The Impact of Psychological Factors on Outcomes for Spinal Cord Stimulation: An Analysis with Long-term Follow-up

Background: For more than 3 decades, spinal cord stimulation (SCS) has successfully beenemployed to treat neuropathic pain. Psychological factors are assumed to be important forthe efficacy of SCS. However, the impact of psychological factors on the outcome of SCS hasonly rarely been studied.Objectives: The aim of this study was to determine the influence of psychological factorssuch as anxiety and depression, perceived disability, and self efficacy on the outcome of SCSin a representative clinical sample.Study design: Retrospective study.Setting: Academic university interdisciplinary pain center.Methods: We reviewed the records of 60 consecutive patients who had been treated at ourinstitution with lumbar, thoracic, or cervical neurostimulators between July 1, 2008, and June30, 2012. Information with respect to age, gender, diagnosis, age at time of implantation,disease duration, the preoperative Hospital Anxiety and Depression Test, German Version(HADS-D), the Pain Disability Index (PDI) and preoperative pain scores on an 11 point NumericRating Scale (NRS) were recorded. In addition, a questionnaire was mailed to participants thatcontained the following items: pain scores on the NRS with and without stimulation, timeintervals of stimulation, paresthesia coverage, treatment satisfaction and medication intake,anxiety/depression (HADS-D and Beck Depression Index II [BDI-II]), PDI, and self efficacy usingthe Fragebogen zur Erfassung der schmerzspezifischen Selbstwirksamkeit (FESS).Results: Preoperative HADS-D, PDI, and NRS pain scores were not different in those patientswith an unsuccessful trial and those who underwent IPG implantation. Long-term outcomeswere not affected by pre-implantation HADS-D or PDI scores. FESS scores showed a stronginverse correlation with HADS-D, BDI-II, and PDI scores and showed a tendency towardscorrelation with the percentage of pain reduction. HADS-D and PDI scores improved afterSCS therapy.Limitations: Retrospective study.Conclusion: The outcome of SCS therapy could not be predicted on the basis of testedpsychological factors anxiety/depression and pain-related disability. FESS correlated inverselywith HADS-D, BDI-II, and PDI scores and showed a tendency towards correlation with thepercentage of pain reduction. Further research is needed to define the impact of psychologicalfactors on SCS outcomes.Key words: Spinal cord stimulation, clinical efficacy, paresthesia, psychological factors,anxiety, depression, disability, self-efficacy