MR images were obtained in a 1.5T MR system (Ingenia, Philips, Best, The Netherlands) using an 8-channel head coil.Clinical variables were evaluated at two different time points baseline and 12 months after SCS implantation or conventional medication. An ad hoc database was created to evaluate the different variables involved in pain , including sociodemographic variables (age, gender, level of studies and marital status), clinical variables (anxiety, depression, sleeping hours, resilience, NRS, the Pain Detect Questionnaire (PD-Q)) , and the images obtained from the fMRI.