Psychological Factors as Outcome Predictors for Spinal Cord Stimulation

The mechanism of action of spinal cord stimulation (SCS) is poorly understood and the success of treatment can depend on factors beyond the technical aspects of implantation. The aim of this retrospective analysis is the identification of preimplantation psychological values that may predict outcome of SCS treatment.

The retrospective analysis consisted of data from 83 patients who underwent SCS implantation from 2005 to 2013. Preimplantation evaluation included pain severity, sleep interference and distress each recorded with a numeric rating scale (NRS 0-10), depression and anxiety (Hospital Anxiety and Depression Score-HADS), catastrophizing (Pain Catastrophizing Scale-PCS), and patient's confidence in performing daily activity (Pain Self-Efficacy Questionnaire-PSEQ).

A fall in pain score of greater than 50% at one year follow up was the criteria applied to divide patients into two groups. Group A consisted of 39 patients whose pain score fell more than 50% and group B consisted of 44 patients whose pain score fell less than 50% at one year follow up. The median preimplantation pain score was comparable between the two groups. However, the preimplantation scores for sleep interference, HADS-depression, PCS and PSEQ, were significantly worse in group B. Receiver operating characteristic (ROC) curve analysis and univariate regression show that HADS-depression >10 and PSEQ ≤18 are risk factors for failure of SCS treatment, but only sleep interference, assessed with NRS >7 out of 10 was found to be an independent predictor of a less optimal outcome in multiple logistic regression.

Sleep interference appears to be an independent risk factor for unsuccessful SCS therapy.