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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 been employed to treat neuropathic pain. Psychological factors are assumed to be important for the efficacy of SCS. However, the impact of psychological factors on the outcome of SCS has only rarely been studied.


OBJECTIVES
The aim of this study was to determine the influence of psychological factors such as anxiety and depression, perceived disability, and self efficacy on the outcome of SCS in 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 our institution with lumbar, thoracic, or cervical neurostimulators between July 1, 2008, and June 30, 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 Numeric Rating Scale (NRS) were recorded. In addition, a questionnaire was mailed to participants that contained the following items: pain scores on the NRS with and without stimulation, time intervals of stimulation, paresthesia coverage, treatment satisfaction and medication intake, anxiety/depression (HADS-D and Beck Depression Index II [BDI-II]), PDI, and self efficacy using the Fragebogen zur Erfassung der schmerzspezifischen Selbstwirksamkeit (FESS).


RESULTS
Preoperative HADS-D, PDI, and NRS pain scores were not different in those patients with an unsuccessful trial and those who underwent IPG implantation. Long-term outcomes were not affected by pre-implantation HADS-D or PDI scores. FESS scores showed a strong inverse correlation with HADS-D, BDI-II, and PDI scores and showed a tendency towards correlation with the percentage of pain reduction. HADS-D and PDI scores improved after SCS therapy.


LIMITATIONS
Retrospective study.


CONCLUSION
The outcome of SCS therapy could not be predicted on the basis of tested psychological factors anxiety/depression and pain-related disability. FESS correlated inversely with HADS-D, BDI-II, and PDI scores and showed a tendency towards correlation with the percentage of pain reduction. Further research is needed to define the impact of psychological factors on SCS outcomes.